Estimating antigenic distances between GII.4 human norovirus strains

Abstract

Human norovirus (HuNoV) is an etiological agent of acute gastroenteritis. Viral protein 1 (VP1) is the major capsid protein and the determinant of antigenicity in HuNoV. GII.4 has been the dominant VP1-genotype in most of HuNoV seasons. Here an attempt was made to estimate the magnitude of antigenic difference, defined as the antigenic distance, between GII.4 HuNoV strains from the comparison of amino acid sequences for VP1. Antigenic distance was estimated more accurately assuming an exponential decline in the amount of increase in the antigenic distance along with an increment in the number of amino acid differences than assuming a constant increase. Although antigenic sites A, C, D, E, and G appeared to be the major determinant of antigenicity, estimation accuracy was sometimes improved by adding other regions. These results suggested that it may be suitable to construct a model based on the entire region of VP1 for estimating antigenic distances between GII.4 HuNoV strains.