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Intracellular differentiation of Leishmania amazonensis promastigotes to amastigotes: presence of megasomes, cysteine proteinase activity and susceptibility to leucine-methyl ester

Published online by Cambridge University Press:  06 April 2009

L. Galvao-Quintao ,
S. C. Alfieri ,
A. Ryter  and
M. Rabinovitch
L. Galvao-Quintao
Affiliation:
Unité d’ Immunoparasitologie, Institut Pasteur et CNRS (URA 361)
S. C. Alfieri
Affiliation:
Unité d’ Immunoparasitologie, Institut Pasteur et CNRS (URA 361)
A. Ryter
Affiliation:
Unité de Microscopie électronique, Institut Pasteur et CNRS (URA 1148), 25 rue du Dr Roux, 75724 Paris Cedex 15, France
M. Rabinovitch
Affiliation:
Unité d’ Immunoparasitologie, Institut Pasteur et CNRS (URA 361)
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Summary

Intracellular differentiation of Leishmania promastigotes to amastigotes is a critical step in the establishment of infection. In this report three related features of mexicana subspecies amastigotes were used to follow the differentiation of the parasites within macrophages. Early after infection, (a) parasites did not contain ultrastructurally recognizable megasomes, (b) cysteine proteinase activity of parasite lysates was not detected in gelatin-containing acrylamide gels, and (c) parasites were essentially resistant to L-leucine-methyl ester (Leu-OMe). Typical megasomes were first identified on the 5th day, were more prevalent on day 7, and underwent swelling in macrophages exposed to Leu-OMe. Cysteine proteinase activity was first detected on day 3 and increased thereafter. Susceptibility to Leu-OMe of parasites studied in situ or isolated from infected macrophages increased with time of intracellular residence and by 7 days approached that of amastigotes isolated from mouse lesions. In contrast, parasites derived from either promastigotes or amastigotes were equally susceptible to another leishmanicidal compound, tryptophanamide (Trp-NH2). The results provide additional support for the involvement of megasomes and their cysteine proteinases in parasite killing by Leu-OMe, and highlight the slow pace of the intracellular differentiation of L. amazonensis promastigotes to amastigotes.

Keywords

Leishmania amazonensismegasomecysteine proteinasesleucine-methyl ester
Type
Research Article
Information
Parasitology , Volume 101 , Issue 1 , August 1990 , pp. 7 - 13
Copyright
Copyright © Cambridge University Press 1990

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