An Oral versus Intranasal Prime/Boost Regimen Using Attenuated Human Rotavirus or VP2 and VP6 Virus-Like Particles with Immunostimulating Complexes Influences Protection and Antibody-Secreting Cell Responses to Rotavirus in a Neonatal Gnotobiotic Pig Model

We determined the impact of mucosal prime/boost regimens and vaccine type ( attenuated Wa human rotavirus [AttHRV] or nonreplicating Wa 2/6 rotavirus-like particles [VLP]) on protection and antibody-secreting cell (ASC) responses to HRV in a neonatal gnotobiotic pig disease model. Comparisons of delivery routes for AttHRV and evaluation of nonreplicating VLP vaccines are important as alternative vaccine approaches to overcome risks associated with live oral vaccines. Groups of neonatal gnotobiotic pigs were vaccinated using combinations of oral ( PO) and intranasal ( IN) inoculation routes as follows: (i) 3 oral doses of AttHRV (AttHRV3 x PO); (ii) AttHRV3 x IN; (iii) AttHRVPO, then 2/6VLP2 x IN; (iv) AttHRVIN, then 2/6VLP2 x IN; and ( v) mock-inoculated controls. Subsets of pigs from each group were challenged with virulent Wa HRV [P1A(8) G1] (4 weeks post-primary inoculation) to assess protection. The AttHRVPO + 2/6VLP2 x IN pigs had the highest protection rates against virus shedding and diarrhea (71% each); however, these rates did not differ statistically among the vaccine groups, except for the AttHRVIN + 2/6VLPIN group, which had a significantly lower protection rate (17%) against diarrhea. The isotype, magnitude, and tissue distribution of ASCs were analyzed by enzyme-linked immunospot assay. The highest mean numbers of virus-specific IgG and IgA ASCs were observed pre- and postchallenge in both intestinal and systemic lymphoid tissues of the AttHRVPO + 2/6VLPIN group. Thus, the AttHRVPO + 2/6VLPIN vaccine regimen using immunostimulating complexes ( ISCOM) and multiple mucosal inductive sites, followed by AttHRV3 x PO or IN regimens, were the most effective vaccine regimens, suggesting that either AttHRVPO + 2/6VLPIN or AttHRV3 x IN may be an alternative approach to AttHRV3 x PO for inducing protective immunity against rotavirus diarrhea.