The increase in risk factors for leishmaniasis worldwide

Molecular mechanisms of antimony resistance in Leishmania

Leishmaniasis causes significant morbidity and mortality worldwide. The disease is endemic in developing countries of tropical regions, and in recent years economic globalization and increased travel have extended its reach to people in developed countries. In the absence of effective vaccines and vector-control measures, the main line of defence against the disease is chemotherapy. Organic pentavalent antimonials [Sb(V)] have been the first-line drugs for the treatment of leishmaniasis for the last six decades, and clinical resistance to these drugs has emerged as a primary obstacle to successful treatment and control. A multiplicity of resistance mechanisms have been described in resistantLeishmaniamutants developedin vitroby stepwise increases of the concentration of either antimony [Sb(III)] or the related metal arsenic [As(III)], the most prevalent mechanism being upregulated Sb(III) detoxification and sequestration. With the availability of resistant field isolates, it has now become possible to elucidate mechanisms of clinical resistance. The present review describes the mechanisms of antimony resistance inLeishmaniaand highlights the links between previous hypotheses and current developments in field studies. Unravelling the molecular mechanisms of clinical resistance could allow the prevention and circumvention of resistance, as well as rational drug design for the treatment of drug-resistantLeishmania.

Interaction of sitamaquine with membrane lipids of Leishmania donovani promastigotes

Sitamaquine is an 8-aminoquinoline which is active by the oral route for the treatment of life-threatening visceral leishmaniasis caused by Leishmania donovani, with an IC50 of 29.2 microM against the promastigote form in vitro. At high concentration (100 microM), sitamaquine affected parasite motility, morphology and growth in a way that was only partially reversible. As a first approach to determine its mechanism of action, we describe the interaction of sitamaquine with parasite membrane components, representing the first barrier to be crossed by the drug. Analysis of the physicochemical interactions of sitamaquine with monolayers of phospholipids and sterols at the air-water interface showed that these interactions only occurred in the presence of anionic phospholipids. Thus, electrostatic interactions between positively charged sitamaquine and the negative polar headgroups are a pre-requisite for subsequent hydrophobic interactions between the sitamaquine aromatic ring and the alkyl chains of phospholipids leading to drug insertion into the monolayer.

How much disease burden can be prevented by environmental interventions?

There is very little systematically collected evidence on the overall contribution of environmental risk factors to the global burden of disease. The World Health Organization (WHO) recently completed a comprehensive, systematic, and transparent estimate of the disease burden attributable to the environment highlighting the full potential for environmental interventions to improve human health. This report is the result of a systematic literature review on environmental risks completed by a survey of expert opinion using a variant of the Delphi method. More than 100 experts provided quantitative estimates on the fractions of 85 diseases attributable to the environment. They were asked to consider only the contributions of the "reasonably modifiable environment"-that is, the part of environment that can plausibly be changed by existing interventions. The report estimates that 24% of the global burden of disease was due to environmental risk factors. Environmental factors were judged to play a role in 85 of the 102 diseases taken into account. Major diseases were, for example, diarrheal diseases with fractions attributable to the environment of 94%, lower respiratory infections with 41%, malaria with 42%, and unintentional injuries with 42%. The evidence shows that a large proportion of this "environmental disease burden" could be averted by existing cost-effective interventions such as clean water, clean air, and basic safety measures. In children, 34% of the disease burden is attributable to the environment, and much of this burden is in developing countries.

Leishmania and sand flies: proximity to woodland as a risk factor for infection in a rural focus of visceral leishmaniasis in west central Venezuela

OBJECTIVE

To relate entomological, epidemiological and geographical data to understand the transmission dynamics of visceral leishmaniasis (VL) in a closed focus in western Venezuela.

METHODS

Spatial and temporal patterns of Lutzomyia pseudolongipalpis, the most prevalent phlebotomine sand fly species (99.7%), were studied in El Brasilar, Curarigua, Lara State, Venezuela, a small rural community of 20 dwellings and 118 inhabitants. The sand fly population was monitored using Centers for Disease Control light traps monthly throughout 1 year in the domestic and sylvatic habitats and for 3 months in all inhabited houses.

RESULTS

Temporal variation followed the yearly bimodal pattern of precipitation with the highest population densities in April and December. Infection with flagellates suggestive of Leishmania spp. was detected in 0.01% of 10,026 dissected females of L. pseudolongipalpis, which proved to be highly endophilic. Prevalence of Leishmania infection in people, as measured by the leishmanin skin test, was correlated with distance of the houses from the woodland and with sand fly abundance. A logistic regression model showed that for people who live in the village, the proximity to the woodland (linear) should be considered a risk factor for Leishmania infection (binary) (z = -2.02, P = 0.04, OR = 0.98, 95% CI = 0.97-0.99). This was consistent with the association between the proportion of VL infection and the log of sand fly abundance, which was negatively correlated with distance from the woodland.

CONCLUSION

We discuss strategies that might be useful in controlling VL transmission in this endemic focus.

Leishmaniasis

Epidemiology, disease patterns, immunology, diagnosis, treatment and control measures of leishmaniasis are described. Various issues relating to leishmaniasis are highlighted: the relative lack of importance given to this disease is compared with other infections, climate change and its possible effect on extension of endemicity of this infection, and new diagnostic tests that are helping better diagnosis, especially in resource-poor areas. Other important aspects discussed include the potential for newer oral treatment to change the way this disease is managed; leishmania-HIV coinfection and groups at risk; and the development of an effective vaccine.

Leishmania infantum leishmaniasis in corticosteroid--treated patients

Background

The number of leishmaniasis cases associated with immunosuppression has increased regularly over the past 20 years. Immunosuppression related to HIV infection, immunosuppressive treatment, organ transplantation, and neoplastic diseases increases the risk for Leishmania-infected people to develop visceral illness.

Case presentation

Three cases of Leishmania infantum leishmaniasis in corticosteroid (CS)-treated patients are reported: an isolated lingual leishmaniasis in a farmer treated with CS for asthma, a severe visceral leishmaniasis associated with cutaneous lesions in a woman with myasthenia gravis, and a visceral involvement after cutaneous leishmaniasis in a man receiving CS.

Conclusion

Physicians should recognise CS-treated patients as a population likely to be immunesuppressed. In immunodeficiency conditions, unusual forms of leishmaniasis can develop and foster the risk of a diagnostic delay and of poor response to therapy.

Diagnosis of canine leishmaniasis in the endemic area of Belo Horizonte, Minas Gerais, Brazil by parasite, antibody and DNA detection assays

Canine leishmaniasis caused by Leishmania chagasi (L. infantum) is found throughout the South American continent, including Brazil, and dogs are considered to be the main reservoir host for this parasite. To support the implementation of a diagnostic protocol for surveillance of the disease in the region of Belo Horizonte (Minas Gerais, Brazil) we have compared the sensitivity and specificity of two serological tests, indirect immunofluorescent antibody test (IFAT) and direct agglutination test (DAT), with the combination of direct microscopy-culture-PCR as the gold standard, using samples obtained from 103 dogs in the city of Belo Horizonte, Minas Gerais. The currently used standard serodiagnostic test, IFAT, had a sensitivity of 100% and its specificity was 74% compared to the gold standard of the study. The sensitivity and specificity of the DAT were 100% and 91%, respectively. On the basis of this study it is recommended to change from the IFAT to DAT for the serodiagnosis of canine leishmaniasis because of the superior specificity of the test combined with its user-friendliness.

Incidence and time course of Leishmania infantum infections examined by parasitological, serologic, and nested-PCR techniques in a cohort of naive dogs exposed to three consecutive transmission seasons

Most experience in the comparison of diagnostic tools for canine leishmaniasis comes from cross-sectional surveys of dogs of different ages and breeds and in cases with unknown onset and duration of leishmaniasis. A longitudinal study was performed on 43 beagle dogs exposed to three transmission seasons (2002 to 2004) of Mediterranean leishmaniasis and examined periodically over 32 months through bone marrow microscopy and nested PCR (n-PCR), lymph node culture, serology (immunofluorescent-antibody test), and evaluation of clinical parameters. Starting from January 2003, the highest rate of positives was detected by n-PCR at all assessments (from 23.3% to 97.3%). Sensitivities of serologic and parasitological techniques were lower but increased with time, from 15.8% to 75.0 to 77.8%. Some dogs that tested positive by n-PCR but negative by other tests ("subpatent infection") remained so until the end of the study or converted to negative in subsequent assessments, whereas all dogs with positive serology and/or microscopy/culture ("asymptomatic patent infection") exhibited progressive leishmaniasis; 68% of them developed clinical disease ("symptomatic patent infection") during the study, at 7 (range, 3 to 14) months after being positive to all tests. Postexposure infection incidences were high and were significantly different between 2002 and 2003 exposures (39.5% and 91.7%, respectively). The time course of infection was highly variable in each dog, with three patterns being identified: (i) rapid establishment of a patent condition (0 to 2 months from detection of infection); (ii) a prolonged subpatent condition (4 to 22 months) before progression; and (iii) a transient subpatent condition followed by 10 to 21 months of apparent Leishmania-negative status before progression.

Identification and Characterization of a Protein-tyrosine Phosphatase in Leishmania

Leishmania parasites are eukaryotic protozoans responsible for a variety of human diseases known as leishmaniasis, which ranges from skin lesions to fatal visceral infections. Leishmania is transmitted by the bite of an infected sandfly where it exists as promastigotes and, upon entry into a mammalian host, differentiates into amastigotes, which replicate exclusively in macro-phages. The biochemical pathways enabling Leishmania to differentiate and survive in the mammalian host are poorly defined. We have therefore examined the role of protein-tyrosine phosphorylation, which is essential in regulating cell function in higher eukaryotes. Using the recently completed Leishmania genome, we have identified and cloned a Leishmania protein-tyrosine phosphatase (PTP) gene (LPTP1) by virtue of its homology with the human protein-tyrosine phosphatase 1B gene (hPTP1B). The enzyme activity of recombinant LPTP1 was confirmed using a combination of PTP-specific substrates and inhibitors. We further demonstrate, by creating LPTP1 null mutants through gene targeting, that LPTP1 is necessary for survival as amastigotes in mice, but it is dispensable for survival as promastigotes in culture. Human PTPs, including the PTP1B enzyme, are actively pursued drug targets for a variety of diseases. The observations with the LPTP1 mutants in mice suggest that it may also represent a drug target against the mammalian amastigote stage. However, in silico structure analysis of LPTP1 revealed a striking similarity with hPTP1B in the active site suggesting that, although this is an attractive drug target, it may be difficult to develop an inhibitor specific for the Leishmania LPTP1.

Chemotherapy in the treatment and control of leishmaniasis

Drugs remain the most important tool for the treatment and control of both visceral and cutaneous leishmaniasis. Although there have been several advances in the past decade, with the introduction of new therapies by liposomal amphotericin, oral miltefosine and paromomycin (PM), these are not ideal drugs, and improved shorter duration, less toxic and cheaper therapies are required. Treatments for complex forms of leishmaniasis and HIV co-infections are inadequate. In addition, full deployment of drugs in treatment and control requires defined strategies, which can also prevent or delay the development of drug resistance.

Liposomal amphotericin B for the treatment of visceral leishmaniasis

During the past decade, liposomal amphotericin B has been used with increasing frequency to treat visceral leishmaniasis (VL). The World Health Organization convened a workshop to review current knowledge and to develop guidelines for liposomal amphotericin B use for VL. In Europe, liposomal amphotericin B is widely used to treat VL. In Africa and Asia, the VL disease burden is high and drug access is poor; liposomal amphotericin B is available only through preferential pricing for nonprofit groups in East Africa. Clinical trials and experience demonstrate high efficacy and low toxicity for liposomal amphotericin B (total dose, 20 mg/kg) in immunocompetent patients with VL. Combination trials in areas with antileishmanial drug resistance, and treatment and secondary prophylaxis trials in VL-human immunodeficiency virus-coinfected patients, are important to safeguard the current armamentarium and to optimize regimens. The public health community should work to broaden access to preferential liposomal amphotericin B pricing by public sector VL treatment programs.

Treatment options for visceral leishmaniasis

This review summarizes the current developments in therapy for visceral leishmaniasis. With the recent introduction of new drugs, the main limits in reducing deaths from visceral leishmaniasis are difficulty in diagnosis in the field and health inequality--patients lack of access to treatment. No new drugs are currently in the early stages of development. There are good reasons for the use of combination therapy; to prevent further development of resistance against the limited therapeutic options available.

Miltefosine: oral treatment of leishmaniasis

The well-known problems of classic treatment of the leishmaniases with pentavalent antimony (reduced efficacy), difficulties of administration and increasing frequency and severity of adverse events have stimulated the search for new drugs to treat these diseases. Other injectable, oral and topical drugs have not been consistently effective, especially in the modern World. Beginning in 1998, Indian researchers conducted several trials with hexadecylphosphocholine (miltefosine) in patients with visceral leishmaniasis, and in 1999, clinical studies were initiated in Colombia for cutaneous disease. More than 2500 patients have been treated, including patients with diffuse cutaneous leishmaniasis, mucosal disease and patients coinfected with HIV. Cure rates between 91 and 100% were reached with a dose of 2.5 mg/kg/day for 28 days, with no difference between treatment-naive and relapsing patients. Mild gastrointestinal events were present in 35-60% of patients and 10-20% had mild transaminase and creatinine elevations. Miltefosine has potent leishmanicidal activity as a consequence of its interference in parasite metabolic pathways and the induction of apoptosis. Miltefosine is the first effective and safe oral agent with the potential to treat all major clinical presentations of leishmaniasis.

Are New World leishmaniases becoming anthroponoses?

In the New World, leishmaniases are originally wild exoanthropic zoonoses developing in sylvatic ecotopes. For a long time, Leishmania parasites have shown a remarkable plasticity to face modifications in their environment. Now, both geographical extension and numerical increase of leishmaniasis cases in the New World are giving cause for concern. These circumstances might have been provoked by the simple invasion of zoonotic foci by humans. However, dramatic evolutionary mechanisms are also at work in the New World: (i) the reduction of biodiversity associated with anthropogenic environmental changes (deforestation and urbanization); and (ii) the subsequent adaptations and interactions of new vectors and reservoir hosts at the interface with humans. This paper considers that these processes could result in new pathogenic complexes tending to synanthropic zoonoses, if not anthroponoses. Increasing man-made risk factors could thus possibly make leishmaniases a growing public health concern in the New World.

Treatment of visceral leishmaniasis

The Leishmania donovani complex includes L. chagasi and L. infantum, and causes visceral leishmaniasis (VL), a disseminated and potentially fatal form of leishmaniasis. The treatment options for VL are limited. Pentavalent antimonials (Sbv) are the first-line treatment options worldwide except for in Europe and Sbv-unresponsive regions of India. Amphotericin B deoxycholate is the drug of choice in India, as are its lipid formulations in Europe. However, liposomal amphotericin B (AmBisome, Gilead Sciences, Inc.) is the best antileishmanial formulation, but its prohibitive cost limits its use in endemic countries. Preferential pricing of AmBisome for patients with VL may provide hope for these underprivileged patients. Oral miltefosine and paromomycin are the other drugs that have been recently developed. Limited therapeutic options, the potential for development of resistance and serious toxicity associated with antileishmanial drugs necessitates a change in the treatment policy. A shift from monotherapy to multi-drug combinations of short courses delivered at no or affordable cost, through directly observed therapy, seems to be the only way to develop the treatment of this disease.

Antileishmanial and Antibacterial Activity of a New Pyrazole Derivative Designated 4-[2-(1-(Ethylamino)-2-methyl- propyl)phenyl]-3-(4-methyphenyl)-1-phenylpyrazole

Here, we report for the first time the synthesis and the antileishmanial activity of a new pyrazole derivative, namely 4-[2-(1-(ethylamino)-2-methylpropyl)phenyl]-3-(4-methyphenyl)-1-phenylpyrazole). Micromolar concentrations of this compound were found to inhibit the in vitro multiplication of Leishmania tropica, Leishmania major, and Leishmania infantum, three species causing different forms of leishmaniasis. Furthermore, the 50% inhibitory concentration (IC50) values for the compound are only slightly higher than those of amphotericin B, one of the most active antileishmanial agents used as a satisfactory substitute in cases not responding to pentostam. The IC50 values after 48 h for L. tropica, L. major, and L. infantum promastigote growth were 0.48 microg/mL, 0.63 microg/mL and 0.40 microg/mL, respectively for the compound, while they were 0.23 microg/mL, 0.29 microg/mL and 0.24 microg/mL, respectively for amphotericin B. We also tested this compound for its antibacterial activity against several bacteria. The strongest antibacterial activity was observed against Entrococcus feacalis and Staphylococcus aureus with a minimal inhibitory concentration (MIC) of 60 microg/mL.

Visceral leishmaniasis in Brazil: revisiting paradigms of epidemiology and control

In the last 20 years, despite the known underestimation of cases, Brazil registered a marked increase in the incidence of visceral leishmaniasis. The main goal of this review is to reflect on some aspects of this zoonosis in Brazil and also to encourage the discussion in order to find more viable, effective and affordable strategies to be implemented by the Brazilian Leishmaniasis Control Program. The current situation of visceral leishmaniasis in Brazil might be seen as a paradox: the most important aspects of the disease are known, but so far the control of this disease has not yet been achieved. The current control strategies have not been able to prevent the geographical expansion, and even a rise in the incidence and lethality of visceral leishmaniasis. There is a need not only for a better definition of priority areas, but also for the implementation of a fieldwork monitoring system to the disease surveillance that could permit a further evaluation of the control program in areas where visceral leishmaniasis is endemic.

Activity of the Essential Oil from Chenopodium ambrosioides Grown in Cuba against Leishmania amazonensis

BACKGROUND AND METHODS

Current therapy against leishmaniasis is unsatisfactory. Efficacious and safe new drugs are needed. In this study, we show the leishmanicidal effect of an essential oil from Chenopodium ambrosioides against Leishmania amazonensis.

RESULTS

The tested product had a potent inhibitory action against promastigote and amastigote forms, with 50% effective dose values of 3.7 and 4.6 microg/ml, respectively. The essential oil showed a moderate toxicity on macrophages from BALB/c mice. An optimal dose of 30 mg/kg/day was effective when administered during 15 days by intraperitoneal route to BALB/c mice infected experimentally.

CONCLUSION

These studies revealed a potential source for the discovery of novel drugs to combat the leishmaniasis based on the traditional medicine.

Arylanthranilodinitriles: A new biaryl class of antileishmanial agents

A series of anthranilodinitrile-based biaryls were synthesized and evaluated in vitro against extracellular promastigotes and intracellular amastigotes of Leishmania donovani. Among various screened compounds, a biaryl with trifluoromethyl group 5f showed 83% inhibition against promastigotes and 70% inhibition against amastigotes of L. donovani at 8 and 20microg/mL concentrations, respectively.

The current status of zoonotic leishmaniases and approaches to disease control

Leishmaniases are a complex of world-wide diseases with a range of clinical and epidemiological features caused by Leishmania spp. of protozoan parasites. Among 15 well-recognised Leishmania species known to infect humans, 13 have zoonotic nature, which include agents of visceral, cutaneous and mucocutaneous forms of the disease in both the Old and New Worlds. Currently, leishmaniases show a wider geographic distribution and increased global incidence of human disease than previously known. Environmental, demographic and human behavioural factors contribute to the changing landscape of leishmaniasis, which includes increasing risk factors for zoonotic cutaneous leishmaniases and new scenarios associated with the zoonotic visceral leishmaniases. The latter consist of the northward spread of Leishmania infantum transmission in Europe and America, the identification of unusual mammal hosts, and the decline of HIV-Leishmania co-infections in southern Europe following the introduction of the highly active antiretroviral therapy. Few advances have been made in the surveillance and control of the zoonotic leishmaniasis, however a number of tools have been developed for the control of the canine reservoir of L. infantum. These include: (i) several canine vaccine candidates, in particular an FML Leishmania enriched fraction showing good clinical protection, has been registered in Brazil for veterinary use; (ii) a number of insecticide-based preparations have been specifically registered for dog protection against sand fly bites. Laboratory and field studies have shown improved efficacy of these preparations for both individual and mass protection.

New administration model of trans-chalcone biodegradable polymers for the treatment of experimental leishmaniasis

The present study was designed to investigate a new administration model and the antileishmanial activity of a semi-synthetic chalcone, benzylideneacetophenone (trans-chalcone). The antileishmanial activity of this product was first tested in vitro against promastigotes of L. braziliensis, L. tropica, L. infantum and L. amazonensis. An in vivo experiment was carried out using subcutaneous administration of trans-chalcone and implants of synthetic biodegradable polymers, polylactic acid (PLA) and polylactic/glycolic acid (PLGA). This compound showed potent inhibitory effects on the growth of all Leishmania strains examinated. Subcutaneous administration of trans-chalcone at a single dose of 4 mg/kg of body weight reduced lesion development in mice infected with L. amazonensis. A similar inhibition of the lesion growth in mice treated with trans-chalcone and pentamidine was observed. PLA and PGLA implants of trans-chalcone at 4 mg/kg were administered to mice infected with L. amazonensis. PLGA implants induced a highest reduction in the lesion size (31.25%) than PLA implants (10.75%). Treatment in vitro with trans-chalcone at IC50, completely inhibited the pathogenicity of this parasite in vivo. The development of this model provides a new practical technique for delivering drugs and can be useful for experimental leishmaniasis treatment.

Elevated levels of interferon-gamma, interleukin-10, and interleukin-6 during active disease in Indian kala azar

We have evaluated levels of 6 cytokines in sera of 35 patients of kala azar (KA), 29 post kala azar dermal leishmaniasis (PKDL), and 18 healthy controls using cytometric bead array technology. Results indicated significantly high levels of interferon gamma (IFN-gamma), interleukin (IL)-10, and IL-6 during active KA, while tumor necrosis factor alpha (TNF-alpha), IL-2, and IL-4 were minimal. Serum level of cytokines in PKDL was comparable to the controls while TNF-alpha was significantly elevated compared to KA or control. At post-treatment stage, KA patients showed a significant decrement in the levels of IFN-gamma, IL-10, and IL-6; however, IL-6 remained significantly elevated above control levels. Further, comparison of cytokine levels in children and adults revealed elevated level of IL-10 in pediatric cases. SAG unresponsive cases showed significantly elevated levels of IFN-gamma in comparison with the responsive cases. The results depict that type1 response is not depressed during active KA and suggest the possibility that unresponsiveness to type1 stimuli may prevail.

Drug resistance in leishmaniasis

Leishmaniasis is a complex disease, with visceral and cutaneous manifestations, and is caused by over 15 different species of the protozoan parasite genus Leishmania. There are significant differences in the sensitivity of these species both to the standard drugs, for example, pentavalent antimonials and miltefosine, and those on clinical trial, for example, paromomycin. Over 60% of patients with visceral leishmaniasis in Bihar State, India, do not respond to treatment with pentavalent antimonials. This is now considered to be due to acquired resistance. Although this class of drugs has been used for over 60 years for leishmaniasis treatment, it is only in the past 2 years that the mechanisms of action and resistance have been identified, related to drug metabolism, thiol metabolism, and drug efflux. With the introduction of new therapies, including miltefosine in 2002 and paromomycin in 2005-2006, it is essential that there be a strategy to prevent the emergence of resistance to new drugs; combination therapy, monitoring of therapy, and improved diagnostics could play an essential role in this strategy.

In vitro responses of human peripheral blood mononuclear cells to whole-cell, particulate and soluble extracts of Leishmania promastigotes

Whole-cell and soluble extracts of Leishmania promastigotes have both been used as skin test antigens and have also been tested as vaccine candidates. However, the differences in antigenicity between soluble and particulate Leishmania fractions are not known. We evaluated in vitro responses of PBMC from 30 American tegumentary leishmaniasis (ATL) patients and seven noninfected donors to different antigen preparations from Leishmania promastigotes, namely Leishmania amazonensis and L. braziliensis whole-cell extracts, as well as soluble and particulate fractions of L. amazonensis. All Leishmania antigen preparations stimulated significantly higher proliferation and interferon (IFN)-gamma production (but not interleukin (IL)-10 production) in PBMC from the leishmaniasis patients than in cells from the control subjects. The L. braziliensis whole-cell extract stimulated significantly higher cell proliferation and IFN-gamma production than the L. amazonensis whole-cell extract in the group of patients but not in the control group. This result can be explained by the fact that the patients were infected with L. braziliensis. Again in the group of patients, the PBMC proliferative responses as well as the levels of IFN-gamma and IL-10 stimulated by L. amazonensis whole-cell extract were significantly greater than those elicited by the L. amazonensis soluble fraction but were not significantly different from those elicited by the L. amazonensis particulate fraction. We found a higher antigenicity of the particulate fraction as compared to the soluble fraction, what suggests that the antigens present in the particulate fraction account for most of the antigenicity of whole-cell Leishmania promastigote antigen extracts.

Cloning, expression, and purification of a novel recombinant antigen from Leishmania donovani

Visceral leishmaniasis (VL) is a major health problem in the tropical and subtropical regions of the world. The conventional methods for diagnosis of Old World Visceral leishmaniasis are difficult, insensitive, and hazardous. There is no recombinant antigen from old world Leishmania species which can be commercially used for rapid diagnosis. There is an urgent need for a less invasive and accurate method. Here, we report a recombinant antigen from Indian Leishmania donovani for its diagnosis. The kinesin gene of a L. donovani clinical isolate (KE16) from India was PCR amplified for cloning and the immunodominant domain was expressed in Escherichia coli. This recombinant protein or Ld-rKE16 was evaluated for serodiagnosis of Indian kala-azar by ELISA. The recombinant antigen was found to be 100% sensitive and specific for Old World VL cases from India, Pakistan, China, and Turkey. The antigen showed no cross-reactivity with sera from other endemic diseases or healthy controls. The expressed Ld-rKE16 antigen is highly specific and sensitive for diagnosing visceral and post-kala-azar dermal leishmaniasis and is ready for commercialization.

Randomized, double-blind, placebo-controlled study on the immunogenicity of the leishmanin skin test

A positive reaction to the leishmanin skin test (LST) indicates previous contact with Leishmania antigens and is a useful criterion for the diagnosis of cutaneous leishmaniasis. In leishmaniasis vaccine trials, selection of volunteers has always been based on skin testing. During 1999 we performed a randomized controlled study in order to evaluate the immunogenicity of the LST. Fifty-nine (29 male and 30 female) healthy volunteer undergraduate students from the Medical School of Volta Redonda, Rio de Janeiro State, Brazil, with no evidence of previous infection with Leishmania, were randomly assigned into 2 groups: 29 subjects received LST and 30 received a placebo (merthiolate-phosphate-buffered saline). All volunteers received LST 41 d after the first injection of LST or placebo. Blood samples were taken immediately before the applications of LST or placebo for the assessment of Leishmania antigen-induced proliferation and cytokine production in peripheral blood mononuclear cell cultures. A significant increase in proliferative responses to L. braziliensis (P < 0.005) and L. amazonensis (P = 0.01) antigens as well as in L. braziliensis antigen-induced interferon-gamma production (P < 0.01) followed the application of LST but not the administration of the placebo. A single LST application is therefore able to induce Leishmania-specific cell-mediated immune responses. This observation should be considered in human trials of candidate vaccines against leishmaniasis.

Cutaneous leishmaniasis vector control perspectives using lambdacyhalothrin residual house spraying in El Ingenio, Miranda State, Venezuela

An indoor vector control trial was carried out between December 1996 and February 1997, with the aim of reducing the population densities of Lutzomyia ovallesi, the proven vector of cutaneous leishmaniasis (CL) in El Ingenio, Miranda State, Venezuela. Houses were matched according to their structure ("bahareque" [mud and straw], concrete, and wood) and randomly assigned to a control group (n = 19) or a treated group (n = 20) that was sprayed with 25 mg/m(2) of lambdacyhalothrin. This dose was selected on the basis of a laboratory susceptibility test of Lu. ovallesi to pyrethroids. Sandfly abundance was measured using CDC light traps 7-79 d post-intervention, by which time the sandfly population in control houses had declined to very low levels, at what was the end of the transmission season. Catches of total females, fed females, and males were significantly lower in sprayed than in control houses immediately after treatment. Catches of total females and males in sprayed houses recovered, reaching the level of control houses after 7 and 11 weeks, respectively. Bioassays following WHO protocols using contact cones on a sandfly laboratory colony showed a short residual effect of the insecticide explaining these results. In contrast, there was no tendency for catches of fed females in the sprayed houses to recover during the course of the trial. Previous studies of adult population dynamics showed a short season of high abundance. Combined with these results, we believe that 2 indoor sprayings with lambdacyhalothrin, the first at the beginning of November and the second at the beginning of January, would considerably reduce the Lu. ovallesi population, and control CL transmission in this and other foci where this sandfly is considered to be the main vector.

[Clinical findings of tegumentary leishmaniasis in children under five years of age in an endemic area of Leishmania (Viannia) braziliensis]

A retrospective study was performed in a field clinic to characterize the clinical findings of tegumentary leishmaniasis in children from 0 to 5 years old. The clinical records of 4,464 patients were analyzed at the Primary Health Center of Corte de Pedra, Presidente Tancredo Neves, Bahia, Brazil, from May 1987 to December 1995. Four hundred and ninety one (11.8%) children were identified among 4,275 new cases of tegumentary leishmaniasis registered at this Unit. The gender ratio (M:F) for children under six years was 1.1:1. Cutaneous lesions predominated (98%), mainly skin ulcers (99%) located above the waist (p<0.05). Thirty five percent had multiple lesions. The observed magnitude of the disease in children, the similar proportion of cases in both genders and the location of the lesions suggest the possibility of peri or intradomiciliary transmission.

Development of a genetic assay to distinguish between Leishmania viannia species on the basis of isoenzyme differences

BACKGROUND

Tegumentary leishmaniasis in Latin America is caused mainly by Leishmania viannia braziliensis complex parasites. L. braziliensis and Leishmania viannia peruviana are the 2 predominant Leishmania species in Peru. L. braziliensis is more virulent, because it can cause mucocutaneous leishmaniasis, known as espundia, that results in severe facial destruction. Early identification of the species that causes the initial cutaneous infection would greatly help to prevent mucocutaneous leishmaniasis, because it would allow more aggressive treatment and follow-up. However, because of the close genetic similarity of L. braziliensis and L. peruviana, there currently exists no simple assay to distinguish between these species.

METHODS

We cloned the mannose phosphate isomerase gene from both L. braziliensis and L. peruviana. It is the only known isoenzyme capable of differentiating between L. braziliensis and L. peruviana in multilocus enzyme electrophoresis. Interestingly, only a single nucleotide polymorphism was found between the mannose phosphate isomerase genes from L. braziliensis and L. peruviana, resulting in an amino acid change from threonine to arginine at amino acid 361. A polymerase chain reaction assay was developed to distinguish the single nucleotide polymorphism of the mannose phosphate isomerase gene to allow for the specific identification of L. braziliensis or L. peruviana.

RESULTS

This assay was validated with 31 reference strains that were previously typed by multilocus enzyme electrophoresis, successfully applied to patient biopsy samples, and adapted to a real-time polymerase chain reaction assay.

CONCLUSIONS

This innovative approach combines new genetic knowledge with traditional biochemical fundamentals of multilocus enzyme electrophoresis to better manage leishmaniasis in Latin America.

Identification of developmentally-regulated proteins in Leishmania panamensis by proteome profiling of promastigotes and axenic amastigotes

We have employed proteomics to identify proteins upregulated in the amastigote life-stage of Leishmaniapanamensis, using axenically-differentiated forms as models of authentic intracellular parasites. Resolution of the soluble proteomes of axenic amastigotes and promastigotes by two-dimensional electrophoresis (2DE) in the neutral pI range (5-7) revealed equivalent numbers of protein spots in both life-stages (644-682 using Coomassie Blue and 851-863 by silver staining). Although representing a relatively low proportion (8.1-10.8%) of the predicted 8000 gene products of Leishmania, these proteome maps enabled the reproducible detection of 75 differentially-regulated protein spots in amastigotes, comprising 24 spots "uniquely" expressed in this life-stage and 51 over-expressed by 1.2-5.7-fold compared to promastigotes. Of the 11 amastigote-specific spots analysed by mass spectrometry (MS), 5 yielded peptide sequences with no orthologues in Leishmania major, and the remaining 6 were identified as 7 distinct proteins (some of which were truncated isoforms) representing several functional classes: carbohydrate/energy metabolism (fructose 1,6-bisphosphate aldolase, glucose 6-phosphate dehydrogenase, pyruvate dehydrogenase), stress response (heat shock protein [HSP] 83), cell membrane/cytoskeleton (beta-tubulin), amino acid metabolism (cysteine synthase) and cell-cycle (ran-binding protein). Four additional over-expressed spots were tentatively identified as HSPs 60 and 70 and HSP 70-related proteins -1 and -4 by positional analogy with these landmark proteins in the Leishmania guyanensis proteome. Our data demonstrate the feasibility of proteomics as an approach to identify novel developmentally-regulated proteins linked to Leishmania differentiation and intracellular survival, while simultaneously pinpointing therapeutic targets. In particular, the amastigote-specific expression of cysteine synthase underlines the importance of de novo cysteine synthesis both as a potential parasite virulence factor and as a major metabolic difference from mammalian host cells.

Leishmania infantum-induced primary and challenge infections in rhesus monkeys (Macaca mulatta): a primate model for visceral leishmaniasis

Visceral leishmaniasis (VL) was experimentally induced in rhesus macaques (Macaca mulatta) by intravenously inoculating 2 x 10(7)amastigotes/kg of body weight of Leishmania infantum. The macaques developed a systemic disease showing characteristic features of human VL such as fever, diarrhoea, body weight loss, anaemia, hypergammaglobulinaemia and transient lymphocytosis, as well as lymph node, liver and/or spleen enlargement. Nine weeks after infection, one primate showed pronounced weight loss, became moribund and was euthanized. The necropsy findings included granulomas composed of parasite-containing macrophages, lymphocytes and plasma cells in the liver, spleen and lymph nodes. The remaining macaques had a sustained course of infection but developed a mild-to-moderate illness that subsequently showed evidence of self-cure. Of note, pathological findings included a typical cell-mediated immunity-induced granulomatous reaction that had an effect on the control of parasite replication. All infected monkeys responded with increased production of anti-Leishmania-specific IgG antibodies. Despite the fact that clinical resistance to L. infantum was not consistently associated with a parasite-specific cell-mediated immune response, drug-cured macaques from the primary infection acquired immunity to homologous re-infection. These findings point to the feasibility of using the L. infantum macaque model for pre-clinical evaluation of novel chemotherapeutics or vaccine candidates for human VL.

The structure of the transition state of the heterodimeric topoisomerase I of Leishmania donovani as a vanadate complex with nicked DNA

Type IB topoisomerases are essential enzymes that are responsible for relaxing superhelical tension in DNA by forming a transient covalent nick in one strand of the DNA duplex. Topoisomerase I is a target for anti-cancer drugs such as camptothecin, and these drugs also target the topoisomerases I in pathogenic trypanosomes including Leishmania species and Trypanosoma brucei. Most eukaryotic enzymes, including human topoisomerase I, are monomeric. However, for Leishmania donovani, the DNA-binding activity and the majority of residues involved in catalysis are located in a large subunit, designated TOP1L, whereas the catalytic tyrosine residue responsible for covalent attachment to DNA is located in a smaller subunit, called TOP1S. Here, we present the 2.27A crystal structure of an active truncated L.donovani TOP1L/TOP1S heterodimer bound to nicked double-stranded DNA captured as a vanadate complex. The vanadate forms covalent linkages between the catalytic tyrosine residue of the small subunit and the nicked ends of the scissile DNA strand, mimicking the previously unseen transition state of the topoisomerase I catalytic cycle. This structure fills a critical gap in the existing ensemble of topoisomerase I structures and provides crucial insights into the catalytic mechanism.

Canine leishmaniasis, Italy

We report the results of a survey to determine the prevalence of canine leishmaniasis and the presence of sand flies in northwestern Italy, where autochthonous foci of canine leishmaniasis have not been reported. Active foci of canine leishmaniasis were identified, which suggests that the disease is now also endemic in continental climate areas.

Sandfly fauna in a military training area endemic for American tegumentary leishmaniasis in the Atlantic Rain Forest region of Pernambuco, Brazil

The aim of this study was to characterize the sandfly fauna in a military training area situated in the "Zona da Mata" region of Pernambuco State, Brazil, where human cases of American tegumentary leishmaniasis (ATL) had been observed, caused by Leishmania (Viannia) braziliensis. The occurrence of 16 sandfly species in the Marshall Newton Cavalcanti Military Training Camp (CIMNC) indicates an important diversity of sandfly species in this study area. Lutzomyia complexa was the most common species (51.36%) followed by L. choti (43.54%). All the captures were made in areas where training activities were conducted and where clinical cases had been detected in individuals performing training, following this period. The data relating the sandfly behavior to previous data in the same area provides strong evidence for the occurrence of an enzootic cycle of the parasite, and outbreaks followed the period of training activities in the remaining Atlantic Rain Forest and secondary forest areas.

Leishmania donovani: Differential activities of classical topoisomerase inhibitors and antileishmanials against parasite and host cells at the level of DNA topoisomerase I and in cytotoxicity assays

Different classes of topoisomerase (TOP) inhibitors and antitrypanosomatid agents exhibited variable efficacies against Leishmania donovani parasites and human mononuclear cells both at the level of DNA topoisomerase I (TOPI) catalytic activity and in cytotoxicity assays. Bis-benzimidazoles and the diamidine diminazene aceturate exhibited uniformly high efficacies against parasite and host enzymes as well as against parasite and mononuclear cells, but pentamidine showed around 2 orders of magnitude greater specificity for Leishmania TOPI and amastigote cells (P<0.05). The protoberberine coralyne and the flavonoid quercetin were highly potent, but non-selective, inhibitors in vitro, although the latter showed slight selectivity for parasite TOPI. Camptothecin was selective for mononuclear cells at both levels (P<0.05) and sodium stibogluconate was selective only at the enzyme level displaying 30-fold greater potency against parasite TOPI (P<0.05). These data suggest that at least part of pentamidines' leishmanicidal activity may be mediated through TOPI inhibition, and support the feasibility of exploiting differences between Leishmania and human TOPs to develop modified compounds with improved selectivity.

Identification and biochemical characterization of Leishmania strains isolated in Peru, Mexico, and Spain

Eight Leishmania promastigotes were isolated from different geographical areas: three (LP1, LP2, and LP3) from the provincial department La Libertad and the fourth (LP4) from the department of Cajamarca (northern Peru); another three (LM1, LM2, and LM3) in the province of Campeche (Mexico); and the last (LS1) from a clinical case of a dog in Madrid (Spain). The isolates were characterized by carbohydrate cell-surface residues using agglutinations with four purified lectins, by isoenzyme analysis using different isoenzymes, by analysis of kinetoplast DNA (kDNA) restriction fragment length polymorphism using four different restriction endonucleases and by the final metabolite patterns after in vitro culture. These isolates were compared with four reference strains and typified as: Leishmania (Leishmania) donovani, two strains of L. (L.) infantum, and one species of L. (Viania) peruviana. According to our results and the statistical study, the Peruvian isolates represent three different strains: one would be L. (V.) peruviana, another the strain isolated in Cajamarca (LP4) and the third would include the three strains from the department of La Libertad (LP1, LP2, and LP3), these latter three isolates being phylogenetically closer to the reference strain L. (L.) donovani. Meanwhile, the three isolates from Mexico form a group with close phylogenetic relationships to each other. The isolate from Spain belongs to the species L. (L.) infantum. Thus, a close correlation was drawn between the identity of each strain and its geographical origin.

Potential of direct agglutination test based on promastigote and amastigote antigens for serodiagnosis of post-kala-azar dermal leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL) is a dermal complication, a sequel to kala-azar. Diagnosis of PKDL presents a challenge due to the low parasite burden in the lesions. The direct agglutination test (DAT) based on promastigote and amastigote antigens of Leishmania donovani of indigenous isolates was developed to diagnose PKDL, and the results were compared with those of the rk39 strip test. The sensitivities of DAT for antileishmanial antibody detection, based on promastigote and amastigote antigens at a cutoff titer of 1:800 were 98.5% and 100%, respectively, with corresponding specificities of 96.5% and 100%. DAT could correctly detect 100% polymorphic cases and 95.4% macular PKDL cases. In comparison, the rk39 strip test was able to correctly diagnose 95.6% of polymorphic and 86.0% macular PKDL cases. DAT based on axenic amastigote antigen provided 100% sensitivity and specificity, making it particularly useful for macular PKDL cases, which are often missed by the rk39 strip test. Thus, DAT provides a simple, reliable, and inexpensive test for PKDL diagnosis with potential applicability in field conditions.

SELECTIVE ACTION OF FLUOROQUINOLONES AGAINST INTRACELLULAR AMASTIGOTES OF LEISHMANIA (VIANNIA) PANAMENSIS IN VITRO

We have demonstrated that fluoroquinolones, a class of antibacterial agents that act through inhibition of type II DNA topoisomerases, exert selective action against intracellular amastigotes of Leishmania (Viannia) panamensis at concentrations that are achievable in vivo. Drug cytotoxicity assays employing the luciferase reporter gene revealed that intracellular amastigotes were 6.6- to 25.9-fold more sensitive than human macrophages (P < 0.05) to second-generation fluoroquinolones in vitro. The most selective agents (enoxacin and ciprofloxacin) exhibited 2 orders of magnitude greater potency against parasites (50% effective dose [ED50] = 54.9-83.4 microM) than host cells (ED50 = 1,425-1,740 microM). Linear regression analysis of ED50 data confirmed a complete lack of correlation (r = 0.001) between the relative drug sensitivities of parasites and host cells. A potential relationship between the structures of fluoroquinolones and their relative leishmanicidal activities was observed. The key substituents of the basic pyridone beta-carboxylic acid nucleus accounting for enhanced antiparasite potency and selectivity appear to be a nitrogen at position 8 of the bicyclic nucleus (enoxacin), a cyclopropyl substituent at the R1 site (ciprofloxacin), and linkage of the R1 and X8 groups by a CH3CHO bridge to form a tricyclic compound (ofloxacin). These findings support the potential of fluoroquinolones and derivatives as novel antileishmanials and encourage their clinical evaluation.

Risk factors in the spread of leishmaniases: towards integrated monitoring?

Environmental changes, immune status and treatment failure constitute the three major risk factors for the (re-)emergence and spread of leishmaniases. Except for Leishmania-HIV co-infection, these risk factors are not systematically monitored and their interaction is poorly studied and understood. Recently, the multidisciplinary network Leish-Med was launched to document this issue around the Mediterranean and to promote transborder control strategies.

Advances in leishmaniasis

Governed by parasite and host factors and immunoinflammatory responses, the clinical spectrum of leishmaniasis encompasses subclinical (inapparent), localised (skin lesions), and disseminated infection (cutaneous, mucosal, or visceral). Symptomatic disease is subacute or chronic and diverse in presentation and outcome. Clinical characteristics vary further by endemic region. Despite T-cell-dependent immune responses, which produce asymptomatic and self-healing infection, or appropriate treatment, intracellular infection is probably life-long since targeted cells (tissue macrophages) allow residual parasites to persist. There is an epidemic of cutaneous leishmaniasis in Afghanistan and Pakistan and of visceral infection in India and Sudan. Diagnosis relies on visualising parasites in tissue or serology; culture and detection of parasite DNA are useful in the laboratory. Pentavalent antimony is the conventional treatment; however, resistance of visceral infection in India has spawned new treatment approaches--amphotericin B and its lipid formulations, injectable paromomycin, and oral miltefosine. Despite tangible advances in diagnosis, treatment, and basic scientific research, leishmaniasis is embedded in poverty and neglected. Current obstacles to realistic prevention and proper management include inadequate vector (sandfly) control, no vaccine, and insufficient access to or impetus for developing affordable new drugs.

Antileishmanial and trypanocidal activities of new miltefosine liposomal formulations

Liposomes composed of hexadecylphosphocholine/egg phosphatidylcholine/stearylamine (HePC/EPC/SA) 10:10:0.1, 10:10:0.5 and 10:10:1 (molar ratio) (1-3) were prepared and lyophilized. The liposomes were physicochemically characterized (size and zeta-potential) and they were found stable at 4 degrees C over a period of 4 weeks. In vitro, liposomes 1 and 2 were about twice more active than HePC against Leishmania donovani WT whereas liposomes 3 were about three times more active than HePC on HePC-resistant promastigotes. Although liposomes 1-3 were inactive on the in vitro intramacrophage amastigote model, the ability of the liposomes to accumulate within the liver where parasites are located justifies a further in vivo evaluation. We observed that liposome 1 was twice more active than HePC against Trypanosoma brucei brucei bloodstream forms maintained in vitro. In vivo results showed that liposomal HePC seemed to be less toxic than the free drug despite the absence of significant antitrypanosomal activity.

Development of recombinant chimeric antigen expressing immunodominant B epitopes of Leishmania infantum for serodiagnosis of visceral leishmaniasis

Wild canids and domestic dogs are the main reservoir of zoonotic visceral leishmaniasis (VL) caused by Leishmania infantum (syn.: Leishmania chagasi). Serological diagnosis of VL is therefore important in both human and dog leishmaniasis from a clinical and epidemiological point of view. Routine diagnosis of VL is traditionally carried out by immunofluorescent antibody test (IFAT), which is laborious and difficult to standardize and to interpret. In the last decade, however, several specific antigens of Leishmania infantum have been characterized, allowing the development of a recombinant-based immunoassay. Among them, the whole open reading frame encoding K9 antigen, the gene fragment encoding the repetitive sequence of K26, and the 3'-terminal gene fragment of the kinesin-related protein (K39sub) were previously evaluated as diagnostic markers for canine leishmaniasis and proved to be independent in their antibody reactivity. Since sensitivity of serological test is usually higher in multiple-epitope format, in this study the relevant epitopes of K9, K26, and K39 antigens were joined by PCR strategy to produce the chimeric recombinant protein. The resulting mosaic antigen was found highly expressed in Escherichia coli and efficiently purified by affinity chromatography. Antigenic properties of this recombinant antigen were evaluated by indirect enzyme-linked immunosorbent assay (ELISA) using a panel of human and dog sera previously characterized by parasitological and/or serological techniques. Chimeric ELISA showed 99% specificity in both human (n = 180) and canine (n = 343) control groups, while sensitivity was higher in canine VL (96%, n = 213) than in human VL (82%, n = 185). Accordingly, concordance between IFAT and canine chimeric ELISA (k = 0.95, 95% confidence interval = 0.93 to 0.98) was higher than between IFAT and human chimeric ELISA (k = 0.81, 95% confidence interval = 0.76 to 0.87). Results suggest the potential use of this new antigen for routine serodiagnosis of VL in both human and canine hosts.

Leishmania inactivation in human pheresis platelets by a psoralen (amotosalen HCl) and long-wavelength ultraviolet irradiation

BACKGROUND

Leishmania spp. are protozoans that cause skin and visceral diseases. Leishmania are obligate intracellular parasites of mononuclear phagocytes and have been documented to be transmitted by blood transfusion.

STUDY DESIGN AND METHODS

This study examines whether Leishmania can be inactivated in human platelet (PLT) concentrates by a photochemical treatment process that is applicable to blood bank use. Human PLT concentrates were contaminated with Leishmania mexicana metacyclic promastigotes or mouse-derived Leishmania major amastigotes and were exposed to long-wavelength ultraviolet (UV) A light (320-400 nm) plus the psoralen amotosalen HCl.

RESULTS

Neither treatment with amotosalen nor UVA alone had an effect on Leishmania viability; however, treatment with 150 micromol per L amotosalen plus 3 J per cm(2) UVA inactivated both metacyclic promastigotes and amastigotes to undetectable levels, more than a 10,000-fold reduction in viability.

CONCLUSIONS

This study demonstrates the effectiveness of photochemical treatment to inactivate Leishmania in PLT concentrates intended for transfusion. Both metacylic promastigotes, which represent the infectious form from the sand fly vector, and amastigotes, which represent the form that grows in mononuclear phagocytes, were extremely susceptible to photochemical inactivation by this process. Thus, the photochemical treatment of PLT concentrates inactivates both forms of Leishmania that would be expected to circulate in blood products collected from infected donors.

Synthesis and in vitro leishmanicidal activity of 2-(5-nitro-2-furyl) and 2-(5-nitro-2-thienyl)-5-substituted-1,3,4-thiadiazoles

A series of 2-(5-nitro-2-furyl) and 2-(5-nitro-2-thienyl)-5-substituted-1,3,4-thiadiazoles (5a-d and 6a-j) were synthesized and evaluated against Leishmania major promastigotes using (3)H-thymidine incorporation. Most of the compounds showed activity better than the reference drug sodium stibogluconate (Pentostam). The most active compound was 6c (IC(50)=0.1 microM).

Failure of a multi-subunit recombinant leishmanial vaccine (MML) to protect dogs from Leishmania infantum infection and to prevent disease progression in infected animals

We report results of a Phase III trial of the multi-subunit recombinant Leishmania polyprotein MML for the protection of dogs against infection by Leishmania infantum. The antigen, also known as Leish-111f, is the first antileishmanial human vaccine entered Phase I clinical testing. The study was performed in a leishmaniasis endemic area of southern Italy. Three groups of 15 Leishmania-free beagle dogs each, received 3 monthly injections with vaccines A (MML+MPL-SE adjuvant), B (sterile saline = control) and C (MML+Adjuprime adjuvant), respectively, before transmission season 2002. The surviving dogs received a second three-dose vaccine course 1 year later. The dogs were naturally exposed to sandfly bites for 2.5 months in 2002, and for 5 months in 2003. Every 2 months post vaccination, dogs were examined by clinical and immunological evaluation, and by specific serology, microscopy, culture and PCR. A weak lymphoproliferative response to MML was seen in A and C groups throughout the study period. One year after the first vaccine course, the cumulative incidence of leishmanial infections was 40% in group A, 43% in group B and 36% in group C. Two-year post-vaccination (1 year after the second vaccine course) the cumulative incidence was 87% in group A (with three symptomatic cases), 100% in group B (with no symptomatic cases) and 100% in group C (with two symptomatic cases). The efficacy of the MML vaccine as an immunotherapeutic agent for the prevention of disease progression (subpatent infection-->asymptomatic patent infection-->symptomatic patent infection) was evaluated through follow-up of dogs found infected prior to the second vaccination. Among 15 infected animals, progression to a subsequent stage of infection was found in 5/6 dogs of group A, 3/6 of group B and 2/3 of group C. We conclude that vaccination with MML is not effective to prevent leishmaniasis infection and disease progression in dogs under field conditions.

Antiparasitic activity of a triphenyl tin complex against Leishmania donovani

Visceral leishmaniasis is a life-threatening human disease commonly known as kala-azar. Leishmania donovani is the causative agent of this parasitic disease transmitted by the sand fly vector to infect hosts. Triphenyl tin salicylanilide thiosemicarbazone [Ph(3)Sn(OSal.TSCZH)] (TTST) which is an organometallic complex of triphenyl tin has been evaluated to explore possibility to develop a potent chemotherapeutic agent against visceral leishmaniasis. Effect of triphenyl tin complex on growth inhibition and host--parasite interaction were examined both in vitro and in vivo. Release of toxic superoxide radical was measured spectrophotometrically through the formation of blue formazan derived from reduced nitrobluetetrazolium. To understand mode of action of Ph(3)Sn(OSal.TSCZH), superoxide dismutase activity was determined spectrophotometrically by measuring ability of this enzyme to inhibit pyrogallol autoxidation and also by activity staining of the non-denaturing polyacrylamide gels after separating superoxide dismutase. Antileishmanial activity of triphenyl tin complex were found to be effective both in vitro and in vivo at lower concentrations compared to the existing toxic drugs available. IC(50) of Ph(3)Sn(OSal.TSCZH) was calculated as 0.05+/-0.01mg/L. Intracellular survival of the parasite in host macrophages was inhibited by TTST in a dose dependent manner. Parasite burden in spleen was reduced to 87% under TTST treatment (10mg/kg body weight) and under sodium antimony gluconate (20mg/kg body weight) reduced nearly to 65%. Its action as a chemotherapeutic agent is found to be mediated through inhibition of superoxide dismutase and simultaneous release of toxic superoxide radical. We propose that Ph(3) Sn(OSal.TSCZH) may be considered as a prospective candidate to establish a better line of therapeutic process against experimental visceral leishmaniasis.

Immunostimulatory cellular responses of cured Leishmania-infected patients and hamsters against the integral membrane proteins and non-membranous soluble proteins of a recent clinical isolate of Leishmania donovani

Development of an effective immunoprophylactic agent for visceral leishmaniasis (VL) has become imperative due to the increasing number of cases of drug resistance and relapse. Live and killed whole parasites as well as fractionated and recombinant preparations have been evaluated for vaccine potential. However, a successful vaccine against the disease has been elusive. Because protective immunity in human and experimental leishmaniasis is predominantly of the Th1 type, immunogens with Th1 stimulatory potential would make good vaccine candidates. In the present study, the integral membrane proteins (IMPs) and non-membranous soluble proteins (NSPs), purified from promastigotes of a recent field isolate, Leishmania donovani stain 2001, were evaluated for their ability to induce cellular responses in cured patients (n = 9), endemic controls (n = 5) of visceral leishmaniasis (VL) and treated hamsters (n = 10). IMPs and NSPs induced significant proliferative responses (SI 6.3 +/- 4.1 and 5.6 +/- 2.3, respectively; P < 0.01) and IFN-gamma production (356.3 +/- 213.4 and 294.29 +/- 107.6 pg/ml, respectively) in lymphocytes isolated from cured VL patients. Significant lymphoproliferative responses against IMPs and NSPs were also noticed in cured Leishmania animals (SI 7.2 +/- 4.7 & 6.4 +/- 4.1, respectively; P < 0.01). In addition, significant NO production in response both IMPs and NSPs was also noticed in macrophages of hamsters and different cell lines (J774A-1 and THP1). These results suggest that protective, immunostimulatory molecules are present in the IMP and NSP fractions, which may be exploited for development of a subunit vaccine for VL.

Randomized, Double-Blind Clinical Trial of Topical Imiquimod 5% with Parenteral Meglumine Antimoniate in the Treatment of Cutaneous Leishmaniasis in Peru

BACKGROUND

Current treatments for cutaneous leishmaniasis are limited by their toxicity, high cost, and discomfort and the emergence of drug resistance. New approaches, including combination therapies, are urgently needed. We performed a double-blind, randomized trial of therapy with parenteral antimony plus topical imiquimod, an innate immune-response modulator, versus therapy with antimony alone, in subjects with cutaneous leishmaniasis for whom an initial course of antimony therapy had failed.

METHODS

Forty subjects with clinical resistance to antimony were recruited in Lima, Peru, between February 2001 and December 2002. All subjects received meglumine antimoniate (20 mg/kg/day im or iv) and were randomized to receive either topical imiquimod 5% cream (Aldara; 3M Pharmaceuticals) or vehicle control every other day for 20 days. Lesions and adverse events were evaluated during treatment and at 1, 2, 3, 6, and 12 months after the treatment period.

RESULTS

The mean number of lesions was 1.2 per person; 71% of the lesions were facial and 76% were ulcerative. There were no major differences between the groups, and all but 2 subjects completed therapy. Mild adverse events were reported by 73% of the subjects, but only erythema occurred more commonly in the imiquimod group (P < or = .02). Lesions resolved more rapidly in the imiquimod group: 50% of the imiquimod group achieved cure at 1 month after the treatment period versus 15% of the vehicle cream group (P < or = .02); 61% of the imiquimod group at 2 months versus 25% of the vehicle cream group (P < or = .03); and 72% of the imiquimod group at 3 months versus 35% of the vehicle cream group (P < or = .02). Residual scarring in the imiquimod group was less prominent than in the vehicle cream group.

CONCLUSIONS

Combined antimony plus imiquimod treatment was well tolerated, accelerated healing of lesions, and improved scar quality. This therapy may have particular advantages for subjects with facial lesions.