Recombinant Lactococcus Lactis Expressing M1-HA2 Fusion Protein Provides Protective Mucosal Immunity Against H9N2 Avian Influenza Virus in Chickens.

H9N2 subtype avian influenza virus of low pathogenicity (LPAIV) are distributed worldwide and cause enormous economic losses in the poultry industry. Although almost all the chickens immunized with the inactivated vaccine, the disease is still widespread. We speculate that increase mucosal or cellular immune response may contribute to improving the H9N2 virus surveillance. 

In this study, we Bovine Recombinant Proteins constructed a novel Lactococcus lactis (L. lactis) strain expressing a recombinant fusion protein consisting of the M1 and HA2 proteins derived from the H9N2 viral strain endemic conserved antigens. M1-HA2 fusion protein was cloned downstream of the gene encoding the secretory peptide, and we subsequently confirmed that the fusion protein is secreted from L. 

lactis by Western blotting. We assess the immunogenicity and protective effects of recombinant L. lactis this tension. Eight chicken 1-day-old were divided into four groups, and the experimental group orally vaccinated twice with recombinant L. lactis strain. fecal and intestinal samples, sera and bronchoalveolar lavage fluid was collected at 7, 14 and 21 days post-vaccination (DPV). 

Chickens vaccinated with a recombinant L. lactis strains showed significantly increase the levels of serum antibodies, T cell-mediated immune responses, and mucosal secretory IgA (SIgA). Following challenge with H9N2 virus in 21 DPV, chickens vaccinated with the recombinant L. lactis strains showed weight loss, lowering viral titers in the lungs, and reduce the pathological damage lungs.

 In summary, our results suggest that Cat Recombinant Proteins recombinant L. lactis strain H9N2 M1-HA2 express the fusion protein can induce a protective mucosal and systemic immunity. The oral vaccine is the H9N2 virus-specific and is a significant design improvement compared with previous studies. Our study provides a theoretical basis for improving mucosal immune responses to prevent and control the H9N2 virus infection.