A RECOMBINANT LEISHMANIA ANTIGEN THAT STIMULATES HUMAN PERIPHERAL-BLOOD MONONUCLEAR-CELLS TO EXPRESS A TH1-TYPE CYTOKINE PROFILE AND TO PRODUCE INTERLEUKIN-12

Leishmania braziliensis causes cutaneous and mucosal leishmaniasis in humans. Most patients with cutaneous leishmaniasis heal spontaneously and may therefore have developed protective immunity. There appears to be a mixed cytokine profile associated with active cutaneous or mucos al disease, and a dominant T helper (Th)1-type response associated wit h healing. Leishmanial antigens that elicit these potent proliferative and cytokine responses from peripheral blood mononuclear cells (PBMC) are now being identified. Herein, we report on the cloning and expres sion of a L. braziliensis gene homologous to the eukaryotic ribosomal protein eIF4A (LeIF) and patient PBMC responses to rLeIF. Patients wit h mucosal and self-healing cutaneous disease had significantly higher proliferative responses than those with cutaneous lesions. Whereas the parasite lysate stimulated patient PBMC to produce a mixed Th1/Th2-ty pe cytokine profile, LeIF stimulated the production of interferon gamm a (IFN-gamma), interleukin 2 (IL-2), and tumor necrosis factor alpha b ut not IL-4 or IL-10. Recombinant LeIF (rLeIF) downregulated both IL-1 0 mRNA in the ''resting'' PBMC of leishmaniasis patients and LPS-induc ed IL-10 production by patient PBMC, rLeIF also stimulated the product ion of IL-12 in cultured PBMC from both patients and uninfected indivi duals. The production of IFN-gamma by patient PBMC stimulated with eit her rLeIF or parasite lysate was IL-12 dependent, whereas anti-IFN-gam ma monoclonal antibody only partially blocked the LeIF-induced product ion of IL-12. In vitro production of both IFN-gamma and IL-12 was abro gated by exogenous human recombinant IL-10. Therefore, we have identif ied a recombinant leishmanial antigen that elicits IL-12 production an d Th1-type responses in patients as well as IL-12 production in normal human PBMC.