Bivalent DNA vaccination with genes encoding Leishmania major cysteine proteinases type I and II protects mice against infectious challenge

Cysteine proteinases (CPs) of Leishmania are considered to be attractive vaccine candidate in which their immunogenicity and immuno-modulatory effects have been confirmed. We have previously reported that a cocktail of two DNA plasmids encoding Leishmania major cysteine proteinases type I (CPB) and type II (CPA) induces a partial protective response in murine model of cutaneous leishmaniasis. The results also showed that the induced protective response was better than the responses given by each one the plasmids alone. However, in view of the capability of DNA plasmid for encoding several antigens, we investigated the possibility of using a single bivalent DNA vaccine, based on CP genes as an alternative mean of inducing protective immunity. Here we present evidence favoring that CPA and CPB delivered in the same plasmid DNA backbone either in separate locus or as a tandem fused gene induce partial protection against Leishmania major infection in susceptible BALB/c mice. Immunization of mice with these constructs promoted specific T-cell response of Th1 phenotype that is characterized by an increase in production of IFN-?. Our results confirm the previous observation about the possibility of DNA immunization against leishmaniasis using CP genes and lend support to the idea of using a single polyvalent plasmid DNA construct to elicit immune responses to several distinct antigens.