ABSTRACT
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.
Subject(s)
Cysteine Endopeptidases/analysis , Leishmania/isolation & purification , Leishmaniasis/parasitology , Leucine/analogs & derivatives , Animals , Cells, Cultured , Electrophoresis, Polyacrylamide Gel , Female , Leishmania/drug effects , Leishmania/enzymology , Leishmania/ultrastructure , Leucine/pharmacology , Macrophages/parasitology , Male , Mice , Mice, Inbred BALB C , Microscopy, ElectronABSTRACT
Immunoglobulins (Igs) reacting against endothelial and vascular structures and striated muscle cells as well as against cells from a peripheral nerve were detected by indirect immunofluorescent test (IIF) in a rhesus monkey infected for 29 yr with Trypanosoma cruzi. Anti-T. cruzi antibodies in this monkey showed a titer of 1:128 in the IIF test and the direct agglutination test. Tissue-reacting Igs were bound in vivo to the tissues, as was established by direct treatment of a biopsy of the deltoid muscle with Ig-labeled antisera. Electron microscopy of this tissue showed that Igs reacted with the plasma membrane of the muscle cells. Neither tissue-reacting Igs nor specific antibodies were detected in three uninfected adult monkeys.