Comparative study of DNA vaccines encoding various antigens against Leishmania mexicana

Leishmaniases represent an important public health problem in large parts of the world. In the south-east of Mexico, the major species isolated from patients is Leishmania mexicana mexicana, causing localised cutaneous leishmaniasis, and the development of a vaccine is a key objective for the control of this parasite. We thus performed a comparative study of DNA vaccines encoding L. m. mexicana gp63 and CPb, L. m. amazonensis gp46, and L. major LACK to define the best antigen(s) candidate(s). cDNAs encoding these antigens were subcloned into the VR1012 plasmid, and susceptible BALB/c mice were immunised with two i.m. injections of 100 microg of plasmid DNA. All mice immunised with VR1012-GP46, VR1012-CPb and VR1012-GP63 showed increased IgG levels against L. m. mexicana, but not those immunised with VR1012-LACK. Two to three weeks after the last immunisation, mice were challenged by the injection of 4 x 10(6) L. m. mexicana parasites in the foot pad to evaluate protection. Measurement of lesion size indicated that mice immunised with VR012-GP46, VR012-GP63 and VR1012-CPb were partially protected against infection, whereas the other plasmids had no effect. Thus, these plasmids represent good candidates for further development of DNA immunisation against L. m. mexicana.