Comparison of VP4 and VP7 of five murine rotavirus strains

The nucleotide and deduced amino acid sequences of outer capsid proteins VP4 and VP7 of five murine rotavirus strains (EW, EB, EC, EL, EHP) were determined. Comparisons of the VP7 amino acid sequences of the five murine rotavirus strains with rotavirus strains representative of G serotypes 1-14 showed that the murine strains were highly homologous to one another and more closely related to strains representing G3 than to any other G type. Analysis of the VP4 amino acid sequences of the murine strains revealed the presence of at least two murine P types. Therefore, sequence analysis would predict that the murine rotaviruses are G3 or G3-like and represent at least two unique P types (tentatively P17 for EW, EB, EC, and EL and P18 for EHP). When we attempted to categorize the murine strains by serum neutralization tests, our results were less clear. Serum to two murine strains, EHP and EW, displayed one-way reactivity by focus-reduction neutralization assays using several prototype G3 strains. The G3 serotyping monoclonal antibody 159 failed to neutralize EHP and EW, while the G3-specific monoclonal YO-1E2 neutralized EHP, but not EW. A reassortant (A15) containing VP7 from EW and VP4 from RRV was neutralized by these two G3-specific monoclonal antibodies to a level 8- to 20-fold more than EW, but was still 64- to 250-fold less than either SA11 and RRV. These results suggest that VP4 can influence the antigenicity of VP7.