The Journal of Experimental Medicine
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© The Rockefeller University Press, 0022-1007/1998/8/725/ $5.00
The Journal of Experimental Medicine, Volume 188, Number 4, August 17, 1998 725-734

Articles

Cysteine Protease Inhibitors Cure an Experimental Trypanosoma cruzi Infection

Juan C. Engel*, Patricia S. Doyle*, Ivy Hsieh*, and James H. McKerrow*,{ddagger}

From the * Department of Pathology and the {ddagger} Department of Pharmaceutical Chemistry, University of California San Francisco, California 94143

Trypanosoma cruzi is the causative agent of Chagas' disease. The major protease, cruzain, is a target for the development of new chemotherapy. We report the first successful treatment of an animal model of Chagas' disease with inhibitors designed to inactivate cruzain. Treatment with fluoromethyl ketone–derivatized pseudopeptides rescued mice from lethal infection. The optimal pseudopeptide scaffold was phenylalanine-homophenylalanine. To achieve cure of infection, this pseudopeptide scaffold was incorporated in a less toxic vinyl sulfone derivative. N-methyl piperazine-Phe-homoPhe-vinyl sulfone phenyl also rescued mice from a lethal infection. Six of the treated mice survived over nine months, three without further treatment. Three mice that had entered the chronic stage of infection were retreated with a 20-d regimen. At the conclusion of the experiments, five of the six mice had repeated negative hemacultures, indicative of parasitological cure. Studies of the effect of inhibitors on the intracellular amastigote form suggest that the life cycle is interrupted because of inhibitor arrest of normal autoproteolytic cruzain processing at the level of the Golgi complex. Parasites recovered from the hearts of treated mice showed the same abnormalities as those treated in vitro. No abnormalities were noted in the Golgi complex of host cells. This study provides proof of concept that cysteine protease inhibitors can be given at therapeutic doses to animals to selectively arrest a parasitic infection.

Key Words: Chagas' disease • Trypanosoma cruzi • cysteine protease • drug design • protease inhibitors

Address correspondence to James H. McKerrow or Juan C. Engel, Tropical Disease Research Unit, 4150 Clement St., 113B, San Francisco, California 94121. Phone: 415-221-4810, ext. 2625; Fax: 415-750-6947; E-mail: jmck{at}socrates.ucsf.edu or jcengel{at}itsa.ucsf.edu

This research was supported by grants from the National Institutes of Health (AI35707-1) and the American Heart Association (no. 93015380). J.H. McKerrow is a Burroughs Wellcome Molecular Parasitology Scholar.

Abbreviations used: Boc, butyloxycarbonyl; Bsn, benzyl succinic acid; CPI, cysteine protease inhibitors; F, phenylalanine; FMK, fluoromethyl ketone; hF, homophenylalanine; Mu, morpholine urea; Obzl, O-benzyl; Pip, piperazine; tic, tetrahydroisoquinoline 3-carboxylic acid; VAmBzl, valine acetamidomethylbenzyl; VS, vinyl sulfone; VS{varphi}, vinyl sulfone phenyl; Yii, diiodo tyrosine; Z, benzyloxycarbonyl; p.o., per oral.


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