LitCovid-sentences  

PMC:7029759 / 2181-39234 JSONTXT 15 Projects

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Id Subject Object Predicate Lexical cue
T16 0-12 Sentence denotes Introduction
T17 13-126 Sentence denotes A mysterious illness causing pneumonia in December 2019 in Wuhan, China is now growing into a potential pandemic.
T18 127-340 Sentence denotes These pneumonia cases were eventually characterized to be caused by a novel coronavirus (2019-nCoV) 1, of which Severe Acute Respiratory Syndrome (SARS) 2 and Middle East Respiratory Syndrome (MERS) 3 are members.
T19 341-436 Sentence denotes SARS and MERS famously caused their own outbreak concerns when they were originally identified.
T20 437-546 Sentence denotes SARS caused significant economic damage to Hong Kong and Southern China, before spreading to other countries.
T21 547-665 Sentence denotes Ultimately, SARS infected up to 8,098 people and caused 774 deaths according to the World Health Organization (WHO) 4.
T22 666-771 Sentence denotes The novel coronavirus, 2019-nCoV, is now quickly spreading across the world after originating in Wuhan 1.
T23 772-974 Sentence denotes Human-to-human transmission of 2019-nCoV has been confirmed in familial case cluster reports 5, as additional cases continue to be identified in different cities in China and countries around the world.
T24 975-1116 Sentence denotes Clinical symptoms of 2019-nCoV infection include fever, cough, and myalgia or fatigue with pneumonia demonstrated on chest CT scan imaging 6.
T25 1117-1425 Sentence denotes Within China, the city of Wuhan along with several others has been shut down, with individuals not allowed to leave the city in an effort to contain the virus; such efforts are largely unprecedented in a city of this size ( https://www.nytimes.com/2020/01/22/world/asia/coronavirus-quarantines-history.html).
T26 1426-1574 Sentence denotes For now, many travelers are being screened for fever (≥38°C) and reported recent history of travel to Wuhan in order to triage diagnostic testing 7.
T27 1575-1692 Sentence denotes These efforts resemble not only what happened with SARS in 2002–2003, but also the Ebola virus outbreak in 2014–2015.
T28 1693-1832 Sentence denotes During those outbreaks, special protocols were put in place to quarantine any infected individuals and identify patient contacts at risk 8.
T29 1833-1989 Sentence denotes Healthcare workers were also at risk, and despite extensive personal protective equipment measures, clinical providers did get infected in both outbreaks 9.
T30 1990-2196 Sentence denotes There were no specific, antiviral treatments for SARS or Ebola at the time of the outbreaks beyond supportive measures 10, 11, which is a similar situation that healthcare systems are facing with 2019-nCoV.
T31 2197-2331 Sentence denotes The dire situations facing patients in outbreak scenarios demand quick responses by the healthcare community and the biotech industry.
T32 2332-2541 Sentence denotes Unfortunately, many of the traditional options that guide drug development are inadequate for outbreaks; a process that takes years can’t help patients who are dying today, and economies that are being halted.
T33 2542-2658 Sentence denotes In these situations, studies have often been conducted on compassionate use, and clinical trial approvals expedited.
T34 2659-2778 Sentence denotes This was most recently seen in the 2014–2015 Ebola outbreak, where a variety of clinical trial candidates were studied.
T35 2779-2894 Sentence denotes Many of these therapies failed, but ultimately a vaccine did emerge that was fully protective against the virus 12.
T36 2895-3128 Sentence denotes It is important to note that, unlike the current situation with 2019-nCoV, Ebola had already been studied for years and this particular neutralizing vaccine made and tested in preclinical animal models years prior to the outbreak 13.
T37 3129-3418 Sentence denotes For 2019-nCoV, beyond knowing the sequence of spike (S) protein of the coronavirus (GenBank: MN908947.3), there are no studies on how immunogenic this particular protein will be beyond surrogate comparisons to SARS and MERS, which limits the potential ability to quickly produce a vaccine.
T38 3419-3707 Sentence denotes Moreover, while a vaccine would be greatly effective in helping to stop the spread of 2019-nCoV, an effective therapy is also needed for the patients infected with 2019-nCoV today, similar to the situation of Ebola patients needing effective therapies while vaccines were being developed.
T39 3708-3989 Sentence denotes In this article, I will outline different potential treatment options that could be pursued as a therapy for 2019-nCoV virus, keeping the focus on agents that could be rapidly tested in patients today and broadly effective in spite of limited knowledge of the biology of 2019-nCoV.
T40 3990-4122 Sentence denotes Simply stated, there is limited time for basic studies of 2019-nCoV in research labs, while patients need effective therapies today.
T41 4123-4280 Sentence denotes I finally propose the best potential treatment option in my opinion, along with instructions on how to manufacture the therapy for testing in patients today.
T42 4282-4320 Sentence denotes Treatment strategies against 2019-nCoV
T43 4322-4369 Sentence denotes Developing neutralizing antibodies to 2019-nCoV
T44 4370-4597 Sentence denotes Coronavirus entry starts with the S protein binding to a target receptor on the cell surface, where after fusion is mediated at the cell membrane, delivering the viral nucleocapsid inside the cell for subsequent replication 14.
T45 4598-4803 Sentence denotes The S protein is famous for causing syncytial formation between infected cells and other receptor-bearing cells around them, emphasizing that the S protein does not function in just the virion state alone.
T46 4804-5014 Sentence denotes A neutralizing antibody targeting the S protein on the surface of 2019-nCoV is likely the first therapy contemplated by biomedical researchers in academia and industry, providing passive immunity to disease 15.
T47 5015-5199 Sentence denotes The recently published genome sequence of 2019-nCoV (GenBank: MN908947.3) allows researchers to perform gene synthesis in the lab and consider expressing the S protein as an immunogen.
T48 5200-5492 Sentence denotes Traditional methods of screening mice or rabbits for neutralizing antibodies may be too slow for this outbreak, but faster methods such as using phage or yeast display libraries that express antibody fragments could be used quickly to identify lead candidates for viral neutralization 16, 17.
T49 5493-5673 Sentence denotes The challenge is that any antibody candidate would need to be rigorously tested in cell culture and animal models to confirm that it can neutralize 2019-nCoV and prevent infection.
T50 5674-5861 Sentence denotes Furthermore, several isolates would need to be tested that are circulating in the population to try to assess if sufficient breadth of coverage is obtained with the neutralizing antibody.
T51 5862-6191 Sentence denotes Information from other coronaviruses species like SARS would be helpful as to where to target the best epitope in order to produce neutralizing antibodies (the receptor-binding domain in the S protein is a key target) 18, but again this is a slow and challenging process, which may not yield significant gains for several months.
T52 6192-6366 Sentence denotes Moreover, ultimately a cocktail of antibodies may be required to ensure full protection for patients, which would add additional complexity for formulation and manufacturing.
T53 6367-6600 Sentence denotes Like some of the therapeutic options discussed below, the ability to express any lead candidates in lower organisms for protein expression (bacteria, yeast, insect cells) would facilitate faster production of therapy for patients 19.
T54 6601-6836 Sentence denotes An alternative strategy of generating neutralizing antibodies against 2019-nCoV S protein would be to immunize large animals (sheep, goat, cow) with the 2019-nCoV S protein, and then purifying polyclonal antibodies from the animals 20.
T55 6837-7121 Sentence denotes This strategy may serve an expedited service in the setting of an outbreak and has many advantages such as simplifying production and manufacturing, but has limited guarantees that each animal would produce neutralizing antisera, or what the antibody titer would be in each animal 21.
T56 7122-7284 Sentence denotes Moreover, there is also the human immune response against foreign immunoglobulins to other species, which would potentially complicate any treatment scenarios 22.
T57 7285-7453 Sentence denotes In a truly desperate scenario, this strategy may be viable for a short-term, but would not easily scale in the 2019-nCoV outbreak, which is already rapidly multiplying.
T58 7455-7506 Sentence denotes Using oligonucleotides against 2019-nCoV RNA genome
T59 7507-7619 Sentence denotes Beyond targeting the surface proteins of 2019-nCoV, one could also target the RNA genome itself for degradation.
T60 7620-7883 Sentence denotes This RNA genome sequence of 2019-nCoV was recently published (GenBank: MN908947.3), and one strategy that could be considered then, is the use of small interfering RNA (siRNA) or antisense oligonucleotides (ASO) to combat the virus by targeting its RNA genome 23.
T61 7884-7931 Sentence denotes The challenge with this strategy is multi-fold.
T62 7932-8000 Sentence denotes First, the conserved RNA sequence domains of CoV-2019 are not known.
T63 8001-8138 Sentence denotes Identifying conserved sequences is essential in order to optimize siRNA targeting and avoid viral escape of the oligonucleotide strategy.
T64 8139-8277 Sentence denotes One could look at genome homology of 2019-nCoV to the SARS virus for comparison of conserved sequences, but this would still be guesswork.
T65 8278-8359 Sentence denotes A second challenge is how the oligonucleotides would be delivered into the lungs.
T66 8360-8484 Sentence denotes Advances have been made into delivery vehicles such as lipid nanoparticles that can mediate some delivery into the lungs 24.
T67 8485-8650 Sentence denotes It is unknown, however, if enough siRNA’s or ASO’s would be effectively delivered within the lungs to stop the infection or make a difference in its clinical course.
T68 8651-8867 Sentence denotes For example, if 25% of alveolar epithelial cells in the lung had siRNA or ASO in them, that efficiency might be a great success for traditional gene therapy, but would hardly make any difference in a viral infection.
T69 8868-9023 Sentence denotes Such an explanation is also likely why siRNA candidates against Ebola failed in trials 25, despite significant success in preclinical animal models 26, 27.
T70 9024-9188 Sentence denotes Lastly, even if one assumed that siRNA was effective clinically, there is a limited ability to scale up manufacturing of siRNA drugs to a large infected population.
T71 9189-9342 Sentence denotes Current siRNA and ASO therapies are manufactured for rare diseases, and there are no available resources existing to manufacture the medications quickly.
T72 9344-9397 Sentence denotes Repurposing currently available antiviral medications
T73 9398-9565 Sentence denotes Ideal agents to fight 2019-nCoV would be approved small molecule drugs that could inhibit different aspects of the viral life cycle, ultimately inhibiting replication.
T74 9566-9766 Sentence denotes Two classes of potential targets are viral polymerases 28 and protease inhibitors 29, both of which are components of human immunodeficiency virus (HIV) and hepatitis C virus (HCV) antiviral regimens.
T75 9767-9878 Sentence denotes Pilot clinical studies are already ensuing by desperate clinicians with various repurposed antiviral medicines.
T76 9879-9982 Sentence denotes This has been done in every viral outbreak previously with limited success, outside of case reports 30.
T77 9983-10140 Sentence denotes Indeed, during the Ebola outbreak, none of the repurposed small molecule drugs were definitively shown to improve the clinical course across all patients 31.
T78 10141-10378 Sentence denotes The 2019-nCoV could be different, and there are initial positive reports that lopinavir and ritonavir, which are HIV protease inhibitors, have some clinical efficacy against 2019-nCoV, similar to prior studies using them against SARS 32.
T79 10379-10623 Sentence denotes Research should continue to be undertaken to screen other clinically available antivirals in cell culture models of 2019-nCoV, in hopes that a drug candidate would emerge useful against the virus that could be rapidly implemented in the clinic.
T80 10624-10765 Sentence denotes One promising example could be remdesivir, which interferes with the viral polymerase and has shown efficacy against MERS in mouse models 33.
T81 10766-10874 Sentence denotes For further information, reviews of previous drug repurposing efforts for coronaviruses are provided 34, 35.
T82 10875-11049 Sentence denotes Though these repurposed medications may hold promise, it is still reasonable to pursue novel, 2019-nCoV specific therapies to complement potential repurposed drug candidates.
T83 11051-11107 Sentence denotes Passive antibody transfer from convalescent patient sera
T84 11108-11318 Sentence denotes A simple but potentially very effective tool that can be used in infectious outbreaks is to use the serum of patients who have recovered from the virus to treat patients who contract the virus in the future 36.
T85 11319-11450 Sentence denotes Patients with resolved viral infection will develop a polyclonal antibody immune response to different viral antigens of 2019-nCoV.
T86 11451-11648 Sentence denotes Some of these polyclonal antibodies will likely neutralize the virus and prevent new rounds of infection, and the patients with resolved infection should produce 2019-nCoV antibodies in high titer.
T87 11649-11782 Sentence denotes Patients with resolved cases of 2019-nCoV can simply donate plasma, and then this plasma can be transfused into infected patients 37.
T88 11783-11986 Sentence denotes Given that plasma donation is well established, and the transfusion of plasma is also routine medical care, this proposal does not need any new science or medical approvals in order to be put into place.
T89 11987-12189 Sentence denotes Indeed, the same rationale was used in the treatment of several Ebola patients with convalescent serum during the outbreak in 2014–2015, including two American healthcare workers who became infected 38.
T90 12190-12428 Sentence denotes As the outbreak continues, more patients who survived infection will become available to serve as donors to make antisera for 2019-nCoV, and a sizeable stock of antisera could be developed to serve as a treatment for the sickest patients.
T91 12429-12643 Sentence denotes Unfortunately, the exponential growth of the outbreak would work against this strategy, since the growing number of cases would likely outstrip the ability of previous patients to provide donor plasma as treatment.
T92 12644-12775 Sentence denotes Moreover, convalescent patient sera would have significant variability in the potency of antiviral effect, making it less ideal 37.
T93 12776-12984 Sentence denotes While transfusion medicine services should certainly pursue convalescent patient sera as an option right now for patient treatment, it is ultimately limited in its effective scope of controlling the outbreak.
T94 12986-13022 Sentence denotes Proposal for new 2019-nCoV therapies
T95 13023-13223 Sentence denotes The simplest and most direct approach to combating 2019-nCoV during the outbreak would be one to neutralize the virus from entering cells, the function that antibodies normally perform in the body 39.
T96 13224-13463 Sentence denotes For the reasons mentioned above when discussing neutralizing antibodies, it will be difficult to validate a broadly neutralizing antibody quickly, and a challenge to make sure that the mutating RNA virus will not escape its neutralization.
T97 13464-13615 Sentence denotes A cocktail antibody approach could be undertaken as was explored to treat the Ebola pandemic 40, but would add complexity to the manufacturing process.
T98 13616-13742 Sentence denotes However, there is another strategy to pursue in this scenario that does not rely on targeting the viral glycoprotein directly.
T99 13743-13926 Sentence denotes In this strategy, a neutralizing effect could be obtained by targeting the viral receptor protein on the cell surface, thereby blocking the virus from binding to it and gaining entry.
T100 13927-14025 Sentence denotes Fortunately, scientists have already uncovered the identity of the viral receptor in cell culture.
T101 14026-14234 Sentence denotes A recent pre-print publication found that the 2019-nCoV uses the angiotensin-converting enzyme 2 (ACE2) as a receptor for cell entry 41, which is the same receptor that the SARS coronavirus uses for entry 42.
T102 14235-14390 Sentence denotes For both viruses, the coronavirus binds to ACE2 through its S protein on the virion, where after fusion of the viral membrane and cell membrane will occur.
T103 14391-14538 Sentence denotes Subsequently, the RNA virus will replicate its genome inside the cell, and ultimately make new virions that will be secreted to infect other cells.
T104 14539-14705 Sentence denotes The coincidence of SARS and 2019-nCoV using ACE2 receptor opens up the possibility of using the extensive research studied on SARS entry and applying it to 2019-nCoV.
T105 14706-14867 Sentence denotes Based on the SARS literature, several potential blocking strategies could be considered, which were shown to be effective in preventing infection in SARS models.
T106 14869-14911 Sentence denotes Blocking agents that bind to ACE2 receptor
T107 14912-15007 Sentence denotes The first strategy would consist of administering to patients an agent that would bind to ACE2.
T108 15008-15149 Sentence denotes The key advantage here is that the host ACE2 protein will not change, so there is no concern about escape from binding the therapeutic agent.
T109 15150-15358 Sentence denotes Moreover, the virus will not have the ability to mutate and bind an entirely new host receptor in the time frame of this outbreak; such functional relationships are established by evolution over long periods.
T110 15359-15561 Sentence denotes By analogy, the influenza virus changes the mutations on its surface to escape antibody neutralization every year, but it always focuses on using sialic acid on the cell surface as an entry receptor 43.
T111 15562-15617 Sentence denotes There are two known options for agents to bind to ACE2.
T112 15618-15787 Sentence denotes The first is using the small receptor-binding domain (RBD) from the SARS S protein that has been shown to be the key domain that binds the ACE2 receptor during entry 44.
T113 15788-15917 Sentence denotes Administration of this domain, 193 amino acids in size, has been shown to effectively block the entry of SARS in cell culture 44.
T114 15918-16071 Sentence denotes It is well within reason that SARS RBD could be given to patients, thereby binding their ACE2 proteins on target cells, preventing infection ( Figure 1).
T115 16072-16181 Sentence denotes There is also the potential for the equivalent RBD of 2019-nCoV to be produced and used as a therapy as well.
T116 16182-16551 Sentence denotes This strategy assumes SARS and 2019-nCoV share the same binding site on ACE2, which is highly likely given the similar ACE2 binding sites of SARS and NL63 coronavirus The small size of the therapy, similar in size in nanobody domains from camelid antibodies, would enhance the perfusion of the biologic into tissues to more effectively bind to viral entry receptors 45.
T117 16552-16735 Sentence denotes In regards to the outbreak situation that is ongoing, the small protein facilitates the rapid production of the therapy in bacteria potentially, which would help production yields 19.
T118 16736-16936 Sentence denotes Moreover, bacterial production would allow RBD proteins to be produced in a wide range of production facilities today in China, which already has numerous contract research organization operations 46.
T119 16937-17095 Sentence denotes Alternatively, the RBD protein could be attached to an Fc fragment for extended circulation, which was done for an equivalent 212 amino acid domain from MERS.
T120 17096-17281 Sentence denotes The MERS RBD-Fc fusion demonstrated the ability to block viral infection toward cell receptors, as well as to stimulate an immune response against that specific viral domain in mice 47.
T121 17282-17457 Sentence denotes Of note, since the RBD-Fc fusion would bind to normal cells, one would want to eliminate cytotoxic Fc domain functions through mutations that eliminate Fc receptor binding 48.
T122 17458-17467 Sentence denotes Figure 1.
T123 17469-17547 Sentence denotes Therapeutic agents that could be used to block 2019-nCoV from infecting cells.
T124 17548-17637 Sentence denotes Target cells expressing ACE2 include lung and gastrointestinal tissues in the human body.
T125 17638-17751 Sentence denotes The large spike protein on the surface of the coronavirus binds to ACE2 on infected cells, leading to cell entry.
T126 17752-17832 Sentence denotes Three proposed strategies would block this interaction would abrogate infection.
T127 17833-18000 Sentence denotes In the first, the receptor-binding domain (RBD) of the spike protein from SARS or 2019-nCoV would be administered, thereby binding ACE2 and saturating available sites.
T128 18001-18127 Sentence denotes Alternatively, an antibody or single chain antibody fragment (scFv) could be administered against ACE2 to accomplish the same.
T129 18128-18263 Sentence denotes A third strategy would target the coronavirus virions directly by using the ACE2 extracellular domain as bait to bind to spike protein.
T130 18264-18356 Sentence denotes An Fc domain fused to ACE2 would facilitate prolonged circulation of the biologic (ACE2-Fc).
T131 18357-18503 Sentence denotes A second, similar strategy would be to administer an antibody that would bind to ACE2 protein, thereby preventing 2019-nCoV infection ( Figure 1).
T132 18504-18594 Sentence denotes This strategy was shown to effectively block SARS entry and replication in experiments 42.
T133 18595-18771 Sentence denotes While no ACE2 antibody sequences are published in literature indexes, monoclonal antibodies do exist and the associated hybridoma sequences could be cloned in a matter of days.
T134 18772-18923 Sentence denotes There would be no concern for any viral escape from an ACE2 binding antibody, which is an advantage over neutralizing approaches against the S protein.
T135 18924-19029 Sentence denotes There are a couple of design considerations when thinking about how to employ the ACE2 antibody strategy.
T136 19030-19181 Sentence denotes Any effector functions would need to be removed from the Fc domain 49, such that inflammation would not be caused in different tissues expressing ACE2.
T137 19182-19276 Sentence denotes This would retain the long-half life endowed by the Fc domain without any of the side effects.
T138 19277-19519 Sentence denotes The downside of including the Fc domain is the need to use a more expensive mammalian cell production system to preserve proper glycosylation, which would decrease the turnaround time for getting the drug to patients in the outbreak scenario.
T139 19520-19620 Sentence denotes Alternatively, one could just administer a single chain variable fragment (scFv) that binds to ACE2.
T140 19621-19695 Sentence denotes A nanobody or VHH domains from camelids are another option as well 50, 51.
T141 19696-19808 Sentence denotes These could be produced in bacteria, and its small size would allow for rapid permeation into different tissues.
T142 19809-19888 Sentence denotes The downside is the shorter half-life of these molecules without the Fc domain.
T143 19889-19940 Sentence denotes There are several limitations to these two options.
T144 19941-20225 Sentence denotes Regarding the SARS RBD strategy, the body would likely develop an immune response to the SARS protein eventually, although the key intervention period of infection to combat 2019-nCoV would fall under this window of time, where after an immune response for both viruses would develop.
T145 20226-20429 Sentence denotes Alternatively, if one were to use the homologous RBD from 2019-nCoV itself, this immune response would likely be very advantageous since it could yield both a blocking effect and a vaccination effect 52.
T146 20430-20659 Sentence denotes For both strategies, the dose that would be needed to block ACE2 receptors in the body across different organs is unknown, and as is the percentage of ACE2 receptors that would need to be saturated in order to slow the infection.
T147 20660-20869 Sentence denotes The number of ACE2 receptors in the body, which are found in lung and gastrointestinal organs along with vascular endothelial cells among other tissues 53, could ultimately prove prohibitive for this strategy.
T148 20870-21019 Sentence denotes Moreover, the turnover of the ACE2 receptor on the cell surface would also influence how often the therapeutic protein would need to be administered.
T149 21020-21197 Sentence denotes To solve this issue, one could increase the concentration of anti-ACE2 therapy at the crucial site of infection in the lungs, via local administration to lungs via nebulization.
T150 21198-21323 Sentence denotes Lastly, there is the possibility that binding ACE2 directly could paradoxically worsen lung physiology and clinical symptoms.
T151 21324-21538 Sentence denotes A study found that a fusion protein of SARS RBD to Fc domain bound ACE2 in murine lung tissue after administration, exacerbating alveolar edema via ACE2 interaction, which normally counteracts acute lung injury 54.
T152 21539-21706 Sentence denotes This suggests that if one were use an ACE2 binding strategy, it would be best employed early during infection or as a prophylaxis to block the initial viral infection.
T153 21707-21796 Sentence denotes Ultimately, clinical trials in patients would need to investigate these potential issues.
T154 21798-21825 Sentence denotes ACE2 immunoadhesin strategy
T155 21826-22000 Sentence denotes A potentially more promising strategy would be to create an antibody-like molecule that would bind to the coronavirus itself, rather than shielding cells from being infected.
T156 22001-22170 Sentence denotes For this strategy, it is proposed to use a soluble version of the ACE2 receptor that would bind to the S protein of 2019-nCoV thereby neutralizing the virus ( Figure 1).
T157 22171-22257 Sentence denotes Again, the research on the SARS virus suggests this strategy is potentially promising.
T158 22258-22356 Sentence denotes Soluble ACE2 receptor was demonstrated to block the SARS virus from infecting cells in culture 42.
T159 22357-22556 Sentence denotes The reported affinity of soluble ACE2 for the SARS S protein was 1.70 nM, which is comparable to the affinities of monoclonal antibodies 55; it is likely that 2019-nCoV has similar affinity for ACE2.
T160 22557-22873 Sentence denotes In order to use ACE2 as a therapy to treat patients, it would be advisable to convert soluble ACE2 into an immunoadhesin format fused to an immunoglobulin Fc domain (ACE2-Fc), thereby extending the lifespan of the circulating molecule, while also recruiting effector functions of the immune system against the virus.
T161 22874-23123 Sentence denotes While not tested in an animal model, a previous study demonstrated that an ACE2 extracellular domain fused to the human IgG1 domain (ACE2-NN-Ig) was effective in neutralizing SARS coronavirus in vitro, with a 50% inhibitory concentration of 2 nM 56.
T162 23124-23242 Sentence denotes This study provides evidence then that ACE2-Fc could similarly inhibit 2019-nCoV in vitro and potentially in patients.
T163 23243-23409 Sentence denotes An additional advantage of using ACE2 as a 2019-nCoV S protein neutralizing agent is that ACE2 administration could also directly treat the pneumonia pathophysiology.
T164 23410-23579 Sentence denotes A portion of patients with SARS and 2019-nCoV infection develop pneumonia, which is characterized by pulmonary edema and acute respiratory distress syndrome (ARDS) 1, 2.
T165 23580-23751 Sentence denotes The viruses may, in part, cause ARDS through viral-induced ACE2 protein shedding and ACE2 protein decreased expression, both of which are mediated by S protein binding 54.
T166 23752-23954 Sentence denotes Administration of recombinant ACE2 protein has been shown to improve acute lung injury through decreasing angiotensin II levels and the hormones subsequent binding to angiotensin II type 1a receptor 57.
T167 23955-24066 Sentence denotes Recombinant ACE2 can also reduce ARDS in respiratory syncytial virus 58 and H5N1 influenza 59 infection models.
T168 24067-24226 Sentence denotes Based on these promising preclinical studies, recombinant human ACE2 (rhACE2) was moved into clinical trials in order to treat ARDS in critically ill patients.
T169 24227-24335 Sentence denotes A phase I trial demonstrated rhACE2 was well tolerated with no effects seen on the cardiovascular system 60.
T170 24336-24489 Sentence denotes A phase II trial demonstrated on-target efficacy in reducing Ang1-8 peptide levels, but did not show significant modulation of respiratory parameters 61.
T171 24490-24706 Sentence denotes It remains to be seen whether rhACE2 administration has the same clinical benefits in treating ARDS that have been seen in animal models, and whether ACE2-Fc administration could alleviate ARDS in 2019-nCoV patients.
T172 24707-24870 Sentence denotes The proposed therapy for 2019-nCoV patients would consist of the extracellular domain of the ACE2 protein fused to a human immunoglobulin G Fc domain ( Figure 2A).
T173 24871-25057 Sentence denotes Studies have shown that the ACE2 amino acids 18 – 615 appear to be sufficient for SARS S protein binding 62, which also covers the peptidase domain necessary for ACE2 enzymatic function.
T174 25058-25254 Sentence denotes It is possible a smaller portion of the extracellular ACE2 domain would be adequate for S protein binding, although a smaller version would lack enzyme activity beneficial in treating lung injury.
T175 25255-25401 Sentence denotes Further studies are needed to define the minimal ACE2 domain necessary for 2019-nCoV S protein binding to construct even smaller ACE2-Fc proteins.
T176 25402-25647 Sentence denotes While we do not know the structure of the 2019-nCoV S protein or how it binds to the ACE2 receptor yet, it is reasonable for now to assume that the same ACE2 protein domains utilized by the SARS virus are also bound by 2019-nCoV to infect cells.
T177 25648-25657 Sentence denotes Figure 2.
T178 25659-25750 Sentence denotes TherapeuticDesign of the ACE2-Fc fusion protein as a therapy against 2019-nCoV coronavirus.
T179 25751-25869 Sentence denotes ( A) The extracellular domain of ACE2 is appended onto the human immunoglobulin Fc domain, including the hinge region.
T180 25870-26001 Sentence denotes The Fc domain facilitates dimerization of two ACE2 domains. ( B) The amino acid sequence of the ACE2-Fc fusion protein is provided.
T181 26002-26102 Sentence denotes The ACE2 domain consists of amino acids 18–615 of the human ACE2 protein (blue; UniProtKB - Q9BYF1).
T182 26103-26212 Sentence denotes The sequence of the human immunoglobulin G isotype 1 constant region is provided (green; UniProtKB - P01857).
T183 26213-26312 Sentence denotes A secretion signal from a human immunoglobin heavy chain is provided (red; UniProtKB - A0A0C4DH39).
T184 26313-26510 Sentence denotes The advantage of the Fc domain is endowing a longer-half life of the drug, which could enable healthcare workers to potentially be given drug doses prophylactically before seeing infected patients.
T185 26511-26716 Sentence denotes Indeed, the half-life of recombinant ACE2 was extended from less than two hours to over one week in mice when formatted as a recombinant ACE2-Fc therapy in a study evaluating treatment for hypertension 63.
T186 26717-27004 Sentence denotes One difference from the prior blocking agent strategies is that the effector functions of the Fc domain could be retained in this molecule, allowing recruitment of dendritic cells, macrophages, and natural killer cells through the CD16 receptor against viral particles or infected cells.
T187 27005-27311 Sentence denotes This may facilitate faster activation of the host antiviral immune response and elimination of the virus, which was illustrated in a SARS mouse model where Fc engaging antibodies were more potent in eliminating SARS via activation of phagocytic cells compared to antibodies that neutralized virus alone 64.
T188 27312-27646 Sentence denotes Overall, the ACE2-Fc fusion protein would have many of the same benefits of a traditional neutralizing antibody that would be sought as a treatment for the infection, but represent one with maximal breadth and potency since the 2019-nCoV could not escape its neutralization, given the same protein is also its receptor for cell entry.
T189 27647-27885 Sentence denotes Indeed, it has been shown that the pathogenicity of SARS versus the more mild human coronavirus NL63 was related to a lower affinity of NL63 for human ACE2 versus SARS, with NL63 S protein reducing ACE2 levels less than SARS S protein 65.
T190 27886-28022 Sentence denotes Therefore, if 2019-nCoV were to try to escape ACE2 neutralization via decreasing affinity, it would mutate into a less pathogenic virus.
T191 28023-28194 Sentence denotes This is similar to the re-emergent SARS virus in 2003-2004, which had lower affinity for human ACE2 and resulted in less severe infection and no secondary transmission 66.
T192 28195-28344 Sentence denotes Thus, 2019-nCoV could be presented with an evolutionary trap when faced with potential ACE2-Fc therapy, leading toward a more benign clinical course.
T193 28345-28573 Sentence denotes To give some additional support to the potential of a receptor-immunoadhesin being a potential antiviral strategy, it should be noted that CD4-Fc or CD4-IgG was one of the early agents developed as a potential HIV medication 67.
T194 28574-28704 Sentence denotes The protein contained the first two domains of the CD4 receptor that are known to bind gp120 on the surface of infected HIV cells.
T195 28705-28772 Sentence denotes CD4-IgG was shown to neutralize HIV in vitro, preventing infection.
T196 28773-28897 Sentence denotes The protein was also safe when administered in patients, although only limited-to-mild clinical benefit was achieved 68, 69.
T197 28898-29236 Sentence denotes Updated enhanced versions of CD4-IgG have been developed that additionally have a small peptide derived from the co-receptor, CCR5, enhancing affinity and giving even more potent neutralizing activity, essentially 100% of HIV isolates and making rhesus macaques resistant to multiple simian-human immunodeficiency virus challenges 70, 71.
T198 29237-29450 Sentence denotes While HIV and 2019-nCoV are very different viruses, with different cell types, kinetics, and clinical courses, the previous results with HIV are encouraging that this could be a therapeutic strategy for 2019-nCoV.
T199 29451-29683 Sentence denotes If anything, 2019-nCoV is likely more amenable to this neutralizing therapy given that the respiratory virus will only cause an acute infection, unlike HIV, which causes chronic infection in hosts with different cellular reservoirs.
T200 29684-29907 Sentence denotes One potential limitation of the ACE2-Fc strategy is that the increase in levels of extracellular ACE2 could have unknown effects on the body, particularly when elevated for a prolonged time via Fc domain extended half-life.
T201 29908-30054 Sentence denotes Small levels of extracellular ACE2 are already secreted by tissues, so the circulation of this extracellular domain would not be unprecedented 72.
T202 30055-30275 Sentence denotes Moreover, recombinant ACE2 protein was well-tolerated by healthy patients in a phase I trial, and by patients with lung injury in a phase II trial, suggesting treating 2019-nCoV patients with ACE2-Fc will also tolerated.
T203 30276-30502 Sentence denotes If investigators are still concerned, critical amino acid(s) for ACE2 peptidase activity could be mutated to abolish the native function of this sequence, while retaining high affinity binding for SARS and 2019-nCoV S protein.
T204 30503-30795 Sentence denotes Indeed, this possibility was previously investigated in generating an ACE2 and IgG1 fusion protein, which showed that mutation of histidine residues at position 374 and 378 of the ACE2 extracellular domain abolished peptidase activity, but retained high affinity binding to SARS S protein 56.
T205 30796-31015 Sentence denotes Of course, ACE2 peptidase mutation would eliminate the beneficial effects from the recombinant protein delivery of ACE2 in treating lung injury, so it is recommended that retaining ACE2 enzyme activity be pursued first.
T206 31016-31248 Sentence denotes Another potential concern is that receptor binding via an antibody format could inadvertently direct 2019-nCoV toward infecting Fc receptor (CD16) positive cells, which has been shown in vitro for neutralizing antibodies in MERS 73.
T207 31249-31351 Sentence denotes It’s unclear what clinical significance this would have, and to what extent this would happen in vivo.
T208 31352-31455 Sentence denotes Ultimately, clinical trials will be needed to delineate any specific side effects of ACE2-Fc treatment.
T209 31457-31483 Sentence denotes Action plan and discussion
T210 31484-31649 Sentence denotes The chief objective of global health efforts against 2019-nCoV remains to effectively quarantine patients and screen individuals who may be infected to limit spread.
T211 31650-31695 Sentence denotes That objective should continue going forward.
T212 31696-31878 Sentence denotes What is proposed here is an option to at least give infected patients a medication quickly to help alleviate symptoms and prevent death, while vaccine efforts for 2019-nCoV continue.
T213 31879-32069 Sentence denotes This could be enabled through ACE2-Fc providing a triple mechanism of action: (1) Treatment of ACE2 deficiency and lung injury, (2) virus neutralization, and (3) immune effector recruitment.
T214 32070-32182 Sentence denotes Beyond infected patients, ACE2-Fc could provide passive immunity to healthcare works at risk as another benefit.
T215 32183-32389 Sentence denotes Going forward, it is recommended that physicians, scientists, and biotech industry in China and elsewhere pursue manufacturing an ACE2-Fc biologic agent right now, which can immediately advance into trials.
T216 32390-32544 Sentence denotes A variety of different protein expression platforms (CHO, insect, yeast) could be utilized, depending on the particular contract manufacturer’s expertise.
T217 32545-32755 Sentence denotes Gene therapy could even be considered to make ACE2-Fc from a DNA or mRNA platform, but would have additional risk of uncertain delivery strategies and ultimately may slow down progress toward treating patients.
T218 32756-33050 Sentence denotes The goal would be that ACE2-Fc could treat infection in current patients preventing significant morbidities and death, while also serving as a potential prophylactic to give passive immunity to clinical providers on the frontlines, as well as individuals who may have been exposed to the virus.
T219 33051-33263 Sentence denotes Essentially, ACE2-Fc could be the potent neutralizing antibody that the global health community needs to combat 2019-nCoV, today, while also treating the underlying ARDS pathophysiology causing patient mortality.
T220 33264-33390 Sentence denotes It could be scaled much more quickly than convalescent patient sera, which would be dependent on infected individuals to make.
T221 33391-33547 Sentence denotes ACE2-Fc would be resistant to viral escape as well, unlike potential neutralizing monoclonal antibodies that may be developed in the coming weeks to months.
T222 33548-33785 Sentence denotes While a therapeutic strategy is being outlined here, the long-term goal of 2019-nCoV research would remain developing an effective vaccine to yield neutralizing antibodies, likely based on the S protein and specifically, the RBD protein.
T223 33786-33980 Sentence denotes Such trials should happen as soon as possible, but may prove to be challenging to get the right level of immunogenicity, antigen presentation, adjuvant addition, and potent antibody stimulation.
T224 33981-34075 Sentence denotes The virus could continue mutating, foiling different efforts to stimulate protective immunity.
T225 34076-34205 Sentence denotes By comparison, 2019-nCoV cannot escape the ACE2-Fc treatment strategy, since it leverages its own cognate receptor for infection.
T226 34206-34416 Sentence denotes As mentioned above, should 2019-nCoV attempt to escape this therapy via reduced ACE2 affinity binding, it would likely become less pathogenic, similar to the comparison of SARS versus human coronavirus NL63 65.
T227 34417-34683 Sentence denotes Lastly, scaling the dose of any effective vaccine would also prove to be challenging depending on the vector format (e.g. viral vector versus mRNA versus protein), and even a fully protective vaccine would not help patients who are currently infected with the virus.
T228 34684-34836 Sentence denotes In an effort to help aide researchers and industry in China to combat 2019-nCoV, the protein sequence of the ACE2-Fc construct is provided ( Figure 2B).
T229 34837-35007 Sentence denotes Different human Fc domains (IgG1, IgG2, IgG3, or IgG4) could be contemplated, although IgG1 traditionally has the most potency for triggering anti-microbial responses 49.
T230 35008-35104 Sentence denotes Similarly, an ACE2-Fc biologic without active ACE2 peptidase function could be explored as well.
T231 35105-35307 Sentence denotes Given that gene synthesis of this sequence could happen within a week, the gene could be placed within the protein expression platform of choice shortly thereafter leading to protein production quickly.
T232 35308-35522 Sentence denotes The availability of protein A columns and other techniques in the industry to purify antibodies would facilitate ACE2-Fc to quickly be repurposed on existing antibody manufacturing infrastructure existing in China.
T233 35523-35787 Sentence denotes A final benefit of pursuing ACE2-Fc is that it could effectively be used as a therapeutic drug stockpile for future outbreaks of SARS and 2019-nCoV, and any new coronavirus that emerges from a zoonotic reservoir in the future that uses the ACE2 receptor for entry.
T234 35788-35930 Sentence denotes Moreover, coronaviruses that replicate in animals across China and other countries could be studied in order to assess their entry mechanisms.
T235 35931-36140 Sentence denotes By understanding entry in these other animals, one could effectively predict a receptor that could be utilized in any zoonotic transmission event, and build a new receptor immunoadhesin molecule in the future.
T236 36141-36276 Sentence denotes As an example, a similar immunoadhesin, DPP4-Fc, could be envisioned for MERS based on the viral receptor, DPP4, used by that virus 74.
T237 36277-36394 Sentence denotes Beyond coronaviruses, this strategy could be utilized for other viruses where the risk of outbreak potential is high.
T238 36395-36553 Sentence denotes ACE2-Fc could also find use in treating ARDS for other unrelated viruses and causes of acute lung injury, building on the previous clinical trial work 60, 61.
T239 36554-36826 Sentence denotes In summary, ACE2-Fc has the potential to be the neutralizing antibody that healthcare workers need to treat and prevent 2019-nCoV infection today and could play an important role in the cessation of the outbreak if manufacturing based on an available sequence starts soon.
T240 36827-36975 Sentence denotes An alternative 2019-nCoV RBD-Fc fusion could also be pursued, if one desired the dual function of receptor blocking and vaccination in one molecule.
T241 36977-36994 Sentence denotes Data availability
T242 36996-37011 Sentence denotes Underlying data
T243 37012-37053 Sentence denotes No data are associated with this article.