Infectivity of Aflagellar Epimastigotes of Trypanosoma caninum in the DH82 Cell Line and Mouse Peritoneal Macrophages.

Background: Trypanosoma caninum presents aflagellar and flagellar epimastigote, trypomastigote, and spheromastigote forms in axenic cultures. Attempts to utilize trypomastigote forms of T. caninum to develop in vitro and in vivo infection models have failed. To investigate the infection potential of aflagellar epimastigotes, T. caninum interaction studies were performed using DH82 cells and BALB/c mouse peritoneal macrophages in Dulbecco's modified Eagle medium (DMEM)/F-12 medium supplemented with fetal bovine serum and bovine serum albumin. Light-field microscopy, scanning electron microscopy, and transmission electron microscopy were used to analyze these interactions. Regarding T. caninum-macrophage interactions, the following previously unseen results were obtained: (1) the aflagellar epimastigote form of T. caninum infects macrophages, and (2) T. caninum epimastigotes transformed into amastigotes inside macrophages. Aflagellar epimastigotes were seen adhering to and entering macrophages and differentiating to the amastigote form; amastigotes proliferated within the parasitophorous vacuole in macrophages after 15 min. At the final time point (48 h), there were few macrophages arranged on the coverslips, but interacting with free amastigotes of T. caninum, while some of the parasites changed to the flagellar epimastigote form. Considering the lack of information on T. caninum and its importance in public health, this study provides new insights into the biological cycle of T. caninum and parasite-host relationships.