Immunogenicity of candidate chimeric DNA vaccine against tuberculosis and leishmaniasis

Mycobacterium tuberculosis and Leishmania donovani are important intracellular pathogens, especially in Indian context. In India and other South East Asian countries, both these infections are highly endemic and in about 20% cases co-infection of these pathogens is reported. For both these pathogens cell mediated immunity plays most important role. The available treatment of these infections is either prolonged or cumbersome or it is ineffective in controlling the outbreaks and spread. Therefore, potentiation of a common host defense mechanism can be used to prevent both the infections simultaneously. In this study we have developed a novel chimeric DNA vaccine candidate comprising the esat-6 gene of M. tuberculosis and kinesin motor domain gene of L. donovani. After developing this novel chimera, its immunogenicity was studied in mouse model. The immune response was compared with individual constructs of esat-6 and kinesin motor domain. The results showed that immunization with chimeric DNA vaccine construct resulted in stronger IFN-gamma and IL-2 response against kinesin (3012+/-102 and 367.5+/-8.92pg/ml) and ESAT-6 (1334+/-46.5 and 245.1+/-7.72pg/ml) in comparison to the individual vaccine constructs. The reciprocal immune response (IFN-gamma and IL-2) against individual construct was lower (kinesin motor domain: 1788+/-36.48 and 341.8+/-9.801pg/ml and ESAT-6: 867.0+/-47.23 and 170.8+/-4.578pg/ml, respectively). The results also suggest that using the chimeric construct both proteins yielded a reciprocal adjuvant affect over each other as the IFN-gamma production against chimera vaccination is statistically significant (p<0.0001) than individual construct vaccination. From this pilot study we could envisage that the chimeric DNA vaccine construct may offer an attractive strategy in controlling co-infection of leishmaniasis and tuberculosis and have important implication in future vaccine design.