Orally administered microencapsulated reovirus can bypass suckled, neutralizing maternal antibody that inhibits active immunization of neonates

Purified reovirus serotype 1, encapsulated in biodegradable aqueous microcapsules, was found to bypass maternal antibody passively transferred by suckling to neonates. Genetically identical, immunocompetent F-1 scid/(+) mice were generated by the reciprocal crosses of C.B17 scid/scid and normal congenic +/+ adult mice. The immunocompetent +/+ dams were either orally infected with reovirus prior to mating or not. Thus, these immunocompetent F-1 pups developed either in the absence or in presence of passively transferred maternal immunity. The F-1 mice were orally immunized on day 10 with either live virus, microencapsulated reovirus us, or empty microcapsules plus live virus. The immune responses, were assessed in the neonatal gut-associated lymphoid tissues (GALT). Examination of reovirus specific immonoglobulin A in the serum and GALT, taken on days 7, 14, and 21 postimmunization, clearly demonstrated that microencapsulated reovirus could by pass the normal effect of maternal antibodies, passively acquired by suckling, to inhibit active priming of neonates by oral route. These observations seem relevant to the development of efficacious oral vaccines that also allow passive, protective immunity via suckled maternal antibodies while permitting active oral immunization of neonates.