Viscerotropic Leishmania tropical: transformation to amastigotes in cell-free media

Promastigotes of a viscerotropic Leishmania tropica strain, originally isolated from a U.S. veteran returning from the Gulf War, was studied for extracellular transformation to amastigotes. Promastigotes were grown in three different media namely, Schneider's Drosophila, Dulbecco's modified Eagle Medium (D-MEM) and RPMI-1640. For each medium the effect of low pH (5.8), elevated temperature (34 degrees C) and the effect of both conditions combined were compared. Cells were counted and examined for morphological changes daily. Transformation to morphologically typical amastigotes occurred in D-MEM and Schneider's media at each of the three different experimental conditions with maximum transformation occurring on day eight in D-MEM maintained at pH 5.8 and 34 degrees C. Complete transformation was not achieved in RPMI-1640 under any of the experimental conditions described. Transformed amastigotes could successfully infect murine macrophages indicating biological competence. Amastigotes could not be propagated under any of the conditions described herein.