In vitro stimulation of metacyclogenesis in Leishmania braziliensis, L. donovani, L. major and L. mexicana
Promastigotes of Leishmania braziliensis, L. donovani, L. major and L. mexicana recently derived from tissue amastigotes were cultured in Schneider's Drosophila medium supplemented with 20% (v/v) heat-inactivated foetal calf serum and 25 μg gentamicin sulfate/ml at pH 5·5. These cultures produced more metacyclic promastigotes in their stationary-phase populations than others cultured at pH 7·0. Metacyclic promastigotes possessed a short ([less-than-or-eq, slant]8 μm) and narrow ([less-than-or-eq, slant]1·5 μm) cell body with a flagellum twice or more the length of the cell body. Promastigotes from acidic cultures were more resistant to complement-mediated lysis and more infective in vivo than those grown at neutral pH. These results demonstrate that induction of metacyclogenesis by acidic pH is a response conserved across a variety of species of Leishmania.(Received July 28 1997)
(Revised November 1 1997)
(Accepted November 11 1997)
Key Words: Leishmania spp.; promastigote; metacyclic; culture; infectivity; differentiation.
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