Master of Science (MS)


Veterinary Medical Sciences - Pathobiological Sciences

Document Type



West Nile virus (WNV) is one of several flaviruses known to infect mammalian species, including humans. There were 15,257 horse cases reported in 2002 and 1,086 in 2006 in United States. Recently, significant increases in equine and human cases have been reported in United States. Domain III of the WNV envelope protein binds to cellular receptors, and induces a significant portion of the neutralizing antibody response against the virus. CD40 Ligand (CD40L, CD154) enhances productive interactions between T cells and APC and has been shown to function as a potential adjuvant. In this study, we constructed and expressed a fusion protein consisting of the Domain III of WNV envelope protein fused in-frame with the soluble portion of the equine CD40L. Immunizations of rabbits revealed that the recombinant protein induced antibody that specifically reacted with the WNV and neutralized the virus. Similar experiments were performed with horses. Western immunoblots confirmed that vaccinated horses produced antibodies that specifically reacted with the recombinant WNV E DIII proteins. The recombinant DIII protein with TiterMax or CD40L or both as adjuvant(s) induced significantly higher anti-WNV E DIII antibody activities than control and DIII alone groups after first vaccination. The recombinant DIII-CD40L protein vaccine continually induced the anti-WNV E DIII antibody activities without the adjuvant TiterMax. Moreover, the groups immunized with DIII-CD40L+TiterMax and DIII-CD40L showed stronger neutralization activities from week 8 than the other groups, and they maintained the high titers for at least 10 weeks. The results showed that healthy horses vaccinated with recombinant WNV E DIII protein with equine CD40L demonstrated an antigen specific humoral immune response. The responses were enhanced by booster vaccination. Vaccination with this recombinant WNV E DIII-CD40L protein induced a WNV specific immunity in healthy horses that might contribute to protection from WNV-associated disease. CD40L could be utilized as a non-toxic, alternative adjuvant to boost the immunogenicity of subunit vaccines in horses.



Document Availability at the Time of Submission

Release the entire work immediately for access worldwide.

Committee Chair

Dr. Konstantin Gus Kousoulas