ORALLY-ADMINISTERED MICROENCAPSULATED REOVIRUS CAN BYPASS SUCKLED, NEUTRALIZING MATERNAL ANTIBODY THAT INHIBITS ACTIVE IMMUNIZATION OF NEONATES

Purified reovirus serotype 1, encapsulated in biodegradable aqueous mi crocapsules, was found to bypass maternal antibody passively transferr ed 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 wer e orally immunized on day 10 with either live virus, microencapsulated reovirus us, or empty microcapsules plus live virus. The immune respo nses, were assessed in the neonatal gut-associated lymphoid tissues (G ALT). Examination of reovirus specific immonoglobulin A in the serum a nd GALT, taken on days 7, 14, and 21 postimmunization, clearly demonst rated that microencapsulated reovirus could by pass the normal effect of maternal antibodies, passively acquired by suckling, to inhibit act ive priming of neonates by oral route. These observations seem relevan t to the development of efficacious oral vaccines that also allow pass ive, protective immunity via suckled maternal antibodies while permitt ing active oral immunization of neonates.