Reactive oxygen species regulates expression of iron-sulfur cluster assembly protein IscS of Leishmania donovani.

The cysteine desulfurase, IscS, is a highly conserved and essential component of the mitochondrial iron-sulfur cluster (ISC) system that serves as a sulfur donor for Fe-S clusters biogenesis. Fe-S clusters are versatile and labile cofactors of proteins that orchestrate a wide array of essential metabolic processes, such as energy generation and ribosome biogenesis. However, no information regarding the role of IscS or its regulation is available in Leishmania, an evolving pathogen model with rapidly developing drug resistance. In this study, we characterized LdIscS to investigate the ISC system in AmpB-sensitive vs resistant isolates of L. donovani and to understand its regulation. We observed an upregulated Fe-S protein activity in AmpB-resistant isolates but, in contrast to our expectations, LdIscS expression was upregulated in the sensitive strain. However, further investigations showed that LdIscS expression is positively correlated with ROS level and negatively correlated with Fe-S protein activity, independent of strain sensitivity. Thus, our results suggested that LdIscS expression is regulated by ROS level with Fe-S clusters/proteins acting as ROS sensors. Moreover, the direct evidence of a mechanism, in support of our results, is provided by dose-dependent induction of LdIscS-GFP as well as endogenous LdIscS in L. donovani promastigotes by three different ROS inducers: H2O2, menadione, and Amphotericin B. We postulate that LdIscS is upregulated for de novo synthesis or repair of ROS damaged Fe-S clusters. Our results reveal a novel mechanism for regulation of IscS expression that may help parasite survival under oxidative stress conditions encountered during infection of macrophages and suggest a cross talk between two seemingly unrelated metabolic pathways, the ISC system and redox metabolism in L. donovani.

Asymptomatic infection with visceral leishmaniasis in a disease-endemic area in bihar, India.

A prospective study was carried out in a cohort of 355 persons in a leishmaniasis-endemic village of the Patna District in Bihar, India, to determine the prevalence of asymptomatic persons and rate of progression to symptomatic visceral leishmaniasis (VL) cases. At baseline screening, 50 persons were positive for leishmaniasis by any of the three tests (rK39 strip test, direct agglutination test, and polymerase chain reaction) used. Point prevalence of asymptomatic VL was 110 per 1,000 persons and the rate of progression to symptomatic cases was 17.85 per 1,000 person-months. The incidence rate ratio of progression to symptomatic case was 3.36 (95% confidence interval [CI] = 0.75-15.01, P = 0.09) among case-contacts of VL compared with neighbors. High prevalence of asymptomatic persons and clinical VL cases and high density of Phlebotomus argentipes sand flies can lead to transmission of VL in VL-endemic areas.

Short report: Development of post-kala-azar dermal leishmaniasis (PKDL) in miltefosine-treated visceral leishmaniasis.

We report two cases of post-kala-azar dermal leishmaniasis (PKDL), which had subsequently developed after successful treatment of visceral leishmaniasis with miltefosine. Both patients had maculo-nodular lesions all over the body, and they were diagnosed as PKDL by parasitologic examination for Leishmania donovani bodies in a skin snip of lesions. Patients were put on amphotericin B and responded very well for nodular lesions with one course of treatment. However, longer duration of the treatment is needed for total clearance of macular lesions from body surface in PKDL cases. This is the first case report of PKDL in India, which developed after successful treatment of visceral leishmaniasis with miltefosine.

Inhibition of ABC transporters abolishes antimony resistance in Leishmania Infection.

The emergence of antimony (Sb) resistance has jeopardized the treatment of visceral leishmaniasis in various countries. Previous studies have considered the part played by leishmanial parasites in antimony resistance, but the involvement of host factors in the clinical scenario remained to be investigated. Here we show that unlike infection with Sb-sensitive (Sbs) Leishmania donovani, infection with Sb-resistant (Sb r) L. donovani induces the upregulation of multidrug resistance-associated protein 1 (MRP1) and permeability glycoprotein (P-gp) in host cells, resulting in a nonaccumulation of intracellular Sb following treatment with sodium antimony gluconate (SAG) favoring parasite replication. The inhibition of MRP1 and P-gp with resistance-modifying agents such as lovastatin allows Sb accumulation and parasite killing within macrophages and offers protection in an animal model in which infection with Sb r L. donovani is otherwise lethal. The occurrence of a similar scenario in clinical cases is supported by the findings that unlike monocytes from SAG-sensitive kala-azar (KA) patients, monocytes from SAG-unresponsive KA patients overexpress P-gp and MRP1 and fail to accumulate Sb following in vitro SAG treatment unless pretreated with inhibitors of ABC transporters. Thus, the expression status of MRP1 and P-gp in blood monocytes may be used as a diagnostic marker for Sb resistance and the treatment strategy can be designed accordingly. Our results also indicate that lovastatin, which can inhibit both P-gp and MRP1, might be beneficial for reverting Sb resistance in leishmaniasis as well as drug resistance in other clinical situations, including cancer.

Magnitude of unresponsiveness to sodium stibogluconate in the treatment of visceral leishmaniasis in Bihar.

BACKGROUND: The Indian government proposes to eliminate kala-azar, which has been a serious public health problem in Bihar. This study aimed to assess the magnitude of unresponsiveness to sodium stibogluconate in the treatment of new cases of visceral leishmaniasis and to identify the associated factors. METHODS: Patients with clinically and parasitologically confirmed visceral leishmaniasis (n = 182) who had received no prior treatment, were enrolled for the study. The patients were treated with sodium stibogluconate (20 mg/kg body weight; upper limit 850 mg), intramuscularly for 30 days. The vital parameters and side-effects, if any, were monitored. Patients who developed toxicity during treatment were excluded from the study but were given rescue treatment with liposomal amphotericin B. All patients who completed the treatment were followed up for 6 months. RESULTS: Unresponsiveness to sodium stibogluconate at the end of treatment was 43%. It was higher in women (48%) compared to men (40%). A significant association was observed between unresponsiveness and level of endemicity (p = 0.0002), large spleen size (p = 0.04) and immune response (migration inhibition factor) (p = 0.00002). At the end of 6 months' follow up, 27% of patients relapsed, giving a total unresponsiveness rate of 58%. CONCLUSION: Unresponsiveness to sodium stibogluconate is a serious problem in the management of patients with visceral leishmaniasis. In patients with factors associated with nonresponse to sodium stibogluconate, alternative drugs such as miltefosine or amphotericin B should be considered as first-line drugs.

Nexus of infection with human immunodeficiency virus, pulmonary tuberculosis and visceral leishmaniasis: a case report from Bihar, India.

A 37-year-old man was diagnosed as being infected with human immunodeficiency virus (HIV), tuberculosis (TB), tuberculoma of the brain, and visceral leishmaniasis (VL) at the Rajendra Memorial Institute of Medical Sciences in Bihar, India. He had taken anti-tuberculosis therapy (ATT) for two and a half months and had episodes of convulsions with loss of consciousness, tongue bites, and incontinence of urine. The results of a neurologic examination were normal except for a left plantar extensor. He was positive for both HIV-I (confirmed by Western blot) and VL (confirmed by splenic aspirate). Treatment was initiated with amphotericin B lipid complex, a four-drug regimen (rifampicin, isoniazid, ethambutol, and pyrazinamide) of ATT, highly active antiretroviral therapy, anti-convulsants, and other supportive therapies. A repeat computed tomography scan of the brain showed the disappearance of the lesion followed by gliosis. After six months, he was also cured of VL. The triad of infections (HIV, VL, and TB) is a real threat in Bihar as an emerging combination of diseases of public health importance. Keeping these facts in mind, efforts to develop simple and cost effective diagnostic techniques coupled with affordable therapeutic facilities are urgently needed in developing countries.