Mucosal delivery (in ovo and oral) of chitosan nanoparticle-based subunit vaccine enhances resistance against Campylobacter jejuni colonization in broiler chickens

Campylobacter jejuni infection in poultry presents a significant public health concern due to the consumption of contaminated chicken meat and related products. Vaccination has been proposed as a potential mitigation approach to control infections in chickens and reduce the risk of zoonotic transmission. Yet, no commercial vaccines are currently available for controlling this microorganism in chickens. This study aimed to investigate the efficacy of mucosal delivery (in ovo and oral) of multi-antigen chitosan nanoparticle (CNP)-encapsulated vaccines, including C. jejuni lysate and outer membrane proteins (OMPs), administered alone or in combination with the Toll-like receptor ligand CpG ODN as an adjuvant for controlling C. jejuni infection in broilers. The results revealed that administration of CNP-encapsulated OMPs alone or in combination with CpG ODN significantly reduced C. jejuni colonization by 1.2 and 1.24 log₁₀, respectively. In contrast, the groups vaccinated with low or high doses of CNP-encapsulated lysate of C. jejuni reduced it by 1.3 log₁₀. The observed reductions in C. jejuni colonization in vaccinated birds were associated immunologically with a significant elevation of specific IgA antibody levels in bile and the alteration of cytokine gene expression, particularly interleukin (IL)-1β, IL-12, IL-13, interferon (IFN)-γ, and transforming growth factor (TGF)-β in the cecal tonsils of these vaccinated groups. However, no such effects were observed for the groups vaccinated with CpG ODN alone or the soluble form of the C. jejuni lysate. Overall, CNP-encapsulated C. jejuni OMPs or lysate present a potential candidate vaccine to curb C. jejuni infection, with a feasible mucosal delivery approach in broiler chickens.