Oxidized Mannan: A Novel Adjuvant Candidate for Enhancing Immune Responses in Veterinary Rabies Vaccine

Rabies continues to pose a serious public health threat worldwide, with vaccination being the most effective means of prevention. However, commercially available inactivated rabies vaccines often require multiple doses and lack potent adjuvants to enhance their efficacy. This study aimed to investigate the coupling of whole inactivated rabies virus to mannan under oxidizing conditions to improve immune responses against a standard rabies vaccine. We explored the conjugation of whole inactivated rabies virus with oxidized mannan (Rab-OxMan) to enhance immune responses. Mice were immunized intraperitoneally with 350 µg of the Rab-OxMan formulation on days 1 and 7. Two weeks after immunization, serum samples were collected to measure levels of IgG, IgM, and TNF-α using ELISA. The vaccine's potency was also evaluated using the National Institutes of Health (NIH) assay. Our findings showed a significant increase in IgG levels and a decrease in IgM levels in the Rab-OxMan group compared to the Alum-adjuvanted vaccine group (p<0.05). Additionally, TNF-α levels were notably higher in the Rab-OxMan group (p<0.05). Statistical analysis revealed that IgG levels had the highest sensitivity and specificity, with a significant correlation between the measured variables. Importantly, the Rab-OxMan formulation provided 1.8 times greater protection in challenge tests compared to the alum-adjuvanted group. This study is the first to demonstrate that oxidized mannan can serve as a novel adjuvant for veterinary rabies vaccines. The results highlight significant improvements in the immunogenicity and efficacy of rabies vaccines, suggesting a promising strategy for enhancing rabies prevention and potentially reducing the incidence of this deadly disease.