Characterization of Antigenic Relatedness between GII.4 and GII.17 Noroviruses by Use of Serum Samples from Norovirus-Infected Patients.

A novel GII.17 norovirus variant caused major gastroenteritis epidemics in China in 2014 to 2016. To explore the host immune factors in selection of the emergence of this new variant, we characterized its antigenic relatedness with the GII.4 noroviruses that have dominated in China for decades. Through an enzymelinked immunosorbent assay (ELISA) and a histo-blood group antigen (HBGA) blocking assay using sera from GII. 4 and the GII.17 variant-infected patients, respectively, we observed limited cross-immune reactivity by the ELISA but little reactivity by the HBGA blocking assay between GII.4 norovirus and the new GII.17 variant. Our data suggest that, among other possible factors, GII. 4-specific herd immunity had little role in the emergence of the new GII.17 variant. Thus, GII.17 may be an important active antigenic type or immunotype that needs to be considered for future vaccine strategies against human noroviruses.