MPLA and AddaVax Adjuvants Fail to Promote Intramuscular LaAg Vaccine Protectiveness against Experimental Cutaneous Leishmaniasis.

There is so far no vaccine approved for human leishmaniasis, mainly because of the lack of appropriate adjuvants. This study aimed to evaluate in mice the capacity of a mixture of monophosphoryl lipid A (MPLA) and AddaVax adjuvants in enhancing the efficacy of a Leishvacin-like vaccine comprised of whole antigens (LaAg). For that, mice were immunized with LaAg plus MPLA/AddaVax by the intramuscular route (i.m.) prior to challenge with 2 × 10 and 2 × 10 living parasites. Immunization with LaAg alone reduced the lesion growth of the 2 × 10-challenged mice only in the peak of infection, but that was not accompanied by reduced parasite load, and thus not considered protective. Mice given a 2 × 10 -challenge were not protected by LaAg. The association of LaAg with MPLA/AddaVax was able to enhance the cutaneous hypersensitivity response compared with LaAg alone. Despite this, there was no difference in proliferative cell response to antigen ex vivo. Moreover, regardless of the parasite challenge, association of LaAg with MPL/AddaVax did not significantly enhance protection in comparison with LaAg alone. This work demonstrated that MPL/AddaVax is not effective in improving the efficacy of i.m. LaAg vaccine against cutaneous leishmaniasis.