Enhanced Antigen-Specific Delayed-Type Hypersensitivity and Immunoglobulin G2b Responses after Oral Administration of ViableLactobacillus caseiYIT9029 in Wistar and Brown Norway Rats

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Abstract
In this study, the effects of orally administered viableLactobacillus caseiShirota strain YIT9029 on the immunity parameters of Wistar and Brown Norway rats were examined. For this purpose, we used theTrichinella spiralishost resistance model. Two weeks before and duringT. spiralisinfection, rats were fed 109viableL. caseibacteria 5 days per week. TheT. spiralis-specific delayed-type hypersensitivity (DTH) response was significantly enhanced in both Wistar and Brown Norway rats givenL. casei. In both rat strains fedL. casei, serumT. spiralis-specific immunoglobulin G2b (IgG2b) concentrations were also significantly increased. In the model, no significant effects ofL. caseion larval counts or inflammatory reactions in the tongue musculature, body weights, or lymphoid organ weights were observed. Serum specific antibody responses, other than IgG2b, were not changed by feeding ofL. casei. In contrast toL. casei, it was shown that orally administeredBifidobacterium breveorBifidobacterium bifidumhad no influence on the measured infection and immunity indices in the rat infection model. Since the rat DTH response is considered to be a manifestation of Th1 cell-mediated immunity and the IgG2b isotype has been associated with Th1 activity, it was concluded that Th1 cells could play an active role in the immunomodulatory effects of orally administeredL. casei. Furthermore, our data do not indicate that the effect of oral supplementation withL. caseiis dependent on the genetic background of the host.