Flow cytometric detection of Leishmania parasites in human monocyte-derived macrophages: Application to antileishmanial-drug testing

A flow cytometric technique was developed for detection of amastigotes of t he protozoan Leishmania infantum in human nonadherent monocyte-derived macr ophages. The cells were fixed and permeabilized with paraformaldehyde-ethan ol, and intracellular amastigotes were labeled with Leishmania lipophosphog lycan-specific monoclonal antibody, Results showed that flow cytometry prov ided accurate quantification of the infection rates in human macrophages co mpared to the rates obtained by the conventional microscopic technique, wit h the advantage that a large number of cells could be analyzed rapidly. The results demonstrated, moreover, that labeling of intracellular amastigotes could reliably be used to evaluate the antileishmanial activities of conve ntional drugs such as meglumine antimoniate, amphotericin B, pentamidine, a nd allopurinol. They also established that various Leishmania species (L. m exicana, L, donovani) could be detected by this technique In other host-cel l models such as mouse peritoneal macrophages and suggested that the flow c ytometric method could be a valid alternative to the conventional method.