DNA Vaccine Encoding Trypanosoma brucei MSP-B Elicited IgG and IFN-γ Responses and Partial Protection in Immunised Mice.

As an effort towards vaccine development against African trypanosomiasis, we studied key parasite molecules that mediate VSG functions, specifically the major surface protease-B of Trypanosoma brucei that catalyses proteolytic removal of old VSGs for expression of new ones, an important stage-specific function that allows the parasite to survive in its host, thus making it an attractive candidate for vaccine development. Herein, the Tbmsp-b gene was cloned into a pVAX-1 plasmid to produce the pVAX-1-Tbmsp-b construct for DNA vaccine trials. BALB/c mice were immunised by intradermal injection with a 100 μg dose of the construct thrice on Days 0, 21 and 42, then inoculated with 2000 parasites on Day 56. Anti-trypanosome-specific antibody (IgG) and cytokine (IFN-γ) were monitored by ELISA from sera of immunised and unimmunised mice. Immunised mice showed significantly (p < 0.05) higher IgG and IFN-γ responses, lower parasitaemia (by 75% and 51.2% of parasitaemic scores on the first and fifth week of infection) and longevity by up to 22 days compared to unimmunised mice. These results showed that the construct provided partial protection to virulent T. b. brucei (Federe strain) infection in susceptible BALB/c mice, suggesting the potential for using MSP-B as an antigen in DNA vaccine development against African trypanosomiasis.