The outer capsid proteins VP4 and VP7 induce neutralizing antibody against rotavirus. We have investigated in a mouse model the protection mediated by immunization with VP8*, the amino-terminal tryptic fragment of VP4. BALB/c female mice immunized with simian rotavirus SA11 VP6 and VP8* proteins expressed in Escherichia coli were mated with seronegative males. Litters were orally challenged with the SA11 strain (P5B[2], G3) or with the murine rotavirus strain EDIM (P10[16], G3) to verify the degree of protection against diarrhea induced in the newborns. Only those pups born to dams immunized with VP8* did not develop diarrhea after having been orally challenged with the SA11 strain. Pups born to naive dams but foster nursed by VP8*-immunized dams did not develop diarrhea after having been orally infected with the SA11 strain, but they suffered diarrhea when challenged with the EDIM strain. These results support the concepts that (1) VP8* is a highly immunogenic polypeptide that induces effective homotypic protection against disease in pups born to dams immunized with this antigen and (2) in newborn mice the protection against disease is mediated by neutralizing secretory antibodies present in the milk rather than by serum antibodies transferred through the placenta to the offspring.

Between September 1996 and May 1999, the incidence and distribution of the main human rotavirus G genotypes (VP7 associated: G1-G4) and P genotypes (VP4 associated: P[8], P[4], P[6] and P[9]) among children with rotavirus gastroenteritis were determined using reverse transcription and polymerase chain reaction (RT-PCR)-based genotyping methods. From a total of 145 rotavirus strains examined, we identified the G type in 131 (90.3%) and the P type in 127 (87.5%) of the samples. An overall predominance of genotypes P[8] G1 (42.7%) and P[8] G4 (32.4%) was found during the period of study, with much lower incidence of genotypes P[4] G2 (5.5%) and P[8] G3 (2%). P[6] and P[9] types were not detected, neither were unusual combinations of P and G types. A significant genotypic shift was observed: whereas P[8] G4 was the most prevalent genotype during the first year of the study (60%), the genotype P[8] G1 gradually increased to account for 62.3% of the strains analysed in the following winter season. Mixed G types revealing dual infections G1/G4 and G3/G4 were found at low frequency (2%).