Physiological and Biochemical Aspects of Leishmania Development
from: Leishmania: After The Genome (Edited by: Peter J. Myler and Nicolas Fasel). Caister Academic Press, U.K. (2008)
Leishmania are obligate intracellular parasitic protozoa that cycle between the midgut of sand flies (the vector) and phagolysosomes of mammalian macrophages (the host). Host invasion involves attachment to macrophages, phagocytosis and development inside phagolysosomes. During the latter phase, promastigotes (the extracellular form) differentiate into amastigotes (the intracellular form), thus adapting to live in the hydrolytic environment of the lysosome. This chapter summarizes current knowledge about how promastigotes differentiate into amastigotes when surrounded by a phagolysosome milieu. In vivo studies indicate that once inside macrophages, promastigotes start to differentiate into amastigotes only when exposed to an acidic environment, which occurs after infected phagosomes fuse with late endosomes. To study in detail the molecular mechanisms underlying Leishmania differentiation, a model system has been developed where the parasites differentiate outside the host. Host-free differentiation is achieved by shifting cultured promastigotes to a lysosome-like environment and has enabled many insights into parasite life inside phagolysosomes. Here we describe how amastigotes were axenized and the resulting information on Leishmania intracellular development read more ...