Studies on the immunogenicity and protective efficacy of some leishmania vaccine formulations with various adjuvants against murine visceral leishmaniasis

Abstract

Infectious diseases poses risk to humankind and kills millions of people on the earth. Leishmaniasis is also an infectious disease that infects people in different clinical forms. The causative agent of leishmaniasis is protozoan parasite belonging to genus Leishmania. Limited options of treatment against leishmanial infection i.e. only chemotherapies are associated with serious side effects, high cost, and emerging drug resistance. Moreover, no human vaccine is accessible against leishmaniasis. Therefore the current study was planned to assess the efficacy of various vaccine formulations against visceral leishmaniasis caused by L. donovani. Three antigens (heatkilled, formalin-killed, and exosomal) were prepared and used either alone or with adjuvant (AddaVax/gardiquimod/Montanide ISA 201/propolis). The three immunizations were given to BALB/c mice followed by challenge infection and assessment of vaccine efficacy was done at different time points. The cell mediated and humoral immune responses were assessed in addition to parasite burden and levels of effect or molecules. The results of the study showed the efficacy of tested vaccine having antigen alone which were enhanced upon the use of adjuvant. The cell-meditated (DTH and Th1 cytokines) and humoral (IgG2a antibody) immune responses were enhanced in immunized mice after all time points. The most efficacious antigen was heat-killed with no significant difference with formalin-killed antigen. The adjuvants enhanced the vaccine efficacy to the maximum were propolis and Montanide with no significant difference between these two. These vaccines have prospects to be developed as vaccines against leishmanial infection as these generated Th1 protective immune response in mice. newline