Axenic cultivation and characterization ofLeishmania mexicanaamastigote-like forms

Abstract

SUMMARYA new method is described which has made possible the long-term axenic cultivation ofLeishmania mexicanaamastigotelike forms in Schneider'sDrosophilamedium supplemented with 2% (v/v) foetal calf serum. Unlike previous methods, it utilizes direct culture of parasites obtained from the lesions of infected animals rather than adaptation of promastigotesin vitro. Ultrastructural (possession of megasomes), biochemical (cysteine proteinase activity and gelatin SDS-PAGE banding pattern) and infectivity (in vivo) data are presented which show the close similarity of the cultured forms to lesion amastigotes. The axenically cultured forms grew optimally at a temperature of 32–33 °C, providing further evidence for their amastigote nature. It was found that adjustment of the pH of the growth medium to 5·4 was required in order to retain the amastigote morphology of the cultured parasites. This supports the notion that leishmanial amastigotes are acidophiles.