Claudio M. Lezama-Davila

Sex Hormones and Modulation of Immunity against Leishmaniasis

Sex-associated hormones such as estradiol, testosterone and progesterone have all been shown to modulate immune responses, which can result in differential disease outcomes between males and females, as well as between pregnant and nonpregnant females. Most parasitic diseases, including leishmaniasis, usually result in more severe disease in males compared with females. This review highlights our current knowledge concerning the role of sex hormones in modulating leishmaniasis in both clinical settings and experimental disease models.

Role of chemokines in regulation of immunity against leishmaniasis

Successful immunity to Leishmania depends on recruitment of appropriate immune effector cells to the site of infection and chemokines play a crucial role in the process. At the same time, Leishmania parasites possess the ability to modify the chemokine profiles of their host thereby facilitating establishment of progressive infection. Therapeutic and prophylactic strategies targeted at chemokines and their receptors provide a promising area for further research. This review highlights our current knowledge concerning the role of chemokines and their receptors in modulating leishmaniasis in both clinical settings and experimental disease models.

Critical role for phosphoinositide 3-kinase gamma in parasite invasion and disease progression of cutaneous leishmaniasis

Obligate intracellular pathogens such as Leishmania specifically target host phagocytes for survival and replication. Phosphoinositide 3-kinase γ (PI3Kγ), a member of the class I PI3Ks that is highly expressed by leukocytes, controls cell migration by initiating actin polymerization and cytoskeletal reorganization, which are processes also critical for phagocytosis. In this study, we demonstrate that class IB PI3K, PI3Kγ, plays a critical role in pathogenesis of chronic cutaneous leishmaniasis caused by L. mexicana. Using the isoform-selective PI3Kγ inhibitor, AS-605240 and PI3Kγ gene-deficient mice, we show that selective blockade or deficiency of PI3Kγ significantly enhances resistance against L. mexicana that is associated with a significant suppression of parasite entry into phagocytes and reduction in recruitment of host phagocytes as well as regulatory T cells to the site of infection. Furthermore, we demonstrate that AS-605240 is as effective as the standard antileishmanial drug sodium stibogluconate in treatment of cutaneous leishmaniasis caused by L. mexicana. These findings reveal a unique role for PI3Kγ in Leishmania invasion and establishment of chronic infection, and demonstrate that therapeutic targeting of host pathways involved in establishment of infection may be a viable strategy for treating infections caused by obligate intracellular pathogens such as Leishmania.

Sterols with antileishmanial activity isolated from the roots of Pentalinon andrieuxii.

A new cholesterol derivative, pentalinonsterol (cholest-4,20,24-trien-3-one, 1), and a new polyoxygenated pregnane sterol glycoside, pentalinonside (2), together with 18 known compounds, including 14 sterols (3-16), three coumarins (17-19), and a triterpene (20), were isolated from a n-hexane partition of a methanol extract of the roots of the Mexican medicinal plant Pentalinon andrieuxii. Structure elucidation of compounds 1 and 2 was accomplished by spectroscopic data interpretation. All isolates were evaluated in vitro for their antileishmanial activity. Among these compounds, 6,7-dihydroneridienone (15) was found to be the most potent principle against promastigotes of Leishmania mexicana (L. mexicana). The cholesterol analogue, pentalinonsterol (1), together with two known sterols, 24-methylcholest-4,24(28)-dien-3-one (3) and neridienone (16), also exhibited significant leishmanicidal activity in this same bioassay. Compounds 1, 3, 15, 16, cholest-4-en-3-one (4), and cholest-5,20,24-trien-3β-ol (7), showed strong antileishmanial activity against amastigotes of L. mexicana, and 4 was found to be the most potent agent with an IC(50) value of 0.03μM. All the isolates were also evaluated for their cytotoxicity in non-infected bone marrow-derived macrophages, but none of these compounds was found active towards this cell line. The intracellular parasites treated with compounds 1, 3, 4, 15, and 16 were further studied by electron microscopy; morphological abnormalities and destruction of the amastigotes were observed, as a result of treatment with these compounds.

Role of phosphatidylinositol-3-kinase-γ (PI3Kγ)-mediated pathway in 17β-estradiol-induced killing of L. mexicana in macrophages from C57BL/6 mice

We recently demonstrated that 17β‐estradiol (E2) enhances killing of Leishmania mexicana in macrophages from both male and female DBA/2 mouse by increasing nitric oxide (NO) production. Here, we analyzed the effect of E2 on leishmanicidal activity and cytokine production by bone marrow‐derived macrophages (BMDMs) from male and female C57BL/6 mice in vitro, specifically examining the role of phosphatidylinositol‐3‐kinase‐γ (PI3Kγ) in E2‐induced parasite killing. Unlike its effect on macrophages from both male and female DBA/2 mice, E2 only increased leishmanicidal activity in macrophages from female C57BL/6 mice, which was evident by a significant reduction in both infection rates and infection levels compared to sham controls. E2‐treated BMDMs from female C57BL/6 mice expressed higher levels of interferon‐γRα, and also produced more interleukin (IL)‐12, IL‐6 and NO than both the sham controls and E2‐treated male‐derived macrophages. Sham‐treated BMDMs from female PI3Kγ−/− C57BL/6 mice displayed lower infection rates and infection levels compared to sham‐treated wild‐type (WT) macrophages. However E2, unlike its effect on macrophages from female WT C57BL/6 mice, failed to reduce infection rates and infection levels in BMDMs from female PI3Kγ−/− mice. Interestingly, E2‐treated BMDMs from female C57BL/6 mice produced significant amounts of inflammatory cytokines and NO in levels comparable to those observed in sham‐treated PI3Kγ‐deficient macrophages as well as E2‐treated macrophages from WT mice. These findings show that E2 exerts a distinct effect on leishmanicidal activity of macrophages from male versus female C57BL/6 mice. In addition, they suggest that PI3Kγ is not required for E2‐induced cytokine and NO production in L. mexicana‐infected macrophages from female C57BL/6 mice but it may be involved in parasite clearance from these cells.

Lack of CXCR3 Delays the Development of Hepatic Inflammation but Does Not Impair Resistance to Leishmania donovani

CXC chemokine receptor 3 (CXCR3) ligands CXCL9 and CXCL10 are produced at high levels in mice and humans infected with Leishmania donovani, but their contribution to host resistance against L. donovani is not clear. Here, using CXCR3(-/-) mice, we demonstrate that, although CXCR3 regulates early immune cell trafficking and hepatic inflammation during L. donovani infection, it is not essential for immunity against L. donovani, unlike L. major. CXCR3(-/-) C57BL/6 mice show a delayed onset of hepatic inflammation and granuloma formation after L. donovani infection. However, they mount an efficient T helper cell type 1 response, recruit T cells to the liver, and control parasite growth as efficiently as do CXCR3(+/+) C57BL/6 mice.

In vitro Leishmanicidal and Cytotoxic Activities of the Glycoalkaloids from Solanum lycocarpum (Solanaceae) Fruits

Leishmaniasis is an infection caused by a protozoan parasite of the genus Leishmania and is the second most prevalent parasitic protozoal disease after malaria in the world. We report the in vitro leishmanicidal activity on promastigote forms of Leishmania amazonensis and cytotoxicity, using LLCMK2 cells, of the glycoalkaloids from the fruits of Solanum lycocarpum, determined by colorimetric methods. The alkaloidic extract was obtained by acid‐base extraction; solamargine and solasonine were isolated by silica‐gel chromatography, followed by reversed‐phase HPLC final purification. The alkaloidic extract, solamargine, solasonine, as well as the equimolar mixture of the glycoalkaloids solamargine and solasonine displayed leishmanicidal activity against promastigote forms of L. amazonensis, whereas the aglycone solasodine was inactive. After 24 and 72 h of incubation, most of the samples showed lower cytotoxicities (IC50 6.5 to 124 μM) as compared to leishmanicidal activity (IC50 1.1 to 23.6 μM). The equimolar mixture solamargine/solasonine was the most active with an IC50 value of 1.1 μM, after 72 h. Likewise, solamargine was the most active after 24 h with an IC50 value of 14.4 μM, both in comparison with the positive control amphotericin B.

Heat, Oriental sore, and HIV

Department of Dermatology, STD and Leprosy, SP Medical College, Bikaner, Rajasthan, India (N Prasad MBBS, Prof B C Ghiya MD, Prof R A Bumb MD); Institute of Pathology (ICMR), Safdarjung Hospital Campus, New Delhi, India (H Kaushal MSc, P Salotra PhD); and Departments of Pathology and Microbiology, Ohio State University, Columbus, OH, USA (C M Lezama-Davila PhD, A A Satoskar MD, Prof A R Satoskar MD)

Efficacy of short-duration (twice weekly) intralesional sodium stibogluconate in treatment of cutaneous leishmaniasis in India.

Background  Cutaneous leishmaniasis (CL) is caused by Leishmania major and L. tropica in the old world. Bikaner, the ‘Thar Desert’, situated in the north‐western corner of India, is an endemic pocket for CL caused by L. tropica. Skin lesions of CL heal slowly, causing disfiguring scars if remaining untreated. Current recommended treatment for CL comprises systemic administration of sodium stibogluconate (SSG) for 2–3 weeks. Five to seven injections of SSG intralesionally have also been found to be effective.

Cordifolide A, a sulfur-containing clerodane diterpene glycoside from Tinospora cordifolia.

Cordifolide A (1), a novel unprecedented sulfur-containing clerodane diterpene glycoside, together with other two new diterpene glycosides, cordifolides B (2) and C (3), and four known analogues, was isolated from a methanol-soluble extract of the stems of Tinospora cordifolia. The structures of the new compounds were determined on the basis of spectroscopic data interpretation, with that of cordifolide A (1) confirmed by a single-crystal X-ray crystallographic analysis. All isolates were evaluated for their in vitro immunomodulatory activity using mouse bone marrow-derived dentritic cells (BMDCs).