Protective efficacy of Fc targeting conserved influenza virus M2e antigen expressed by Lactobacillus plantarum

- Activation of CD80 and CD86 molecules on DCs by NC8-pSIP409-3M2e-Fc.
- IFN-γ+ producing CD8+ T cells in the MLN were induced by the NC8-pSIP409-3M2e-Fc in mice.
- Total IgA and IgA+B220+ cells in PP and MLN cells were significantly induced by the NC8-pSIP409-3M2e-Fc in mice.
- Specific sIgA and activated B cell in the growth center of PP were induced by the NC8-pSIP409-3M2e-Fc in mice.
- NC8-pSIP409-3M2e-Fc provided 60% and 70% protection against the A/Puerto Rico/8/34(H1N1) and mH9N2 AIV, respectively.

The influenza A (H1N1) virus is a highly contagious acute respiratory disease affecting pigs and humans. This disease causes severe economic loss in many countries, and developing mucosal vaccines is an efficient strategy to control the influenza virus. The neonatal Fc receptor (FcRn) plays an important role in transferring IgG across polarized epithelial cells. In the present study, an oral vaccine was developed using Lactobacillus plantarum to deliver the internal influenza viral protein M2e fused to an IgG Fc fragment. Oral vaccination with recombinant L. plantarum expressing 3M2e-Fc elicited Peyer's patch (PP) DC activation, improved the number of gamma interferon (IFN-γ)-producing T cells and increased the frequency of CD8+IFN-γ+ cells in the mesenteric lymph nodes (MLNs). In addition, the recombinant L. plantarum can induce PP B220+IgA+ expression and enhance specific sIgA secretion and the shaping of growth centers (GCs) in PPs. Furthermore, the data demonstrated that immunization with recombinant L. plantarum expressing 3M2e-Fc markedly reduced the viral load in the lung and protected against H1N1 influenza virus and mouse-adapted H9N2 avian influenza virus (AIV) challenge in BALB/c mice. Collectively, the data also showed that this vaccine strategy provided effective protective immunity against infection with homologous and heterologous influenza viruses in a mouse model and may be useful for future influenza vaccine development.