Comparison of immune response after oral and intranasal immunization with recombinant Lactobacillus casei expressing ETEC F41

Abstract:

Abstract:【Objective】In order to represent a promising strategy for mucosal vaccination, oral or intranasal immunization of Specific Pathogen Free (SPF) BALB/c mice were performed. The mucosal immunity, systemic immune and protective immune responses were compared after immunization with the recombinant Lactobacillus casei (L.casei) harboring enterotoxigenic Escherichia coli (ETEC) F41.【Method】The recombinant fusion proteins were detected by Western blot. Surface localization of the fusion protein was verified by immunofluorescence microscopy and flow cytometry. Six-week-old female SPF BALB/c mice (160 heads) were divided into 4 groups for immunization and control. Oral and intranasal immunization of mice was performed with the recombinant strain L. casei harboring pLA-F41or pLA. For oral immunization, the mice were inoculated daily on days 0 to 4, 7 to 11, 21 to 25, and 49 to 53. A lighter schedule was used for nasal immunization (days 0 to 2, 7 to 9, 21and 49). Specific anti-F41 IgG antibody in the serum and specific anti-F41 secret immunoglobulin A (sIgA) antibody in the lung, intestines, vagina fluid and feces of mice were detected by indirect ELISA. The mice orally or intranasally immunized with pLA-F41 /L. casei and pLA/L. casei were challenged with standard-type ETEC F41 (C83919) (2×103LD50).【Result】Mice immunized with pLA-F41/L.casei could produce remarkable anti-F41antibody level. More than 90% survived in oral immunization group whereas more than 85% survived in intranasal immunization group after challenged with C83919, all dead in the control group. Ninety percent of the pups survived in oral immunization group whereas 80% survived in intranasal immunization group after challenged with C83919, but only a 5% survival rate for pups that were either immunized with a control pLA vector or unimmunized.【Conclusion】Oral or intranasal immunization with recombinant L. casei displaying ETEC F41 antigens on the surface induced effective and similar systemic and mucosal immune responses against the ETEC F41.