EVIDENCE THAT TRYPANOTHIONE REDUCTASE IS AN ESSENTIAL ENZYME IN LEISHMANIA BY TARGETED REPLACEMENT OF THE TRYA GENE LOCUS

Trypanothione reductase (TR), a flavoprotein oxidoreductase central to the unique thiol-redox system that operates in trypanosomatid protozo a, has been proposed as a potential target for the chemotherapy of try panosomatid infections, In this study, targeted gene replacement Was u sed to obtain evidence that TR is an essential cellular component and that its physiological function is crucial for parasite survival. Prec ise replacement of the Leishmania donovani tryA gene encoding TR was o nly possible upon simultaneous expression of the tryA coding region fr om an episome; in its absence, attempted removal of the last tryA alle le invariably led to the generation of an extra copy of tryA, seemingl y as a result of selective chromosomal polysomy. Partial replacement m utants were drastically affected in their ability to survive inside cy tokine-activated macrophages in a murine model of Leishmania infection . As no compensatory mechanism for the partial loss of TR activity was observed in these mutants and as it was not possible to obtain viable Leishmania devoid of TR catalytic activity, specific inhibitors of th is enzyme are likely to be useful anti-leishmanial agents for chemothe rapeutic use.