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Objectives: This study was designed to verify the cytotoxic activity of S-nitrosoglutathione (GSNO) against intracellular Leishmania amastigotes and to test its efficacy as a topical treatment of localized cutaneous leishmaniasis (LCL) in Leishmania major- or Leishmania braziliensis-infected mice., Methods: Cytotoxic activity of GSNO was verified in L. major-infected THP-1 macrophages. S-nitrosated proteins were detected by immunofluorescence. Topical treatment was done by daily application of a solution of GSNO in PBS to the skin ulcer of Leishmania-infected mice. BALB/c and interferon-γ-knockout (IFN-γ-KO) C57BL/6 mice were infected with L. major and L. braziliensis, respectively. Ulcer size was measured weekly and the parasite loads were determined in the lesion and lymph nodes. Controls received PBS topically or amphotericin B (AMB) intravenously., Results: The number of intracellular L. major amastigotes was markedly reduced in GSNO-treated cultures; in these, staining for S-nitrosated proteins was present in the cytoplasm and colocalized with intracellular amastigotes. Topical treatment with GSNO of L. major ulcers in BALB/c mice suppressed lesion growth, reduced the parasite load and induced healing comparable to the effect of intravenously administered AMB. Topical GSNO treatment was also efficient at suppressing lesion growth in IFN-γ-KO mice infected with L. braziliensis., Conclusions: GSNO is cytotoxic to intracellular L. major amastigotes in vitro and had a healing effect on LCL caused by L. major and L. braziliensis in mice. These positive results on the topical therapeutic effect of GSNO in mouse leishmaniasis infections provide the experimental basis for a possible future trial in the treatment of human LCL.

Peripheral blood samples of 138 co-habitants from 25 families with recently diagnosed cases of visceral leishmaniasis in the Metropolitan Region of Belo Horizonte, Minas Gerais, Brazil, were analyzed by indirect fluorescent antibody test (IFAT), rK39 and Leishmania chagasi Enzyme Linked Immunosorbent Assay (ELISA), intradermal skin-test and Polymerase Chain Reaction (PCR) over a 12-month period. The cumulative positivity was significantly higher by PCR (29.7%) than by IFAT, rK39 ELISA, L. chagasi ELISA and intradermal skin-test (5.1%, 6.5%, 14.5% and 2.9%, respectively). In addition, the cytokine profile was measured in 16 of the 138 volunteers, of whom eight were asymptomatic carriers and eight were non-infected co-habitants. The innate immunity cells from asymptomatic carriers displayed, upon in vitro antigenic stimulation, a modulated increase in cytokine synthesis that was distinct from that observed in non-infected volunteers. This study suggests that the identification of a large proportion of asymptomatic carriers is facilitated when more than one diagnostic method is applied and that a mixed pattern of immune response is correlated with clinical status of asymptomatic individuals. These observations suggest also that asymptomatic infection by L. chagasi is a frequent event and that control programs could benefit by including this indicator in their interventions.