Leishmania parasite specific CD4 + synergizes and correlates positively with CD8 + T cells in the production of gamma interferon foll owing immunization of the vervet monkey (Chlorocebus aethiops) model

Abstract

Although there is currently no vaccine against leishmaniasis in routine use anywhere in the world, cases of self cure in cutaneous leishmaniasis, accompanied by solid immunity to reinfection, make vaccine development a feasible control method. Immunity against visceral leishmaniasis is mediated by IFN-γ-inducing parasite specific CD4+and CD8+T cells. We assessed the capacity of Leishmania donovanisonicate antigen delivered with alum-BCG (AlBCG), monophosphoryl lipid A (MPL) or montanide ISA 720 (MISA) to induce parasite specific CD4+and CD8+T cells involved in IFN-γ production following immunization of groups of the vervet monkey model of visceral leishmaniasis. Groups of vervet monkeys were immunized intradermally at three time points on days 0, 28 and 42 andTcell populations involved in the production of IFN-γ measured 21 days after final immunization. Significantly higherCD4+T cells were induced in the group immunized with MISA+Ag compared to the AlBCG+Ag immunized animals (P<0.01) with both groups inducing significantly moreCD4+T cells than other groups (P<0.0001). Levels of CD8+T cells were comparable between AlBCG+Ag and MISA+Ag groups, being significantly higher comparedto the MPL+Ag group (P<0.001).The CD4+T cells significantly correlated positively with CD8+T cells in the studied groups (r=1.00; P=0.0167). We conclude that, immunization with MISA+Ag induces robust CD4+as well as CD8+T cells involved in the production of IFN-γ indicating stronger ability of this adjuvant over AlBCG in directing cellular immune response in the vervet monkey model.