Diffuse cutaneous leishmaniasis responds to miltefosine but then relapses.

BACKGROUND: Diffuse cutaneous leishmaniasis (DCL), although rare, is profoundly incapacitating. At present there is no successful treatment for this progressive protozoan infection, which is associated with the absence of specific cell-mediated immunity (CMI) to Leishmania. This disease shares features with visceral leishmaniasis (VL), including specific CMI inactivity during active disease and a heavy parasitic burden, but VL responds well to treatment. Miltefosine is the first orally administered drug which has shown efficacy in the treatment of VL; it has not been adequately evaluated in the treatment of DCL. OBJECTIVES: To evaluate the efficacy of miltefosine in the treatment of DCL, using clinical, parasitological, histopathological and immunological criteria. METHODS: Sixteen patients with DCL were treated with miltefosine, 2.0-2.5 mg kg(-1) daily, for variable periods of time (75-218 days). Patients were hospitalized for the first month and evaluated every 2 weeks until the termination of treatment with routine laboratory chemistry, percentage clinical improvement, presence of parasites in skin smears, growth of parasites in culture medium and in hamsters, histopathological characteristics of the granulomas, adverse side-effects, and reactivity to leishmanin skin test antigen. Further cycles of treatment were given in some of these patients, particularly after suspension of treatment was followed by relapse. RESULTS: Patients showed dramatic clinical improvement and reduction in the parasite burden by day 15 after the initiation of treatment, which continued while treatment was maintained. By day 45, 15 patients showed 80-90% clinical improvement. Nevertheless, suspension of treatment was followed by the development of new lesions in all but one patient. Inoculation in hamsters was observed to be the most sensitive technique to detect persisting parasites. Adverse events were very mild. CONCLUSIONS: Miltefosine produced a dramatic clinical and parasitological response in patients with DCL and improvement continued during drug administration, but with a single exception all patients presented new lesions after suspension of treatment. There was no histological or skin test evidence to suggest the development of CMI during treatment, which may be an indispensable criterion for the evaluation of potentially effective drugs against DCL.

Specific inhibitory effect of 3-deazaneplanocin A against several Leishmania mexicana and L. braziliensis strains.

The growth inhibitory effect of 3-deazaneplanocin A (c3NpcA) was tested against some pathogenic members of the family of American Trypanosomatidae. Under our culture conditions, c3NpcA displayed a strongly and uniformly leishmanistatic effect on all 23 American Leishmania (L. mexicana and L. brasiliensis) strains in the study (mean dose producing 50% inhibition compared with control parasite growth [ID50] = 96 ng/ml, 0.32 microM), but showed no inhibition against the several T. cruzi and T. rangeli strains tested with concentrations up to 10,000 ng/ml. This compound also induced a substantial expansion of the intracellular pools of both S-adenosylhomocysteine (AdoHcy) and S-adenosylmethionine (AdoMet), as well as a significant diminution of the AdoMet:AdoHcy ratio. Strong AdoHcy hydrolase activity was detected in American Leishmania promastigotes. At at a dose of 200 ng/ml, c3NpcA inhibited S-adenosyl-L-3H-methylmethionine and 3-thymidine incorporation by promastigotes after four days incubation in the presence of the drug. At a dose of 100 ng/ml, c3NpcA eliminated approximately 56% of the L. mexicana and L. brasiliensis from infected human macrophages, compared with simultaneously cultivated controls. Two schedules of 10 consecutive intraperitoneal injections of c3NpcA, with doses ranging from 0.5 to 1.5 mg/kg/day, significantly reduced development of cutaneous leishmanial infection produced in inbred BALB/c mice by L. b. guyanensis inoculation, although a few parasites remained at the inoculation site.

Uptake and metabolism of S-adenosyl-L-methionine by Leishmania mexicana and Leishmania braziliensis promastigotes.

Promastigotes of Leishmania mexicana and Leishmania braziliensis incorporate S-adenosyl-L-[3H-methyl]methionine (AdoMet) against a concentration gradient through a saturable system. This concentrative uptake requires metabolic energy and is sensitive to temperature and sulfhydryl reagents such as N-ethyl maleimide. Intracellular AdoMet exchanges with external AdoMet. At steady state, unaltered ADoMet in the intracellular pool is at about a 1800-fold concentration in relation to that found in the external medium. Glucose, galactose and ribose did not stimulate uptake rates. Incorporated AdoMet goes into the soluble AdoMet pool, where a small fraction is metabolized, chiefly into methylthioadenosine, decarboxylated AdoMet and methanol. After a 60 min pulse the radioactivity associated with the [3H]AdoMet incorporated disappears with a half-time of 2 h. Transmethylation reactions were analyzed following [3H]AdoMet incorporation. Fractionation experiments indicate that 45-62% and 30-42% of the radioactivity is incorporated into lipids and protein methyl esters respectively, with 5-14% present in the soluble pool of parasites. Sinefungin or its cyclic derivative (1 and 10 micrograms ml-1) in the incubation medium produces 58% and 64% inhibition of AdoMet incorporation into Leishmania promastigotes. Most transmethylation reactions are inhibited, as there is a 50% decrease in the total radioactivity present in both the base-labile and lipidic fraction, with a parallel increase in the percentage of radioactivity in the soluble pool. Previous results give evidence of the importance of AdoMet in American Leishmania promastigote metabolism.

Inhibitory effects of sinefungin and its cyclic analog on the multiplication of Trypanosoma cruzi isolates.

Sinefungin and its cyclic analog were evaluated in vitro for activity against the multiplication of Trypanosoma cruzi. When either drug was tested for eight days on twelve T. cruzi epimastigote isolates, an 800-fold difference in drug sensitivity was found. Both drugs were trypanostatics at a concentration range from 0.1 micrograms/ml to 300 micrograms/ml. The 50% effective concentration (EC50) of sinefungin and its cyclic analog at which the growth of a given isolate was inhibited was 0.38 micrograms/ml for sinefungin and 0.31 micrograms/ml for the cyclic analog against the Ma, Marin, OPS-86, Y, and Ya isolates, and > 300 micrograms/ml for sinefungin and 217 micrograms/ml for the cyclic analog against the A-35, Bertoldo, DS, EP, ES, OPS-58, and FL isolates. Incubation of drug-sensitive isolates for more than 10 days in glucose-saline (GS) medium, but not in minimal essential medium, in the presence of a 30-fold EC50 concentration of the drug induced an increase in the drug-resistant population, which maintained this phenotype for several passages in drug-free culture medium. Growth curves were analyzed as a function of parasite inoculum; it was observed that with sinefungin-sensitive T. cruzi epimastigote isolates grown in GS medium in the presence of 10 micrograms/ml of the drug, the inhibitory effects of the drug were dependent on the initial inoculum: 1 x 10(3)-1 x 10(4) parasites/ml were strongly inhibited even after 16 days. Significant impairment of thymidine incorporation into the DNA of parasites by both drugs was observed only in drug-sensitive epimastigote isolates.(ABSTRACT TRUNCATED AT 250 WORDS)