Predominance of G3B and G14 equine group A rotaviruses of a single VP4 serotype in Japan

A total of 65 equine group A rotaviruses (GAR) isolated from diarrheal foal s at 48 farms in Hokkaido, Japan, between 1996 (29 isolates) and 1997 (36 i solates) were characterized for their VP7 and VP4 serotypes by PCR, nucleot ide sequencing, and virus neutralization (VN) tests. By PCR VP7 typing, all isolates were classified as G3 or G14, and the predominant serotype in eac h year was G3 (86%) in 1996 and G14 (53%) in 1997. VN tests with these 20 i solates randomly selected confirmed the specificity of PCR on the bases of complete agreement of the results in these methods (9 G3 and 11 G14), and r evealed that all 9 G3 isolates were subtype G3B. There were five differing amino acid residues in three VP7 antigenic regions between subtypes G3A and G3B. Antiserum to a baculovirus recombinant that expressed P[12] VP4 neutr alized all isolates and P[12] reference strains. These results suggest that genotype P[12] GAR belong to a single VP4 serotype, and that one VP4 and t wo VP7 serotypes (G3B and G14) of GAR were predominant in the equine popula tion in Japan.