Chitosan Nanoparticles as a Novel Nano-Adjuvant for Enhanced Immunogenicity and Protective Efficacy of an Inactivated Pasteurella multocida Serotype A Vaccine

Background: Chitosan nanoparticles have attracted considerable attention as nano-adjuvants due to their excellent biocompatibility, biodegradability, and ability to enhance antigen delivery and immune responses. Pasteurella multocida serotype A is a major etiological agent of respiratory pasteurellosis in sheep, causing significant economic losses to the livestock industry. This study aimed to develop and evaluate chitosan nanoparticles as a novel nano-adjuvant for improving the immunogenicity and protective efficacy of an inactivated P. multocida serotype A vaccine. Methods: Chitosan nanoparticles were synthesized using the ionic gelation method and characterized for particle size, zeta potential, and physicochemical properties. Cytotoxicity was assessed by MTT assay, and the IC'so value was determined. Formalin-inactivated P. multocida antigen was loaded onto the nanoparticles to formulate the nano-adjuvanted vaccine. BALB/c mice received two immunizations, followed by evaluation of serum IgG antibody responses and serum neutralization activity. Protective efficacy was assessed through challenge with a lethal dose of P. multocida serotype A. Results: The synthesized nanoparticles exhibited nanoscale size, positive surface charge, and favorable physicochemical characteristics with minimal cytotoxicity (IC so> ۴۰۰ μg/mL). Immunization with the chitosan nano-adjuvanted vaccine significantly enhanced antigen-specific IgG production and serum neutralizing activity compared with the control group. Following bacterial challenge, the vaccinated group achieved complete protection (۱۰۰% survival), whereas mortality occurred in the control group. Conclusion: Chitosan nanoparticles demonstrated excellent biocompatibility and effectively enhanced both humoral immune responses and protective immunity against P. multocida serotype A. These findings highlight the potential of chitosan nanoparticles as a promising nano-adjuvant platform for the development of next-generation veterinary vaccines.

کلیدواژه ها:

Chitosan nanoparticles ، Nano-adjuvant ، Pasteurella multocida ، Inactivated vaccine ، Immunogenicity ، Veterinary nanomedicine