Identification and characterization of a native epitope common to norovirus strains GII/4, GII/7 and GII/8

Norovirus is an important cause of acute non-bacterial gastroenteritis in humans. The norovirus genus is comprised of at least five genogroups based on sequence differences. The norovirus genogroup II (GII/4) strain is recognized as the predominant genotype worldwide. We expressed a 60 kDa full-length recombinant capsid protein of norovirus GII/4 in Escherichia coli and generated three monoclonal antibodies (MAbs) against it. Western blotting indicated that all three MAbs had reactivity against the recombinant capsid protein and a 58 kDa native capsid protein of norovirus obtained from stool samples. MAb-capture ELISA showed that MAb detected segmental strains within GII antigens in clinical material. To identify the existent range of this epitope, epitope analyses were processed by expressing 12 amino acids of the GST-fusion peptides. The epitope analyses revealed that the MAb N2C3 recognized a continuous native epitope 55WIRNNF60 in the shell domain, which not only belongs to strain GII/4, but also to strains GII/7 and GII/8. This is a new native epitope to be reported for norovirus GII/4.