[ODP-182] The effect of antigen binding and administration route of BLP on its immunogenicity
Mucosal vaccines can trigger protective immune responses at mucosal tissues where the major portal for numerous pathogens. Non-live Bacterium-like particles (BLP) prepared from Lactococcus lactis have been proposed as a novel adjuvant/antigen delivery platform for mucosal vaccines. This study aimed to clarify whether (1) antigen bindings to BLP and (2) administration route (i.e., oral and nasal) can affect the induction of antigen-specific immune responses by BLP. We used Tir, a virulence factor of murine pathogenic bacteria Citrobacter rodentium, as a model antigen. Fusion protein of Tir and LysM (a peptidoglycan binding motif of Lactococcal endopeptidase AcmA) was expressed by E. coli. BLP bound with Tir-LysM (BLP-Tir) and BLP mixed with Tir (BLP+Tir) was orally or nasally administered to mice and Tir-specific antibody responses were measured. Oral administration of BLP-Tir or BLP+Tir induced Tir-specific systemic IgG, but not mucosal IgA, production. In contrast, nasal administration of BLP-Tir or BLP+Tir induced both systemic IgG and mucosal IgA responses to Tir. Additionally, BLP-Tir induced significantly stronger antibody responses than BLP+Tir. These results indicated that (1) antigen binding to BLP via LysM motif enhances the immunogenicity of BLP, and (2) BLP delivery system can induce antigen-specific immune responses only when it administered via the nasal route.