Genetic and Phenotypic Characterization of GII-4 Noroviruses That Circulated during 1987 to 2008

Abstract

The predominance and continual emergence of new variants in GII-4 noroviruses (NVs) in recent years have raised questions about the role of host immunity and histo-blood group antigens (HBGAs) in NV evolution. To address these questions, we performed a genetic and phenotypic characterization of GII-4 variants circulating in the past decade (1998 to 2008). Ninety-three GII-4 sequences were analyzed, and of them, 16 strains representing 6 genetic clusters were selected for further characterization. The HBGA binding properties were determined by both saliva-and oligosaccharide-binding assays using P particles as a model of NV capsid. The antigenic properties were also examined by enzyme immunoassay (EIA), Western blot analysis, and receptor blocking assay, using P-particle-specific antibodies from immunized mice and GII-4 virus-infected patients. Our results showed that 15 of the 16 GII-4 viruses bound to saliva of all A, B, and O secretors. Oligosaccharide binding assays yielded largely consistent results, although the binding affinities to some oligosaccharides varied among some strains. The only nonbinder had a mutation in the binding site. While antigenic variations were detected among the 16 strains, significant cross-blocking on the HBGA binding was also noted. Sequence alignment revealed high conservation of HBGA binding interfaces with some variations in adjacent regions. Taken together, our data suggested that the ability of GII-4 to recognize different secretor HBGAs persisted over the past decade, which may explain the predominance of GII-4 over other genotypes. Our data also indicated that both the host immunity and HBGAs play a role in NV evolution. While host immunity may continue driving NV for antigenic change, the functional selection by the HBGAs tends to lock the architecture of the capsid/HBGA interfaces and allows only limited variations outside the HBGA binding sites. A potential outcome of such counterselection between theses two factors in NV evolution is discussed.Noroviruses (NVs) have been recognized as the most important cause of nonbacterial acute gastroenteritis in both developed and developing countries, affecting people of all ages (13,35,39,44,48,56). They are single-stranded positive-sense RNA viruses belonging to the family Caliciviridae. NVs are highly contagious, spreading by a fecal/oral pathway through person-to-person contact and by contaminated food and/or water and usually causing large outbreaks within closed communities in a variety of settings, such as hospitals, nursing homes, schools, childcare centers, restaurants, cruise ships, and the military (11, 63). Human NVs have been difficult to study due to diverse members and the lack of an efficient cell culture and animal model for human NVs. The cloning of the NV genomes (33,36,73) and subsequent expression of the viral capsid proteins in baculovirus and other expression systems (3, 31, 32) have greatly advanced the research of NVs, including host-virus interaction, immunology, diagnosis, molecular virology, and epidemio...

Monoclonal Antibody-Based Antigenic Mapping of Norovirus GII.4-2002

“…GII. bound to H type 3, Lewis Y, and B trimer (29,48). Consistent with our previous report (29), a ligand binding partner for GII.4-2004 VLP was not identified in this assay, perhaps reflecting residue microvariation occurring within the different GII.…”

“…These data suggest that these antibodies (anti-GII.4-2002-G1, -G2, -G3, and -G4) do not recognize neutralizing epitopes, and although not informative about viral antigenic evolution, they do provide potential diagnostic reagents for detection of broader groups of NoV strains. These antibody reactivity patterns are reminiscent of those generated by immunizing mice with P particles (48), as the antibodies react with denatured capsid protein by Western blot analysis but did not block VLP-ligand interactions. These data underscore an important complication of using Western blot analysis to determine the antigenic relatedness of GII.4 strains.…”

“…Consistent with our previous report (29), a ligand binding partner for GII.4-2004 VLP was not identified in this assay, perhaps reflecting residue microvariation occurring within the different GII. Hunter strains used by different laboratories or the difference between VLP binding compared to P particle binding (29,48). MAb based detection reagents identified GII.…”

Structural Analysis of Histo-Blood Group Antigen Binding Specificity in a Norovirus GII.4 Epidemic Variant: Implications for Epochal Evolution

“…However, some of these changes are in close proximity to HBGA binding sites, particularly site 2, and thus could potentially affect HBGA binding in the 2004 variant. Regarding HBGA binding in the 2004 variants, there have been conflicting reports (9,10,43). To examine if the changes observed for the 2004 P domain structure influence the HBGA binding preference of the 2004 variant, we carried out cocrystallization experiments with both monofucosyl ABH HBGAs and difucosyl secretor Lewis HBGA, for which the structure in complex with GII.4 has not been previously reported.…”

“…4 2004-2005 variants showed that these variants do not bind to any known carbohydrates, and these variants were suggested to have acquired novel receptors or novel carbohydrate ligands (10). Another study using recombinant P particles, higher-order oligomers of the P domain obtained by using a cysteine-linked peptide at one of the termini, indicated that these variants bind to all of the secretor HBGAs although to a lesser extent than those of other variants (43). Finally, most recently, de Rougemont et al, using a variety of binding studies, including surface plasmon resonance with well-characterized VLP preparations, have shown that the 2004-2005 variants bind to both ABH and Lewis secretor HBGAs (9).…”