The in vitro antileishmanial activity of three saponins isolated from ivy, alpha-hederin, beta-hederin and hederacolchiside A(1), was investigated on parasites of the species Leishmania mexicana, in their promastigote and amastigote forms compared with their toxicity versus human monocytes. The results showed that saponins exhibited a strong antiproliferative activity on all stages of development of the parasite but demonstrated a strong toxicity versus human cells. Association of subtoxic concentrations of saponins with antileishmanial drugs such as pentamidine and amphotericin B demonstrated that saponins could enhance the efficiency of conventional drugs on both the promastigote and the amastigote stages of development of the parasite. The results demonstrated moreover that the action of saponins on promastigote membrane was cumulative with those of amphotericin B.

A flow cytometric technique was developed for detection of amastigotes of the protozoan Leishmania infantum in human nonadherent monocyte-derived macrophages. The cells were fixed and permeabilized with paraformaldehyde-ethanol, and intracellular amastigotes were labeled with Leishmania lipophosphoglycan-specific monoclonal antibody. Results showed that flow cytometry provided accurate quantification of the infection rates in human macrophages compared to the rates obtained by the conventional microscopic technique, with the advantage that a large number of cells could be analyzed rapidly. The results demonstrated, moreover, that labeling of intracellular amastigotes could reliably be used to evaluate the antileishmanial activities of conventional drugs such as meglumine antimoniate, amphotericin B, pentamidine, and allopurinol. They also established that various Leishmania species (L. mexicana, L. donovani) could be detected by this technique in other host-cell models such as mouse peritoneal macrophages and suggested that the flow cytometric method could be a valid alternative to the conventional method.Leishmaniases are vector-borne parasitic diseases caused by protozoa of the genus Leishmania. These obligate intracellular parasites replicate in the parasitophorus vacuoles of macrophages (3, 6) and produce life-threatening disorders widely distributed in tropical, subtropical, and Mediterranean countries (Division of Control of Tropical Diseases, World Health Organization, http://www.who.int/ctd/html/leish.html). Several clinical syndromes are subsumed under the term leishmaniasis according to the localization of the parasites in mammalian tissues, notably, visceral, cutaneous, and mucosal leishmaniases. Parasites of the species Leishmania infantum, identified as a causative agent of the visceral form of leishmaniasis, have been shown to be endemic in France (Division of Control of Tropical Diseases, World Health Organization).Since the 1940s, the generally accepted therapy for all forms of leishmaniasis consisted of pentavalent antimonial agents, used as first-line clinical treatment (7, 23); however, antileishmanial therapy has been a bewildering subject largely because of the complexity of the disease. Moreover, the recent appearance of clinical resistance to meglumine antimoniate (8,13) and the small number of efficient second-line antileishmanial drugs raised the necessity to develop new methods for the rapid assessment of the antileishmanial activities of chemical compounds.Various in vitro host-cell models such as mouse peritoneal macrophages (4), human monocytes (U-937) (16), or Chinese hamster ovary (CHO) cells (26) have been created to study infection of mammalian cells with Leishmania parasites and to test the antileishmanial activities of new molecules. In these models, infection rates were usually measured by microscopic examination of adherent cells. In the present study, we investigated the possibility of using flow cytometry for the rapid and reliable detection of possible antileishmanial drug...

In vitro comparisons demonstrated that the efficacy of albendazole, albendazole-sulfoxide, and albendazole-sulfone against pathogenicEncephalitozoon species was proportional to the degree of oxidation at a concentration of >10−3 μg/ml. Furthermore, at a concentration of <10−2 μg/ml, benzimidazoles were more effective against Encephalitozoon cuniculi and Encephalitozoon hellem than againstEncephalitozoon intestinalis.

Thalidomide was evaluated for its in vitro activity againstEncephalitozoon species by using the MRC-5 cell system. A cytotoxic effect was observed for concentrations of 101μg/ml (P < 105) and 5 μg/ml (P < 105). Thalidomide did not significantly inhibit the growth of any of the microsporidia under study. These data suggest that thalidomide is not an etiologic treatment in microsporidial enteritis.