Mononuclear cells from patients recovered from cutaneous leishmaniasis respond to Leishmania major amastigote class I nuclease with a predominant Th1-like response.

The Leishmania major amastigote class I nuclease (LmaCIN) is a developmentally regulated protein that is highly expressed in the amastigote stage of L. major. This protein is homologous to the P4 nuclease of L. pifanoi, which has been shown to induce protective immune response in a murine model. To evaluate LmaCIN as a potential human vaccine candidate, cellular immune responses to recombinant LmaCIN were examined in individuals recovered from Old World cutaneous leishmaniasis. Peripheral blood mononuclear cells (PBMC) from patients recovered from L. major infection were cultured either with recombinant LmaCIN or autoclaved L. major (ALM) as control. rLmaCIN induced significant proliferation of PBMC from 90% of recovered patients. Phenotypic analysis of proliferating cells showed that CD8(+) cells were the predominant cell type proliferating in response to rLmaC1N. Screening of culture supernatants for cytokines showed that rLmaCIN induced high levels of interferon (IFN)-gamma (mean +/- s.e.m.: 1398 +/- 179 pg/ml) associated with little interleukin (IL)-10 and little or no IL-5 production. These findings show that LmaCIN is immunogenic in humans during L. major infection and that it can elicit immunological responses relevant to immunoprophylaxis of leishmaniasis.