The interaction of Leishmania donovani promastigotes and human fibroblasts in vitro
Schwartzman, J.D.; Pearson, R.D.
American Journal of Tropical Medicine and Hygiene 34(5): 850-855
1985
ISSN/ISBN: 0002-9637 PMID: 4037177 Document Number: 257905
L. donovani promastigotes derived from infected hamster spleens, in either log phase or stationary phase growth, associated with human foreskin fibroblasts in vitro and assumed the morphological characteristics of amastigotes. This apparent conversion was noted within hours at 26 degrees C, 32 degrees C or 37 degrees C; in the continued presence of promastigotes, increasing numbers of amastigote-like forms were seen for 2 weeks at 26 degrees C or 32 degrees C. At 37 degrees C amastigote-like forms declined sharply after 6 days. Multiplication of amastigote-like forms was not observed at any temperature, this was also true of freshly isolated amastigotes from hamster spleens which associated with fibroblasts but did not multiply. Approximately 0.1% of promastigotes appeared to convert per day. Amastigote-like forms were seen within fibroblasts by transmission electron microscopy, surrounded by a closely applied host membrane. Scanning electron microscopy showed promastigotes with their flagellae under or within fibroblasts, but phagocytosis was not observed. These experiments suggest that the conditions required for promastigote-to-amastigote conversion may be different from those required for amastigote multiplication, and the mammalian core body temperature may not be required for promastigote conversion. Leishmania donovani (Sudan III strain) promastigotes, from the logarithmic or stationary phase of cultures, were observed to associate with human foreskin fibroblasts in vitro. The transformation of associated promastigotes to an amastigote-like form occurred within a period of hours at 26, 32 or 37 degrees C. Electron microscopy showed the intracellular position of some amastigotes, surrounded by a host cell-derived membrane, but phagocytosis was not observed. An increase in the numbers of amastigote-like forms was seen at 26 and 32 degrees C for 2 weeks but the number of these forms declined after 6 days at 37 degrees C. There was no evidence of multiplication of these amastigotes.S.L. Croft.