Nelfinavir is effective in inhibiting the multiplication and aspartic peptidase activity of Leishmania species, including strains obtained from HIV-positive patients.

OBJECTIVES: There is a general lack of effective and non-toxic chemotherapeutic agents for leishmaniasis and there is as yet no study about the effect of HIV peptidase inhibitors (HIV PIs) on Leishmania/HIV-coinfected patients. In the present work, we performed a comparative analysis of the spectrum of action of HIV PIs on different Leishmania spp., including strains obtained from HIV-positive patients receiving or not receiving antiretroviral treatment. METHODS: The effects of nelfinavir and saquinavir on Leishmania proliferation were assessed by means of a colorimetric assay (MTT). Subsequently, the effect of nelfinavir on aspartic peptidase activity from Leishmania spp. was assessed by following the degradation of the fluorogenic substrate MCA-G-K-P-I-L-F-F-R-L-K-DNP-Arg-NH(2). RESULTS: Nelfinavir was capable of significantly reducing the multiplication of many Leishmania reference strains and isolates obtained from HIV-positive patients receiving or not receiving antiretroviral treatment. Leishmania major growth was inhibited by ≈ 50%, while all other flagellates were strongly inhibited (at least 94%), except for a Leishmania chagasi strain obtained from an HIV-positive patient under treatment with highly active antiretroviral therapy (HAART). Culture of this isolate in the presence of nelfinavir induced a considerable reduction in the aspartic peptidase activity. In addition, nelfinavir was also capable of inhibiting the aspartic peptidase activity of all Leishmania strains tested. CONCLUSIONS: The present data contribute to the study of the effect of HIV PIs on Leishmania infection and add new insights into the possibility of exploiting aspartic peptidases as promising targets in order to generate novel medications to treat leishmaniasis.

HIV aspartyl peptidase inhibitors interfere with cellular proliferation, ultrastructure and macrophage infection of Leishmania amazonensis.

BACKGROUND: Leishmania is the etiologic agent of leishmanisais, a protozoan disease whose pathogenic events are not well understood. Current therapy is suboptimal due to toxicity of the available therapeutic agents and the emergence of drug resistance. Compounding these problems is the increase in the number of cases of Leishmania-HIV coinfection, due to the overlap between the AIDS epidemic and leishmaniasis. METHODOLOGY/PRINCIPAL FINDINGS: In the present report, we have investigated the effect of HIV aspartyl peptidase inhibitors (PIs) on the Leishmania amazonensis proliferation, ultrastructure, interaction with macrophage cells and expression of classical peptidases which are directly involved in the Leishmania pathogenesis. All the HIV PIs impaired parasite growth in a dose-dependent fashion, especially nelfinavir and lopinavir. HIV PIs treatment caused profound changes in the leishmania ultrastructure as shown by transmission electron microscopy, including cytoplasm shrinking, increase in the number of lipid inclusions and some cells presenting the nucleus closely wrapped by endoplasmic reticulum resembling an autophagic process, as well as chromatin condensation which is suggestive of apoptotic death. The hydrolysis of HIV peptidase substrate by L. amazonensis extract was inhibited by pepstatin and HIV PIs, suggesting that an aspartyl peptidase may be the intracellular target of the inhibitors. The treatment with HIV PIs of either the promastigote forms preceding the interaction with macrophage cells or the amastigote forms inside macrophages drastically reduced the association indexes. Despite all these beneficial effects, the HIV PIs induced an increase in the expression of cysteine peptidase b (cpb) and the metallopeptidase gp63, two well-known virulence factors expressed by Leishmania spp. CONCLUSIONS/SIGNIFICANCE: In the face of leishmaniasis/HIV overlap, it is critical to further comprehend the sophisticated interplays among Leishmania, HIV and macrophages. In addition, there are many unresolved questions related to the management of Leishmania-HIV-coinfected patients. For instance, the efficacy of therapy aimed at controlling each pathogen in coinfected individuals remains largely undefined. The results presented herein add new in vitro insight into the wide spectrum efficacy of HIV PIs and suggest that additional studies about the synergistic effects of classical antileishmanial compounds and HIV PIs in macrophages coinfected with Leishmania and HIV-1 should be performed.