Abstract
BackgroundCutaneous leishmaniasis due to L. braziliensis (CL) is characterized by a positive delayed type hypersensitivity test (DTH) leishmania skin test (LST) and high IFN-γ production to soluble leishmania antigen (SLA). The LST is used for diagnosis of CL and for identification of individuals exposed to leishmania infection but without disease. The main aim of the present study was to identify markers of exposure to L. braziliensis infection.Methodolgy/Principal FindingsThis cohort study enrolled 308 household contacts (HC) of 76 CL index cases. HC had no active or past history of leishmaniasis. For the present cross-sectional study cytokines and chemokines were determined in supernatants of whole blood culture stimulated with SLA. Of the 308 HC, 36 (11.7%) had a positive LST but in these IFN-γ was only detected in 22 (61.1%). Moreover of the 40 HC with evidence of IFN-γ production only 22 (55%) had a positive LST. A total of 54 (17.5%) of 308 HC had specific immune response to SLA. Only a moderate agreement (Kappa = 0.52; 95% CI: 0.36–0.66) was found between LST and IFN-γ production. Moreover while enhancement of CXCL10 in cultures stimulated with SLA was observed in HC with DTH+ and IFN-γ+ and in patients with IFN-γ+ and DTH−, no enhancement of this chemokine was observed in supernatants of cells of HC with DTH+ and IFN-γ−.Conclusions/SignificanceThis study shows that in addition of LST, the evaluation of antigen specific IFN-γ production should be performed to determine evidence of exposure to leishmania infection. Moreover it suggests that in some HC production of IFN-γ and CXCL10 are performed by cells not involved with DTH reaction.
Highlights
American tegumentary leishmaniasis (ATL) is caused predominantly by Leishmania braziliensis, L. guaynensis, L. mexicana and L. amazonensis [1,2]
One striking observation was that while CXCL10 production was detected in soluble leishmania antigen (SLA) stimulated cultures of household contacts (HC) with a negative leishmania skin test (LST) but producers of IFN-c, absence or very low production of CXCL10 was observed in SLA stimulated cultures of individuals who, despite having a positive delayed type hypersensitivity test (DTH), had an absence of IFN-c production to SLA
The documentation of a positive LST in the absence of current or past history of cutaneous leishmaniasis (CL) is the only test that has been used to identify individuals who have a subclinical form of L. braziliensis infection [6,7]
Summary
American tegumentary leishmaniasis (ATL) is caused predominantly by Leishmania braziliensis, L. guaynensis, L. mexicana and L. amazonensis [1,2]. A concordance between DTH and in vitro tests of cell mediated immune response is expected, discordant results between IFN-c production and tuberculin skin test (TST) have been shown in individuals with latent tuberculosis [8,9,10]. Cutaneous leishmaniasis due to L. braziliensis (CL) is characterized by a positive delayed type hypersensitivity test (DTH) leishmania skin test (LST) and high IFN-c production to soluble leishmania antigen (SLA). While enhancement of CXCL10 in cultures stimulated with SLA was observed in HC with DTH+ and IFN-c+ and in patients with IFN-c+ and DTH2, no enhancement of this chemokine was observed in supernatants of cells of HC with DTH+ and IFN-c2
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