Morphological changes and serological reactions in cultured Leishmania donovani promastigotes

Promastigotes of Leishmania donovani cultured in liquid media gradually changed from a majority of elongated forms through a predominance of intermediate spindle-shaped parasites to a majority of round forms, often aflagellate. Quantitative and qualitative differences among these subpopulations, separated on Percoll gradients, could be demonstrated when they were run on SDS-PAGE gels and stained from proteins or carbohydrates. When cultures containing a majority of one or other form were used as antigenic substrate in serological tests (ELISA and immunofluorescence) the older, round forms were more highly reactive with patients' sera. These forms may represent different phases of the parasite, related to function, and the density variations would provide a convenient method to separate them.