Genetic Diversity and Histo-Blood Group Antigen Interactions of Rhesus Enteric Caliciviruses

Recently, we reported the discovery and characterization of Tulane virus (TV), a novel rhesus calicivirus (CV) (T. Farkas, K. Sestak, C. Wei, and X. Jiang, J. Virol. 82:5408-5416, 2008). TV grows well in tissue culture, and it represents a new genus within Caliciviridae, with the proposed name of Recovirus. We also reported a high prevalence of CV antibodies in macaques of the Tulane National Primate Research Center (TNPRC) colony, including anti-norovirus (NoV), anti-sapovirus (SaV), and anti-TV (T. Farkas, J. Dufour, X. Jiang, and K. Sestak, J. Gen. Virol. 91:734-738, 2010). To broaden our knowledge about CV infections in captive nonhuman primates (NHP), 500 rhesus macaque stool samples collected from breeding colony TNPRC macaques were tested for CVs. Fifty-seven (11%) samples contained recovirus isolates. In addition, one NoV was detected. Phylogenetic analysis classified the recovirus isolates into two genogroups and at least four genetic types. The rhesus NoV isolate was closely related to GII human NoVs. TV-neutralizing antibodies were detected in 88% of serum samples obtained from primate caretakers. Binding and plaque reduction assays revealed the involvement of type A and B histo-blood group antigens (HBGA) in TV infection. Taken together, these findings indicate the zoonotic potential of primate CVs. The discovery of a genetically diverse and prevalent group of primate CVs and remarkable similarities between rhesus enteric CVs and human NoVs opens new possibilities for research involving in vitro and in vivo models of human NoV gastroenteritis.Caliciviruses (CV) are important human and animal pathogens, causing a wide variety of diseases in their respective hosts. The family Caliciviridae consists of five established genera (Norovirus, Sapovirus, Lagovirus, Vesivirus, and Nebovirus). Recently, two new calicivirus genera have been proposed, represented by the Tulane virus (Recovirus) and the St. Valerien-like viruses (Valovirus) (11-13, 24, 36, 37, 39).NoVs are recognized as the leading cause of epidemics of gastroenteritis (GE), causing 80 to 90% of nonbacterial GE outbreaks and more than 50% of all food-related GE outbreaks (7, 8, 29). They are also an important cause of sporadic GE in both children and adults. Based on phylogenetic analysis, NoVs are divided into five genogroups and more than 30 genetic clusters or genotypes (9, 46). This high genetic and, likely, antigenic variation, combined with the lack of a tissue culture or animal model, represent major obstacles for NoV research.NoVs with close genetic and antigenic relatedness to human NoVs have been isolated from various animal species (6, 28, 33, 41). This not only provided opportunities for using some of these viruses as surrogates for human NoV research (44) but also raised the concern of the possible zoonotic nature of CV gastroenteritis.Based on results of in vitro binding assays, volunteer challenge studies, and the analysis of NoV outbreaks, it was proposed that histo-blood group antigens (HBGA), including the ABO, Lewis, and secretor-type HBGAs, function as the NoV receptors (17, 19, 20, 27, 32). The involvement of other host factors in NoV replication and susceptibility to infection also has been implicated (14, 43).Previously, we reported the isolation and characterization of a novel CV (Tulane virus; TV) from stool samples of juvenile rhesus macaques (11). TV represents a newly proposed genus (Recovirus) within Caliciviridae that phylogenetically shares a common origin with NoVs; however, TV can be grown in tissue culture (11). We also reported a high prevalence of anti-NoV, anti-SaV binding, and anti-TV-neutralizing (VN) antibodies in colony macaques, suggesting that CV infections are frequent in captive nonhuman primates (NHP) (10). The few NoV challenge studies conducted also suggest that NHPs are susceptible to NoV infection. Chimpanzees inoculated with the Norwalk virus developed seroresponses and virus shedding but without the manifestation of clinical disease (45). Subekti et al. reported the development of clinical illness characterized by diarrhea, dehydration, vomiting, and virus shedding in newborn pigtail macaques inoculated with the Toronto virus (40). In a study conducted by Rockx et al., one of the three rhesus macaques infected with Norwalk virus developed virus-specific IgM and IgG responses and shed the virus for 19 days postinoculation (38). To date, however, direct evidence of natural NoV or SaV infection in NHPs is missing. Moreover, the prevalence and genetic diversity of recoviruses have yet to be studied.In this study, we undertook the molecular detection and genetic analysis of CVs circulating in colony macaques and examined the role of HBGAs in recovirus infection.