Immunotherapy against visceral leishmaniasis with the nucleoside hydrolase-DNA vaccine ofLeishmania donovani

The nucleoside hydrolase (NH36) ofLeishmania (L.) donovaniis a vital enzyme which releases purines or pyrimidines of foreign DNA to be used in the synthesis of parasite DNA. As a bivalent DNA vaccine, the VR1012-NH36 was immunoprotective against visceral and cutaneous murine leishmaniasis. In this work we tested the immunotherapy againstLeishmania (L.) chagasiinfection, using two doses of 100 or 20μg VR1012-NH36 vaccine (i.m. route), and, as a possible immunomodulator, aqueous garlic extract (8mg/kg/day by the i.p. route), which was effective in immunotherapy of cutaneous murine leishmaniasis. Liver parasitic load was significantly reduced following treatment with 100μg (91%) and 20μg (77%) of the DNA vaccine, and by 20μg DNA vaccine and garlic extract (76%) (p=0.023). Survival was 33% for saline controls, 100% for the 100μg vaccine, and 83 and 67% for the 20μg vaccine with and without garlic extract addition, respectively. Garlic treatment alone did not reduce parasite load (p>0.05), but increased survival (100%). The NH36-DNA vaccine was highly effective as a new tool for the therapy and control of visceral leishmaniasis, while the mild protective effect of garlic might be related to an unspecific enhancement of IFN-γ secretion.