A recombinant Leishmania antigen that stimulates human peripheral blood mononuclear cells to express a Th1-type cytokine profile and to produce interleukin 12.

Abstract

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 mucosal disease, and a dominant T helper (Th)1-type response associated with 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 expression of a L. braziliensis gene homologous to the eukaryotic ribosomal protein eIF4A (LeIF) and patient PBMC responses to rLeIF. Patients with 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-type cytokine profile, LeIF stimulated the production of interferon gamma (IFN-gamma), interleukin 2 (IL-2), and tumor necrosis factor alpha but not IL-4 or IL-10. Recombinant LeIF (rLeIF) downregulated both IL-10 mRNA in the "resting" PBMC of leishmaniasis patients and LPS-induced IL-10 production by patient PBMC. rLeIF also stimulated the production of IL-12 in cultured PBMC from both patients and uninfected individuals. The production of IFN-gamma by patient PBMC stimulated with either rLeIF or parasite lysate was IL-12 dependent, whereas anti-IFN-gamma monoclonal antibody only partially blocked the LeIF-induced production of IL-12. In vitro production of both IFN-gamma and IL-12 was abrogated by exogenous human recombinant IL-10. Therefore, we have identified a recombinant leishmanial antigen that elicits IL-12 production and Th1-type responses in patients as well as IL-12 production in normal human PBMC.

Immunogenicity in dogs of three recombinant antigens (TSA, LeIF and LmSTI1) potential vaccine candidates for canine visceral leishmaniasis

“…These antigens have been successfully shown to induce an excellent protection against cutaneous leishmaniasis in the murine and non-human primate models [9,30,41] and currently are been tested in Phase I/II human vaccine clinical trials. Because these antigens are highly conserved among the Leishmania species and are expressed in both the amastigote and the promastigote forms of the parasites [39,40,46], they could be useful as a component of a panLeishmania vaccine [20]. Despite the possibility that a single antigen could by itself induce good protection, we chose to test a mixture of these three proteins because a cocktail of several antigens is conceivably a better vaccine for both prophylactic and therapeutic applications because a vaccine containing a broader range of protective epitopes is unlikely to suffer from MHC related unresponsiveness in a heterogeneous population.…”

“…Over the past years, several Leishmania recombinant antigens have been identified and demonstrated to have promising vaccine potential to cutaneous leishmaniasis [39,[44][45][46]. Three highly conserved antigens among the Leishmania genus, TSA, LmSTI1 and LeIF, have been shown to induce excellent protection in both the murine and non-human primate models of the human disease [8,41].…”

Immunization with a Recombinant Stage-Regulated Surface Protein fromLeishmania donovaniInduces Protection Against Visceral Leishmaniasis

“…However, rapid decay in IL-12 production, reaching baseline levels within 24 h of STAg administration, results from the induction of a state of DC paralysis, rather than death (38). Among leishmanial Ags, LeIF has been shown to be a potent inducer of IL-12 from monocyte-derived human DC (39) and from murine macrophages (40) in vitro. It remains to be determined whether LeIF directly stimulates murine DC, either in vitro or in vivo.…”

Dendritic Cell (DC)-Based Protection Against an Intracellular Pathogen Is Dependent Upon DC-Derived IL-12 and Can Be Induced by Molecularly Defined Antigens

“…The intriguing properties of the Leishmania protein LeIF, which has been shown to be a potent stimulator of the innate immune system (43) and to elicit IL-12 production and Th1-type responses in PBMC from leishmaniasis patients (24), prompted us to explore the efficacy of this Ag in inducing protective immunity to L. major infection upon delivery by DC. For this purpose, the N-terminal half of LeIF (aa 1-226), which is known to contain the IL-12/IFN-␥-inducing regions of the molecule (37), was expressed as recombinant protein in E. coli and purified by affinity chromatography using the Ni-NTA matrix.…”

“…The Leishmania homolog of receptor for activated C kinase (LACK) is a highly conserved intracellular protein that has been shown to play an important role in the immunopathogenesis of experimental L. major infections (21,22), and vaccination with DNA encoding LACK induces protection against a challenge with parasites (23). Leishmania homolog of eukaryotic ribosomal elongation and initiation factor 4a (LeIF) is a Leishmania protein that elicits IL-12 production and a Th1 response of human PBMCs (24). The protective Leishmania surface protease gp63 (25) has been implicated in infectivity and intracellular survival of the parasites (26).…”