Lactobacillus plantarum vaccine vector expressing hemagglutinin provides protection against H9N2 challenge infection

• IFN-γ cytokines, and CD107a+ producing CD3+CD8+ T cells in the spleen and MLN were induced by the NC8-pSIP409-HA-DCpep in mouse models.
• NC8-pSIP409-HA-DCpep provided 100% protection against the mouse-adapted H9N2 virus (H9N2 m-AV) and reduced virus replication in the lungs after challenge with H9N2 m-AV.
• NC8-pSIP409-HA-DCpep induced strong T cell immune response in the PBMC in chickens.
• IgG and sIgA were significantly induced by the NC8-pSIP409-HA-DCpep in chickens.
• Oral vaccination with NC8-pSIP409-HA-DCpep induced protective immunity against H9N2 AIVs in chickens.

Hemagglutinin (HA) has been demonstrated as an effective candidate vaccine antigen against AIVs. Dendritic cell-targeting peptide (DCpep) can enhance the robustness of immune responses. The purpose of this study was to evaluate whether DCpep could enhance the immune response against H9N2 AIV when utilizing Lactobacillus plantarum NC8 (NC8) to present HA-DCpep in mouse and chicken models. To accomplish this, a mucosal vaccine of a recombinant NC8 strain expressing HA and DCpep that was constructed in a previous study was employed. Orally administered NC8-pSIP409-HA-DCpep elicited high serum titers of hemagglutination-inhibition (HI) antibodies in mice and also induced robust T cell immune responses in both mouse and chicken models. Orally administered NC8-pSIP409-HA-DCpep elicited high serum titers of hemagglutination-inhibition (HI) antibodies in mice and also induced robust T cell immune responses in both mouse and chicken models. These results revealed that recombinant L. plantarum NC8-pSIP409-HA-DCpep is an effective vaccine candidate against H9N2 AIVs.