PMC:7108609 / 18447-20819 JSONTXT

{"project":"2_test","denotations":[{"id":"18818423-9111133-45167057","span":{"begin":447,"end":451},"obj":"9111133"},{"id":"18818423-1711864-45167058","span":{"begin":601,"end":605},"obj":"1711864"},{"id":"18818423-15728127-45167059","span":{"begin":730,"end":734},"obj":"15728127"},{"id":"18818423-11895782-45167060","span":{"begin":917,"end":921},"obj":"11895782"},{"id":"18818423-17243893-45167061","span":{"begin":1969,"end":1973},"obj":"17243893"},{"id":"18818423-17392154-45167062","span":{"begin":1991,"end":1995},"obj":"17392154"},{"id":"18818423-15293861-45167063","span":{"begin":2366,"end":2370},"obj":"15293861"},{"id":"T15837","span":{"begin":447,"end":451},"obj":"9111133"},{"id":"T36835","span":{"begin":601,"end":605},"obj":"1711864"},{"id":"T73925","span":{"begin":730,"end":734},"obj":"15728127"},{"id":"T8851","span":{"begin":917,"end":921},"obj":"11895782"},{"id":"T14162","span":{"begin":1969,"end":1973},"obj":"17243893"},{"id":"T86490","span":{"begin":1991,"end":1995},"obj":"17392154"},{"id":"T27175","span":{"begin":2366,"end":2370},"obj":"15293861"}],"text":"Probably due to mimicry of A or B antigens by flora or infectious bacteria, individuals acquire anti-A or -B blood group antibodies to the antigen that they do not synthesize. These so-called natural anti-histo-blood group antibodies have long been suspected to play a role in anti-viral immunity since viruses may carry ABH structures as terminal carbohydrate motifs of their envelope glycoproteins or possibly as inserted glycolipids (Greenwell 1997). In line with this concept, a monoclonal anti-A was shown to neutralize HIV produced by lymphocytes from blood group A donors only (Arendrup et al. 1991). More recently, anti-A or -B from human serum were shown to sensitize HIV to complement-mediated inactivation (Neil et al. 2005). Likewise, measles virus produced by cells expressing either A or B histo-blood group epitopes was neutralized by natural anti-HBGAs in a complement-dependent manner (Preece et al. 2002). Though these in vitro data suggest that natural anti-HBGAs may provide protection against some viruses, they have not been substantiated by epidemiological observations so far. If natural anti-A or -B serum antibodies provide protection, it is expected that during an outbreak, blood group O individuals should experience a lower risk of infection than non-blood group O individuals. This has not been observed for either HIV or measles virus at present. Yet, it is precisely what was observed in the case of a hospital outbreak of SARS in Hong Kong, where O blood group individuals appeared at a much lower risk of being infected by SARS-CoV than subjects of other blood types (Cheng et al. 2005). Interestingly, SARS-CoV infects cells that express ABH antigens according to the individual's ABO phenotype. Indeed, SARS-CoV infection has been documented in pneumocytes, enterocytes of the small intestine as well as in cells of the kidney distal tubular epithelium, all cell types known to be able to synthesize ABH antigens (Chen and Subbarao 2007; Gu and Korteweg 2007). Since the glycosylation of viral glycoproteins necessitates the glycosylation machinery of the infected cell, viral particles synthesized in cells that may express that histo-blood group antigens are expected to be tagged with these antigenic motifs, and therefore natural antibodies directed against these carbohydrate tags may have a protective role (Seymour et al. 2004)."}