FOXP3 and visceral leishmaniasis: CBA, cytometric bead array; CD, cluster of differentiation; CL, cutaneous leishmaniasis; CTLA-4, cytotoxic T-lymphocyte-associated protein 4; ELISA, enzyme-linked immunosorbent assay; Foxp3, forkhead box protein P3; IL, interleukin; IFN, interferon; NASBA, nucleic acid sequence-based amplification; PKDL, post kala-azar dermal leishmaniasis; RT-PCR, real-time polymerase chain reaction; VL, visceral leishmaniasis; TGF, transforming growth factor TNF, tumor necrosis factor.