IL-10- and TGF-β-Mediated Susceptibility in Kala-azar and Post-kala-azar Dermal Leishmaniasis: The Significance of Amphotericin B in the Control of Leishmania donovani Infection in India

Visceral leishmaniasis (VL) or kala-azar is known to be associated with a mixed Th1-Th2 response, and effective host defense requires the induction of IFN-γ and IL-12. We address the role of the differential decline of IL-10 and TGF-β in response to sodium antimony gluconate (SAG) and amphotericin B (AmB), the therapeutic success of SAG and AmB in Indian VL, and the significance of IL-10 and TGF-β in the development and progression of post-kazla-azar dermal leishmaniasis (PKDL). In the active disease, PBMC from VL patients showed suppressed Ag-specific lymphoproliferation, IFN-γ and IL-12 production, and elevation of IL-10 and TGF-β. Cure corresponded with an elevation in IFN-γ and IL-12 production and down-regulation of IL-10 and TGF-β. Both CD4 + and CD8 + T cells were involved in IFN-γ and IL-10 production. Interestingly, the retention and maintenance of residual IL-10 and TGF-β in some SAG-treated individuals and the elevation of IL-10 and TGF-β in PKDL, a sequel to kala-azar, probably reflects the role of these cytokines in reactivation of the disease in the form of PKDL. Contrastingly, AmB treatment of VL resulted in negligible TGF-β levels and absolute elimination of IL-10, reflecting the better therapeutic activity of AmB and its probable role in the recent decline in PKDL occurrences in India. Moreover, elucidation of immune responses in Indian PKDL patients revealed a spectral pattern of disease progression where disease severity could be correlated inversely with lymphoproliferation and directly with TGF-β, IL-10, and Ab production. In addition, the enhancement of CD4 + CD25 + T cells in active VL, their decline at cure, and reactivation in PKDL suggest their probable immunosuppressive role in these disease forms.