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CORD-19:04c300fc145b27f210fe05c52a93de14920c17bc JSONTXT 9 Projects

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Id Subject Object Predicate Lexical cue
T1 0-65 Sentence denotes THE APPLICATION OF MONOCLONAL ANTIBODIES I N THE STUDY OF VIRUSES
T2 67-75 Sentence denotes Abstract
T3 78-246 Sentence denotes Since their initial description (Kohler and Milstein, 1975) monoclonal antibodies have made a profound impression on all areas of biological research and biotechnology.
T4 247-412 Sentence denotes The basic property of a monoclonal antibody, that of combining specifically with one epitope (or family of related epitopes), can be used to supply a wealth of data.
T5 413-609 Sentence denotes A single monoclonal antibody can provide information on protein "relatedness," structure, function, synthesis, processing, cellular or tissue distribution and on the association between molecules.
T6 610-776 Sentence denotes Any attempt to separate the ways in which these data are gathered must be to some extent artificial since one study frequently yields results relevant to other areas.
T7 777-874 Sentence denotes However, it is appropriate to differentiate between the broad areas of virological investigation.
T8 875-955 Sentence denotes The contribution of monoclonal antibodies within each area can then be assessed.
T9 956-1223 Sentence denotes Thus, diagnostic virology, taxonomy, and epidemiology (Section 11) can be considered separately from the biochemical and molecular biological investigations described in Section 111; Section IV deals with the interaction of virus and host at the whole organism level.
T10 1224-1436 Sentence denotes Consequently, the selection of virus variants is dealt with in Section I11 where information concerning protein structure or function has been obtained, and also in Section IV where pathogenesis was investigated.
T11 1437-1646 Sentence denotes It is not intended in this review to provide an exhaustive list of all publications in which monoclonal antibodies have been used, but rather to illustrate how monoclonal antibodies can be applied in virology.
T12 1647-1836 Sentence denotes Other reviews of different aspects have recently been published (Antczak, 1982; Blann, 1981; Kennett, 1981; Nowinski et al., 1983; Sinkovics and Dreesman, 1983; Yewdell and Gerhard, 1981) .
T13 1837-2030 Sentence denotes It is important to emphasize that monoclonal antibody techniques are rarely applied in isolation, but are normally backed up with investigations using the more classical biochemical approaches.
T14 2031-2569 Sentence denotes For instance the recognition of separate active sites for hemagglutination and neuraminidase activity on the Sendai virus HN protein (Portner, 1981) involved experiments using temperature-sensitive mutations and chemical inhibitors as well as competitive antibody binding assays and selection of virus variants, and the proof of relationship between turkey (H1N1) influenza, and swine viruses involved RNA/RNA hybridization and replication studies as well as the observation of monoclonal antibody cross reactions (Hinshaw et al., 1983) .
T15 2570-2906 Sentence denotes Furthermore, there are limitations to the information that antibody studies can provide; structural studies for instance ultimately depend on the orientation of an antibody binding site on the various structural levels of the protein, amino acid sequence, three-dimensional structure, and even intermolecular associations (Section 111).
T16 2907-3092 Sentence denotes The principle of monoclonal antibody production, that of fusing a short lived antibody-producing cell derived from an immunized animal with a permanent myeloma cell line, is well known.
T17 3093-3149 Sentence denotes This has been recently reviewed (Gerhard et al., 1980) .
T18 3150-3309 Sentence denotes It is, however, necessary to consider the production of the immunogen, since it may be necessary to enrich for, or preferentially expose, a particular antigen.
T19 3310-3539 Sentence denotes Thus, in the production of measles virus-specific antibodies (Bohn et al., 1982) , heating of the antigen in the presence of 1% sodium dodecyl sulfate (SDS) led to the derivation of antibodies specific for the matrix (M) protein.
T20 3540-3695 Sentence denotes Similar treatment in the presence of reducing agents favoured the production of antibodies directed to the phosphoprotein (P) and nucleocapsid protein (N).
T21 3696-3833 Sentence denotes If the protein against which monoclonal antibodies are desired is sufficiently immunogenic, it is not necessary to use pure preparations.
T22 3834-4031 Sentence denotes Whole cell antigen was used in the production of antibodies directed against respiratory syncitial virus (RSV) (CGte et al., 1981) and against polyoma virus T antigen (Dilworth and Griffin, 1982) .
T23 4032-4256 Sentence denotes Also, if cross reacting, e.g., group specific antibodies are required, it is possible to perform the primary inoculation with one antigen, and the boosting inoculation with the cross reacting antigen (Gerhard et al., 1978) .
T24 4257-4471 Sentence denotes It is not appropriate to consider here the immunological techniques used in detail, but the interested reader is referred to a review of techniques used in conjunction with polyclonal sera (van Regenmortel, 1981) .
T25 4472-4581 Sentence denotes However, it is relevant to consider the limitations of these processes when applied to monoclonal antibodies.
T26 4582-4699 Sentence denotes First, the majority of monoclonal antibodies dc not cause immunoprecipitation of the antigen with which they combine.
T27 4700-4781 Sentence denotes This may be related to the fact that only one epitope is recognized per molecule.
T28 4782-4874 Sentence denotes Consequently, extensive cross linking and stabilization of immune complexes is not possible.
T29 4875-5033 Sentence denotes Therefore, immunoprecipitation by monoclonal antibodies requires the addition of a cross-linking agent such as staphylococcus protein A or antiimmunoglobulin.
T30 5034-5155 Sentence denotes The antigen is only retained by one binding site and only the most strongly combining monoclonal antibodies will succeed.
T31 5156-5223 Sentence denotes This problem may be diminished in the case of a multimeric protein.
T32 5224-5326 Sentence denotes Second, most immune precipitation procedures involve the use of detergent in the precipitation buffer.
T33 5327-5401 Sentence denotes This is necessary to prevent nonspecific contamination of the precipitate.
T34 5402-5483 Sentence denotes However, this detergent will have some destabilizing effect on protein structure.
T35 5484-5631 Sentence denotes Monoclonal antibodies are often sensitive to minor conformational change (Section II1,B) and consequently may be rendered nonreactive in this test.
T36 5632-5751 Sentence denotes It may be necessary to experiment with detergent type and concentration in order to achieve satisfactory precipitation.
T37 5752-5853 Sentence denotes The specificity of monoclonal antibodies, compared with hyperimmune serum, is illustrated in Fig. 1 .
T38 5854-6118 Sentence denotes The adverse effect of alterations in protein conformation may be aggravated in western blot procedures where antigens are often totally denatured for separation on sodium dodecyl sulfate (SDS)polyacrylamide gels before testing with antibody (Towbin et al., 1979) .
T39 6119-6205 Sentence denotes However, the method does have applications (Braun et al., 1983; Roseto et al., 1983) .
T40 6206-6272 Sentence denotes Immune precipitation is not suitable for quantitation of antigens.
T41 6273-6384 Sentence denotes This type of information is extracted from radioimmunoassay (RIA) or enzyme-linked immunosorbent assay (ELISA).
T42 6385-6611 Sentence denotes These processes are exten-sively applied during the initial screening for successful production of monoclonal antibodies, in diagnostic virology (Section I1,A) or in a modified form in competitive binding assays (Section 111).
T43 6612-6734 Sentence denotes These procedures score only the combination of antibody and antigen and give no information on the nature of that antigen.
T44 6735-6979 Sentence denotes Detergent conditions are frequently milder than those used in immunoprecipitation, but the attachment of antigen to the solid support necessary in many cases for these tests can itself result in conformational alteration (Bruck et al., 1982a) .
T45 6980-7227 Sentence denotes Information on the histological and intracellular location of antigen is obtained from techniques such as immune fluorescence (IF) and immune electron microscopy (IEM) using electron-dense or enzymatic markers (reviewed by van Regenmortel, 1981) .
T46 7228-7391 Sentence denotes These techniques have been widely used in diagnostic virology (Section II,A) as well as in studies of viral protein synthesis and virus maturation (Section 111,B).
T47 7392-7590 Sentence denotes In addition to the traditional techniques of serology, neutralization (NT), hemagglutination inhibition (HI), complement fixation (CF), and hemolysin inhibition (HLI) have been extensively employed.
T48 7591-7765 Sentence denotes In the following it is shown how application of these techniques in experiments utilizing monoclonal antibodies can be made in the study of all areas of virological research.
T49 7766-7949 Sentence denotes The reaction of a single antibody with an epitope is characterized by the equilibrium constant of the combination; this is reflected in the binding assays described above (Section I).
T50 7950-8235 Sentence denotes Although any one antibody is elicited by the exposure of an epitope to the immune system, it will react with many other epitopes to a greater or lesser extent, depending on the degree of fit between the would-be target site on the antigen and the combining site on the antibody itself.
T51 8236-8454 Sentence denotes In practical terms the epitope must possess some form of similarity to the parent epitope before any combination at all is detect- Vero cells were infected with measles virus Edmonston and labeled with [35S]methionine.
T52 8455-8521 Sentence denotes Lysates were prepared and used in immunoprecipitation experiments.
T53 8522-8972 Sentence denotes Proteins immunoprecipitated by track 1, rabbit hyperimmune antimeasles serum; track 2, rabbit preimmune control serum; tracks 3-5, monoclonal antibodies specific for the H protein; tracks 6-8, monoclonal antibodies specific for the Nprotein; tracks 9-16, monoclonal antibodies specific for the matrix protein; track 17, control monoclonal antibody, raised against coronavirus antigen; track 18, total infected cell lysate without immunoprecipitation.
T54 8973-9175 Sentence denotes Note that the antibodies used in tracks 6,7, and 8 are strongly mutually competitive in radioimmunoassay competitive binding experiments, but only one is also active in the immunoprecipitation reaction.
T55 9176-9221 Sentence denotes Reproduced with permission from Carter et al.
T56 9222-9271 Sentence denotes Nature (London) 1983. able in the binding assays.
T57 9272-9460 Sentence denotes This specificity of reaction provides the basis for the detection of subtle differences between the gene products of related viruses and thus the differentiation of one virus from another.
T58 9461-9672 Sentence denotes An alteration in the efficiency with which any one antibody combines with its target constitutes only a small part of the overall reaction of polyclonal antiserum with antigen and is consequently not detectable.
T59 9673-9847 Sentence denotes The use of antibodies with uniform specificity thus permits very fine analysis of epitope/antibody interactions and therefore of structural alteration in the target molecule.
T60 9848-10014 Sentence denotes Indeed this approach greatly exceeds conventional serology in specificity, and has led to the recognition of differences between viruses previously thought identical.
T61 10015-10205 Sentence denotes Monoclonal antibodies are capable of detecting differences of one amino acid, formerly only demonstrated by recourse to peptide fingerprinting or oligonucleotide mapping of the viral genome.
T62 10206-10385 Sentence denotes This approach has therefore revolutionized the techniques of virus identification, providing in many cases a simplification in the test procedure and yielding a more rapid result.
T63 10386-10594 Sentence denotes Used in this way, monoclonal antibodies find application in two main areas, first, in the field of rapid diagnosis of virus disease in man, animals, and plants, and second, in the extension of virus taxonomy.
T64 10595-10791 Sentence denotes These investigations could lead to more effective vaccination programs or disease treatment, and to a greater understanding of the relationships between viruses, their evolution, and epidemiology.
T65 10792-10903 Sentence denotes Rapid and accurate diagnosis of viral infection is of obvious importance to the clinician and to public health.
T66 10904-11035 Sentence denotes Wands et al. (1981) have summarized the criteria for selection of a monoclonal antibody for use as a diagnostic reagent as follows:
T67 11036-11038 Sentence denotes 1.
T68 11039-11233 Sentence denotes High affinity for antigen, both to permit efficient combination with low concentrations of antigen and to more efficiently displace host antibodies which may already coat primary biopsy samples.
T69 11234-11236 Sentence denotes 2.
T70 11237-11378 Sentence denotes It may be directed toward an area of the molecule not normally recognized efficiently by the host's own antibodies, and not therefore masked.
T71 11379-11381 Sentence denotes 3.
T72 11382-11517 Sentence denotes The antibody should be directed against an often repeated antigenic determinant that is readily accessible, e.g., a virus coat protein.
T73 11518-11520 Sentence denotes 4.
T74 11521-11608 Sentence denotes Multivalence: this may increase sensitivity, and IgM was found more effective than IgG.
T75 11609-11849 Sentence denotes If the antibody is not carefully chosen, it may give less satisfactory results than usual serological procedures (Phillips et al., 19821 , and cross reaction with host cell polypeptides should be carefully excluded (Fujinami et al., 1983) .
T76 11850-12064 Sentence denotes The application of monoclonal antibodies in diagnosis can be illustrated by reference to the following viruses; herpes, hepatitis B, rabies, flaviviruses, picornaviruses, and influenza; this list is not exhaustive.
T77 12065-12376 Sentence denotes Cytomegalovirus is a human herpesvirus (human beta herpesvirus 5) which has gained prominence in recent years following latent virus reactivation and disease in immunosuppressed, organ transplant recipients or patients with some other immune deficiency syndrome (Peterson et al., 1980; Thomas et al., 1975a,b) .
T78 12377-12509 Sentence denotes Recently monoclonal antibodies have been developed which are directed against virus structural polypeptides Pereira et al., 1982~) .
T79 12510-12601 Sentence denotes Some of these have proven able to detect CMV infection in biopsy specimens by the IF test .
T80 12602-12862 Sentence denotes Antibodies specific for herpes simplex viruses types 1 and 2 (Balachandran et Pereira et al., 1982b; Showalter et al., 1981) have also been used to type these viruses directly in cells from herpetic lesions (Balachandran et al., 1982a; Peterson et al., 1983) .
T81 12863-13068 Sentence denotes These tests yielded identical results to the more time consuming process of virus isolation and typing by restriction endonuclease mapping, and results were superior to those obtained by standard serology.
T82 13069-13410 Sentence denotes A similar procedure has also proved successful in the identification of varicella zoster (human herpesvirus 3) in cells obtained from vesicular skin lesions (Forghani et al., 1982) ' and monoclonal antibodies are now available which could be useful for typing Epstein -Barr virus (human gamma herpesvirus 4) (Mueller-Lantzsch et al., 1981) .
T83 13411-13517 Sentence denotes Herpes viruses can also be distinguished by a rapid enzyme immune filtration test (Richman et al., 1982) .
T84 13518-13686 Sentence denotes Marek's disease (MD) virus is a herpes virus of chickens normally diagnosed by reference antisera directed against the Marek's associated tumor surface antigen (MATSA).
T85 13687-13863 Sentence denotes Monoclonal antibodies have been obtained (Lee et al., 1983b) specific for MATSA, andused with success in the identification of Marek's disease in chickens (Lee et al., 1983a) .
T86 13864-14011 Sentence denotes Use of this test should help prevent confusion with lymphoid leukosis, since both diseases produce similar symptoms and are of economic importance.
T87 14012-14186 Sentence denotes Monoclonal antibodies produced against hepatitis B virus (HBV) (Wands et al., 1981) have been used to obtain a similar improvement in sensitivity over conventional diagnosis.
T88 14187-14335 Sentence denotes The application of monoclonal antibodies in RIA was found to detect HBV surface antigen even in patients who were negative by conventional testing .
T89 14336-14476 Sentence denotes This was subsequently confirmed by the demonstration that the new test detected antigenantibody complexes invisible by the former procedure.
T90 14477-14581 Sentence denotes These complexes were shown to be virus related by DNA hybridization techniques (Shafritz et al., 1982) .
T91 14582-14795 Sentence denotes All four serotypes of Dengue virus can be distinguished by monoclonal antibodies and have been applied with success to the identification of fresh low passage, virus isolates in an IF test (Henchal et al., 1983) .
T92 14796-14879 Sentence denotes This was found just as reliable, but faster, than the usual plaque reduction tests.
T93 14880-15072 Sentence denotes Influenza A and B viruses could be readily distinguished and, in some cases, typed satisfactorily even when there was insufficient virus present to permit hemagglutination inhibition testing .
T94 15073-15174 Sentence denotes Finally monoclonal antibodies may find widespread future use in the diagnosis of plant virus disease.
T95 15175-15376 Sentence denotes Recent work with antibodies specific for tobacco mosaic virus was able to distinguish two orchid strains which were previously thought identical with the tabomavirus type strain (Briand et al., 1982) .
T96 15377-15495 Sentence denotes The further use of monoclonal antibodies in the wider aspects of diagnosis has been reviewed (Nowinski et al., 1983) .
T97 15496-15628 Sentence denotes Further application of monoclonal antibodies to virus identification has been made in the fields of virus epidemiology and taxonomy.
T98 15629-15751 Sentence denotes In this manner the antibodies permit a fine analysis of intervirus relationships at both structural and biological levels.
T99 15752-15878 Sentence denotes Monoclonal antibodies have been used to compare vaccine strains of yellow fever virus (YFV) derived in different laboratories.
T100 15879-16019 Sentence denotes This confirmed the required similarity between vaccines in use and these strains could also be differentiated from virulent field isolates .
T101 16020-16244 Sentence denotes A similar comparison of wild type polio virus andvaccine strains, Saukett and Sabin, has also been conducted (Crainic et al., 1981; Ferguson et al., 1982; Humphrey et al., 1982; Minor et al., 1982; Osterhaus et al., 1981a) .
T102 16245-16445 Sentence denotes The use of monoclonal antibodies in the study of rabies infection has provided an important insight into the mechanism of virus pathogenicity (Section IV) and into the variation between virus strains.
T103 16446-16581 Sentence denotes Many workers have compared field isolates using monoclonal antibodies directed against the virus glycoprotein and nucleocapsid protein.
T104 16582-16755 Sentence denotes In this way differences have been found between viruses previously considered identical Charlton et al., 1982; Digoutte, 1982; Schneider, 1982; Witkor and Koprowski, 1980; .
T105 16756-16847 Sentence denotes This may have an important bearing on instances in which vaccine failure has been observed.
T106 16848-16956 Sentence denotes Variation in the nucleocapsid protein is probably not so important in this respect (Charlton et al., 1982) .
T107 16957-17084 Sentence denotes Such differences also exist between morbilliviruses (Giraudon and Wild, 1981a,b; Server et al., 1982; ter Meulen et aL, 1981) .
T108 17085-17455 Sentence denotes In addition, monoclonal antibodies have permitted analysis of the similarities and differences between hapadnaviruses (C8te et al., 1982) , parvoviruses (Burtonboy et al., 1982; Parrish et al., 1982) , rotaviruses Gary et al., Greenberg et al., 1983) , bunyaviruses (Gonzalez-Scarano et al., 1982) and to identify Zinga virus as Rift Valley fever (Meegan et al., 1983) .
T109 17456-17553 Sentence denotes At the present time the virus best characterized with monoclonal antibodies is that of influenza.
T110 17554-17680 Sentence denotes The three-dimensional structure has been determined for both the hemagglutinin (HA) and neuraminidase (NA) ; Section III,A,3).
T111 17681-17767 Sentence denotes The maintenance of influenza within the human population is related to two mechanisms.
T112 17768-17959 Sentence denotes First, exchange of the hemagglutinin gene with one derived from an animal virus accomplishes a complete antigenic change (antigenic shift) in the virus and permits widespread human infection.
T113 17960-18034 Sentence denotes Preexisting immunity is thus overcome and a worldwide pandemic may result.
T114 18035-18214 Sentence denotes In the periods between antigenic shift, a more gradual alteration occurs in the virus proteins (antigenic drift) which in some cases may permit reinfection of the host population.
T115 18215-18473 Sentence denotes Monoclonal antibodies have naturally been applied to these most interesting phenomena in an attempt to demonstrate the relationships between human, animal, and avian virus species, and also to demonstrate antigenic drift both in the field and the laboratory.
T116 18474-18612 Sentence denotes Monoclonal antibodies provide the sensitivity required to analyze subtle structural alterations and are therefore well suited to the task.
T117 18613-18719 Sentence denotes The seal influenza virus A/seal/Massachusetts/l/80 (H7N7) has been compared with viruses of avian origin .
T118 18720-18894 Sentence denotes A close relationship was noted between hemagglutinin molecules from those sources suggesting avian viruses might have played a role in the evolution of the seal virus strain.
T119 18895-19140 Sentence denotes In other studies differences have been noted between 25 avian (H4) influenza strains which may be related to the original host (Fukushi et al., 1982) and differences have been observed between neuraminidase (NA) molecules (Holmes et al., 1982) .
T120 19141-19240 Sentence denotes Antigenic drift has been demonstrated among field isolates of influenza A (Underwood, 1982) and B .
T121 19241-19411 Sentence denotes In addition nonneutralized HA or NA variants are readily selected by using monoclonal antibodies to apply selection pressure (Natali et al., 1981; Webster et al., 1982) .
T122 19412-19510 Sentence denotes This demonstrates how such a process might occur under immunological pressure applied by the host.
T123 19511-19749 Sentence denotes At least some of these laboratory selected variants might have been able to spread in the population since they were not neutralized by many samples of sera from potential hosts which did recognize the parent virus (Natali et al., 1981) .
T124 19750-19949 Sentence denotes In contrast to the ready demonstration of variability among the influenza viruses, tick-borne encephalitis virus (TBE) isolates have remained very similar over the last 26 years (Heinz et ab, 1982) .
T125 19950-20043 Sentence denotes Ready differentiation between viruses permits analysis of virus spread within the population.
T126 20044-20114 Sentence denotes At least two variants of influenza B could coexist in the population .
T127 20115-20285 Sentence denotes The respective epidemiologies of herpes simplex virus 1 and 2 have also been studied and one patient may suffer from both viruses simultaneously (Peterson et al., 1983) .
T128 20286-20394 Sentence denotes Monoclonal antibodies have permitted the analysis of mixed infections with closely related viruses in uitro.
T129 20395-20563 Sentence denotes Thus, interference and exclusion were demonstrated between Dengue virus types 2 and 3, but a small proportion of cells could be doubly infected (Dittmar et al., 1982) .
T130 20564-20818 Sentence denotes The use of these reagents permits the identification of the polypeptides carrying virus taxonomic markers (group, type, etc.) as demonstrated by Simian agent 12 , adenovirus 5 (Russell et al., 1981) , and herpes virus (McLean et Showalter et al., 1981) .
T131 20819-20950 Sentence denotes This type of analysis could also indicate polypeptides which have been structurally conserved during the course of virus evolution.
T132 20951-21048 Sentence denotes The advantges of a technique which permits rapid and efficient virus identification are enormous.
T133 21049-21123 Sentence denotes However, it is essential that the monoclonal antibody is chosen with care.
T134 21124-21305 Sentence denotes Many will recognize carbohydrate determinants of glycosylated polypeptides, and this modification is influenced by the host cell in which the virus is grown (Klenk and Rott, 1980) .
T135 21306-21481 Sentence denotes At least one instance is known where the type-specific target present on HSV glycoproteins synthesized in Hep-2 cells was not reactive when the virus was grown in Vero cells .
T136 21482-21583 Sentence denotes Second, the ability to detect differences is influenced by the technique used (Kendal et al., 1981) .
T137 21584-21815 Sentence denotes Binding of monoclonal antibody to antigen may or may not disrupt the biological function of that protein; this could lead to errors if the tests involved monitor antibody binding indirectly by inhibition of target protein function.
T138 21816-21929 Sentence denotes For this reason, procedures which simply demonstrate antibody binding are to be preferred in diagnostic virology.
T139 21930-22030 Sentence denotes Immunofluorescence is the method of choice for this purpose since it is rapid and relatively simple.
T140 22031-22181 Sentence denotes Furthermore, it is applicable directly to biopsy samples and provides additional information on the histological distribution of the antigen examined.
T141 22182-22469 Sentence denotes However, binding alone is an insufficient guide for research purposes, since the functional significance of the same epitope may vary with the virus strain and mutations may render an antibody unable to inhibit protein function without abolishing antibody binding (Kendal et al., 1981) .
T142 22470-22578 Sentence denotes It is necessary therefore to perform a number of tests in order to extract the maximum possible information.
T143 22579-22724 Sentence denotes Monoclonal antibodies provide us with a tool which is able to examine the individual protein within a structure as complicated as the whole cell.
T144 22725-22805 Sentence denotes It is possible to investigate, both in uitro and in viuo, the role of a protein.
T145 22806-22941 Sentence denotes It is also possible to determine the active areas of the molecule and to monitor its synthesis and processing within the infected cell.
T146 22942-23088 Sentence denotes The ability to distinguish related proteins can be used to provide a genetic marker in recombination experiments (Gonzalez-Scarano et al., 1982) .
T147 23089-23194 Sentence denotes The combination of antibody with antigen can be used to provide structural information on several levels.
T148 23195-23426 Sentence denotes First, just as it is possible to identify proteins carrying a taxonomic marker, so it is possible to identify a protein as performing a particular function once an antibody is available which is capable of inhibiting that function.
T149 23427-23553 Sentence denotes Second, antibodies binding to the same target protein differ in their capacity to produce function inhibition of that protein.
T150 23554-23707 Sentence denotes A panel of monoclonal antibodies is frequently divided into groups according to their effects on the activity of a target protein, or family of proteins.
T151 23708-23771 Sentence denotes In this way epitopes may be assigned a functional significance.
T152 23772-23981 Sentence denotes If certain assumptions are made, it is then possible to conduct competitive binding analyses to arrange the antibody sites relative to each other, and a schematic map of the molecule's surface can be drawn up.
T153 23982-24069 Sentence denotes Frequently virus variants can be selected to which a given antibody can no longer bind.
T154 24070-24182 Sentence denotes These may also be analyzed for loss of protein function or loss of capacity to bind other monoclonal antibodies.
T155 24183-24250 Sentence denotes In this way the map can be refined, or indeed constructed entirely.
T156 24251-24403 Sentence denotes Third, in order to explain function in terms of structure it is necessary to orientate the map thus obtained with the physical structure of the antigen.
T157 24404-24686 Sentence denotes This can be done by determination of the amino acid alterations produced in the variants described above, either directly by partial proteolysis and examination of those molecule fragments bound by the antibody, or from genome sequence determination in the region of the alteration.
T158 24687-24795 Sentence denotes Active amino acid residues can thus be distinguished and positioned in the primary structure of the protein.
T159 24796-24986 Sentence denotes The location of the antibody binding site is then known if the three-dimensional structure of the protein has been determined, or clues may be obtained from immune electron microscopy (IEM).
T160 24987-25088 Sentence denotes The whole process described above has met with varying success in application to a number of viruses.
T161 25089-25216 Sentence denotes The most complete of such determina-tions has been derived in the study of the influenza virus hemagglutinin and neuraminidase.
T162 25217-25349 Sentence denotes The target protein of a monoclonal antibody is usually detected by radioimmune precipitation or western blot procedures (Section I).
T163 25350-25654 Sentence denotes In this manner, those proteins to which neutralizing antibodies are directed have been determined, e.g., VP1 in poliovirus (Osterhaus et al., 1981b; Thorpe et al., 1982) , VP2 in Bluetongue virus Letchworth and Appleton, 1983) , and gp 56 in Venezuelan equine encephalitis virus (Roehrig et at., 1982a) .
T164 25655-25809 Sentence denotes The glycoprotein GP-1 of the coronavirus MHV was proven responsible for cell attachment and virus spread through cell/cell fusion (Collins et al., 1982) .
T165 25810-25989 Sentence denotes A modified immunoprecipitation experiment has demonstrated that a subset of the SV40 T antigen present in the infected cell is able to bind to the virus origin of DNA replication.
T166 25990-26176 Sentence denotes The antibody used in this work was apparently capable of distinguishing between T antigen with this activity and T antigen which could not perform this function (Scheller et al., 1982) .
T167 26177-26533 Sentence denotes A similar analysis has identified the cellular RNA polymerase which binds to the adenovirus 2 promotor in vitro (Dahmus and Kedinger, 1983) , and microinjection techniques have demonstrated that antibody specific to the transformation related protein p53 in 3T3 cells is capable of preventing the seruminduced onset of DNA synthesis (Mercer et al., 1982) .
T168 26534-26715 Sentence denotes Although the last two experiments are concerned with the function of cellular proteins, this approach has an obvious application in the study of virus replication and transcription.
T169 26716-26814 Sentence denotes Such an approach could also investigate the involvement of host -cell proteins in these processes.
T170 26815-27020 Sentence denotes Further insight into the function of tumour virus proteins in transformed cell survival has come from work involving monoclonal antibodies specific for p15 E, a structural component of type C retroviruses.
T171 27021-27229 Sentence denotes This protein was detected in cancer effusions and found to be highly efficient at blocking monocyte response to chemoattractants, a function which could protect a cancer from attack (Cianciolo et al., 1981) .
T172 27230-27356 Sentence denotes This analysis seeks to define active areas of the protein in terms of epitopes recognized by a panel of monoclonal antibodies.
T173 27357-27561 Sentence denotes In the main these experiments have been conducted on virus surface proteins which have easily monitored biological functions such as hemagglutination, neutralization, hemolysis, or neuraminidase activity.
T174 27562-27654 Sentence denotes In principle, the same approach could be extended to any protein with a measurable activity.
T175 27655-27760 Sentence denotes Combination of antibody with antigen can have a variety of effects, de-pending on the site of attachment.
T176 27761-27908 Sentence denotes Some functions which might previously have been thought associated, have been found separable when highly specific monoclonal antibodies were used.
T177 27909-28236 Sentence denotes A polyclonal monospecific serum which coats the protein surface with antibody will normally inhibit all protein functions, but a monoclonal antibody, which binds away from the active site need not have any detectable effect at all (Burstin et al., 1982; Massey and Schochetman, 1981; Pinter et al., 1982; Thorpe et al., 1982) .
T178 28237-28592 Sentence denotes By means of this function inhibition analysis, a panel of monoclonal antibodies specific for the measles virus hemagglutinin was divided into five groups : group 1 antibodies had no detectable activity, in HI or NT assays; group 2 exhibited HI activity but failed to neutralize virus; group 3 consisted of antibodies with similar activities in both tests.
T179 28593-28721 Sentence denotes Antibodies of group 4 revealed a significantly higher activity in the HI than the NT tests whereas this was reversed in group 5.
T180 28722-28832 Sentence denotes The antibodies used in that study were deliberately selected from those which had undetectable HLI activities.
T181 28833-29017 Sentence denotes This report therefore documents the separation of hemagglutination (a model for virus attachment to its target cell) from hemolysis (a model for virus penetration by fusion reactions).
T182 29018-29094 Sentence denotes This indicates that the requirements underlying these reactions must differ.
T183 29095-29428 Sentence denotes Both of these tests in fact are artificial, since the virus does not normally act to cross link cells, or to lyse the cell it is about to attack, and these results indicate that it is possible to prevent stable cell cross linking in circumstances which still permit sufficient virus/cell association for action of the fusion protein.
T184 29429-29688 Sentence denotes Similarly, antibodies may inhibit hemagglutination but still permit sufficient cell contact such that infection is not inhibited (Burstin et al., 1982; Gentry et al., 1982; Gonzalez-Scarano et al., 1982; Kimura-Kiroda and Yasui, 1983; ter Meulen et al., 1981.
T185 29689-29794 Sentence denotes This type of analysis provides clues that the functional areas of a multifunctional protein are distinct.
T186 29795-29891 Sentence denotes For instance the paramyxovirus HN protein has two activities, cell attachment and neuraminidase.
T187 29892-30181 Sentence denotes These probably reside at different areas of the molecule since some monoclonal antibodies inhibit only neuraminidase (Orvell and Grandien, 1982) , and virus variants have been obtained under monoclonal antibody selection pressure which are deficient only in neuraminidase (Portner, 1981) .
T188 30182-30277 Sentence denotes In the same way, antibodies are known which neutralize virus without blocking hemagglutination.
T189 30278-30370 Sentence denotes Presumably these antibodies bind to sites important in virus penetration but not absorption.
T190 30371-30535 Sentence denotes This phenomenon is exemplified by Sendai virus (Miura et al., 1982) , influenza virus , Sindbis virus (Chanas et al., 1982a) , and reovirus (Burstin et al., 1982) .
T191 30536-30709 Sentence denotes Other biological functions have been used to characterize epitopes defined by competition ELISA on the envelope glycoprotein of bovine leukemia virus (Bruck et al., 1982a) .
T192 30710-30895 Sentence denotes This analysis concentrated on BLV/ VSV pseudotype formation inhibition, polykaryotosis inhibition (cell/cell fusion following infection), and complement fixation (Bruck et al., 1982b) .
T193 30896-31134 Sentence denotes Monoclonal antibodies directed to virus surface proteins are generally more readily produced, but as more become available specific for virus internal proteins, this approach can be expected to yield further information on their function.
T194 31135-31444 Sentence denotes A function inhibihon assay has been applied to delineate that area of the SV40 T antigen involved in ATPase activity (Clark et d., 1981) and to demonstrate that some areas of the influenza and VSV nucleocapsid proteins may be associated with the transcription process (De et al., 1982; van Wyke et d., 1981) .
T195 31445-31579 Sentence denotes Once epitopes are identified it is necessary to determine their topological relationship to each other on the surface of the molecule.
T196 31580-31706 Sentence denotes This is conveniently achieved by a competitive binding analysis although selection of variants has also been extensively used.
T197 31707-31766 Sentence denotes Competitive binding is frequently examined in RIA or ELISA.
T198 31767-31943 Sentence denotes One monoclonal antibody carries the appropriate marker and unlabeled antibodies are assessed for their capacity to inhibit the combination of the labeled antibody with antigen.
T199 31944-32032 Sentence denotes If competition is observed, the antibodies are said to belong to the same binding group.
T200 32033-32151 Sentence denotes However, several precautions must be taken in the interpretation of data before meaningful conclusions can be reached.
T201 32152-32242 Sentence denotes It is assumed that two antibodies are mutually competitive if their binding sites overlap.
T202 32243-32396 Sentence denotes The binding site of a second antibody is then wholly or partially masked by the binding of the first antibody and binding is truly competitive in nature.
T203 32397-32463 Sentence denotes However, this is not the only explanation for such an observation.
T204 32464-32623 Sentence denotes Binding sites may be distinct but close together, such that the bulk of the first antibody molecule sterically prevents access of a second to its binding site.
T205 32624-32737 Sentence denotes These two possibilities cannot be readily distinguished but do at least both imply proximity of attachment sites.
T206 32738-32921 Sentence denotes In fact, a monoclonal antibody bound to a single epitope on its target protein may have considerable "swivel" movement available to it rendering steric effects relatively unimportant.
T207 32922-33046 Sentence denotes Stone and Nowinski (1980) reported that two IgG molecules (MW 150K) could bind noncompetitively to a retrovirus 15K protein.
T208 33047-33185 Sentence denotes However, immunoglobulin class may well be important here since oligomeric IgM would obviously provide a greater steric hindrance than IgG.
T209 33186-33312 Sentence denotes If steric effects are suspected they may be minimized by the use of monomeric antigen-binding submolecular antibody fragments.
T210 33313-33457 Sentence denotes It is however quite possible that allosteric inhibitory effects might also occur which would be indistinguishable from true competitive binding.
T211 33458-33628 Sentence denotes Indeed positive allosteric effects have been observed and antibody pairs identified which bind synergistically (Lefrancois and Lyles, 1982a,b; Lubeck and Gerhard, 1982) .
T212 33629-33721 Sentence denotes Similar effects resulting in competition may be widespread but are difficult to demonstrate.
T213 33722-33961 Sentence denotes Combination of monoclonal antibody with influenza neuraminidase modifies the reaction kinetics (Mountford et al., 1982) and combination with HSV glycoprotein can alter the pattern obtained by partial proteolysis (Eisenberg et al., 1982a) .
T214 33962-34041 Sentence denotes These effects could also be mediated by antibody-induced conformational change.
T215 34042-34171 Sentence denotes Finally, two antibodies directed at the same site will compete in a manner related to their relative avidities or concentrations.
T216 34172-34345 Sentence denotes Taking an extreme case, a weakly binding antibody would not show detectable competition with a labeled, strongly binding immunoglobulin, but the reverse is clearly not true.
T217 34346-34492 Sentence denotes In practice a spectrum of relative interference efficiencies will probably be obtained (Lefrancois and Lyles, 1982a,b; Stone and Nowinski, 1980) .
T218 34493-34618 Sentence denotes The extent of interference obtained will be influenced by the antibody avidity as well as the proximity of the binding sites.
T219 34619-34785 Sentence denotes For this reason binding sites should not be distinguished on the basis of the extent of competition, it is the observation of competition itself which is significant.
T220 34786-34966 Sentence denotes Furthermore, while the observation of competition assigns two antibodies to the same binding group, it is not sufficient to separate them merely on the basis of failure to compete.
T221 34967-35142 Sentence denotes Any such noncompeting antibodies should be examined in the reverse experiment (i.e., with the other partner carrying the marker) to exclude avidity effects as described above.
T222 35143-35246 Sentence denotes If this procedure fails to reveal competition, then allocation to separate binding groups is justified.
T223 35247-35474 Sentence denotes Alternatively, determination of antibody avidity may obviate the need for this analysis but one-way competition effects can still occur even in the case of antibodies of similar avidity and concentration (Carter et al., 1982) .
T224 35475-35557 Sentence denotes The reasons for this are unknown but might involve some form of allosteric effect.
T225 35558-35804 Sentence denotes Determination of antibody avidity may be performed by a rapid method (Jackson et al., 1983) or relative antibody avidities may be estimated from RIA saturation curves (Carter et al., 1982; Massey and Schochetman, 1981; Stone and Nowinski, 1980) .
T226 35805-35885 Sentence denotes The competitive binding procedure has been applied with success to many viruses.
T227 35886-36174 Sentence denotes Monoclonal antibodies specific for the measles virus hemagglutinin were grouped into five sets on the basis of their ability to influence the biological functions of that molecule and these were then sorted into three binding groups by competition radioimmunoassay (Carter et ul., 1982) .
T228 36175-36456 Sentence denotes A similar approach has produced a detailed map of the VSV G protein including epitopes instrumental in virus neutralization in which determinants were identified as cross-reacting or specific to the strains Indiana or New Jersey (Lefrancois and Lyles, 1982a,b; Volk et al., 1982) .
T229 36457-36673 Sentence denotes Japanese encephalitis virus (Kimura-Kiroda and Yasui, 1983) and RNA tumor viruses (Bruck et al., 1982a,b; Massey and Schochetman, 1981; Niman and Elder, 1982; Pinter et al., 1982) have also been extensively analyzed.
T230 36674-36771 Sentence denotes The binding group analysis forms a sensitive probe for alterations in protein surface structure .
T231 36772-36979 Sentence denotes The manner in which the sample is prepared can also influence the conformation and/or exposure of the reacting epitopes and this should be considered in the design of such experiments (Bruck et al., 1982b) .
T232 36980-37138 Sentence denotes The second approach to the problem of arranging binding sites relative to each other is to select virus variants under monoclonal antibody selection pressure.
T233 37139-37213 Sentence denotes In the case of neutralizing antibodies this is relatively straightforward.
T234 37214-37323 Sentence denotes Nonneutralizing antibodies could also be applied to enveloped viruses if used in conjunction with complement.
T235 37324-37483 Sentence denotes Virus variants may then be isolated to which the selecting antibodies can no longer bind, or in which antibody combination no longer results in neutralization.
T236 37484-37630 Sentence denotes These viruses are then tested with a panel of monoclonal antibodies to determine which other antibodies also show altered binding characteristics.
T237 37631-37682 Sentence denotes In this way, a map of epitopes can be constructed .
T238 37683-37921 Sentence denotes The virus variants are commonly already present in the population at a frequency of (Emini et al., 1982; Portner et aL, 1980; Prabhakar et al., 1982; Webster et al., 1982) which presumably represents the error rate in virus transcription.
T239 37922-38071 Sentence denotes This results in amino acid substitutions either within the antibody binding site or at a position which influences the structure of the binding site.
T240 38072-38204 Sentence denotes This type of experiment provides a finer analysis of the relationships between binding sites because steric hindrance is eliminated.
T241 38205-38303 Sentence denotes Variant selection and mapping has been applied in the main to the HA and NA proteins of influenza.
T242 38304-38442 Sentence denotes The extremely detailed studies performed by Laver et al., (1979 Laver et al., ( ,1980a and Gerhard et al., (1981) exemplify this approach.
T243 38443-38669 Sentence denotes However, regardless of the method in which epitope topography is determined, the schematic map thus produced must be oriented on the physical structure of the protein and this necessitates a detailed knowledge of the molecule.
T244 38670-38726 Sentence denotes Two approaches have been used to achieve this objective.
T245 38727-38949 Sentence denotes First, antibody binding sites can be localized to a particular peptide fragment following partial proteolysis, and second, the amino acid substitutions occurring in the antibody-selected variant proteins can be determined.
T246 38950-39041 Sentence denotes Niman and Elder (1982) have conducted a comprehensive analysis of the Rauscher virus gp 70.
T247 39042-39191 Sentence denotes Products of partial proteolysis were identified by reactivity with antisera directed against synthetic polypeptides predicted from the gene sequence.
T248 39192-39249 Sentence denotes The other polypeptides were assigned by peptide map-ping.
T249 39250-39336 Sentence denotes In this way a linear proteolytic leavage map could be derived for 8 different enzymes.
T250 39337-39530 Sentence denotes Monoclonal antibodies were then analyzed for their ability to immunoprecipitate various polypeptide fragments and their binding sites could then be assigned in the molecule's primary structure.
T251 39531-39689 Sentence denotes It was found that antibody binding sites were closely grouped in two areas which presumably reflected regions of the protein exposed for immunological attack.
T252 39690-40082 Sentence denotes A similar analysis located eight epitopes, previously defined by their reaction with a panel of monoclonal antibodies, in the proteolytic cleavage map of gp 70 from murine leukemia virus (Pinter et al., 19821, and antibody sites have also been localized on gp 51 of bovine leukemia virus, a 15K molecular weight fragment contained areas involved in biological activity (Bruck et al., 1982b) .
T253 40083-40296 Sentence denotes Similarly, a herpes simplex virus glycoprotein type common determinant has been localized to a 12K fragment of a larger (38K) peptide which also contained two type-specific determinants (Eisenberg et al., 1982a) .
T254 40297-40413 Sentence denotes Other studies have located the active site of SV40 T antigen ATPase by means of well characterized deletion mutants.
T255 40414-40553 Sentence denotes It was found that enzyme activity and antibody binding required the region of the A gene from 0.37 to 0.29 map units (Clark et al., 1981) .
T256 40554-40706 Sentence denotes Provided the primary sequence of the molecule is known, virus variants can supply highly specific information on the location of antibody binding sites.
T257 40707-40889 Sentence denotes Unlike antibody binding to a peptide fragment, however, it is not possible to be absolutely certain that the amino acid affected actually constitutes part of the binding site itself.
T258 40890-40957 Sentence denotes This method has been extensively applied in the study of influenza.
T259 40958-41102 Sentence denotes Amino acid alterations can be detected by peptide mapping (Laver et al., 1979 (Laver et al., , 1980b or genome sequencing (Caton et al., 1982) .
T260 41103-41234 Sentence denotes Since the three-dimensional structure of the influenza hemagglutinin is now available these binding sites could be easily located .
T261 41235-41374 Sentence denotes Analogy with this model has permitted the location of such sites on other strains of influenza (Caton et ul., 1982; Jackson et al., 1982) .
T262 41375-41666 Sentence denotes These studies have revealed the presence of distinct areas on the HA molecule within which the amino acid substitutions predominantly occurred, These areas were also implicated in the production of antigenic variation associated with the process of antigenic drift (reviewed by Ward, 1981) .
T263 41667-41826 Sentence denotes The three-dimensional structure of the influenza virus NA molecule is now known permitting the location of monoclonal antibody binding sites to be identified .
T264 41827-42024 Sentence denotes This also provided insight into those areas of the molecule involved in enzyme function and previously identified by monoclonal antibodies as well as locations in which antigenic drift could occur.
T265 42025-42232 Sentence denotes This level of refinement in our knowledge of structure, function, and anti-genicity has so far been reached only in influenza but a similar approach has located the neutralization sites of poliovirus type 3.
T266 42233-42398 Sentence denotes This was found to be a small (eight amino acid) sequence in protein VP1 Minor et al., 1983) ; however no three-dimensional structure is yet available for this virus.
T267 42399-42626 Sentence denotes A further clue to antibody binding site location may be obtained from immune electron microscopy in which the antibody is used in conjunction with an electron-dense material such as ferritin or hemocyanin (Gonda et al., 1981) .
T268 42627-42853 Sentence denotes Chanas et al. (1982a) demonstrated that hemagglutination inhibiting monoclonal antibodies attached near the tip of the Sindbis virus peplomer, while hemolysin inhibiting antibodies attached lower down, near the virus membrane.
T269 42854-43077 Sentence denotes A similar situation has also been demonstrated in influenza and may explain the separation of hemagglutination inhibition and neutralization exhibited by monoclonal antibodies specific for the HA protein of seal influenza .
T270 43078-43298 Sentence denotes In just the same way as monoclonal antibodies provide a sensitive probe for virus detection in diagnosis (Section I1,A) so they can also be used to detect low amounts of individual virus proteins within the infectedcell.
T271 43299-43367 Sentence denotes In this way they can answer questions of molecular and cell biology.
T272 43368-43553 Sentence denotes They can thus provide information concerning temporal and spatial separation of protein formation and accumulation, and data on protein modification and processing in the infected cell.
T273 43554-43762 Sentence denotes Many studies have been performed to demonstrate temporal control of protein synthesis within the lytic virus infection, e.g., Sendai virus (Orvell and Grandien, 1982; and measles virus (Norrby et al., 1982) .
T274 43763-43825 Sentence denotes It is not the object of this review to list all these studies.
T275 43826-43968 Sentence denotes Rather we shall consider persistent infections where normal protein synthesis is modified or controlled such that virus and cells may coexist.
T276 43969-44199 Sentence denotes Interesting information has been gathered in this area which frequently involves low levels of infected cells or proteins within those cells and monoclonal antibodies are thus admirably suited for investigation of this phenomenon.
T277 44200-44391 Sentence denotes Measles virus is associated with a persistent slowly progressing fatal infection of the human central nervous system (CNS) termed subacute sclerosing panencephalitis (SSPE) (reviewed by ter .
T278 44392-44541 Sentence denotes This disease is associated with a failure to produce mature virus or to develop the typical measles virus cytopathology, cell fusion in brain tissue.
T279 44542-44681 Sentence denotes An examination of the patients' immune response during this illness demonstrated a lack of antibodies directed against the virus matrix (M)
T280 44682-44691 Sentence denotes protein .
T281 44692-44853 Sentence denotes A direct search by immunoprecipitation and western blot techniques has failed to demonstrate the production of this protein in infected brain or brain explants .
T282 44854-45002 Sentence denotes The clinical importance of this disease has prompted an examination of measles virus polypeptide expression in persistently infected cells in uitro.
T283 45003-45198 Sentence denotes Studies using several monoclonal antibodies failed to detect M protein in persistently infected tissue culture cell lines (SSPE cell lines) derived from SSPE patient brain (Carter et al., 1984) .
T284 45199-45370 Sentence denotes Although this method did permit identification of M protein in a laboratory-established persistent infection which was previously thought not to express this polypeptide .
T285 45371-45483 Sentence denotes Monoclonal antibodies thus provide excellent evidence that matrix protein is not synthesized in SSPE cell lines.
T286 45484-45639 Sentence denotes The lack of this major structural polypeptide is thought to prevent virus particle maturation and account for the slowly progressing nature of the disease.
T287 45640-45831 Sentence denotes Measles virus persistently infected cells show a low expression of membrane glycoproteins (Norrby et al., 1982) ' although expression is normally sufficient to permit development of syncytia.
T288 45832-46158 Sentence denotes The expression of virus polypeptides has also been investigated within mouse brain persistently infected with lymphocytic choriomeningitis (LCM) virus (Oldstone and Buchmeier, 1982; Rodriguez et al., 1983) , Sendai virus , and on the surface of spleen cells from mice infected with Friend leukemia virus (Britt et al., 1981) .
T289 46159-46253 Sentence denotes In these cases the level of virus glycoproteins detected on the cell surface was also reduced.
T290 46254-46384 Sentence denotes Perhaps this is one way in which persistently infected cells evade the immune system and thus permit the maintenance of infection.
T291 46385-46633 Sentence denotes Monoclonal antibodies permit the selective detection of virus-specific transformation markers on the transformed cell surface, e.g., Epstein -Barr virus (Kintner and Sugden, 1981; Slovin et al., 1982) and Marek's disease virus (Lee et al., 1983b) .
T292 46634-46780 Sentence denotes Antibodies further permit the detection and characterization of transformation specific proteins as well as some investigations of their function.
T293 46781-46886 Sentence denotes Monoclonal antibodies directed against the v-ras gene product of Harvey sarcoma virus have been produced.
T294 46887-47158 Sentence denotes The products of the v-rczs gene family in viruses, transformed and normal cells were shown to share similarities, and the antibodies were able to confirm that the protein is located at the inner surface of the membrane and binds guanine nucleotides (Furth et al., 1982) .
T295 47159-47276 Sentence denotes In addition, a tumor antigen of adenovirus 5 has been shown to accumulate in the cell nucleus (Sarnow et al., 1982) .
T296 47277-47383 Sentence denotes The specificity of the monoclonal antibody confers the ability to react with a family of related proteins.
T297 47384-47632 Sentence denotes This property is particularly relevant where precursorproduct relationships exist (as in proteolysis), or where similar sequences of proteins might occur in different molecules, e.g., following a recombination or readthrough event in transcription.
T298 47633-47807 Sentence denotes If the precursors never reach appreciable levels within the cell or the shared sequences are small, the cross reacting proteins are difficult to detect with polyclonal serum.
T299 47808-47983 Sentence denotes Small virus-specific polypeptides which reacted with monoclonal antibodies specific for glycoproteins A and B were detected in HSV-infected Vero cells (Pereira et al., 1981) .
T300 47984-48157 Sentence denotes These were not identified in virus-infected Hep-2 cells and were later shown to be proteolytically related to the intact forms of the glycoproteins (Pereira et al., 1982a) .
T301 48158-48244 Sentence denotes Families of related proteins were also detected in this manner in CMV infected cells .
T302 48245-48362 Sentence denotes A 15K cleavage product of the measles virus nucleocapsid protein has also been identified (Carter and Baczko, 1983) .
T303 48363-48484 Sentence denotes This type of analysis defines aprotein family but does not indicate whether the submolecular fragments serve any purpose.
T304 48485-48651 Sentence denotes Furthermore, care should always be taken to ensure that the protein precipitation is not caused by a spurious cross reaction with a host cell polypeptide (Section V).
T1 48652-48737 Sentence denotes Monoclonal antibodies have also permitted the identification of novel virus proteins.
T2 48738-49034 Sentence denotes A new cell surface marker was discovered on B cell lines known to harbor EBV (Slovin et al., 1982) , a new HSV glycoprotein has also been detected and characterized (Balachandran et aL, 1981 ) and a new protein (gp 70) was detected in leukemic cells from mice infected with Friend leukemia virus.
T3 49035-49271 Sentence denotes This protein was apparently derived from a virus produced by a recombination event during infection, and had lost cross reactivity with a monoclonal antibody specific for the ecotropic Friend murine leukemia virus (Britt et al., 1981) .
T4 49272-49418 Sentence denotes An unusual form of composite protein was demonstrated in measles virus infected BGM cells and was apparently not produced in other infected cells.
T5 49419-49567 Sentence denotes The protein was detected because it cross-reacted with a monoclonal antibody specific for nucleocapsid protein, but the new molecule was 24K larger.
T6 49568-49742 Sentence denotes Peptide mapping analysis showed that it apparently contained all the nucleocapsid peptides plus some new ones whose origin could not be determined (Wild and Giraudon, 1982) .
T7 49743-49854 Sentence denotes No precursor -product relationship could be demonstrated between this new protein and the nucleocapsid protein.
T8 49855-49941 Sentence denotes The origin of this protein is still obscure but a readthrough mechanism was suggested.
T9 49942-50072 Sentence denotes A similar finding has also been reported using monoclonal antibodies in the study of HSV 1 and 2 infections (Zweig et al., 1980) .
T10 50073-50269 Sentence denotes A polypeptide was observed which was larger than the nucleocapsid protein and contained additional peptides but apparently had no precursorproduct relationship to the smaller nucleocapsid protein.
T11 50270-50353 Sentence denotes Following its synthesis, a protein may mature through posttranslational processing.
T12 50354-50589 Sentence denotes Processing in the sense used here includes covalent modification through glycosylation, posttranslational cleavage etc, as well as maturation by conformational changes often associated with the formation of intermolecular associations.
T13 50590-50745 Sentence denotes This concept is particularly relevant in the context of virus assembly where stable associations must occur leading to the production of a viable particle.
T14 50746-50918 Sentence denotes Conformational change is probably involved in this process and may perform a regulatory function as in tobacco mosaic virus assembly (Butler, 1971; Klug and Durham, 1971 ).
T15 50919-50921 Sentence denotes a.
T16 50922-50949 Sentence denotes Modification and Transport.
T17 50950-51064 Sentence denotes The novel proteins formed by proteolysis in some HSV-infected cells have already been mentioned (Section III,B,2).
T18 51065-51223 Sentence denotes These proteins are degraded only in some cell types (Pereira et al., ,1982a which suggests this process is not a functionally important processing phenomenon.
T19 51224-51484 Sentence denotes However, monoclonal antibodies have been used in pulse-chase experiments to demonstrate genuine modification of proteins through glycosylation (Balachandran et al., 1981) and also to demonstrate temporal regulation of their synthesis (Showalter et al., 1981) .
T20 51485-51574 Sentence denotes Misra et al., (1982) have studied the maturation of an HSV-1 early glycoprotein (GVP-11).
T21 51575-51703 Sentence denotes These workers discovered that tunicamycin-sensitive glycosylation was necessary for the cell surface expression of this protein.
T22 51704-51921 Sentence denotes However, monoclonal antibodies may not react with the unmodified form of a protein (only one antibody from a panel of 65 directed against measles virus H protein reacted with the unmodified product formed in vitro; M.
T23 51922-51924 Sentence denotes J.
T24 51925-52063 Sentence denotes Carter, unpublished observation) and consequently might not always provide an adequate probe for the expression of the polypeptide moiety.
T25 52064-52115 Sentence denotes A polyclonal serum should therefore always be used.
T26 52116-52181 Sentence denotes Opposite results have been obtained with measles virus H protein.
T27 52182-52330 Sentence denotes Glycosylation was not required for insertion into the rough endoplasmic reticulum and intracellular transport of the protein to the plasma membrane.
T28 52331-52479 Sentence denotes This detailed study also elucidated intermediates formed in the protein modification pathway leading to the mature molecule (Bellini et al., 1983) .
T29 52480-52705 Sentence denotes A comprehensive immunofluorescence study using monoclonal antibodies has examined the distribution of a number of Moloney murine leukemia proteins on the infected cell membrane (Satake et al., 1981; Satake and Luftig, 1983) .
T30 52706-52891 Sentence denotes These workers were able to demonstrate that the mem-brane sites at which virus antigens accumulated were often distinct and differentially controlled by the cellular microtubule system.
T31 52892-53047 Sentence denotes In addition, they were able to demonstrate by double dot immunofluorescence that two virus-specific antigens, P15 and P15 E, accumulated at the same sites.
T32 53048-53139 Sentence denotes This association between a gag and an env gene product may be important for virus assembly.
T33 53140-53227 Sentence denotes In the formation of a virus particle stable intermolecular associations must be formed.
T34 53228-53338 Sentence denotes It is likely that protein combination to form virus structural components will involve conformational changes.
T35 53339-53425 Sentence denotes Protein conformation could also be altered artifactually during extraction procedures.
T36 53426-53711 Sentence denotes Although some antibodies seem to recognize a sequence of amino acids, most monoclonal antibodies possess a sensitivity to the conformation of the epitope that cannot be visualized using a polyclonal serum, and this permit investigations into this complex field of structural isomerism.
T37 53712-53916 Sentence denotes Alternatively the development of intermolecular associations must result in the masking of some epitopes and therefore the inhibition of combination with antibody directed toward that area of the protein.
T38 53917-54153 Sentence denotes Monoclonal antibodies could distinguish readily between native and unfolded forms of the Sindbis virus glycoprotein El (Roehrig et al., 1982b) and between native (N) and heated (H) forms of the poliovirus capsid Icenogle et al., 1981) .
T39 54154-54293 Sentence denotes In the latter case it was also shown that the irreversible conversion of N to H could be accomplished by some acidic isolation procedures .
T40 54294-54415 Sentence denotes This explained an earlier finding that some capsids were in the H form inside the infected cell (Ferguson et al., 1981) .
T41 54416-54530 Sentence denotes More biologically relevant information concerning virus assembly has also been derived from studies of poliovirus.
T42 54531-54619 Sentence denotes Two monoclonal antibodies were obtained which bound to poliovirion precursor structures.
T43 54620-54814 Sentence denotes The sites recognized were different, one antibody bound to infectious virions, 80 S empty capsids in the N form and to 14 S precursor subunits, the other bound only to virions and empty capsids.
T44 54815-54868 Sentence denotes Neither antibody bound to the heat-treated particles.
T45 54869-55049 Sentence denotes Furthermore, the antibody binding sites were both shown to be located on VP1 by chemical cross linking, but neither antibody bound well to free VP1 in the native or denatured form.
T46 55050-55127 Sentence denotes This indicated the sites recognized were formed only in the capsid structure.
T47 55128-55330 Sentence denotes However, variants could readily be selected which did not express these sites, so it is likely that the areas recognized by these antibodies are not vital for structural integrity (Emini et al., 1982) .
T48 55331-55571 Sentence denotes Similar data have been reported for foot and mouth disease virus (FMDV) where monoclonal antibodies have been obtained which can distinguish between complete (146s) virions and their precursor (12 S) subunits (McCullogh and Butcher, 1982) .
T49 55572-55816 Sentence denotes These two studies demonstrate that unique antigenic sites are created during picornavirus maturation and explain earlier reports that neutralizing antibodies could only be elicited by using the mature polio virion as immunogen (Dernick, 1981) .
T50 55817-56012 Sentence denotes A similar effect has been demonstrated in the case of TMV where some monoclonal antibodies react only with the nucleocapsid, and others only with the protein monomer (Dietzgen and Sander, 1982) .
T51 56013-56279 Sentence denotes Although the former class must recognize a new site caused by conformational change or formed at molecular junctions, the latter class of antibodies could be directed at a site which is either masked in the protein complex or destroyed through conformational change.
T52 56280-56403 Sentence denotes The pathway of adenovirus hexon polymerization has also been investigated with conformation-specific monoclonal antibodies.
T53 56404-56564 Sentence denotes The monomeric or denatured hexon protein lacks antigenic determinants in common with the trimeric capsomere, a situation reminiscent of the picornavirus capsid.
T54 56565-56754 Sentence denotes Using these conformation-sensitive monoclonal antibodies, Cepko and Sharp (1982) have shown that trimerization of the hexon protein involves a nonstructural lOOK virus-specific polypeptide.
T55 56755-56870 Sentence denotes Three hexon molecules bind to this protein in the monomeric configuration and are released as a trimeric capsomere.
T56 56871-56973 Sentence denotes The capsomeric conformation is adopted concomitantly with release from the 100K "scaffolding" protein.
T57 56974-57206 Sentence denotes A structural rearrangement may also occur during release of CMV since some antibodies are able to react with determinants and neutralize infectious virus but are unable to bind to the same proteins on the surface of infected cells .
T58 57207-57369 Sentence denotes Conformational changes are believed important in the development of fusion protein activity by the influenza virus hemagglutinin at low pH (Skehel et al., 1982) .
T59 57370-57536 Sentence denotes Monoclonal antibodies have been used to demonstrate this structural change directly, and to locate areas involved in the molecule's structure (Daniels et al., 1983) .
T60 57537-57635 Sentence denotes Virus architecture, that is the proximity of structural proteins, is also amenable to examination.
T61 57636-57824 Sentence denotes For instance gp 56 and gp 50 have been shown closely associated on the Venezuelan equine encephalitis (VEE) virus envelope by means of competitive binding studies (Roehrig et al., 1982a) .
T62 57825-57981 Sentence denotes A similar examination showed that the influenza hemagglutinin was close to the cellular H-2K histocompatibility antigen on the surface of the infected cell.
T63 57982-58081 Sentence denotes A complex is not apparently formed since these antigens did not cocap (Hackett and Askonas, 1982) .
T64 58082-58303 Sentence denotes On the mature influenza virus envelope however, the HA protein is often found in close association with the NA protein, since monoclonal antibodies specific for hemagglutinin may have a neuraminidase inhibiting activity .
T65 58304-58539 Sentence denotes Frequently, virus-specific products associate with cellular proteins and this can be demonstrated by competitive binding assays or coprecipitation experiments (Carroll and Gurney, 1982; Ferracini et al., 1982; Sarnow et al., 1982) . c.
T66 58540-58550 Sentence denotes Mutations.
T67 58551-58639 Sentence denotes Structural change can also result from the acquisition of mutations by the virus genome.
T68 58640-58747 Sentence denotes During persistent infection a virus genome is able to accumulate mutations rapidly (Holland et al., 1979) .
T69 58748-58844 Sentence denotes The resulting structural alterations in virus proteins can be detected by monoclonal antibodies.
T70 58845-58998 Sentence denotes Differences have been found in the glycoproteins synthesized by lytic transforming EBV and by the nontransforming virus shed from persistent infections .
T71 58999-59098 Sentence denotes Such changes have also been demonstrated in the measles virus hemagglutinin by immunofluorescence .
T72 59099-59257 Sentence denotes A similar process has been detected by alterations in competitive binding behavior using monoclonal antibodies specific for the measles virus matrix protein .
T73 59258-59326 Sentence denotes In this study an apparent separation of binding groups was observed.
T74 59327-59466 Sentence denotes A monoclonal antibody was found to have lost its capacity to compete with a second even though both still immunoprecipitated the M protein.
T75 59467-59564 Sentence denotes This example illustrates that the detection of structural change is dependent on the method used.
T76 59565-59772 Sentence denotes An examination based solely on radioimmune precipitation may be superior in detecting certain changes which "loosen" the protein and render it more susceptible to the action of detergents in the buffer used.
T77 59773-59948 Sentence denotes However, changes in relative avidity, topography, or allostery would not be detected provided antibody avidity was still sufficiently high to permit precipitation (Section I).
T78 59949-60038 Sentence denotes Similarly, detergent produced effects might not be detected in the competition RIA alone.
T79 60039-60240 Sentence denotes In any analysis of virus-specific protein structure and function, it is always desirable to obtain pure preparations of the protein in question to permit in uitro experimentation or vaccine production.
T80 60241-60379 Sentence denotes One obvious example of the use to which monoclonal antibodies can be put is in the preparation of affinity columns for such purifications.
T81 60380-60583 Sentence denotes It is not appropriate to list here all instances in which this has been performed, but any review of the application of monoclonal antibody technology would be incomplete without mention of this subject.
T82 60584-60772 Sentence denotes The application of the technique is exemplified in the purification of glycoproteins from HSV 1 and 2 (Eisenberg et al., 1982b) and the measles virus hemagglutinin (Bellini et al., 1981) .
T83 60773-60922 Sentence denotes When used in RIA or ELISA monoclonal antibodies provide a convenient and accurate method for the quantitation of viral proteins (Lutz et al., 1983) .
T84 60923-61010 Sentence denotes The study of a virus as a pathogen is more complicated than studies conducted in uitro.
T85 61011-61092 Sentence denotes These examinations frequently cross the boundary between virology and immunology.
T86 61093-61129 Sentence denotes Monoclonal antibodies may be used to
T87 61131-61223 Sentence denotes The isolation of nonneutralizable virus variants has already been discussed (Section II1,A).
T88 61224-61316 Sentence denotes These variants can also be applied in studies of pathogenicity as well as protein structure.
T89 61317-61521 Sentence denotes Spontaneous virus variants occur at a high frequency (lo-*) in Coxsackie B4 virus populations (Prabhaker et al., 1982) and this may explain the high variation in disease pattern produced by these viruses.
T90 61522-61617 Sentence denotes Possibly alterations in the virus attachment protein might result in an altered tissue tropism.
T91 61618-61716 Sentence denotes However, the most interesting data have so far emerged from studies of rabies and influenza virus.
T92 61717-61827 Sentence denotes The selection of naturally arising antigenic variants in the rabies virus glycoprotein was first reported by .
T93 61828-62093 Sentence denotes Coulon et al.(1982a,b) applied this method to select variants using three monoclonal antibodies and noted that while two antibodies led to the isolation of variants indistinguishable in virulence from the parent virus stock, one antibody selected avirulent viruses.
T94 62094-62332 Sentence denotes These variants were very similar to the parental virus by all other criteria, but differed in their capacity to evoke a strong and rapid immune response which could lead to successful defense against the infection (Coulon et al., 1982~) .
T95 62333-62458 Sentence denotes More monoclonal antibodies were then used to locate the virulence-related epitope on an antigenic map (Coulon et al., 1983) .
T96 62459-62604 Sentence denotes Similar experiments led Dietzschold et al., (1983) to the identification of a single amino acid change in nonpathogenic variants of rabies virus.
T97 62605-62734 Sentence denotes The arginine residue present in the virulent virus glycoprotein at position 333 was substituted in all avirulent variants tested.
T98 62735-62829 Sentence denotes Such differences have been identified (Section I1,B) at other positions in the virus proteins.
T99 62830-62901 Sentence denotes Broadly similar results have also been obtained in studies of reovirus.
T100 62902-63014 Sentence denotes Monoclonal antibodies which neutralized the virus (Burstin et al., 1982) were used in the selection of variants.
T101 63015-63108 Sentence denotes These variants were found to exhibit reduced neurovirulence compared with the parent strain .
T102 63109-63252 Sentence denotes The altered epitope was also demonstrated to be the major site of recognition for virus specific cytotoxic lymphocytes (Finberg et al., 1982) .
T103 63253-63455 Sentence denotes The use of monoclonal antibodies in the study of antigenic drift in influenza virus has already been discussed in the context of the structural information derived from such experiments (Section II1,A).
T104 63456-63667 Sentence denotes Although antigenic drift has been studied mainly in the HA molecule (Natali et al., 1981; Underwood, 1982; it may also occur in the neuraminidase but its extent may be restricted in some species of avian virus .
T105 63668-63773 Sentence denotes Knowledge of the basis for such drift is now approaching that for the HA molecule (Colman et aZ., 1983) .
T106 63774-63912 Sentence denotes The subject is mentioned again here since it has a direct bearing on the pathogenesis and survival of influenza viruses in the population.
T107 63913-63987 Sentence denotes The role of the HA in this drift has recently been reviewed (Ward, 1981) .
T108 63988-64138 Sentence denotes Monoclonal antibodies can be applied in order to mimic the immune response and to gain insight into the effect of immunological pressure on the virus.
T109 64139-64428 Sentence denotes Experiments using monoclonal antibodies to block cytotoxic lymphocyte action have demonstrated that the epitopes recognized by these cells may be identical to (Finberg et al., 1982) or distinct from (Lefrancois and Lyles, 1983b) those regions to which neutralizing antibodies are directed.
T110 64429-64538 Sentence denotes The host immune response has been implicated in the maintenance of measles virus persistence leading to SSPE.
T111 64539-64647 Sentence denotes As described in Section JII,B, the disease is associated with a defect in the production of virus M protein.
T112 64648-64869 Sentence denotes Some evidence has been gathered that suggests the hosts' immune response itself may actually modulate the synthesis of virus polypeptides and consequently help to bring this situation about (Fujinami and Oldstone, 1979 ).
T113 64870-65094 Sentence denotes This has been modelled in uiuo where inoculation of a hyperimmune anti-measles virus antiserum was found to alter the characteristics of disease in intracerebrally inoculated BALB/c mice, a delayed disease was then produced.
T114 65095-65317 Sentence denotes Inoculation of monoclonal antibody specific for the virus hemagglutinin protein was also able to induce this effect although monoclonal antibody directed against the nucleocapsid protein could not (Rammohan et al., 1981) .
T115 65318-65409 Sentence denotes A similar process has been demonstrated with a measles virus persistent infection in uitto.
T116 65410-65579 Sentence denotes Antiserum treatment of C6 cells persistently infected with measles virus led to a drastic reduction in the expression of virus polypeptides (Barrett and Koschel, 1983) .
T117 65580-65656 Sentence denotes Once again monoclonal antibody to H, but not N could produce this effect (P.
T118 65657-65659 Sentence denotes N.
T119 65660-65694 Sentence denotes Barrett, personal communication) .
T120 65695-65806 Sentence denotes Antibody to surface glycoprotein can also prolong experimental Sindbis virus infection (Chanas et al., 1982a) .
T121 65807-65921 Sentence denotes Antibodies with neutralizing activity were active in this respect while those which lacked this property were not.
T122 65922-65989 Sentence denotes This is also reflected in the measles virus system described above.
T123 65990-66135 Sentence denotes Monoclonal antibodies which neutralized the virus seemed to be exclusively active in producing the alteration in virus polypeptide expression (P.
T124 66136-66138 Sentence denotes N.
T125 66139-66173 Sentence denotes Barrett, personal communication) .
T126 66174-66279 Sentence denotes However, it is also true that under some circumstances monoclonal antibodies can enhance virus infection.
T127 66280-66491 Sentence denotes Flaviviruses, in combination with antibody, are able to infect cells bearing Fc receptors through a cross bridging mediated by the antibody (Chanas et al., 1982b; Peiris et al., 1982; Schlesinger et al., 1983) .
T128 66492-66619 Sentence denotes However, use of monoclonal antibodies has demonstrated that the virus epitope to which the antibody is bound is also important.
T129 66620-66816 Sentence denotes Brandt et al. (1982) found only flavivirus type common determinants were effective, and second, that some cells were unable to support YFV replication even when antibody enhancement was attempted.
T130 66817-66938 Sentence denotes Consequently the presence of the Fc receptor on the target cell surface is not alone sufficient for productive infection.
T131 66939-67018 Sentence denotes Use of monoclonal antibodies for therapeutic purposes is as yet in its infancy.
T132 67019-67086 Sentence denotes It is likely that the antibodies would be used in three main areas.
T133 67087-67175 Sentence denotes First, in emergency, injection of a neutralizing antibody can aid recovery from disease.
T134 67176-67345 Sentence denotes Human monoclonal antibodies are now becoming available (Crawford et al., 1983; Sikora and Neville, 1982) and are likely to produce fewer problems with allergic reaction.
T135 67346-67452 Sentence denotes Animal experiments in the mouse have indicated that monoclonal antibodies will be beneficial in this area.
T136 67453-67775 Sentence denotes Neutralizing antibodies are able to localize HSV infection and prevent spread to the nervous system (Kapoor et al., 1982) , promote recovery from ocular infection (Rector et al., 1982) or protect against a later footpad challenge (Dix et al., 1981) , and antibodies to any herpesvirus glycoprotein had protective activity.
T137 67776-67972 Sentence denotes Intravenous inoculation of monoclonal antibody specific for the virus hemagglutinin was found to protect mice from the invariably lethal consequences of intracerebral injection with influenza WSN.
T138 67973-68082 Sentence denotes This action was however dependent upon the breakdown of the blood-brain barrier (Doherty and Gerhard, 1981) .
T139 68083-68211 Sentence denotes The ability of antibody to function in this way is not simply correlated with its anti-virus action measured by in uitro assays.
T140 68212-68488 Sentence denotes Nonneutralizing antibodies protect mice from HSV (Balachandran et al., 1982c; Rector et al., 1982) or Sindbis virus (Schmaljohn et al., 1982) , and Mathews and Roehrig (1982) found nonneutralizing antibodies could also protect mice from Japanese equine encephalitis infection.
T141 68489-68689 Sentence denotes Antibodies of high avidity protected with greater efficiency than those of lower avidity, but antibodies directed against epitopes instrumental in neutralizing the virus were effective at lower doses.
T142 68690-68821 Sentence denotes This work therefore implicates the tightness of attachment as well as site of combination with antigen in efficiency of protection.
T143 68822-69032 Sentence denotes Some evidence suggests that complement is not involved in protection by monoclonal antibodies and suggests the process is mediated by an antibody-dependent cell-mediated cytolysis (Balachandran et al., 1982~) .
T144 69033-69138 Sentence denotes Second, monoclonal antibodies will be applied to the selection of avirulent viruses for vaccine purposes.
T145 69139-69210 Sentence denotes Rabies virus has already been described in this context (Section IV,A).
T146 69211-69318 Sentence denotes Heterogeneity among Coxsackie (Prabhakar et al., 1982) or bluetongue viruses ) may permit such an approach.
T147 69319-69424 Sentence denotes The antibodies could also be used in the preparation of pure subunit vaccines (Osterhaus et al., 1981b) .
T148 69425-69547 Sentence denotes Finally, when combined with a cytotoxic agent, monoclonal antibodies provide a specific cell killing tool (Davies, 1981) .
T149 69548-69693 Sentence denotes Specific cytotoxicity has already been demonstrated using this technique (Blythman et al., 1981; Krolick et al., 1980; Youle and Neville, 1980) .
T150 69694-69927 Sentence denotes Monoclonal antibodies allow us to view the fate of a protein in the infected cell, from synthesis to virus assembly, as a continuous process and hint at the interaction between virus-specific gene products and the cellular machinery.
T151 69928-70121 Sentence denotes The use of monoclonal antibodies provides valuable insight into the working of the protein both as an enzyme and as a target for the host immune response, evolving in reaction to that response.
T152 70122-70273 Sentence denotes As three-dimensional structures of more molecules are determined, so this work should extend our understanding of virus protein structure and function.
T153 70274-70423 Sentence denotes In the foregoing discussion it has been emphasized how the specificity of a monoclonal antibody can be applied to the study of all areas of virology.
T154 70424-70579 Sentence denotes In each case it is the specificity of the antibody which has proved useful, and even permitted the identification of related but hitherto unknown proteins.
T155 70580-70706 Sentence denotes However, this very specificity also provides the basis for spurious cross reactivity not normally present in polyclonal serum.
T156 70707-70862 Sentence denotes In general, an appropriately absorbed monospecific antiserum will recognize many epitopes and thus coat a considerable area of a protein's exposed surface.
T157 70863-71020 Sentence denotes A single epitope repeated on another protein would cross react, but this would be masked by the vast majority of antibodies reacting with the target antigen.
T158 71021-71073 Sentence denotes In the case of a monoclonal antibody this is not so.
T159 71074-71278 Sentence denotes A target molecule may have only one site for the antibody and if this is shared with another protein a considerable cross reaction could be detected, even in the abscence of extensive structural homology.
T160 71279-71501 Sentence denotes It has been calculated (Crawford et al., 1982 ) that a primary sequence of four amino acids (a not unusual size for an antibody binding site) might occur some 15 times in the average cell's complement of protein sequences.
T161 71502-71902 Sentence denotes However, monoclonal antibody cross reactions would be expected much less frequently than this because (1) the amino acid sequence must be expressed on the surface of the molecule, (2) antibodies may recognize a sequence in a given conformation or state of modification, (3) protein sequence does not normally occur at random, and (4) antibody binding sites are often larger than this (Atassi, 1975) .
T162 71903-72084 Sentence denotes Furthermore, it would be very difficult for an animal to produce an antibody response to an epitope which was likely to cross react, merely on a random basis, with a "self" epitope.
T163 72085-72200 Sentence denotes However, this could perhaps be tolerated as a small constituent of a total non-self-cross-reacting immune response.
T164 72201-72285 Sentence denotes Consequently, it is likely that fortuitous cross reaction may be comparatively rare.
T165 72286-72416 Sentence denotes Nevertheless, many cross reactions have been reported which are at present not understood (reviewed by Lane and Koprowski, 1982) .
T166 72417-72602 Sentence denotes Several of these (Crawfordet al., 1982; Lane and Hoeffler, 1980) involve cross rections between SV40 T antigen and host proteins or between SV40 T and t antigens (Harlow et al., 1981) .
T167 72603-72829 Sentence denotes In the former case there is good reason to believe that some of these antibodies recognize epitopes on functionally related host proteins, and which therefore may be constrained to some degree of overall structural similarity.
T168 72830-72977 Sentence denotes Whether this represents an evolutionarily conserved structure, or one which has arisen by independent convergent evolutionary processes is unknown.
T169 72978-73158 Sentence denotes However, cross reaction at the monoclonal antibody level cannot be assumed indicative of any extensive structural or functional similarity without considerable supporting evidence.
T170 73159-73370 Sentence denotes The application of monoclonal antibodies in conventional serological reactions, permitting the differentiation of closely related, serologically cross-reacting proteins has already been discussed in this review.
T171 73371-73603 Sentence denotes In addition, the process described above provides an entirely new dimension to these procedures and might thus permit the identification of functionally related proteins which bear no evidence of cross reaction with polyclonal sera.
T172 73604-73813 Sentence denotes Consequently application of monoclonal antibodies has not only improved information obtained from well established assay procedures, but may also lead to processes yielding an entirely new type of information.