SINGLE-POINT MUTATIONS MAY AFFECT THE SEROTYPE REACTIVITY OF SEROTYPEG11 PORCINE ROTAVIRUS STRAINS - A WIDENING SPECTRUM

A panel of single and double neutralization-resistant escape mutants o f serotype G11 porcine rotavirus strains A253 and YM, selected with G1 1 monotype-and serotype-specific neutralizing monoclonal antibodies (M Abs) to VP7, was tested in neutralization assays with hyperimmune sera raised against rotavirus strains of different serotypes, Escape mutan ts with an amino acid substitution in antigenic region A (amino acids [aa] 87 to 101) resulting in a residue identical or chemically similar to those present at the same positions in serotype G3 strains, at pos itions 87 for strain A253 and 96 for strain YM, were significantly mor e sensitive than the parental strains to neutralization with sera agai nst some serotype G3 strains, Also, one YM antigenic variant (YM-5E6.1 ) acquired reactivity by enzyme-linked immunosorbent assay with MAbs 1 59, 57/8, and YO-1E2, which react with G3 strains, but not with the se rotype G11 parental strain YM, Cross-adsorption studies suggested that the observed cross-neutralization by the G3-specific sera was due to the sera containing antibodies reactive with the parental strain plus antibodies reactive,vith the epitope(s) on the antigenic variant that mimick the serotype G3 specific one(s), Moreover, antibodies reactive with antigenic region F (aa 235 to 242) of VP7 might also be involved since cross-reactivity to serotype G3 was decreased in double mutants carrying an additional mutation, which creates a potential glycosylati on site at position 238. Thus, single point mutations can affect the s erotype reactivity of G11 porcine rotavirus strains with both monoclon al and polyclonal antibodies and may explain the origin of rotavirus s trains with dual serotype specificity based on sequence divergence of VP7.