Lactococcus lactis anchoring avian infectious bronchitis virus multi-epitope peptide EpiC induced specific immune responses in chickens.

Mucosal immunity is critical in preventing infectious bronchitis virus (IBV) infection. To deliver viral antigens to the mucosal immune system of chickens safely and effectively, we constructed a Lactococcus lactis strain carrying IBV multi-epitope gene EpiC fused with the gene of the cell-wall anchoring domain of Staphylococcus aureus protein A. SDS-PAGE and Western blot results indicated that the fused peptide was located partially on the cell surface. Oral and nasal inoculation with the recombinant L. lactis of chickens elicited significantly high humoral and mucosal immune responses, especially in the nasally immunized group. Eighty percent chickens of the nasally immunized group with recombinant L. lactis did not show any clinical signs after a lethal dose challenge with IBV SAIBk strain, while all the non-recombinant L. lactis immunized chickens exhibited obvious and typical symptoms. These results indicate that needle-free recombinant lactococci anchoring the IBV antigen makes a promising vaccine candidate against the spread of IB.