Oral immunization with recombinant Lactococcus lactis expressing the hemagglutinin of the avian influenza virus induces mucosal and systemic immune responses.

Aims: The aim of the study in this article is to explore a safe, convenient and effective oral mucosal vaccine candidate against highly pathogenic avian influenza. Materials & methods: We have constructed an oral mucosal vaccine, LL36EH, by use of the genetically stable θ-replicating vector pMG36E, which expressed the fusion protein hemagglutinin 1 (HA1) in a live carrier, Lactococcus lactis MG1363. LL36EH was administered orally to mice three times at 2-week intervals. The specific serum IgG and mucosal IgA antibodies were detected and evaluated at different time points after immunization. Results: The results showed that LL36EH could significantly induce specific anti-HA1 IgA antibody in the intestine and specific anti-HA1 IgG antibody in the serum (p < 0.05). Additionally, when the splenic lymphocytes isolated from immunized mice were stimulated by HA1 antigen in vitro, splenic lymphocyte proliferative reaction and secretions of the cytokines IFN-γ and IL-4 were also significantly increased. Most import...