Identification of cell surface carbohydrate and antigenic changes between noninfective and infective developmental stages of Leishmania major promastigotes.

Differentiation of Leishmania major promastigotes from a noninfective to an infective stage has been demonstrated for promastigotes growing within axenic culture and within the sandfly vector. We have been attempting to identify specific biochemical or antigenic changes that are associated with the development of infective-stage promastigotes. In this report we demonstrate that during growth, cultured L. major promastigotes undergo selective changes in surface carbohydrates, determined by their agglutination by plant lectins. Thus, although all promastigotes from logarithmic (log)-phase cultures were agglutinated by the two-D-galactose-binding lectins, peanut agglutinin (PNA) and Ricinus communis, identical concentrations of these lectins failed to agglutinate approximately 50% of L. major promastigotes from the stationary-phase cultures. These changes in lectin-agglutinating properties are consistent with the fact that log-phase promastigotes represent a homogeneous population of noninfective parasites, whereas up to 50% of the stationary-phase organisms appear to be transformed into infective-stage promastigotes, as determined by their ability to survive within normal resident mouse peritoneal macrophages in vitro. The identities of the populations defined by infectivity and PNA agglutination were confirmed by the purification of PNA-unagglutinated promastigotes from stationary-phase cultures, which demonstrated that 100% of these promastigotes were able to establish intracellular infections. Lectin-purified, infective-stage promastigotes from the stationary phase were compared with noninfective promastigotes from the log phase for the purpose of identifying stage-specific antigens. On the basis of Western blot analysis and the immunoprecipitation of surface-labeled organisms, we have identified an antigen of roughly 116,000 Mr that is expressed on the surface of infective but not noninfective promastigotes.