Cell-mediated responses and protection elicited by a carbohydrate-lipid-containing fraction extracted from Leishmania major promastigotes.

Carbohydrate-lipid-containing fractions (CLF) extracted from Leishmania major promastigotes and recognized by sera from immune but not from normal human donors were evaluated for their capacity to elicit cell-mediated responses. It was found that one of these fractions, CLF-1, stimulated the in vitro response of lymphocytes from immune but not from normal human donors. A similarly extracted fraction from L. donovani parasites also elicited an in vitro response by cells from donors immune to L. major. The response was mediated by antigen-presenting cells, and specific Leu 3+ Leu 2- T cells from a human T-cell line responded to the antigen. In vivo, the CLF-1 elicited delayed-type hypersensitivity (DTH) response in L. major-immunized C3H mice, which was comparable to the DTH response elicited by freeze-thawed and sonicated L. major promastigotes. C3H mice were vaccinated with CLF-1 prior to challenge with live L. major promastigotes. Mice vaccinated with CLF-1-containing liposomes showed a significant degree of protection to challenge. These results suggest that the carbohydrate-lipid-containing fraction described here may represent a functional antigenic entity from Leishmania parasites.