Protection Against ETEC F41 After Intranasal Immunization with Recombinant Lactobacillus casei

【Objective】 The use of live Lactobacillus casei as an antigen delivery system elicit mucosal immunity and thus represents a promising strategy for mucosal vaccination to prevent ETEC F41 infection.【Method】 The recombinant fusion proteins were detected by SDS-PAGE and Western blot.Surface localization of the fusion protein was verified by immunofluorescence microscopy and flow cytometry.Intranasal immunization of SPF Balb/c mice was performed with recombinant strain harboring pLA-F41/L.casei and pLA/L.casei.Specific anti-F41 IgG antibody in the serum and specific anti-F41 secret immunoglobulin A(sIgA) antibody in the lung,intestines,vigna fluid and feces of mice were detected by indirect ELISA after intranasal immunization.The mice intranasaly immunized with pLA-F41/L.casei and pLA/L.casei were challenged with standard-type ETEC F41(C83919).【Result】 Mice immunized with pLA-F41/L.casei could produce remarkable anti-F41 antibody level.More than 80% of mice survived after challenged with C83919(2×103LD50).All the mice immunized with a control L.casei harboring pLA vector were died.Eighty-five percent of the pups survived after challenged with C83919,but only a 5% survival rate for pups that were either immunized with a control L.casei harboring pLA vector or unimmunized.【Conclusion】 These results indicate that mucosal immunization with recombinant L.casei expressing ETEC F41 fimbriae protein on its surface provides an effective means for eliciting protective immune response against the ETEC F41.