Maternal antibody-mediated protection against gastroenteritis due to rotavirus in newborn mice is dependent on both serotype and titer of antibody.

In order to evaluate the role of passively acquired, rotavirus-specific antibodies in protection against diarrhea, we inoculated mouse dams with rotaviruses of various serotypes, and their newborns were orally challenged with a primate rotavirus (simian SA-11). Dams were immunized by using a regimen that included repeated inoculations administered either orally or intraperitoneally with adjuvant. The serum antibody response detected in dams by radioimmunoassay and plaque-reduction neutralization after parenteral immunization was approximately 15-fold and 80-fold greater, respectively, than that found after oral "hyperimmunization." Parenteral immunization with rotavirus serotypes either homotypic or heterotypic to the challenge virus protected suckling mice against diarrhea; protection was closely correlated with the in vitro neutralizing activity of maternal serum against the challenge virus. Oral immunization with only rotavirus strains homotypic to the challenge virus afforded protection; the lower immune response after oral immunization with rotaviruses heterotypic to the challenge virus resulted in a titer of neutralizing antibody to the challenge virus below the protective threshold. From our current studies it appears that antibody-mediated passive protection against rotavirus challenge is dependent on both serotype and titer of antibody.