LEISHMANIA PIFANOI AMASTIGOTE ANTIGEN P-4 - EPITOPES INVOLVED IN T-CELL RESPONSIVENESS IN HUMAN CUTANEOUS LEISHMANIASIS

In experimental murine cutaneous leishmaniasis, the purified Leishmani a pifanoi amastigote protein P-4 has been shown to induce significant protection against infection. Further, recent studies examining the re sponse of peripheral blood mononuclear cells (PBMC); from Leishmania b raziliensis-infected human patients have demonstrated that the P-4 pro tein selectively elicits a significant T(H)1-like response. Because a T(H)1-like response is associated with cure, epitope studies were cond ucted to further evaluate the human response to P-4. PBMC from confirm ed cutaneous leishmaniasis patients infected with L. braziliensis in R io de Janeiro, Brazil, an area where the disease is endemic, were exam ined for T-cell proliferation and/or cytokine production in response t o whole-parasite homogenate, isolated P-4 protein, and/or P-4 peptides . Twenty of the 22 patients (91%) examined responded to the native P-4 protein by proliferation and/or gamma interferon (IFN-gamma) producti on. According to the proliferation data, PBMC from 14 patients (64%) w ere found to respond to the intact P-4 proteid (stimulation index of g reater than or equal to 2.5). Fifty-seven percent of the P-4-responsiv e patients studied responded to at least one of the P-4 peptides; 11. individual peptides were found to elicit a proliferative response. Of 17 patients examined for cytokine production, no PBMC produced detecta ble interleukin il in response to P-4 protein or peptides. However, PB MC from 14 patients (82%) produced significant levels of IFN-gamma (gr eater than or equal to 20 pg/ml) in response to native P-4 protein. Ni neteen of the 23 peptides mere found to elicit an IFN-gamma response f rom at least two patients. These data indicate that multiple epitopes spanning the entire P-4 molecule are responsible for the T(H)1-like im mune response observed, indicating that the intact P-4 amastigote mole cule, rather than selected peptides, may prove to be the most useful f or leishmaniasis vaccine development.