Natural history, clinical evolution, and the host-parasite interaction in New World cutaneous Leishmaniasis

The Elimination Status of Visceral Leishmaniasis in Southeast Asia Region

PURPOSE

Visceral leishmaniasis (VL) is caused by an intracellular parasite that is transmitted to humans by sandfly bites. It is prevalent throughout Asia, Africa, the Americas, and the Mediterranean area, where 147 million people are at risk of contracting the illness. The manifestation of heterotrophic illness relies on both Leishmania implicated and the host's immunological response, ranging from asymptomatic to severe leishmaniasis with potentially lethal effects.

METHOD

We reviewed the literature (published till 31st December 2023) on the worldwide situation of leishmaniasis, standard and novel detection techniques, and traditional and modern treatment strategies and endeavors to eliminate VL. Moreover, epidemiological data was collected from the World Health Organization's publicly available databases. GraphPad Prism Version 8 was used to analyze and produce figures based on the epidemiological data.

RESULTS

Diagnosis of parasites in tissues or serology is commonly employed. Diagnosis by identifying parasite DNA using molecular techniques is becoming more popular. Despite recent findings of L. donovani resistance to pentavalent antimoniate medications, it continues to be the cornerstone in the medical management of VL. Amphotericin B and its lipid formulations, injectable paromomycin, and oral miltefosine are among the new therapy options being researched. The number of reported VL cases has reduced remarkably over the last decade due to human interventions made to eliminate VL. Particularly countries from the South East Asian region have experienced momentous progress in reducing VL cases and eliminating this disease from this region. Owing to the robust elimination programs, countries such as Bangladesh has eliminated VL as a public health concern. India and Nepal are on the verge of its elimination.

CONCLUSION

Rapid diagnosis, effective and inexpensive treatment, simple access to newly discovered medications, appropriate vector control, and a well-designed vaccine are all required for the elimination of this disease burden in impoverished areas of the globe.

The Role of Senescent CD8+T Cells in the Pathogenesis of Disseminated Leishmaniasis

Disseminated leishmaniasis (DL) caused by L. braziliensis is characterized by the presence of 10 to more than 1000 lesions spread on the body. While protection against Leishmania is mediated by macrophages upon activation by IFN-γ produced by CD4+T cells, the pathology of disseminated leishmaniasis (DL) could be mediated by macrophages, NK, and CD8+T cells. Herein, we evaluate the participation of senescent CD8+T cells in the pathogenesis of DL. Methods: Peripheral blood mononuclear cells (PBMCs), biopsies, co-cultures of CD8+T cells with uninfected and infected macrophages (MØ), and PBMC cultures stimulated with soluble L. braziliensis antigen (SLA) for 72 h from patients with cutaneous leishmaniasis (CL) and DL were used to characterize senescent CD8+T cells. Statistical analysis was performed using the Mann-Whitney and Kruskal-Wallis tests, followed by Dunn's. Results: Patients with DL have an increase in the frequency of circulating CD8+T cells that present a memory/senescent phenotype, while lesions from DL patients have an increase in the frequency of infiltrating CD8+T cells with a senescent/degranulation phenotype. In addition, after specific stimuli, DL patients' circulating CD8+T with memory/senescent profile, showing degranulation characteristics, increased upon SLA stimuli, and those specific CD8+T cells from DL patients had an increased degranulation phenotype, causing more apoptosis of infected target cells. Conclusions: DL patients show a higher frequency of cytotoxic senescent CD8+T cells compared to CL patients, and that could promote the lysis of infected cells, although without parasite killing, releasing Leishmania to the extracellular compartment, contributing to the spread of parasites.

Review of Leishmaniasis Treatment: Can We See the Forest through the Trees?

There are three known clinical syndromes of leishmaniasis: cutaneous (CL), mucocutaneous (MCL), and visceral disease (VL). In MCL and VL, treatment must be systemic (either oral or intravenous), while CL treatment options vary and include observation-only localized/topical treatment, oral medications, or parenteral drugs. Leishmaniasis treatment is difficult, with several factors to be considered. First, the efficacy of treatments varies among different species of parasites prevalent in different areas on the globe, with each species having a unique clinical presentation and resistance profile. Furthermore, leishmaniasis is a neglected tropical disease (NTD), resulting in a lack of evidence-based knowledge regarding treatment. Therefore, physicians often rely on case reports or case series studies, in the absence of randomized controlled trials (RCT), to assess treatment efficacy. Second, defining cure, especially in CL and MCL, may be difficult, as death of the parasite can be achieved in most cases, while the aesthetic result (e.g., scars) is hard to predict. This is a result of the biological nature of the disease, often diagnosed late in the course of disease (with possible keloid formation, etc.). Third, physicians must consider treatment ease of use and the safety profile of possible treatments. Thus, topical or oral treatments (for CL) are desirable and promote adherence. Fourth, the cost of the treatment is an important consideration. In this review, we aim to describe the diverse treatment options for different clinical manifestations of leishmaniasis. For each currently available treatment, we will discuss the various considerations mentioned above (efficacy, ease of use, safety, and cost).

Malaria and leishmaniasis: Updates on co-infection

Malaria and leishmaniasis are endemic parasitic diseases in tropical and subtropical countries. Although the overlap of these diseases in the same host is frequently described, co-infection remains a neglected issue in the medical and scientific community. The complex relationship of concomitant infections with Plasmodium spp. and Leishmania spp. is highlighted in studies of natural and experimental co-infections, showing how this "dual" infection can exacerbate or suppress an effective immune response to these protozoa. Thus, a Plasmodium infection preceding or following Leishmania infection can impact the clinical course, accurate diagnosis, and management of leishmaniasis, and vice versa. The concept that in nature we are affected by concomitant infections reinforces the need to address the theme and ensure its due importance. In this review we explore and describe the studies available in the literature on Plasmodium spp. and Leishmania spp. co-infection, the scenarios, and the factors that may influence the course of these diseases.

Assessment of Immune and Clinical Response in Patients with Mucosal Leishmaniasis Treated with Pentavalent Antimony and Pentoxifylline

Mucosal leishmaniasis (ML) is a severe form of tegumentary leishmaniasis associated with a persistent inflammatory response. High levels of TNF, IFN-γ, CXCL9 and CXCL10 are found in ML patients, and the association of pentoxifylline with antimony is more effective in decreasing the healing time in ML patients when compared to antimony alone. The present study aimed to investigate the existence of a correlation between cytokine and chemokine production and ML severity and evaluate the potential value of cytokine and chemokine production as marker of therapeutic response in ML patients. This prospective study included 86 subjects in an area of endemic Leishmania braziliensis transmission. Patients diagnosed with ML were classified into clinical stages ranging from I to V according to disease severity. TNF, IFN-γ, CXCL9 and CXCL10 levels were quantified in the supernatant of the mononuclear cell cultures by ELISA before and after treatment with antimony alone or antimony plus pentoxifylline. The median TNF level in the group with mild disease (Stages I-II) was 1064 pg/mL (142-3738 pg/mL), while, in the group with moderate or severe disease (Stages III-V), it was 1941 pg/mL (529-5294 pg/mL) (p = 0.008). A direct correlation was observed between ML clinical severity and levels of TNF production (r = 0.44, p = 0.007). Patients who were treated with antimony and pentoxifylline healed significantly faster than those treated with antimony alone (52 vs. 77 days, hazard ratio = 0.60; 95% confidence interval = 0.38-0.95, p = 0.013). Therapeutic failure was higher in the group that received antimony alone (25% vs. 7%; p = 0.041). There was a significant decrease in CXCL9 after therapy of ML in both groups (p = 0.013; p = 0.043). TNF levels are associated with the severity of mucosal diseases, and pentoxifylline associated with antimony should be the recommended therapy for ML in countries where liposomal amphotericin B is not available.

Leishmania V. braziliensis infection in asymptomatic domestic animals within an endemic region in the Northeast of Brazil

Background:

American cutaneous leishmaniasis is a commonly neglected, vector-borne tropical parasitic disease that is a major public health concern in Brazil. Leishmania (Viannia) braziliensis is the main species associated with the disease. Accurate diagnosis is based on epidemiological surveillance, clinical assessment, and laboratory testing. Leishmania (V.) braziliensis has been detected in several wild and synanthropic mammals. Their epidemiological role has not been entirely elucidated. This study aimed to assess potential L. braziliensis infections in asymptomatic domestic animals, by molecular and serological testing in endemic areas, in the metropolitan region of Recife.

Methods:

Blood samples and conjunctival fluids were collected from 232 animals (canids, felids, equines, and caprines) for the detection of L. braziliensis using molecular tests (conventional and real-time polymerase chain reaction [PCR and qPCR]). For immunological detection, blood samples from 115 dogs were assessed using enzyme-linked immunosorbent assay.

Results:

Real-time quantitative PCR showed positive results for blood and conjunctival samples in all investigated species. The results of the blood and conjunctival samples were 68.2% and 26.9% in Canis familiaris, 100% and 41.7% in Felis catus, 77.3% and 30.8% in Equus caballus/Equus asinus, and 50% and 33.3% in Capra hircus samples, respectively.

Conclusions:

Results from this study adds valuable information to our understanding of the role of asymptomatic domestic animals, L. braziliensis life cycle, and American cutaneous leishmaniasis in Northeast Brazil.

A Mouse Model of Ulcerative Cutaneous Leishmaniasis by Leishmania (Viannia) panamensis to Investigate Infection, Pathogenesis, Immunity, and Therapeutics

A mouse model of cutaneous leishmaniasis (CL) by Leishmania (Viannia) panamensis (L(V)p) that reproduces the characteristics of the human disease remains elusive. Here we report the development of a CL model that uses a mouse-adapted L(V)p isolate to reproducibly induce a dermal disease with a remarkable similarity to human CL. BALB/c mice infected intradermally in the ear with 105 stationary UA-946 L(V)p promastigotes develop a progressive cutaneous disease that exhibits the typical ulcerated lesions with indurated borders observed in CL patients. Although most of parasites in the inoculum die within the first week of infection, the survivors vigorously multiply at the infection site during the following weeks, paralleling disease appearance and aggravation. Regional lymphadenopathy as well as lymphatic dissemination of parasites to draining lymph nodes (dLN) was evidenced early after infection. Viable parasites were also isolated from spleen at later timepoints indicating systemic parasitic dissemination, but, strikingly, no signs of systemic disease were observed. Increasing numbers of myeloid cells and T lymphocytes producing IFNγ and IL-4 were observed in the dLN as disease progressed. A mixed adaptive L(V)p-specific T cell-mediated response was induced, since ex vivo recall experiments using dLN cells and splenocytes revealed the production of type 1 (IFNγ, IL-2), type 2 (IL-4, IL-13), regulatory (IL-10), and inflammatory (GM-CSF, IL-3) cytokines. Humoral adaptive response was characterized by early production of IgG1- followed by IgG2a-type of L(V)p-specific antibodies. IFNγ/IL-4 and IgG2a/IgG1 ratios indicated that the initial non-protective Th2 response was redirected toward a protective Th1 response. In situ studies revealed a profuse recruitment of myeloid cells and of IFNγ- and IL-4-producing T lymphocytes to the site of infection, and the typical histopathological changes induced by dermotropic Leishmania species. Evidence that this model is suitable to investigate pharmacological and immunomodulatory interventions, as well as for antigen discovery and vaccine development, is also presented. Altogether, these results support the validity and utility of this novel mouse model to study the pathogenesis, immunity, and therapeutics of L(V)p infections.

Host–Pathogen Interaction in Leishmaniasis: Immune Response and Vaccination Strategies

Leishmaniasis is a zoonotic and vector-borne infectious disease that is caused by the genus Leishmania belonging to the trypanosomatid family. The protozoan parasite has a digenetic life cycle involving a mammalian host and an insect vector. Leishmaniasisis is a worldwide public health problem falling under the neglected tropical disease category, with over 90 endemic countries, and approximately 1 million new cases and 20,000 deaths annually. Leishmania infection can progress toward the development of species–specific pathologic disorders, ranging in severity from self-healing cutaneous lesions to disseminating muco-cutaneous and fatal visceral manifestations. The severity and the outcome of leishmaniasis is determined by the parasite’s antigenic epitope characteristics, the vector physiology, and most importantly, the immune response and immune status of the host. This review examines the nature of host–pathogen interaction in leishmaniasis, innate and adaptive immune responses, and various strategies that have been employed for vaccine development.

Rapid Clinical Management of Leishmaniasis in Emergency Department: A Case Report with Clinical Review of Recent Literature

Simple Summary

In this article, we have briefly described the various forms of leishmania infection occur in emergency settings as well as the principal differential diagnoses, and we propose a decision algorithm to facilitate its early recognition in the emergency department (ED). Regarding the last point, the costs and validity of the most common modern diagnostic technologies have been examined, with particular attention to their sensibility and specificity; particularly, rk39-based RTD has been examined. To reinforce the importance of a quick diagnosis performed in the emergency room, we introduce a rather paradigmatic case report of a 19-year-old patient presenting with suspected lymphoproliferative disease and subsequently addressed to the incorrect hospital ward. As often happens, signs and symptoms tended toward the diagnosis of a hematologic disease rather than an infectious one: therefore, it is crucial to include a variety of diagnostic possibilities when a patient presents with fever and associated lympho-adenomegaly with minor symptoms: Leishmaniasis always needs to be considered among them.

Abstract

Systemic or localized lympho-adenomegaly is a common cause of access to the emergency department (ED), and differential diagnosis is often complicated. The combination of anamnesis, physical examination, laboratory tests, and instrumental diagnosis are extremely important to orientate toward a rapid and correct therapy, even if a prompt discrimination of the etiology of this lymphadenomegaly is not often possible. Our aim with this review is to improve the management of a differential diagnosis between hematological and infective diseases as leishmaniasis in ED and suggest quick diagnostic techniques that might be useful for early identification. Together in the review, we describe a case report of a young man affected from visceral leishmaniasis who presented to our ED and was incorrectly addressed to the wrong ward for the study of his condition. Subsequently, we focus on the clinical presentation of visceral leishmaniasis and compare it to the most common differential diagnoses that are usually taken into account in the management of such patients.

Role of host genetics and cytokines in Leishmania infection

Cytokines and chemokines are important regulators of innate and specific responses in leishmaniasis, a disease that currently affects 12 million people. We overviewed the current information about influences of genetically engineered mouse models of cytokine and chemokine on leishmaniasis. We found that genetic background of the host, parasite species and sub-strain, as well as experimental design often modify effects of genetically engineered cytokine genes. Next we analyzed genes and QTLs (quantitative trait loci) that control response to Leishmania species in mouse in order to establish relationship between genetic control of cytokine expression and organ pathology. These studies revealed a network-like complexity of the combined effects of the multiple functionally diverse QTLs and their individual specificity. Genetic control of organ pathology and systemic immune response overlap only partially. Some QTLs control both organ pathology and systemic immune response, but the effects of genes and loci with the strongest impact on disease are cytokine-independent, whereas several loci modify cytokines levels in serum without influencing organ pathology. Understanding this genetic control might be important in development of vaccines designed to stimulate certain cytokine spectrum.

Spatiotemporal Variability of Zoonotic Cutaneous Leishmaniasis Based on Sociodemographic Heterogeneity. The Case of Northeastern Iran, 2011-2016

Zoonotic cutaneous leishmaniasis (ZCL) is one of the most prevalent zoonoses in Iran, especially in central and northeastern Iran. This research aimed to examine whether there were spatiotemporal clusters of ZCL cases, and if so, whether there were differences in clustering according to age, sex, area of residence, and occupation. Spatial analysis, including global and local spatial autocorrelations, inverse distance weighting, and space-time scan statistics, were used to determine potential clusters in the villages of Golestan from 2011-2016. Several spatially significant (p < 0.05) clusters were observed in the north and northeastern regions, and most persisted until the last year of the study period. Children (0-10 years) living in rural settings were more likely to have an infection than those living in other areas. Although the disease was centered in the northern regions, housekeepers, females, and patients aged 21-30 and 41-50 years were found to be the high-risk groups in the southern areas. The seasonal pattern indicated that the outbreak mainly began in late summer, peaked in October, and diminished in December. By exploring spatiotemporal variations of ZCL by sociodemographic information, this study was able to identify priority areas for decision-makers in healthcare and resource allocation.

Clinical Presentation and Response to Therapy in Children with Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) caused by Leishmania braziliensis occurs predominantly in adult males. Herein, we compare the clinical presentation and the response to antimony therapy of CL in children versus adults. Participants included 571 patients with CL; of these, 129 were children (age ≤ 12 years). Cure was defined as the complete healing of ulcer in the absence of raised borders at day 90 after initiation of therapy. Failure was defined by the presence of an active ulcer or a scar with elevated borders at day 90. In comparison with adults, children had shorter duration of illness, more lesions in the head, and smaller ulcers. Risk factors for therapeutic failure were younger age, shorter duration of disease, higher number of lesions, and larger size of the biggest ulcer. When age was categorized in ≤ 12-year-olds (children versus adults), it predicted therapeutic failure with statistical significance at day 60 but not at day 90. In conclusion, our data indicate that there are significant differences in the clinical presentation of CL between children and adults. Physicians caring for children with CL should be aware that lesions may take longer to heal and remain alert for the possibility of higher odds of therapeutic failure in this group.

Molecular diagnosis of protozoan parasites by Recombinase Polymerase Amplification

Infections caused by protozoan parasites affect millions of people around the world. Traditionally, diagnosis was made by microscopy, which is insensitive and in some cases not specific. Molecular methods are highly sensitive and specific, but equipment costs and personnel training limit its availability only to specialized centers, usually far from populations with the highest risk of infection. Inexpensive methods that can be applied at the point of care (POC), especially in places with limited health infrastructure, would be a major advantage. Isothermal amplification of nucleic acids does not require thermocyclers and is relatively inexpensive and easy to implement. Among isothermal methods, recombinase polymerase amplification (RPA) is sensitive and potentially applicable at POC. We and others have developed RPA diagnostic tests to detect protozoan parasites of medical importance. Overall, our results have shown high specificity with limits of detection similar to PCR. Currently, the optimization of RPA for use at the POC is under development, and in the near future the tests should become available to detect protozoan infections in the field. In this review we discuss the current status, challenges, and future of RPA in the field of molecular diagnosis of protozoan parasites.

Prevalence of and Factors Associated with Negative Microscopic Diagnosis of Cutaneous Leishmaniasis in Rural Peru

Cutaneous leishmaniasis is endemic to South America where diagnosis is most commonly conducted via microscopy. Patients with suspected leishmaniasis were referred for enrollment by the Ministry of Health (MoH) in Lima, Iquitos, Puerto Maldonado, and several rural areas of Peru. A 43-question survey requesting age, gender, occupation, characterization of the lesion(s), history of leishmaniasis, and insect-deterrent behaviors was administered. Polymerase chain reaction (PCR) was conducted on lesion materials at the Naval Medical Research Unit No. 6 in Lima, and the results were compared with those obtained by the MoH using microscopy. Factors associated with negative microscopy and positive PCR results were identified using χ² test, t-test, and multivariate logistic regression analyses. Negative microscopy with positive PCR occurred in 31% (123/403) of the 403 cases. After adjusting for confounders, binary multivariate logistic regression analyses revealed that negative microscopy with positive PCR was associated with patients who were male (adjusted odds ration [OR] = 1.93 [1.06-3.53], P = 0.032), had previous leishmaniasis (adjusted OR = 2.93 [1.65-5.22], P < 0.0001), had larger lesions (adjusted OR = 1.02 [1.003-1.03], P = 0.016), and/or had a longer duration between lesion appearance and PCR testing (adjusted OR = 1.12 [1.02-1.22], P = 0.017). Future research should focus on further exploration of these underlying variables, discovery of other factors that may be associated with negative microscopy diagnosis, and the development and implementation of improved testing in endemic regions.

Leishmania (Viannia) braziliensis isolated from the saliva of patients in a cutaneous leishmaniasis-endemic area of northeastern Brazil

Several studies have described the use of non-invasive collection methods, mostly based on the detection of parasite DNA, for diagnosis. However, no Leishmania specimens have been isolated from saliva. Here, we report the first isolation of Leishmania braziliensis from the saliva of humans with cutaneous leishmaniasis but without lesions on their mucosa. The isolates were obtained from salivary fluid inoculated in hamsters and were tested by multilocus enzyme electrophoresis. Seven samples from 43 patients suspected of having the disease were identified for in vivo culture. These findings suggest that saliva is a clinical sample that allows the isolation of Leishmania sp.

Dynamics of American tegumentary leishmaniasis in a highly endemic region for Leishmania (Viannia) braziliensis infection in northeast Brazil

Background

American Tegumentary Leishmaniasis (ATL) caused by Leishmania braziliensis is endemic in Corte de Pedra, Northeast Brazil. Most L. braziliensis infections manifest as localized cutaneous leishmaniasis (CL). Disseminated manifestations include mucosal leishmaniasis (ML), present at a low constant level for several decades, and newly emerging disseminated leishmaniasis (DL). Surprisingly, DL has recently surpassed ML in its spatial distribution. This led us to hypothesize that distinct forms of ATL might spread in different patterns through affected regions.

Methodology/Principal findings

We explored the incidence and geographic dispersion of the three clinical types of ATL over a span of nearly two decades in Corte de Pedra. We obtained the geographic coordinates of the homes of patients with ATL during 1992–1996, 1999–2003 and 2008–2011. The progressive dispersion of ML or DL in each time period was compared to that of CL in 2008–2011 with the Cusick and Edward’s geostatistical test. To evaluate whether ATL occurred as clusters, we compared each new case in 2008–2011 with the frequency of and distance from cases in the previous 3 to 12 months. The study revealed that DL, ML and CL actively spread within that region, but in distinct patterns. Whereas CL and DL propagated in clusters, ML occurred as sporadic cases. DL had a wider distribution than ML until 2003, but by 2011 both forms were distributed equally in Corte de Pedra. The incidence of ML fluctuated over time at a rate that was distinct from those of CL and DL.

Conclusions/Significance

These findings suggest that CL and DL maintain endemic levels through successive outbreaks of cases. The sporadic pattern of ML cases may reflect the long and variable latency before infected patients develop clinically detectable mucosal involvement. Intimate knowledge of the geographic distribution of leishmaniasis and how it propagates within foci of active transmission may guide approaches to disease control.

American tegumentary leishmaniasis (ATL) caused by Leishmania braziliensis is characterized by lesions to the skin and/or mucosal surfaces of the oropharynx. It is widely distributed in endemic regions of northeast Brazil and has been difficult to control. Three common clinical forms of L. braziliensis infections are localized skin ulcers called cutaneous leishmaniasis (CL), mucosal leishmaniasis (ML) affecting mucosal surfaces, and disseminated leishmaniasis (DL), a recently described form with widespread skin lesions. Using GPS and epidemiologic data we explored the incidence and pattern of spread of ATL in the highly endemic region of Corte de Pedra, Brazil between 1992 and 2011. Geographic clusters of CL and DL cases were observed. In contrast, there was a sporadic non-clustered pattern of ML cases in the study area. The numbers of new cases of CL and DL presented similar fluctuation during the study period, but ML incidences were never correlated to those of CL and DL. We conclude that all forms of ATL actively spread within affected foci, but in different patterns. CL and DL cases occur in clusters suggesting active spread of causative parasite strains, whereas ML cases occurred in a sporadic pattern suggesting it may emerge due to factors such as host immunity or environmental conditions.

Pharmacokinetics of Miltefosine in Children and Adults with Cutaneous Leishmaniasis

An open-label pharmacokinetics (PK) clinical trial was conducted to comparatively assess the PK and explore the pharmacodynamics (PD) of miltefosine in children and adults with cutaneous leishmaniasis (CL) in Colombia. Sixty patients, 30 children aged 2 to 12 years and 30 adults aged 18 to 60 years, were enrolled. Participants received miltefosine (Impavido) at a nominal dose of 2.5 mg/kg/day for 28 days. Miltefosine concentrations were measured in plasma and peripheral blood mononuclear cells by liquid chromatography-tandem mass spectrometry of samples obtained during treatment and up to 6 months following completion of treatment, when therapeutic outcome was determined. Fifty-two patients were cured, 5 pediatric patients failed treatment, and 3 participants were lost to follow-up. Leishmania (Viannia) panamensis predominated among the strains isolated (42/46; 91%). Noncompartmental analysis demonstrated that plasma and intracellular miltefosine concentrations were, overall, lower in children than in adults. Exposure to miltefosine, estimated by area under the concentration-time curve and maximum concentration, was significantly lower in children in both the central and intracellular compartments (P < 0.01). Leishmania persistence was detected in 43% of study participants at the end of treatment and in 27% at 90 days after initiation of treatment. Clinical response was not dependent on parasite elimination. In vitro miltefosine susceptibility was similar for Leishmania strains from adults and children. Our results document PK differences for miltefosine in children and adults with cutaneous leishmaniasis that affect drug exposure and could influence the outcome of treatment, and they provide bases for optimizing therapeutic regimens for CL in pediatric populations. (This study has been registered at ClinicalTrials.gov under identifier NCT01462500.)

Diagnosis and Treatment of Leishmaniasis: Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) and the American Society of Tropical Medicine and Hygiene (ASTMH)

It is important to realize that leishmaniasis guidelines cannot always account for individual variation among patients. They are not intended to supplant physician judgment with respect to particular patients or special clinical situations. The IDSA and ASTMH consider adherence to these guidelines to be voluntary, with the ultimate determinations regarding their application to be made by the physician in the light of each patient's individual circumstances.

Pediatric Cutaneous Leishmaniasis in an Endemic Region in Turkey: A Retrospective Analysis of 8786 Cases during 1998-2014

BACKGROUND

Cutaneous leishmaniasis (CL) is a major public health concern in Turkey and Sanliurfa represents the most endemic city in Turkey. Although children are most commonly affected by CL, detailed studies of pediatric CL in Turkey are lacking.

METHODOLOGY/PRINCIPAL FINDINGS

In this report we retrospectively evaluated clinical and epidemiological data of 8786 pediatric CL cases, and how children respond to antimonial therapy. CL was observed most frequently in children between 6-10 years old. Interestingly this group showed shorter duration of disease and smaller lesions compared to 0-5 year and 11-15 year old groups. Females were more affected in all groups. Lesion localization and types varied among groups, with 0-5 year old presenting head/neck and mucosal lesions, and more often suffered from recidivans type, this could be associated to the longest duration of the disease in this group. Eleven-15 year old group showed fewer lesions in the head/neck but more generalized lesions. Evaluation of treatment response revealed that intra-lesional treatment was preferred over intramuscular treatment. However, 0-5 year old received intramuscular treatment more often than the other groups. Furthermore, the majority of 0-5 year old group which received intra-lesional treatment did not received subsequent intra-lesional cycles, as did children in the range of 6-15 years old.

CONCLUSIONS/SIGNIFICANCE

We report an increase in pediatric CL patients within the last four years. Analysis of pediatric CL patients by age revealed significant differences in CL progression. The data suggest that children between 0-5 years old responded better than other groups to intralesional treatment, since they received more often a single cycle of IL treatment, although follow up observation is required since they were more prone to develop recidivans. Eleven-15 year old patients comprise the largest percentage of patients receiving two or three cycles of intralesional treatment, suggesting that this group did not respond efficiently to intralesional treatment and highlighting the need for more effective therapeutic strategies against CL.

An Innovative Field-Applicable Molecular Test to Diagnose Cutaneous Leishmania Viannia spp. Infections

Cutaneous and mucosal leishmaniasis is widely distributed in Central and South America. Leishmania of the Viannia subgenus are the most frequent species infecting humans. L. (V.) braziliensis, L. (V.) panamensis are also responsible for metastatic mucosal leishmaniasis. Conventional or real time PCR is a more sensitive diagnostic test than microscopy, but the cost and requirement for infrastructure and trained personnel makes it impractical in most endemic regions. Primary health systems need a sensitive and specific point of care (POC) diagnostic tool. We developed a novel POC molecular diagnostic test for cutaneous leishmaniasis caused by Leishmania (Viannia) spp. Parasite DNA was amplified using isothermal Recombinase Polymerase Amplification (RPA) with primers and probes that targeted the kinetoplast DNA. The amplification product was detected by naked eye with a lateral flow (LF) immunochromatographic strip. The RPA-LF had an analytical sensitivity equivalent to 0.1 parasites per reaction. The test amplified the principal L. Viannia species from multiple countries: L. (V.) braziliensis (n = 33), L. (V.) guyanensis (n = 17), L. (V.) panamensis (n = 9). The less common L. (V.) lainsoni, L. (V.) shawi, and L. (V.) naiffi were also amplified. No amplification was observed in parasites of the L. (Leishmania) subgenus. In a small number of clinical samples (n = 13) we found 100% agreement between PCR and RPA-LF. The high analytical sensitivity and clinical validation indicate the test could improve the efficiency of diagnosis, especially in chronic lesions with submicroscopic parasite burdens. Field implementation of the RPA-LF test could contribute to management and control of cutaneous and mucosal leishmaniasis.

Cutaneous leishmaniasis is a parasitic disease transmitted by the bite of sandflies that produces skin ulcers. The severe, disfiguring form of the disease is characterized by parasite dissemination to the mucosa of the nose and palate. Current diagnosis is based on microscopy which has low sensitivity in chronic cases. Molecular methods (PCR) that detect parasite DNA are highly sensitive but costs and personnel training make it impossible to implement it in resource-limited areas. We developed a novel molecular method (RPA-LF) that could be applied in the field because it does not require sophisticated equipment. It is also very sensitive and specific to detect the principal Leishmania species that produce cutaneous leishmaniasis in Latin America. Future field implementation of RPA-LF could have a positive impact on disease management and control.

Further Evidence of an Association between the Presence of Leishmania RNA Virus 1 and the Mucosal Manifestations in Tegumentary Leishmaniasis Patients

Tegumentary Leishmaniasis (TL) is endemic in Latin America, and Brazil contributes approximately 20 thousand cases per year. The pathogenesis of TL, however, is still not fully understood. Clinical manifestations vary from cutaneous leishmaniasis (CL) to more severe outcomes, such as disseminated leishmaniasis (DL), mucosal leishmaniasis (ML) and diffuse cutaneous leishmaniasis (DCL). Many factors have been associated with the severity of the disease and the development of lesions. Recent studies have reported that the presence of Leishmania RNA virus 1 infecting Leishmania (Leishmania RNA virus 1, LRV1) is an important factor associated with the severity of ML in experimental animal models. In the present study, 156 patients who attended Rondonia's Hospital of Tropical Medicine with both leishmaniasis clinical diagnoses (109 CL; 38 ML; 5 CL+ML; 3 DL and 1 DCL) and molecular diagnoses were investigated. The clinical diagnosis were confirmed by PCR by targeting hsp70 and kDNA DNA sequences and the species causing the infection were determined by HSP70 PCR-RFPL. The presence of LVR1 was tested by RT-PCR. Five Leishmania species were detected: 121 (77.6%) samples were positive for Leishmania (Viannia) braziliensis, 18 (11.5%) were positive for Leishmania (V.) guyanensis, 3 (1.8%) for Leishmania (V.) lainsoni, 2 (1.3%) for Leishmania (Leishmania) amazonensis and 2 (1.3%) for Leishmania (V.) shawi. Six (3.9%) samples were positive for Leishmania sp. but the species could not be determined, and 4 (2.6%) samples were suggestive of mixed infection by L. (V.) braziliensis and L. (V.) guyanensis. The virus was detected in L. braziliensis (N = 54), L. guyanensis (N = 5), L. amazonensis (N = 2), L. lainsoni (N = 1) and inconclusive samples (N = 6). Patients presenting with CL+ML, DL and DCL were excluded from further analysis. Association between the presence of the virus and the disease outcome were tested among the remaining 147 patients (CL = 109 and ML = 38). Of them, 71.1% (n = 27) mucosal lesions were positive for LRV1, and 28.9% (n = 11) were negative. In cutaneous lesions, 36.7% (n = 40) were positive and 63.3% (n = 69) were negative for LRV1. The ratio P(ML|LRV1+)/P(ML|LRV1-) was 2.93 (CI95% 1.57…5.46; p<0.001), thus corroborating the hypothesis of the association between LRV1 and the occurrence of mucosal leishmaniasis, as previously described in animal models; it also indicates that LRV1 is not the only factor contributing to the disease outcome.

Leishmaniasis is an infectious disease caused by protozoa of the genus Leishmania. Tegumentary Leishmaniasis (TL) is characterized by a variety of clinical forms, ranging from simple skin lesions to more severe lesions with mucosal destruction. The mechanisms by which some patients develop a severe form of the disease remain unclear. It is already known that the immune statuses of the host and parasite species are key factors influencing the clinical outcome of the disease, but is not known which are the factors that influence the parasite’s tropism to the mucosal regions. Recently, a virus found infecting Leishmania, Leishmania RNA virus 1 (LRV1), has also been reported as one important factor contributing to the disease severity. The present article reports, among 147 investigated patients from the Brazilian Western Amazon, a higher frequency of LRV1 among patients with mucosal lesions compared to patients with cutaneous lesions, statistically demonstrating that the virus is related to the worsening of the disease, increasing the risk of developing mucosal injury by almost 3 times.

The Comparative Genomics and Phylogenomics of Leishmania amazonensis Parasite

Leishmaniasis is an infectious disease caused by Leishmania species. Leishmania amazonensis is a New World Leishmania species belonging to the Mexicana complex, which is able to cause all types of leishmaniasis infections. The L. amazonensis reference strain MHOM/BR/1973/M2269 was sequenced identifying 8,802 codifying sequences (CDS), most of them of hypothetical function. Comparative analysis using six Leishmania species showed a core set of 7,016 orthologs. L. amazonensis and Leishmania mexicana share the largest number of distinct orthologs, while Leishmania braziliensis presented the largest number of inparalogs. Additionally, phylogenomic analysis confirmed the taxonomic position for L. amazonensis within the “Mexicana complex”, reinforcing understanding of the split of New and Old World Leishmania. Potential non-homologous isofunctional enzymes (NISE) were identified between L. amazonensis and Homo sapiens that could provide new drug targets for development.

MyD88 and TLR9 dependent immune responses mediate resistance to Leishmania guyanensis infections, irrespective of Leishmania RNA virus burden

Infections with Leishmania parasites of the Leishmania Viannia subgenus give rise to both localized cutaneous (CL), and metastatic leishmaniasis. Metastasizing disease forms including disseminated (DCL) and mutocutaneous (MCL) leishmaniasis result from parasitic dissemination and lesion formation at sites distal to infection and have increased inflammatory responses. The presence of Leishmania RNA virus (LRV) in L. guyanensis parasites contributes to the exacerbation of disease and impacts inflammatory responses via activation of TLR3 by the viral dsRNA. In this study we investigated other innate immune response adaptor protein modulators and demonstrated that both MyD88 and TLR9 played a crucial role in the development of Th1-dependent healing responses against L. guyanensis parasites regardless of their LRV status. The absence of MyD88- or TLR9-dependent signaling pathways resulted in increased Th2 associated cytokines (IL-4 and IL-13), which was correlated with low transcript levels of IL-12p40. The reliance of IL-12 was further confirmed in IL12AB^−/− mice, which were completely susceptible to infection. Protection to L. guyanensis infection driven by MyD88- and TLR9-dependent immune responses arises independently to those induced due to high LRV burden within the parasites.

Comparative analysis of the tissue inflammatory response in human cutaneous and disseminated leishmaniasis

Cutaneous leishmaniasis (CL) is the most frequent clinical form of tegumentary leishmaniasis and is characterised by a single or a few ulcerated skin lesions that may disseminate into multiple ulcers and papules, which characterise disseminated leishmaniasis (DL). In this study, cells were quantified using immunohistochemistry and haematoxylin and eosin staining (CD4+, CD68+, CD20+, plasma cells and neutrophils) and histopathology was used to determine the level of inflammation in biopsies from patients with early CL, late CL and DL (ulcers and papules). The histopathology showed differences in the epidermis between the papules and ulcers from DL. An analysis of the cells present in the tissues showed similarities between the ulcers from localised CL (LCL) and DL. The papules had fewer CD4+ T cells than the DL ulcers. Although both CD4+ cells and macrophages contribute to inflammation in early CL, macrophages are the primary cell type associated with inflammation intensity in late ulcers. The higher frequency of CD20+ cells and plasma cells in lesions demonstrates the importance of B cells in the pathogenesis of leishmaniasis. The number of neutrophils was the same in all of the analysed groups. A comparison between the ulcers from LCL and DL and the early ulcers and papules shows that few differences between these two clinical forms can be distinguished by observing only the tissue.

American tegumentary leishmaniasis caused by Leishmania (Viannia) braziliensis: assessment of parasite genetic variability at intra- and inter-patient levels

Background

The genetic variability of Leishmania (Viannia) braziliensis was assessed at intra and interpatient levels of individuals with different clinical manifestations of American tegumentary leishmaniasis (ATL).

Methods

Fifty-two samples, of which 13 originated from cutaneous lesions and 39 from mucosal lesions, provided by 35 patients, were examined by low-stringency single-specific-primer PCR (LSSP-PCR) and phenetic analysis. Genetic variability of L. (V.) braziliensis, in kinetoplast DNA (kDNA) signatures, was compared both from different patients and from different lesions of the same patient. Phenetic analysis was performed to evaluate the degree of heterogeneity of the kDNA minicircles. In order to evaluate inter and intrapatient L. (V.) braziliensis genetic variability, the percentage of shared bands and analysis of the coefficients of similarity were analyzed.

Results

Different genetic profiles, representing kDNA signatures of the parasite, were obtained by LSSP-PCR analysis of each sample. Phenetic analysis grouped genetic profiles of different levels of differentiation from more similar to most divergent. The percentage of shared bands at the inter and intrapatient levels was 77% and 89%, respectively. Comparison of the average inter and intrapatient coefficients of similarity and their standard deviations were statistically significant (p < 0.001).

Conclusion

Genetic variability at the intrapatient level was less pronounced than that between different patients. A conceptual model was proposed to better understand the complexity at both levels.

Recurrent visceral leishmaniasis in an immunocompetent patient: a case report

Introduction

Current treatment options for visceral leishmaniasis (pentavalent antimony, amphotericin B, liposomal amphotericin B and mitelfosine) achieve long-term clinical cure in the majority of immunocompetent patients. Disease relapse is usually provoked by T-cell number or function impairment (corticosteroid or cytotoxic therapy, transplant recipients, advanced human immunodeficiency virus disease).

Case presentation

We report a case of visceral leishmaniasis with multiple relapses in a 75-year-old Greek immunocompetent man. Visceral leishmaniasis relapses occurred despite appropriate treatment with liposomal amphotericin B 3mg/kg/day on days one to five, 14 and 21 (for the first episode and the first relapse) and mitelfosine 150mg/day for 28 days (for the second relapse). The third relapse was treated with high-dose liposomal amphotericin B (10mg/kg for two consecutive days), followed by a secondary prophylaxis of 3mg/kg once per month, which prevented disease reappearance during one year of follow-up.

Conclusion

An unusual case of recurrent visceral leishmaniasis in an older immunocompetent patient was treated with high-dose liposomal amphotericin B and a monthly prophylaxis with no evidence of a relapse after one year of follow-up.

Detection of Leishmania RNA virus in Leishmania parasites

Background

Patients suffering from cutaneous leishmaniasis (CL) caused by New World Leishmania (Viannia) species are at high risk of developing mucosal (ML) or disseminated cutaneous leishmaniasis (DCL). After the formation of a primary skin lesion at the site of the bite by a Leishmania-infected sand fly, the infection can disseminate to form secondary lesions. This metastatic phenotype causes significant morbidity and is often associated with a hyper-inflammatory immune response leading to the destruction of nasopharyngeal tissues in ML, and appearance of nodules or numerous ulcerated skin lesions in DCL. Recently, we connected this aggressive phenotype to the presence of Leishmania RNA virus (LRV) in strains of L. guyanensis, showing that LRV is responsible for elevated parasitaemia, destructive hyper-inflammation and an overall exacerbation of the disease. Further studies of this relationship and the distribution of LRVs in other Leishmania strains and species would benefit from improved methods of viral detection and quantitation, especially ones not dependent on prior knowledge of the viral sequence as LRVs show significant evolutionary divergence.

Methodology/Principal Findings

This study reports various techniques, among which, the use of an anti-dsRNA monoclonal antibody (J2) stands out for its specific and quantitative recognition of dsRNA in a sequence-independent fashion. Applications of J2 include immunofluorescence, ELISA and dot blot: techniques complementing an arsenal of other detection tools, such as nucleic acid purification and quantitative real-time-PCR. We evaluate each method as well as demonstrate a successful LRV detection by the J2 antibody in several parasite strains, a freshly isolated patient sample and lesion biopsies of infected mice.

Conclusions/Significance

We propose that refinements of these methods could be transferred to the field for use as a diagnostic tool in detecting the presence of LRV, and potentially assessing the LRV-related risk of complications in cutaneous leishmaniasis.

The endosymbiosis of viruses in microbes is a well-described and prevalent environmental partnership, where viruses offer their cellular host incentives of fitness in exchange for the use of their metabolic machinery. We have recently exposed this as an important factor in certain metastatic leishmaniases of South America, where the nucleic acid of a virus residing within some Leishmania parasites acts as a potent innate immunogen causing a destructive inflammatory response, which worsens disease. Leishmania RNA Virus (LRV) exists within many species of Leishmania as a stable infection; these LRV positive strains have been found throughout South America in cutaneous leishmaniases that are often complicated by the occurrence of infectious metastasis with an underlying hyperinflammatory response. In this report, we describe the use of an anti-dsRNA monoclonal antibody (J2), which specifically recognizes dsRNA in a quantitative and sequence-independent fashion. Refined versions of these methods could be transferred to the field as diagnostic tools for detecting the presence of LRV (or other dsRNA viruses), and potentially assessing the LRV-related risk of complicated cutaneous leishmaniasis.

The potential economic value of a cutaneous leishmaniasis vaccine in seven endemic countries in the Americas

Cutaneous leishmaniasis (CL) and its associated complications, including mucocutaneous leishmaniasis (MCL) and diffuse CL (DCL) have emerged as important neglected tropical diseases in Latin America, especially in areas associated with human migration, conflict, and recent deforestation. Because of the limitations of current chemotherapeutic approaches to CL, MCL, and DCL, several prototype vaccines are in different states of product and clinical development. We constructed and utilized a Markov decision analytic computer model to evaluate the potential economic value of a preventative CL vaccine in seven countries in Latin America: Bolivia, Brazil, Colombia, Ecuador, Mexico, Peru, and Venezuela. The results indicated that even a vaccine with a relatively short duration of protection and modest efficacy could be recommended for use in targeted locations, as it could prevent a substantial number of cases at low-cost and potentially even result in cost savings. If the population in the seven countries were vaccinated using a vaccine that provides at least 10 years of protection, an estimated 41,000-144,784 CL cases could be averted, each at a cost less than the cost of current recommended treatments. Further, even a vaccine providing as little as five years duration of protection with as little as 50% efficacy remains cost-effective compared with chemotherapy; additional scenarios resembling epidemic settings such as the one that occurred in Chaparral, Colombia in 2004 demonstrate important economic benefits.

Consecutive cutaneous and visceral leishmaniasis manifestations involving a novel Leishmania species in two HIV patients in Thailand

Leishmaniasis is an emerging disease in Thailand. Herein, we report on two human immunodeficiency virus (HIV)-infected patients with leishmaniasis who presented with overlapping manifestations between cutaneous and visceral leishmaniasis. Sequencing analysis of the internal transcribed spacer 1 (ITS1) of the ribosomal RNA gene showed that the species was identical to a new species recently described in Thailand. The detection of DNA of this Leishmania species in saliva may have important implications for transmission and epidemiological studies.

Vaccine Development Against Leishmania donovani

Visceral leishmaniasis (VL) caused by Leishmania donovani and Leishmania infantum/chagasi represents the second most challenging infectious disease worldwide, leading to nearly 500,000 new cases and 60,000 deaths annually. Zoonotic VL caused by L. infantum is a re-emergent canid zoonoses which represents a complex epidemiological cycle in the New world where domestic dogs serve as a reservoir host responsible for potentially fatal human infection and where dog culling is the only measure for reservoir control. Life-long immunity to VL has motivated development of prophylactic vaccines against the disease but very few have progressed beyond the experimental stage. No licensed vaccine is available till date against any form of leishmaniasis. High toxicity and increasing resistance to the current chemotherapeutic regimens have further complicated the situation in VL endemic regions of the world. Advances in vaccinology, including recombinant proteins, novel antigen-delivery systems/adjuvants, heterologous prime-boost regimens and strategies for intracellular antigen presentation, have contributed to recent advances in vaccine development against VL. Attempts to develop an effective vaccine for use in domestic dogs in areas of canine VL should be pursued for preventing human infection. Studies in animal models and human patients have revealed the pathogenic mechanisms of disease progression and features of protective immunity. This review will summarize the accumulated knowledge of pathogenesis, immune response, and prerequisites for protective immunity against human VL. Authors will discuss promising vaccine candidates, their developmental status and future prospects in a quest for rational vaccine development against the disease. In addition, several challenges such as safety issues, renewed and coordinated commitment to basic research, preclinical studies and trial design will be addressed to overcome the problems faced in developing prophylactic strategies for protection against this lethal infection.

A proposed new clinical staging system for patients with mucosal leishmaniasis

Mucosal leishmaniasis (ML) occurs mainly in areas where Leishmania braziliensis is transmitted. It affects predominantly the nasal mucosa and, in more severe forms, can lead to significant tissue destruction. There is no standard method for grading the severity of disease. We categorised 50 patients with ML according to a proposed new clinical staging system. Their age ranged from 10 to 86 y (mean ± SD: 36 ± 16 y) and 43 (86%) patients were male. The different degrees of evolution of mucosal disease, from the initial stage to the more severe long-term cases, enabled ML to be graded into five stages. Stage I is characterised by nodular lesions of the mucosa without ulceration. Stage II is represented by superficial mucosal ulcerations with concomitant fine granular lesions. Stage III is characterised by deep mucosal ulcerations with granular tissue formation. In stage IV there are irreversible lesions leading to perforation of the cartilaginous nasal septum with necrosis. In stage V the nasal pyramid is compromised with alterations of facial features as a consequence of severe tissue destruction. These stages may be useful in characterising the severity of the lesion and optimising therapeutic outcome.

Epidemiological and clinical changes in American tegumentary leishmaniasis in an area of Leishmania (Viannia) braziliensis transmission over a 20-year period

The Health Post of Corte de Pedra is located in a region endemic for American tegumentary leishmaniasis (ATL) in the Brazilian state of Bahia, and it treats 500-1,300 patients annually. To describe temporal changes in the epidemiology of ATL, we reviewed a random sample of 10% of patient charts (N = 1,209) from 1988 to 2008. There was a twofold increase in the number of cases over the 20-year period, with fluctuations in 10-year cycles. Patients were most frequently male, between the ages of 10 and 30 years, and engaged in agricultural labor; 4.3% of patients had mucosal disease, and 2.4% of patients had disseminated disease. Over the study period, the number of disseminated cases increased threefold, the proportion of cases in younger patients and agricultural workers decreased, and the proportion of patients residing in coastal areas increased. ATL is on the rise in Bahia, with a 10-year periodicity and evolving changes in epidemiology and manifestations of disease.

An experimental approach to studying the effectiveness and safety of meglumine antimoniate formulations

Among the problems associated to leishmaniasis, the two most outstanding ones are the lack of a vaccine and the adverse effects caused by drugs use for its control. Meglumine antimoniate compounds are the first-line drugs in the treatment for cutaneous leishmaniasis (the most prevalent form of the disease in Colombia); nevertheless, they are far from being ideal drugs due to their toxicity (not to mention the emergence of drug-resistant parasites), all of which has prompted current search for new strategies to improve their safety. This work assesses the effectiveness and safety (toxicity including new aspects related with immunotoxicity not reported previously) of two different meglumine antimoniate formulations using an in vitro and in vivo murine model. The results evidence that although both injectable formulations induce an equally efficient (clearance of intracellular parasites), both give rise to adverse effects, including a preferential immunomodulation on Balb/c mice and in a lesser proportion on ICR mice. These results are comparable to human trials reporting variable reactions when following the same treatment regimen. The model presented herein is proposed as a tool for evaluating the effectiveness and safety of meglumine antimoniate-based antileishmanial formulations.

Leishmania RNA virus controls the severity of mucocutaneous leishmaniasis

Mucocutaneous leishmaniasis is caused by infections with intracellular parasites of the Leishmania Viannia subgenus, including Leishmania guyanensis. The pathology develops after parasite dissemination to nasopharyngeal tissues, where destructive metastatic lesions form with chronic inflammation. Currently, the mechanisms involved in lesion development are poorly understood. Here we show that metastasizing parasites have a high Leishmania RNA virus-1 (LRV1) burden that is recognized by the host Toll-like receptor 3 (TLR3) to induce proinflammatory cytokines and chemokines. Paradoxically, these TLR3-mediated immune responses rendered mice more susceptible to infection, and the animals developed an increased footpad swelling and parasitemia. Thus, LRV1 in the metastasizing parasites subverted the host immune response to Leishmania and promoted parasite persistence.

T-bet, GATA-3, and Foxp3 expression and Th1/Th2 cytokine production in the clinical outcome of human infection with Leishmania (Viannia) species

BACKGROUND

T cell differentiation determines susceptibility and resistance to experimental cutaneous leishmaniasis, yet mixed T1/Th2 responses characterize the clinical spectrum of human infection with Leishmania (Viannia) species.

MATERIALS AND METHODS

To discern the interrelationship of T cell differentiation and outcome of human infection, we examined factors that regulate T cell differentiation and Th1/Th2 cytokine responses in asymptomatic infection, active and historical chronic and recurrent cutaneous leishmaniasis. T-bet, GATA-3, Foxp3, and cytokine gene expression were quantified by real-time polymerase chain reaction and correlated with interleukin 2, interferon gamma, tumor necrosis factor alpha, interleukin 4, interleukin 13, and interleukin 10 secretion during in vitro response to live Leishmania panamensis.

RESULTS

Higher GATA-3 expression than T-bet expression occurred throughout the 15 days of coculture with promastigotes; however, neither transcription nor secretion of interleukin 4 was detected. A sustained inverse correlation between GATA-3 expression and secretion of proinflammatory cytokines interferon gamma and tumor necrosis factor alpha was observed in asymptomatic infection. In contrast, higher T-bet expression and a higher ratio of T-bet to GATA-3 characterized active recurrent disease. Down-regulation of T-bet and GATA-3 expression and increased interleukin 2 secretion, compared with control subjects, was directly correlated with Foxp3 expression and interleukin 13 secretion in chronic disease.

CONCLUSIONS

Regulation of the inflammatory response rather than biased Th1/Th2 response distinguished asymptomatic and recalcitrant outcomes of infection with Leishmnania viannia species.

Cutaneous and mucocutaneous leishmaniasis

Leishmaniasis is a cluster of diseases caused by protozoa in the genus Leishmania. There are three basic clinical forms: cutaneous, mucocutaneous, and visceral leishmaniasis. The present review focuses on the diagnosis and treatment of cutaneous and mucocutaneous leishmaniasis. Characteristics of both the human host and the parasite species influence the clinical disease manifestations that range from asymptomatic exposure, to self-healing skin ulcers, to life-threatening widespread destructive ulcerations. Whether through medical treatment or through spontaneous resolution, skin ulcerations generally result in disfiguring scars with significant social and economic impact. Tests to confirm the diagnosis should be performed on patients who have recently visited endemic areas and have skin or mucosal manifestations consistent with leishmaniasis. Treatment depends on the species of Leishmania and the risk of widespread or disfiguring disease. Because of increasing trends in global travel, educating health care providers to recognize and treat leishmaniasis in both endemic and non-endemic countries is imperative.

Organization and evolution of two SIDER retroposon subfamilies and their impact on the Leishmania genome

Background

We have recently identified two large families of extinct transposable elements termed Short Interspersed DEgenerated Retroposons (SIDERs) in the parasitic protozoan Leishmania major. The characterization of SIDER elements was limited to the SIDER2 subfamily, although members of both subfamilies have been shown to play a role in the regulation of gene expression at the post-transcriptional level. Apparent functional domestication of SIDERs prompted further investigation of their characterization, dissemination and evolution throughout the Leishmania genus, with particular attention to the disregarded SIDER1 subfamily.

Results

Using optimized statistical profiles of both SIDER1 and SIDER2 subgroups, we report the first automated and highly sensitive annotation of SIDERs in the genomes of L. infantum, L. braziliensis and L. major. SIDER annotations were combined to in-silico mRNA extremity predictions to generate a detailed distribution map of the repeat family, hence uncovering an enrichment of antisense-oriented SIDER repeats between the polyadenylation and trans-splicing sites of intergenic regions, in contrast to the exclusive sense orientation of SIDER elements within 3'UTRs. Our data indicate that SIDER elements are quite uniformly dispersed throughout all three genomes and that their distribution is generally syntenic. However, only 47.4% of orthologous genes harbor a SIDER element in all three species. There is evidence for species-specific enrichment of SIDERs and for their preferential association, especially for SIDER2s, with different metabolic functions. Investigation of the sequence attributes and evolutionary relationship of SIDERs to other trypanosomatid retroposons reveals that SIDER1 is a truncated version of extinct autonomous ingi-like retroposons (DIREs), which were functional in the ancestral Leishmania genome.

Conclusion

A detailed characterization of the sequence traits for both SIDER subfamilies unveils major differences. The SIDER1 subfamily is more heterogeneous and shows an evolutionary link with vestigial DIRE retroposons as previously observed for the ingi/RIME and L1Tc/NARTc couples identified in the T. brucei and T. cruzi genomes, whereas no identified DIREs are related to SIDER2 sequences. Although SIDER1s and SIDER2s display equivalent genomic distribution globally, the varying degrees of sequence conservation, preferential genomic disposition, and differential association to orthologous genes allude to an intricate web of SIDER assimilation in these parasitic organisms.

Cytokines, signaling pathways, and effector molecules required for the control of Leishmania (Viannia) braziliensis in mice

Cutaneous leishmaniasis is caused by protozoan parasites of the genus Leishmania. The mechanisms of pathogen control have been established primarily in the mouse model of Leishmania major infection, but they might not hold true for other Leishmania species associated with cutaneous disease. Here, we analyzed the role of cytokines, signaling components, and effector molecules in the control of New World cutaneous leishmaniasis due to L. braziliensis. Unlike L. major, L. braziliensis caused small, nonulcerative, and self-healing skin swelling in C57BL/6 mice, as well as BALB/c mice. In contrast to the results obtained for L. mexicana, mice deficient for interleukin-12 or its key signaling molecule, signal transducer and activator of transcription 4, rapidly succumbed to severe visceral leishmaniasis. Infection of tumor necrosis factor knockout mice with L. braziliensis led to progressive, nonhealing skin lesions with erosions and hemorrhagic ulcerations, but in contrast to the results with L. major, only 20 to 30% of the mice developed fatal visceral disease. As seen with L. major, mice with a deleted inducible nitric oxide synthase gene (iNOS(-/-)) were unable to contain L. braziliensis in the skin, whereas the control of the parasite in the spleen remained unimpaired. Unlike what happens in L. major infections, NADPH oxidase had no impact on the course of disease in L. braziliensis-infected mice. These results not only define essential components of a protective immune response to L. braziliensis but also illustrate that the requirements for the control of cutaneous leishmaniasis vary between different parasite species.

Genetic susceptibility to infectious disease: lessons from mouse models of leishmaniasis

Susceptibility to infectious disease is influenced by multiple host genes, most of which are low penetrance QTLs that are difficult to map in humans. Leishmaniasis is a well-studied infectious disease with a variety of symptoms and well-defined immunological features. Mouse models of this disease have revealed more than 20 QTLs as being susceptibility genes, studies of which have made important contributions to our understanding of the host response to infection. The functional effects of individual QTLs differ widely, indicating a networked regulation of these effects. Several of these QTLs probably also influence susceptibility to other infections, indicating that their characterization will contribute to our understanding of susceptibility to infectious disease in general.

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.

Is Leishmania (Viannia) braziliensis preferentially restricted to the cutaneous lesions of naturally infected dogs?

Nineteen dogs naturally infected with Leishmania (Viannia) braziliensis were studied in order to determine the presence of the parasite outside cutaneous lesions. Eleven (57.9%) animals showed single cutaneous or mucosal lesions and eight (42.1%) presented two or three lesions. Twenty-eight active lesions were biopsied. Isolation in culture and characterization by enzyme electrophoresis were possible in 100% of cases and amastigote forms were visualized upon histopathological examination in three samples (n=25, 12%). Isolation of the parasite in culture from peripheral blood and intact skin fragments obtained from the scapular region was negative in all animals, as was the histopathological analysis of skin from this region. Serological reactivity determined by an immunofluorescent antibody test and/or enzyme-linked immunosorbent assay was demonstrated in 15 animals. The results obtained suggest that L. braziliensis preferentially remains at the site of lesion, in contrast to the systemic distribution of parasites observed in dogs infected with L. (Leishmania) chagasi. A better understanding of this aspect may help direct diagnostic and control strategies applicable to areas characterized by the simultaneous occurrence of the cutaneous and visceral forms of leishmaniasis, as is the case for the Municipality of Rio de Janeiro, Brazil.