Immune responses of chickens inoculated with recombinant Lactobacillus expressing the haemagglutinin of the avian influenza virus

Aims: To develop a safe, effective and convenient vaccine for the prevention of highly pathogenic avian influenza (HPAI), we have successfully constructed a recombinant lactobacillus (LDL17-pH) that expresses the foreign HPAI protein, haemagglutinin 1 (HA1 ).

Methods and results: The mucosal and systemic immune responses that are triggered by LDL17-pH following the oral administration to 10-day-old chickens were evaluated. The results showed that LDL17-pH could significantly increase the specific anti-HA1 IgA antibody level in the mucosa and the anti-HA1 IgG level in sera. Tissues were isolated from trachea and Peyer's patches(PPs)and caecal tonsils of chickens, and gene expression was analysed via real-time quantitative PCR.

Conclusions: The results showed that LDL17-pH could significantly induce the specific anti-HA1 IgA antibody level in the trachea and intestine and the specific anti-HA1 IgG antibody level in the serum (P < 0·05). Additionally, LDL17-pH was in the capacity to induce the expression of cytokines IFN-γ, TLR-2 and AvBD-9 in the PPs and caecal tonsils. Most importantly, the chickens that were immunized with LDL17-pH were protected against lethal challenge of the H5N1 virus to some extent.

Significance and impact of the study: Therefore, LDL17-pH could be a promising oral vaccine candidate against HPAI.