Differential sensitivity of New World Leishmania spp. promastigotes to complement-mediated lysis: correlation with the expression of three parasite polypeptides.

American tegumentary leishmaniasis is caused by Leishmania of the subgenera Leishmania and Viannia. In this paper, we demonstrate that promastigotes of these two subgenera display distinct characteristic patterns of complement sensitivity during growth in vitro. Using fresh normal human serum in lytic assays, we show that while promastigotes of two species of the subgenus Leishmania differentiate into forms that are more resistant to the lytic action of complement, promastigotes of three species of the subgenus Viannia remain sensitive to complement mediated lysis during all stages of their growth in vitro. Complement resistance of the subgenus Leishmania is temporary, reaching its peak at the beginning of the stationary phase of growth, and decreasing thereafter. By sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) we detected in L. amazonensis (subgenus Leishmania), but not in L. guyanensis (subgenus Viannia), three polypeptides whose expression parallels the resistance of promastigotes to complement-mediated lysis.