Synergistic effects of oral inoculation with recombinant Lactobacillus plantarum NC8 Co-expressing interleukin-2, interleukin-17b and interleukin-26 on infectious bronchitis vaccination in chickens

Vaccination against Infectious Bronchitis Virus (IBV) stands as a proven, effective approach for significantly curtailing chicken mortality rates in the poultry sector. Recent extensive research has thoroughly explored this area. Our study validates that a specifically engineered Lactobacillus plantarum NC8 strain, capable of co-producing a fusion protein encompassing chicken interleukin-2 (IL-2), IL-17B, and IL-26 (termed NC8-ChIL2/17B/26), amplifies the comprehensive immune response elicited by the IBV vaccine. We assessed its immune-enhancing potential by orally co-administering it with the IBV vaccine to healthy chickens. Following this, we employed ELISA to gauge IBV-specific IgG, IL-2, IL-4, IL-6, and interferon-gamma (IFN-γ) levels in the serum. Likewise, we measured secretory immunoglobulin A (sIgA) levels in the bronchia and intestines. Flow cytometry was utilized to evaluate CD4⁺/8⁺ lymphocyte ratios, while quantitative PCR determined the expression of specific immune-regulating genes. The findings revealed that the NC8-ChIL2/17B/26 group demonstrated elevated levels of pertinent cytokines, antibodies, and CD4⁺/8⁺ T cells relative to the control groups. Moreover, genes such as Toll-like receptor (TLR) 3, TLR7, IL-1β, IL-22, TGF-β, and B-cell lymphoma (BCL)-6 exhibited significantly higher expression in the NC8-ChIL2/17B/26 cohort. Additionally, viral loads in the vaccinated groups were markedly lower compared to those in the control groups, underscoring the better protective efficacy against the potent IBV strain. In essence, our research indicates that oral administration of NC8-ChIL2/17B/26 augments the overall immune response to the IBV vaccine in chickens, positioning it as a secure and efficacious adjuvant for chicken IBV vaccines.