New perspectives on a subclinical form of visceral 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.

Galactokinase-like protein from Leishmania donovani: Biochemical and structural characterization of a recombinant protein

Leishmaniasis is a spectrum of conditions caused by infection with the protozoan Leishmania spp. parasites. Leishmaniasis is endemic in 98 countries around the world, and resistance to current anti-leishmanial drugs is rising. Our work has identified and characterised a previously unstudied galactokinase-like protein (GalK) in Leishmania donovani, which catalyses the MgATP-dependent phosphorylation of the C-1 hydroxyl group of d-galactose to galactose-1-phosphate. Here, we report the production of the catalytically active recombinant protein in E. coli, determination of its substrate specificity and kinetic constants, as well as analysis of its molecular envelope using in solution X-ray scattering. Our results reveal kinetic parameters in range with other galactokinases with an average apparent Km value of 76 μM for galactose, Vmax and apparent Kcat values with 4.46376 × 10-9 M/s and 0.021 s-1, respectively. Substantial substrate promiscuity was observed, with galactose being the preferred substrate, followed by mannose, fructose and GalNAc. LdGalK has a highly flexible protein structure suggestive of multiple conformational states in solution, which may be the key to its substrate promiscuity. Our data presents novel insights into the galactose salvaging pathway in Leishmania and positions this protein as a potential target for the development of pharmaceuticals seeking to interfere with parasite substrate metabolism.

A breath of fresh air: impact of insect-borne protozoan parasites on the respiratory system

The protozoan parasites Plasmodium, Leishmania, and Trypanosoma are transmitted by hematophagous insects and cause severe diseases in humans. These infections pose a global threat, particularly in low-resource settings, and are increasingly extending beyond the current endemic regions. Tropism of parasites is crucial for their development, and recent studies have revealed colonization of noncanonical tissues, aiding their survival and immune evasion. Despite receiving limited attention, cumulative evidence discloses the respiratory system as a significant interface for host-pathogen interactions, influencing the course of (co)infection and disease onset. Due to its pathophysiological and clinical implications, we emphasize that further research is needed to better understand the involvement of the respiratory system and its potential to improve prevention, diagnosis, treatment, and interruption of the chain of transmission.

Leishmaniasis and Tularemia Coinfection: A Case Report of Neglected Causes of Cervical Lymphadenopathy

Leishmania and tularemia are infectious diseases that both can present with lymphadenopathy. Leishmania typically causes visceral or cutaneous forms, while tularemia can result in glandular tularemia characterized by lymphadenitis. We report a case of a patient presenting with localized cervical lymphadenopathy diagnosed with both leishmaniasis and tularemia. This case underscores the importance of considering both pathogenic agents in the differential diagnosis of localized lymphadenitis. Early treatment is crucial to prevent the dissemination of these infections.

Is there an overestimation of dengue compared with that of other acute febrile syndromes in childhood?

A group of children with clinical suspicion of dengue were assessed to determine if there was an overestimation of dengue compared with that of leptospirosis and leishmaniasis. This descriptive and analytical cross-sectional study, based on the active search of participants with acute febrile illness, was conducted at two pediatric hospitals. The collection of clinical and epidemiological data was performed using questionnaires, and laboratory tests specific for dengue were performed using immunochromatographic, serological, and molecular methods. Dengue-negative samples were assessed for Leptospira and Leishmania spp. using molecular tests. Data were assessed using analysis of variance (ANOVA), the chi-square test, and Fisher's exact test. In total, 86 participants were evaluated, of whom 39 (45%) were positive for dengue fever, 4 (5%) for leptospirosis, and 1 (1%) for leishmaniasis. Forty-two participants (49%) presented dengue-like symptoms. The predominant age range for the virus was 3-10 years. Most clinical manifestations were nonspecific, with frequent concomitant gastrointestinal and respiratory symptoms. Furthermore, we found that the acute febrile syndrome in childhood persists as a challenge for health professionals, especially in the early days of the disease, due to a plurality of diagnostic hypotheses, associated with the difficulty of establishing well-defined symptoms in children, especially in infants. Dengue fever continues to be a frequent pathology with acute febrile infections in childhood; however, there is an overestimation of the disease, especially in endemic regions, when one considers only the clinical epidemiological diagnosis.

Failure to Detect Leishmania in the Blood of Patients with Old-World Cutaneous Leishmaniasis: Implications for Blood Donation

Cutaneous leishmaniasis (CL) is endemic in Israel, caused mainly by Leishmania major (L. major) and L. tropica. In addition, returning travelers import another leishmanial species such as L. braziliensis. Although we are dealing with a skin disease, the blood bank in Israel does not accept blood donations from people infected with CL in cases of multiple lesions due to the possibility of transfusion. Our purpose was to investigate the prevalence of Leishmania in the blood of patients with active or previous CL. This pilot study screened patients with active or previous CL for parasites in their blood. All patients were infected in Israel or were returning travelers with leishmaniasis acquired in Latin America. Patients were seen at the Sheba Medical Center. In addition, patients were seen at their homes in L. tropica and L. major endemic regions in Israel. Blood samples were taken from each patient for culture and polymerase chain reaction (PCR). Altogether 62 blood samples were examined (L. tropica = 26, L. major = 33, and L. braziliensis = 3). Twenty-seven patients had an active disease and 35 were recovered. All blood cultures and PCR were negative for parasites except one blood sample that was PCR positive for L. braziliensis. The findings of our study, although a small sample, suggest that people with active or recent CL caused by L. major and L. tropica, do not harbor parasites in their blood. Thus, their exclusion from blood donation should be revisited. Further studies are needed with larger sample size and highly sensitive tests.

Visceral Leishmaniasis Urbanization in the Brazilian Amazon Is Supported by Significantly Higher Infection Transmission Rates Than in Rural Area

This was an open cohort prospective study (2016−2018) that analyzed the prevalence and incidence rates of human Leishmania (L.) infantum chagasi-infection and the evolution of their clinical-immunological profiles in distinct urban and rural scenarios of American visceral leishmaniasis (AVL) in Pará State, in the Brazilian Amazon. These infection profiles were based on species-specific DTH/IFAT-IgG assays and clinical evaluation of infected individuals, comprising five profiles: three asymptomatic, Asymptomatic Infection [AI], Subclinical Resistant Infection [SRI], and Indeterminate Initial Infection [III]; and two symptomatic, Subclinical Oligosymptomatic Infection [SOI] and Symptomatic Infection [SI = AVL]. The two distinct scenarios (900 km away) were the urban area of Conceição do Araguaia municipality and the rural area of Bujaru municipality in the southeast and northeast of Pará State. Human populations were chosen based on a simple convenience sampling design (5−10% in each setting), with 1723 individuals (5.3%) of the population (32,464) in the urban area and 1568 individuals (8.9%) of the population (17,596) in the rural one. A serological survey (IFAT-IgG) of canine infection was also performed in both scenarios: 195 dogs in the urban area and 381 in the rural one. Prevalence and incidence rates of human infection were higher in the urban area (20.3% and 13.6/100 person-years [py]) than in the rural setting (14.1% and 6.8/100-py). The AI profile was the most prevalent and incident in both urban (13.4% and 8.1/100-py) and rural (8.3% and 4.2/100-py) scenarios, but with higher rates in the former. An III profile case evolved to SOI profile after four weeks of incubation and another to SI (=AVL) after six. The prevalence of canine infection in an urban setting (39.2%) was also higher (p < 0.05) than that (32%) in the rural zone. AVL urbanization in Pará State, in the Brazilian Amazon, has led to infection rates significantly higher than those in rural sites, requiring more intense control measures.

Visceral leishmaniasis elimination in India: progress and the road ahead

INTRODUCTION

As of 2021, visceral leishmaniasis (VL) elimination program has met with success in reducing the rate of VL to target levels in many locales, but there is persistence of low-level disease and sporadic outbreaks, sometimes in new locations. Thus, there is an urgent need to identify knowledge gaps and factors that impede total VL elimination.

AREA COVERED

We reviewed the progress and current status of VL elimination program. We discuss the knowledge gaps influencing the success of elimination program and strategies to be required to ensure VL elimination as a public health problem is achieved and sustained.

EXPERT OPINION

VL elimination is considered technically possible and operationally feasible owing to focal nature of transmission, absence of an animal reservoir, single vector, availability of an effective diagnostic test, use of a single dose of liposomal amphotericin B along with a strong political commitment. Substantial progress has been made in the reduction of VL incidence rates in the country. However, there are many challenges remain that need to be addressed if the elimination goal is to be reached and sustained. These are increasing relapse, outbreaks in new foci and increasing number of PKDL and HIV-VL co-infections.

Identification of asymptomatic Leishmania infections: a scoping review

BACKGROUND

Asymptomatic Leishmania infection may play an important role in the transmission of the parasite in endemic areas. At present there is no consensus on the definition of asymptomatic Leishmania infection, nor is there a safe and accessible gold standard test for its identification.

METHODS

This paper presents a scoping review to summarize definitions of asymptomatic Leishmania infection found in the literature, as well as to detail the approach (molecular, serological, cellular, and/or parasitological tests) used by researchers to identify this asymptomatic population. A scoping review of published and gray literature related to asymptomatic Leishmania infection was conducted; retrieved citations were screened based on predefined eligibility criteria, and relevant data items were extracted from eligible articles. The analysis is descriptive and is presented using tables, figures, and thematic narrative synthesis.

RESULTS

We conducted a screening of 3008 articles, of which 175 were selected for the full review. Of these articles, we selected 106 that met the inclusion criteria. These articles were published between 1991 and 2021, and in the last 5 years, up to 38 articles were reported. Most of the studies were conducted in Brazil (26%), Spain (14%), India (12%), Bangladesh (10%), and Ethiopia (7%). Of the studies, 84.9% were conducted in the immunocompetent population, while 15.1% were conducted in the immunosuppressed population (HIV, immunosuppressive drugs, and organ transplantation population). We report 14 different techniques and 10 strategies employed by researchers to define asymptomatic Leishmania infection in an endemic area.

CONCLUSIONS

The definition of asymptomatic Leishmania infection is not unified across the literature, but often includes the following criteria: residence (or extended stay) in a Leishmania-endemic area, no reported signs/symptoms compatible with leishmaniasis, and positive on a combination of serological, molecular, cellular, and/or parasitological tests. Caution is recommended when comparing results of different studies on the subject of asymptomatic infections, as the reported prevalence cannot be confidently compared between areas due to the wide variety of tests employed by research groups. More research on the importance of asymptomatic immunosuppressed and immunocompetent Leishmania-positive populations in leishmaniasis epidemiology is required.

Vitamin d and leishmaniasis: Neither seasonal nor risk factor in canine host but potential adjuvant treatment through cbd103 expression

Vitamin D (VitD) deficiency has been shown to be a risk factor for a plethora of disorders. We have shown that dogs with clinical leishmaniasis presented lower VitD serum levels than non-infected dogs, and even lower than those with asymptomatic infection. However, if VitD deficiency is a risk factor to develop clinical leishmaniasis remains to be answered. It is also unknown if VitD participates in Leishmania control. First, we retrospectively analysed VitD concentration in serum samples from 36 healthy dogs collected in different periods of the year concluding that there isn't a seasonal variation of this vitamin in dogs. We also included 9 dogs with clinical leishmaniasis and 10 non-infected healthy dogs, in which we measured VitD levels at the beginning of the study, when all dogs were negative for serology and qPCR, and 1 year later. Whereas non-infected dogs showed no change in VitD levels along the study, those developing clinical leishmaniasis showed a significant VitD reduction at the end of the study (35%). When we compared VitD concentration between the two groups at the beginning of the study, no differences were detected (43.6 (38-59) ng/mL, P = 0.962). Furthermore, an in vitro model using a canine macrophage cell line proved that adding active VitD leads to a significant reduction in L. infantum load (31.4%). Analyzing expression of genes related to VitD pathway on primary canine monocytes, we showed that CBD103 expression was significantly enhanced after 1,25(OH)2D addition. Our results show that VitD concentration is neither seasonal nor a risk factor for developing canine leishmaniasis, but it diminishes with the onset of clinical disease suggesting a role in parasitic control. Our in vitro results corroborate this hypothesis and point out that VitD regulates infection through CBD103 expression. These results open the possibility for studies testing VitD as an adjuvant in leishmaniasis therapy.

Leishmania infantum (syn. L. chagasi) parasites affect the release of soluble CD14 by infected macrophages

Functionally, cluster of differentiation 14 (CD14) is a co-receptor of the complex formed by lipopolysaccharide (LPS) and LPS-binding protein expressed on the membrane of a variety of cells. However, CD14 can be shed from the cell membrane into the circulation as soluble CD14 (sCD14) upon cell activation. Previously, our group reported that elevated sCD14 serum levels were associated with the clinical and laboratory findings in the context of visceral leishmaniasis (VL), but not in the context of LPS stimulation or bacterial infection. In the present study, we investigated the secretion dynamics of sCD14 in the context of Leishmania infantum (syn. L. chagasi) in vitro infection. Macrophages from treated VL patients and delayed-type hypersensitivity positive (DTH⁺) subjects were infected with L. infantum (syn. L. chagasi) promastigotes, and the infection index was evaluated (number of amastigotes per 100 infected macrophages). Additionally, the levels of sCD14, Inteleukin (IL)10, IL-6 and tumour necrosis factor alpha (TNF-α) were measured in the culture supernatants using the Luminex assay. Interestingly, the release of sCD14 was inversely correlated with the L. infantum (syn. L. chagasi) infection index. Of note, the release of sCD14 was upregulated and downregulated in the context of infected macrophages from DTH⁺ subjects and treated VL patients, respectively. Additionally, we also observed that the levels of sCD14 in the culture supernatants were positively correlated with the levels of TNF-α, IL-6 and IL-10. Therefore, our data suggest that macrophages from treated VL patients and DTH⁺ subjects respond differently to L. infantum (syn. L. chagasi) infection in the context of the release of sCD14; therefore, the release of sCD14 may be associated with the outcome of VL.

Comparison of Three In-House Real PCR Assays Targeting Kinetoplast DNA, the Small Subunit Ribosomal RNA Gene and the Glucose-6-Phosphate Isomerase Gene for the Detection of Leishmania spp. in Human Serum

To perform PCR from serum for the diagnosis of visceral leishmaniasis is convenient and much less invasive than the examination of deeper compartments such as bone marrow. We compared three Leishmania-specific real-time PCRs with three different molecular targets (kinetoplast DNA, the small subunit-ribosomal RNA-(ssrRNA-)gene, the glucose-6-phosphate isomerase-(gpi-)gene) regarding their sensitivity and specificity in human serum. Residual sera from previous diagnostic assessments at the German National Reference Center for Tropical Pathogens Bernhard Nocht Institute for Tropical Medicine Hamburg and the Swiss Tropical and Public Health Institute were used. The sensitivities of kinetoplast DNA-PCR, ssrRNA-gene PCR, and gpi-PCR were 93.3%, 73.3%, and 33.3%, respectively, with 15 initial serum samples from visceral leishmaniasis patients, as well as 9.1%, 9.1%, and 0.0%, respectively, with 11 follow-up serum samples taken at various time points following anti-leishmanial therapy. Specificity was 100.0% in all assays as recorded with 1.137 serum samples from deployed soldiers and migrants without clinical suspicion of visceral leishmaniasis. Kinetoplast-DNA PCR from serum was confirmed as a sensitive and specific approach for the diagnosis of visceral leishmaniasis. The results also indicate the suitability of serum PCR for diagnostic follow-up after therapy, in particular regarding therapeutic failure in case of persisting positive PCR results.

Evaluation of molecular techniques to visceral leishmaniasis detection in asymptomatic patients: a systematic review

INTRODUCTION

Visceral leishmaniasis (VL) is a systemic and neglected parasitic disease. Its main symptoms are fever, splenomegaly with or without hepatomegaly, and anemia, however, most individuals remain asymptomatic. Due to the lack of a gold standard and the limitations of current diagnostic techniques, where parasitology is ethically unfeasible for individuals without symptoms and serological tests do not differentiate between past and present disease, molecular methodologies are the most suitable.

AREAS COVERED

We performed a systematic review analyzing the molecular techniques based on PCR used, so far, to detect asymptomatic cases of VL in humans. Structured searches were carried out on PubMed, LILACS, Scopus, and Web of Science databases without time and language restrictions. Two reviewers evaluated the studies, performed data extraction, and quality assessment by assigning scores.

EXPERT OPINION

qPCR using RNA targets can be used in the diagnosis of asymptomatic cases of human VL, due to its characteristics. We recommend further studies to analyze the methodology, mainly observing the use of different rRNA targets. Therefore, we hope that this technique contributed to the construction of public policies that address the diagnosis and handling of asymptomatic patients.

Factors associated with human visceral leishmaniasis cases during urban epidemics in Brazil: a systematic review

Visceral leishmaniasis (VL) is endemic in 70 countries and has been reported in 12 countries of Latin America, with over 90% of the cases reported in Brazil, where epidemics have occurred since 1980. The objective of this review is to describe the factors associated with the occurrence of VL epidemics in humans in urban areas. A systematic review was conducted according to the PRISMA-P guidelines. The databases PubMed (by Medline), Cochrane Library, Embase, Amed, LILACS and grey literature [Google Scholar and handsearch of the database of the Information System for Notifiable Diseases (SINAN) of Brazil's Unified Health System] were used. The protocol was registered under PROSPERO (CRD42019128998). Climatic, environmental factors and indicators of urban social structure were described as influencing the outbreaks in the North and Northeast regions. Gender and age characteristics were related to a greater chance of developing VL in the Central-West, Northeast and Southeast regions. Vector indicators showed a positive correlation with the incidence of VL in studies in the Northeast region. In the Southeast and Northeast regions, studies revealed the presence of dogs with positive correlation with VL. Knowledge gaps remain regarding the contribution to the increase in the risk factors described in ecological approaches, as no analysis was performed at the individual level, and it is still necessary to discuss the influence of other associated elements in epidemic episodes in the spread of VL.

A critical review of the applicability of serological screening for Leishmaniasis in blood banks in Brazil

Leishmaniasis is a group of diseases caused by several species of protozoa. It is a major public health concern in its visceral form, accounting annually for 59,000 deaths, and an estimated 12 million infected patients per year. The importance of VL resides not only in its high incidence and wide distribution but also in the possibility of the disease progressing to the severe and lethal forms, especially in children and immunosuppressed individuals, when associated with malnutrition and concomitant infections. This study is a bibliographical review, aiming to understand the sensitivity and specificity parameters of the tests used to detect Leishmaniasis, as well as to understand if there is any relevance in proposing a serological screening for Leishmaniasis in blood banks. In general, we observed that there are currently several types of tests for detecting Leishmaniasis: parasitological, serological and molecular. In such tests, many serological methods and kits are available for the detection of asymptomatic visceral leishmaniasis, but there is variability in sensitivity and specificity among the methods. The gold standard for the diagnosis of visceral leishmaniasis is the parasitological method, through the aspiration of bone marrow, with higher sensitivity by splenic puncture. Due to the relevance of the disease and the available data from research centers, there is evidence to propose a transfusion serological screening for visceral Leishmaniasis, pointing to the need for further studies.

preADMET analysis and clinical aspects of dogs treated with the Organotellurium compound RF07: A possible control for canine visceral leishmaniasis?

Tellurium compounds have been described as potential leishmanicides, bearing promising leishmanicidal and antimalarial effects. Therefore, the present study investigated the pharmacological potential of the organotellurane compound RF07 through preADMET parameters, such as absorption, distribution, metabolism and excretion. After studying the pharmacokinetic properties of RF07, studies were carried out on dogs naturally infected with visceral leishmaniasis after the administration of RF07, in order to assess pathophysiological parameters. Thus, dogs were divided into 4 groups with administration of daily intraperitoneal injections for 3 weeks (containing RF07 or placebo). During the trial, hematological parameters, renal and hepatic toxicity were evaluated. Serum urea, creatinine, alkaline phosphatase, transaminases (GOT and GPT), as well as hemogram results, were evaluated before the first administration and during the second and third weeks after the start of the treatment. In dogs with VL, RF07 improved liver damage, regulated GPT levels and significantly decreased leukocyte count, promoting its regularization. These phenomena occurred at the end of the third week of treatment. The administration of RF07 promoted a significant decrease in the average levels of GOT and GPT after the third week of treatment and did not significantly alter the hematological parameters. The application of RF07 in the treatment of visceral leishmaniasis suggests that it is an alternative to the disease, since the reversal of clinical signs in dogs with VL requires the use of 0.6 mg/kg.

Prevalence and associated factors of asymptomatic leishmaniasis: a systematic review and meta-analysis

Asymptomatic leishmaniasis is believed to play important role in maintaining the transmission of Leishmania spp. within endemic communities. Therefore, the efforts to eliminate leishmaniasis are daunting if we cannot manage asymptomatic leishmaniasis well. To clarify the global prevalence and factors associated with the asymptomatic Leishmania infection, we assessed the prevalence of asymptomatic leishmaniasis by a systematic review followed by meta-analyses. In addition, factors associated with the asymptomatic leishmaniasis versus symptomatic were also analyzed. We included all of the original articles alluding to the human asymptomatic leishmaniasis that was confirmed by at least one laboratory diagnosis method regardless of age, sex, race, and ethnicity of the patients, study design, publication date or languages. In total, 111 original articles were chosen for the data extraction. Based on our meta-analyses of the original articles reporting asymptomatic leishmaniasis mostly in endemic areas, the prevalence of asymptomatic leishmaniasis was 11.2% [95% confidence interval (CI) 8.6%-14.4%] in general population, 36.7% [95% CI 27.6%-46.8%] in inhabitants living in the same or neighboring household to the symptomatic patients, and 11.8% [95% CI 7.1%-19%] in HIV infected patients. Among individuals with leishmaniasis, 64.9% [95% CI 54.7%-73.9%] were asymptomatic and males were more susceptible to develop symptoms, with OR=1.88, 95% CI 1.19-2.99, P=0.007. Meta-regression analysis showed no significant change in the prevalence of asymptomatic leishmaniasis during the last 40 years.

Purified Splenic amastigotes of Leishmania donovani-Immunoproteomic approach for exploring Th1 stimulatory polyproteins

Visceral leishmaniasis (VL) represents one of the most challenging infectious diseases worldwide. The reason that once infected, patient develops immunity against Leishmania parasite has paved way to develop prophylactic vaccines against disease, but only some of these have moved ahead for clinical trials. Herein, the study to explore novel and potential vaccine candidates was extended to pathogenic form of parasite, that is, amastigote form which is less explored due to complexity of its purification process. Methods and results. Classical protocol of purification of splenic amastigotes was modified to obtain highly pure amastigotes which was confirmed by Western blotting in support with proteomics studies. Fractionation and sub-fractionation of purified splenic amastigotes revealed four sub-fractions, belonging to 97 to 68 kDa and 68 to 43 kDa ranges, which showed long-lasting protection with remarkable Th1-type cellular responses in hamsters vaccinated with these sub-fractions (LTT, NO, QRT-PCR). Further proteomics analysis, to identify and understand the precise nature and function of these protective protein sub-fractions, identified a total of 47 proteins including twenty-five hypothetical proteins/unknowns. Amastigote stage has potential Th1-stimulatory vaccine candidates, notably, among identified proteins, major were uncharacterized proteins/hypothetical proteins, which once characterized may serve as novel and potential vaccine candidates/drug targets.

Clinical and Immunological Features of Human Leishmania (L.) infantum-Infection, Novel Insights Honduras, Central America

Leishmania (Leishmania) infantum is the etiological agent of both American visceral leishmaniasis (AVL) and non-ulcerated cutaneous leishmaniasis (NUCL) in Honduras. Although AVL is the most severe clinical form of infection, recent studies have shown that human immune response to parasite infection can result in a clinical-immunological spectrum. The overall prevalence rate of infection and clinical-immunological profiles of the L. (L.) infantum infection in Amapala municipality, South Honduras was determined. We examined 576 individuals with diagnosis based on combined ELISA (IgG/IgM) and DTH assays. We also used genus-specific kDNA PCR and Hsp70 PCR-RFLP for NUCL cases. Clinical evaluation found 82% asymptomatic and 18% symptomatic individuals. All symptomatic cases (n = 104) showing NUCL were positive for parasites. We identified L. (L.) infantum species in 100% of the skin lesion scrapings and in 90% of the blood samples from NUCL cases studied. A total of 320 asymptomatic individuals were exposed (ELISA+ and/or DTH+), providing an overall L. (L.) infantum prevalence of 73.6%. Clinical, parasitological, and immunological evaluations suggest seven infection profiles, three asymptomatic and four symptomatic. This represents the first report on clinical and immunological features of human L. (L.) infantum-infection in Amapala municipality, Honduras.

Sirolimus enhances the protection achieved by a DNA vaccine against Leishmania infantum

Background

Leishmaniases are a group of neglected tropical parasitic diseases, mainly affecting vulnerable populations of countries with poor socioeconomic status. Development of efficient vaccines is a priority due to the increasing incidence of drug resistance and toxicity to current treatments. In the search for a safe and efficient protective vaccine for human and dog visceral leishmaniases, we analyzed the suitability of the immunomodulatory drug sirolimus (SIR) to boost a preventive DNA vaccine against leishmaniasis. SIR is an already marketed drug that has been described to boost immune protection against different disease models and has also emerged as a promising therapeutic drug against L. major.

Methods

Syrian hamsters were treated with SIR concomitantly with the administration of a DNA vaccine formulation consisting in four plasmids carrying the Leishmania genes LACK, TRYP, PAPLE22 and KMPII, respectively. Two weeks after the last vaccination, the animals were infected intraperitoneally with L. infantum parasites. Five weeks post-infection the parasite load was measured by real-time PCR in target tissues and immune response was evaluated by determining anti-Leishmania specific antibodies in combination with cytokine expression in the spleen.

Results

Our results show that the DNA vaccine itself efficiently reduced the burden of parasites in the skin (P = 0.0004) and lymph nodes (P = 0.0452). SIR administration also enhanced the protection by reducing the parasite load in the spleen (P = 0.0004). Vaccinated animals with or without SIR co-treatment showed lower IFN-γ expression levels than those found in the spleen of control animals. mRNA expression levels of NOS2 and IL-10 were found to be significantly higher in the vaccinated plus SIR treated group.

Conclusions

Co-administration of SIR enhances a DNA vaccination regimen against L. infantum, improving the reduction of parasite load in skin, lymph node and spleen. The analysis of immune markers in the spleen after challenge suggests that the trend to recover naïve levels of IFN-γ and IL-10, and the concurrent higher expression of NOS2, may be responsible for the protection induced by our vaccine co-administered with SIR.

Prospection of immunological biomarkers for characterization and monitoring of asymptomatic Leishmania (Leishmania) infantum infection

In areas endemic for Leishmania infantum, an asymptomatic infection may be an indicator of the extent of transmission. The main goal of this study was to evaluate the applicability of measuring circulating immunological biomarkers as an alternative strategy to characterize and monitor L. infantum asymptomatic infections in combination with serological methods. To this end, 179 children from a region endemic for visceral leishmaniasis (VL), aged 1-10 years old, selected from a cross-sectional study, were identified as asymptomatic (n = 81) or uninfected (n = 98) by qPCR and/or serological tests (ELISA using L. infantum soluble antigen and rK39), and, together with serum samples of children diagnosed with VL (n = 43), were subjected to avidity tests and cytokine levels measurement. Avidity rates (AR) ranging from 41 to 70% were found in 29 children (66%) from the asymptomatic group. On the other hand, high AR (above 70%) were observed in 27 children (64%) from the VL group. Logistic Regression and Classification and Regression Tree (CART) analyses demonstrated that lower AR and IFN-γ production associated with higher IL-17A levels were hallmarks in asymptomatic L. infantum infections. Therefore, this study proposes an association of immunological biomarkers that can be used as a complementary strategy for the characterization and monitoring of asymptomatic VL infections in children living in endemic areas.

TLR4 abrogates the Th1 immune response through IRF1 and IFN-β to prevent immunopathology during L. infantum infection

A striking feature of human visceral leishmaniasis (VL) is chronic inflammation in the spleen and liver, and VL patients present increased production levels of multiple inflammatory mediators, which contribute to tissue damage and disease severity. Here, we combined an experimental model with the transcriptional profile of human VL to demonstrate that the TLR4-IFN-β pathway regulates the chronic inflammatory process and is associated with the asymptomatic form of the disease. Tlr4-deficient mice harbored fewer parasites in their spleen and liver than wild-type mice. TLR4 deficiency enhanced the Th1 immune response against the parasite, which was correlated with an increased activation of dendritic cells (DCs). Gene expression analyses demonstrated that IRF1 and IFN-β were expressed downstream of TLR4 after infection. Accordingly, IRF1- and IFNAR-deficient mice harbored fewer parasites in the target organs than wild-type mice due to having an increased Th1 immune response. However, the absence of TLR4 or IFNAR increased the serum transaminase levels in infected mice, indicating the presence of liver damage in these animals. In addition, IFN-β limits IFN-γ production by acting directly on Th1 cells. Using RNA sequencing analysis of human samples, we demonstrated that the transcriptional signature for the TLR4 and type I IFN (IFN-I) pathways was positively modulated in asymptomatic subjects compared with VL patients and thus provide direct evidence demonstrating that the TLR4-IFN-I pathway is related to the nondevelopment of the disease. In conclusion, our results demonstrate that the TLR4-IRF1 pathway culminates in IFN-β production as a mechanism for dampening the chronic inflammatory process and preventing immunopathology development.

Visceral leishmaniasis (VL) is one of the most lethal neglected tropical diseases and is caused by Leishmania parasites. Most subjects infected with Leishmania present subclinical VL symptoms, and their immune response is mediated by Th1 cells and immunoregulatory mechanisms. However, when infection progresses to disease, VL patients present increased levels of inflammatory mediators in the serum which are related to the severity of disease. During infection, Toll-like receptors (TLRs) interact with Leishmania parasites and contribute to the outcome of the disease. Herein, we report that TLR4 signaling hampers the chronic immune response during VL to prevent immunopathology. TLR4 triggers the activation of IRF1 and thus induces the transcription of IFN-β, which in turn acts directly on Th1 cells to limit the production of IFN-γ. In addition, a transcription analysis of human VL samples provides direct evidence demonstrating that the TLR4-IFN-I pathway is related to the asymptomatic form of the disease. Collectively, our findings reveal that TLR4 hampers the Th1 immune response through IRF1 and IFN-β to prevent immunopathology during VL.

Impact of dogs with deltamethrin-impregnated collars on prevalence of visceral leishmaniasis

Leishmaniasis is a vector borne zoonosis which is classified as a neglected tropical disease. Among the three most common forms of the disease, Visceral Leishmaniasis (VL) is the most threatening to human health, causing 20,000 to 30,000 deaths worldwide each year. Areas where VL is mostly endemic have unprotected dogs in community and houses. The "presence of dogs usually increases VL risk for humans since dogs are the principal reservoir host for the parasite of the disease. Based on this fact, most earlier studies consider culling dogs as a control measure for the spread of VL. A more recent control measure has been the use of deltamethrin-impregnated dog collars ( D I D C s) to protect both humans and dogs by putting D I D C s on dogs neck. The presence of dogs helps to grow the sandfly population faster by offering a more suitable blood-meal source. On the other hand, the presence of D I D C s on dogs helps to reduce sandfly population by the lethality of deltamethrin insecticide. This study brings an ecological perspective to this public health concern, aiming to understand the impact of an additional host (here, protected dogs) on disease risk to a primary host (here, humans). To answer this question, we compare two different settings: a community without dogs, and a community with dogs protected with D I D C . Our analysis shows the presence of protected dogs can reduce VL infection risk in humans. However, this disease risk reduction depends on dogs' tolerance for sandfly bites.

Leishmania infection: Misdiagnosis as cancer and tumor-promoting potential

Given the prevalence of cancer and leishmaniasis worldwide, the presence of these two pathologies in the same tissue sample may be merely fortuitous. The clinical outcome of both diseases is under the control of innate and adaptive immunity, and in both cases these progressive diseases are characterized by an impaired host Th1 response. As a consequence, the Th2 cytokine microenvironment occurring in progressive leishmaniasis may potentially promote tumor cell proliferation and vice versa. On the other hand, clinical aspects of subclinical cutaneous or visceral leishmaniasis sometimes closely resemble those observed in various neoplasms thus leading to misdiagnosis. In this review, we present recent findings on the association between leishmaniasis and malignant disorders. Our review includes HIV positive, HIV negative subjects and patients whose HIV status has not been established. Leishmaniasis mimicking a malignant disorder was confirmed and extended to unreported neoplastic disorders including squamous cell carcinoma, T-cell and B-cell lymphoma, oral and intranasal tumors and granulomas. Thus, leishmaniasis should be considered in the differential diagnosis and course of various cancers in Leishmania endemic areas or in patients with travel history to these areas. We also listed recent reports showing that Leishmania can promote cancer development in immunocompromised as well as in immunocompetent patients. The potential mechanisms supporting this promoting effect are discussed.

Live Leishmania tarentolae secreting HNP1 as an immunotherapeutic tool against Leishmania infection in BALB/c mice

AIM

Several disadvantages about chemotherapy for leishmaniasis has reinforced discovery of novel therapeutic agents especially immunotherapeutics. HNP1, as a member of the mammalian antimicrobial peptides family, is an attractive molecule due to its broad functional spectrum. Here, the in vivo potency of HNP1 in transgenic Leishmania tarentolae as an immunotherapy tool against Leishmania major-infected BALB/c mice was examined.

METHODS & RESULTS

3 weeks after infection with L. major, the treatment effect of L. tarentolae-HNP1-EGFP was pursued. The results were promising in respect to parasite load control and Th1 immune response polarization compared with controls.

CONCLUSION

Immunotherapy by live L. tarentolae secreting HNP1 can elicit cellular immune response in a susceptible mouse model in order to control L. major infection.

Detection of Leishmania donovani in peripheral blood of asymptomatic individuals in contact with patients with visceral leishmaniasis

BACKGROUND

The majority of individuals infected with Leishmania donovani complex remain asymptomatic. They may act as transmission reservoirs for visceral leishmaniasis (VL). We investigated sero-prevalence of L. donovani complex amongst those closely associated with patients with VL and whether these sero-reactive individuals had Leishmania parasites in their peripheral blood. Other risk factors were also investigated.

METHODS

A total of 257 individuals in contact with patients with VL were tested for anti-Leishmania antibodies by rK39 immunochromatographic test (rK39 ICT), ELISA using promastigote antigen (p-ELISA) and indirect fluorescent antibody test (IFAT). Buffy coats of rK39 ICT positive individuals were cultured; sero-reactive buffy coats were tested for Leishmania DNA by ITS1 PCR. DNA obtained from culture was sequenced to confirm Leishmania species. Risk factors were evaluated for each sero-positive sample.

RESULTS

The results showed 29.2% (75/257) prevalence by serological tests: 14.4% (37/257) were positive by rK39 ICT, 25.3% (65/257) by p-ELISA, 18.3% (47/257) by IFAT and 10.9% (28/257) by all three serological methods. Ten percent (3/30) of cultures were positive for Leishmania promastigotes. Only 3% (2/74) sero-reactive buffy coats were positive for DNA; sequence analysis revealed L. donovani species. Significant risk factors were age, working as farmers, domestic animals in household and proximity to animal shelters.

CONCLUSIONS

Asymptomatic family members of patients with VL can carry live L. donovani in peripheral blood and may act as potential reservoirs.

GENBANK ACCESSION NUMBER

BankIt1863680 Leishmania KT921417 (DNA sequences of the ribosomal ITS1 region of L. donovani).

Induction of haem oxygenase-1 increases infection of dog macrophages by L. infantum

We aimed to induce and inhibit HO-1, ascertaining its effect on infection rate, parasite load and the levels of superoxide, reactive oxygen species (ROS), nitric oxide (NO), TNF-alpha and IL-10 in cultured macrophages from healthy dogs infected by Leishmania infantum. Macrophages obtained from 15 healthy dogs were cultured alone or infected with L. infantum, with or without association of HO-1 inducer and inhibitor. The infection rate and the parasite load were determined by the number of infected macrophages and number of promastigotes per macrophage, respectively. HO-1 levels and gene expression, as well as IL-10 and TNF-alpha levels were also measured in these cultures. Superoxide, ROS and NO levels in macrophages were measured through flow cytometry. Induction of HO-1 increased the infection rate and parasite load, while its inhibition decreased the infection rate and IL-10 production. There was a positive correlation between HO-1 and infection rate or parasite load. Increased infection rate was associated with decreased superoxide, ROS and NO levels. Induction of HO-1 metabolism in dogs infected by L. infantum is possibly one of the mechanisms responsible for increasing the infection of macrophages, mainly through reduction in the oxidative and nitrosative metabolisms of these cells.

Comparative analyses of whole genome sequences of Leishmania infantum isolates from humans and dogs in northeastern Brazil

The genomic sequences of 20 Leishmania infantum isolates collected in northeastern Brazil were compared with each other and with the available genomic sequences of 29 L. infantum/donovani isolates from Nepal and Turkey. The Brazilian isolates were obtained in the early 1990s or since 2009 from patients with visceral or non-ulcerating cutaneous leishmaniasis, asymptomatic humans, or dogs with visceral leishmaniasis. Two isolates were from the blood and bone marrow of the same visceral leishmaniasis patient. All 20 genomic sequences display 99.95% identity with each other and slightly less identity with a reference L. infantum genome from a Spanish isolate. Despite the high identity, analysis of individual differences among the 32 million base pair genomes showed sufficient variation to allow the isolates to be clustered based on the primary sequence. A major source of variation detected was in chromosome somy, with only four of the 36 chromosomes being predominantly disomic in all 49 isolates examined. In contrast, chromosome 31 was predominantly tetrasomic/pentasomic, consistent with its regions of synteny on two different disomic chromosomes of Trypanosoma brucei. In the Brazilian isolates, evidence for recombination was detected in 27 of the 36 chromosomes. Clustering analyses suggested two populations, in which two of the five older isolates from the 1990s clustered with a majority of recent isolates. Overall the analyses do not suggest individual sequence variants account for differences in clinical outcome or adaptation to different hosts. For the first known time, DNA of isolates from asymptomatic subjects were sequenced. Of interest, these displayed lower diversity than isolates from symptomatic subjects, an observation that deserves further investigation with additional isolates from asymptomatic subjects.

Canine Leishmaniasis Progression is Associated with Vitamin D Deficiency

The relationship between vitamin D deficiency and the risk of suffering from a plethora of health disorders, ranging from autoimmune processes to infectious diseases has been widely described. Nonetheless, the potential role of vitamin D in visceral leishmaniasis remains uncharacterized. In the Mediterranean basin, where the dog is leishmania’s main peri-domestic reservoir, control measures against the canine disease have shown beneficial effects on the incidence of human leishmaniasis. In this study, we measured the vitamin D levels in serum samples from a cohort of 68 healthy and disease dogs from a highly endemic area and we have also studied the relationship of these levels with parasitological and immunological parameters. The sick dogs presented significantly lower (P < 0.001) vitamin D levels (19.6 ng/mL) than their non-infected (31.8 ng/mL) and the asymptomatic counterparts (29.6 ng/mL). In addition, vitamin D deficiency correlated with several parameters linked to leishmaniasis progression. However, there was no correlation between vitamin D levels and the Leishmania-specific cellular immune response. Moreover, both the leishmanin skin test and the IFN-γ levels displayed negative correlations with serological, parasitological and clinical signs. Further studies to determine the functional role of vitamin D on the progression and control of canine leishmaniasis are needed.

The Preventive Control of Zoonotic Visceral Leishmaniasis: Efficacy and Economic Evaluation

Zoonotic Visceral Leishmaniasis (ZVL) is one of the world's deadliest and neglected infectious diseases, according to World Health Organization. This disease is one of major human and veterinary medical significance. The sandfly and the reservoir in urban areas remain among the major challenges for the control activities. In this paper, we evaluated five control strategies (positive dog elimination, insecticide impregnated dog collar, dog vaccination, dog treatment, and sandfly population control), considering disease control results and cost-effectiveness. We elaborated a mathematical model based on a set of differential equations in which three populations were represented (human, dog, and sandfly). Humans and dogs were divided into susceptible, latent, clinically ill, and recovery categories. Sandflies were divided into noninfected, infected, and infective. As the main conclusions, the insecticide impregnated dog collar was the strategy that presented the best combination between disease control and cost-effectiveness. But, depending on the population target, the control results and cost-effectiveness of each strategy may differ. More and detailed studies are needed, specially one which optimizes the control considering more than one strategy in activity.

Mathematical modelling for Zoonotic Visceral Leishmaniasis dynamics: A new analysis considering updated parameters and notified human Brazilian data

Brazil is one of the highest endemic countries for Zoonotic Visceral Leishmaniasis: according to the Brazilian Ministry of Health, the annual number of new human cases and deaths due to this disease has been increasing for the last 20 years. In addition, regarding the Americas, the specific relationship between canine and human for Visceral Leishmaniasis dynamics is still not well understood. In this work we propose a new model for Zoonotic Visceral Leishmaniasis, based on the models previously published by Burattini et al. (1998) and Ribas et al. (2013). Herein, we modeled the disease dynamics using a modified set of differential equations from those two authors, considering the same assumptions (inclusion of human, dog and sandfly populations, all constants over time). From this set of equations we were able to calculate the basic reproduction number R 0 and to analyze the stability and sensitivity of the system to the parameters variability. As main result, when the stability of the system is reached, the normalized reporting human cases rate is estimated in 9.12E-08/day. This estimation is very close to the 2015 report from Araçatuba city, 5.69E-08/day. We also observed from stability and sensitivity analysis that the activity of sandfly population is critical to introduction and maintenance of Zoonotic Visceral Leishmaniasis in the population. In addition, the importance of dog as source of infection concentrates on latent dog, since it does not show clinical symptoms and signs and, therefore, has a great contribution to disease dissemination. As conclusion, considering the presently ethical issues regarding to elimination of positive dog in Brazil and the highly sensitivity of disease dynamics on sandfly population, we recommend that the sandfly population control should be prioritized.

Progress in the Mathematical Modelling of Visceral Leishmaniasis

The leishmaniases comprise a complex of diseases characterized by clinical outcomes that range from self-limiting to chronic, and disfiguring and stigmatizing to life threatening. Diagnostic methods, treatments, and vector and reservoir control options exist, but deciding the most effective interventions requires a quantitative understanding of the population level infection and disease dynamics. The effectiveness of any set of interventions has to be determined within the context of operational conditions, including economic and political commitment. Mathematical models are the best available tools for studying quantitative systems crossing disciplinary spheres (biology, medicine, economics) within environmental and societal constraints. In 2005, the World Health Assembly and government health ministers of India, Nepal, and Bangladesh signed a Memorandum of Understanding to eliminate the life threatening form of leishmaniasis, visceral leishmaniasis (VL), on the Indian subcontinent by 2015 through a combination of early case detection, improved treatments, and vector control. The elimination target is <1 case/10,000 population at the district or subdistrict level compared to the current 20/10,000 in the regions of highest transmission. Towards this goal, this chapter focuses on mathematical models of VL, and the biology driving those models, to enable realistic predictions of the best combination of interventions. Several key issues will be discussed which have affected previous modelling of VL and the direction future modelling may take. Current understanding of the natural history of disease, immunity (and loss of immunity), and stages of infection and their durations are considered particularly for humans, and also for dogs. Asymptomatic and clinical infection are discussed in the context of their relative roles in Leishmania transmission, as well as key components of the parasite-sandfly-vector interaction and intervention strategies including diagnosis, treatment and vector control. Gaps in current biological knowledge and potential avenues to improve model structures and mathematical predictions are identified. Underpinning the marriage between biology and mathematical modelling, the content of this chapter represents the first step towards developing the next generation of models for VL.

Canine-Based Strategies for Prevention and Control of Visceral Leishmaniasis in Brazil

Visceral leishmaniasis (VL) is a zoonosis found worldwide. Its incidence has increased in Brazil in recent years, representing a serious public and animal health problem. The strategies applied in Brazil are questionable and are not sufficient to control the disease. Thus, we have compared the efficacy of some of the currently available strategies focused on dogs to prevent and control zoonotic VL in endemic areas by optimizing a mathematical model. The simulations showed that the elimination of seropositive dogs, the use of insecticide-impregnated dog collars, and the vaccination of dogs significantly contribute to reducing the prevalence of infection in both canines and humans. The use of insecticide-impregnated collars presented the highest level of efficacy mainly because it directly affected the force of infection and vector-dog contact. In addition, when used at a coverage rate of 90%, insecticide-impregnated collar was able to decrease the prevalence of seropositive dogs and humans to zero; moreover, because of the easy application and acceptance by the targeted population, these collars may be considered the most feasible for inclusion in public policies among the three simulated measures. Vaccination and euthanasia were efficacious, but the latter method is strongly criticized on ethical grounds, and both methods present difficulties for inclusion in public policies. When we compared the use of euthanasia and vaccination at coverages of 70 and 90%, respectively, the proportion of infected populations were similar. However, on evaluating the implications of both of these methods, particularly the negative aspects of culling dogs and the proportion of animals protected by vaccination, the latter measure appears to be the better option if the total cost is not significantly higher. The comparison of complications and advantages of different control strategies allows us to analyze the optimal measure and offer strategies to veterinary and public health authorities for making decisions to prevent and control zoonotic VL. Hence, improvements in both public and animal health can be achieved in regions with scenarios similar to that considered in the present study; such scenarios are characteristically found in some areas of Brazil and other countries.

Recombinant K39 Dipstick Immunochromatographic Test: A New Tool for the Serodiagnosis of Canine Leishmaniasis

The spread of human leishmaniasis has prompted the scientific community to study dogs as reservoirs for Leishmania infantum. Canine leishmaniasis (CanL) is widespread in the Mediterranean area with a prevalence of up to 50%. The first step toward controlling the disease is to monitor its distribution, mainly in stray dogs. The validity of a recombinant K39 (rK39) dipstick test,a commercially available for the serodiagnosis of human leishmaniasis, was evaluated using sera from 165 dogs selected on the basis of positive or negative lymph node smears at parasitological examination. The results were compared with the indirect fluorescent antibody test (IFAT) (cutoff 1:80). Sera from a group of dogs with other diagnosed diseases but negative for leishmaniasis were also tested to evaluate any cross-reactivity. Various procedures were used for testing whole blood samples. The relative specificity of the rK39 dipstick and IFAT was 100% (97 of 97) and 98.97% (96 of 97), whereas the relative sensitivity was 97.06% (66 of 68) and 98.53% (67 of 68), respectively. The results of the dipstick and IFAT corresponded except for 2 sera (k = 0.987). This data confirm the usefulness of rK39 antigen for diagnosing CanL both in symptomatic and asymptomatic dogs. The rK39 dipstick proved to be a rapid, sensitive, and specific test that may be very useful in the field for large-scale screening and also in veterinary practice, requiring minimal equipment and operator expertise.

Risk Factors Associated with Human Visceral Leishmaniasis in an Urban Area of Bahia, Brazil

BACKGROUND

The early diagnosis of asymptomatic, acute, and subclinical Leishmania infections remains a challenge for controlling visceral leishmaniasis (VL). Individuals with acute VL represent <1% of Leishmania infections occurring in active transmission endemic areas. In this cross-sectional study with a prospective follow-up, we explored the risk factors associated with acquisition of Leishmania infection in an area with newly identified endemic VL.

MATERIALS AND METHODS

Ninety-four households were randomly selected from the study area, which included a population of 213 individuals (10% of the total population of Pé de Areia, Bahia, Brazil). Clinical and epidemiological surveys were prospectively performed to detect cases of asymptomatic infections, acute VL, and subclinical VL, using the leishmanin skin test (LST), and serological response to two Leishmania-specific antigens: rK39 and rK26.

RESULTS

Within the 92 households included in the study, the prevalence of Leishmania infection in individuals detected by positive serology was 91/197 (46.2%; 95% CI: 0.3937-0.5316) and by LST was 29/114 (25.4%; 95% CI: 0.1834-0.3414). Reactivity to both antigens was detected in 64/197 individuals (32.5%; 95% CI: 0.2634-0.3931). Among 89 individuals diagnosed with leishmaniasis, we found acute VL in one (1%), subclinical VL in 20 (22.5%), and asymptomatic Leishmania infection in 68 (76.4%) subjects. Use of repellents and bed nets showed no significant protection (prevalence ratio [PR] = 1.01, p = 1.0). Interestingly, individuals residing in houses with a sand backyard had significant protection against Leishmania infection (PR = 1.24, p = 0.049) compared to those with a different type or no backyard. Moreover, the presence of cat or dog at home was also not a risk factor (dog: PR = 1.14, 95% CI: 0.80-1.64; and cat: PR = 1.19, 95% CI: 0.78-1.81). We conclude that in newly discovered areas of transmission of L. infantum infection with sylvatic reservoirs, periodic surveys may be helpful in identifying risk factors for infection and optimizing prevention guidelines.

The Severity of Visceral Leishmaniasis Correlates with Elevated Levels of Serum IL-6, IL-27 and sCD14

BACKGROUND

Visceral leishmaniasis (VL) is a severe disease caused by infection with protozoa of the genus Leishmania. Classic VL is characterized by a systemic infection of phagocytic cells and an intense activation of the inflammatory response. It is unclear why 90% of infected individuals do not develop the disease while a minority develop the classical form. Furthermore, among those that develop disease, a small group progresses to more severe form that is unresponsive to treatment. The presence of inflammatory mediators in serum could theoretically help to control the infection. However, there is also a release of anti-inflammatory mediators that could interfere with the control of parasite multiplication. In this study, we took advantage of the spectrum of outcomes to test the hypothesis that the immune profile of individuals infected with Leishmania (L.) infantum is associated with the development and severity of disease.

METHODOLOGY/PRINCIPAL FINDINGS

Sera from patients with confirmed diagnosis of VL were evaluated for the presence of numerous molecules, and levels compared with healthy control and asymptomatic infected individuals.

CONCLUSIONS/PRINCIPAL FINDINGS

Although differences were not observed in LPS levels, higher levels of sCD14 were detected in VL patients. Our data suggest that L. infantum may activate the inflammatory response via CD14, stimulating a generalized inflammatory response with production of several cytokines and soluble molecules, including IFN-γ, IL-27, IL-10, IL-6 and sCD14. These molecules were strongly associated with hepatosplenomegaly, neutropenia and thrombocytopenia. We also observed that IL-6 levels greater than 200 pg/ml were strongly associated with death. Together our data reinforce the close relationship of IFN-γ, IL-10, IL-6, TNF-α and IL-27 in the immune dynamics of VL and suggest the direct participation of sCD14 in the activation of the immune response against L. infantum.

Tolerance to Trypanosomatids: A Threat, or a Key for Disease Elimination?

So far, research on trypanosomatid infections has been driven by 'disease by disease' approaches, leading to different concepts and control strategies. It is, however, increasingly clear that they share common features such as the ability to generate long-lasting asymptomatic infections in their mammalian hosts. Trypanotolerance, long integrated in animal African trypanosomiasis control, historically refers to the ability of cattle breeds to limit Trypanosoma infection and pathology, but has only recently been recognized in humans. Whilst trypanotolerance is absent from the vocabulary on leishmaniasis and Chagas disease, asymptomatic infections also occur. We review the concept of trypanotolerance across the trypanosomatids and discuss the importance of asymptomatic carriage in the current context of elimination.

Post-kala-azar dermal leishmaniasis and leprosy: case report and literature review

Background

Post-kala-azar dermal leishmaniasis (PKDL) is a dermal complication of visceral leishmaniasis (VL), which may occur after or during treatment. It has been frequently reported from India and the Sudan, but its occurrence in South America has been rarely reported. It may mimic leprosy and its differentiation may be difficult, since both diseases may show hypo-pigmented macular lesions as clinical presentation and neural involvement in histopathological investigations. The co-infection of leprosy and VL has been reported in countries where both diseases are endemic. The authors report a co-infection case of leprosy and VL, which evolved into PKDL and discuss the clinical and the pathological aspects in the patient and review the literature on this disease.

Case presentation

We report an unusual case of a 53-year-old female patient from Alagoas, Brazil. She presented with leprosy and a necrotizing erythema nodosum, a type II leprosy reaction, about 3 month after finishing the treatment (MDT-MB) for leprosy. She was hospitalized and VL was diagnosed at that time and she was successfully treated with liposomal amphotericin B. After 6 months, she developed a few hypo-pigmented papules on her forehead. A granulomatous inflammatory infiltrate throughout the dermis was observed at histopathological examination of the skin biopsy. It consisted of epithelioid histiocytes, lymphocytes and plasma cells with the presence of amastigotes of Leishmania in macrophages (Leishman’s bodies). The diagnosis of post-kala-azar dermal leishmaniasis was established because at this time there was no hepatosplenomegaly and the bone marrow did not show Leishmania parasites thus excluding VL. About 2 years after the treatment of PKDL with liposomal amphotericin B the patient is still without PKDL lesions.

Conclusion

Post-kala-azar dermal leishmaniasis is a rare dermal complication of VL that mimics leprosy and should be considered particularly in countries where both diseases are endemic. A co-infection must be seriously considered, especially in patients who are non-responsive to treatment or develop persistent leprosy reactions as those encountered in the patient reported here.

Spontaneous remission of fully symptomatic visceral leishmaniasis

BACKGROUND

Visceral leishmaniasis (VL), i.e., infection with Leishmania sp. associated with high fever, weight loss, massive splenomegaly and markedly altered laboratory parameters, is generally fatal if untreated. The possibility of transient spontaneous remission of fully symptomatic visceral leishmaniasis (VL) has been mentioned but, to our knowledge) has never been documented.

CASE PRESENTATION

We report the first documented history of a patient with overt, confirmed VL experiencing a complete remission in the absence of any anti-leishmanial therapy. The diagnosis of VL at the time of the self-resolving episode was strongly suspected based on clinical presentation and presence of antileishmanial antibody, then unequivocally confirmed years later by the presence of an amastigote on a stored smear and the positive quantitative PCR with Leishmania-specific primers from the material scraped from this same slide

CONCLUSION

This report demonstrates that complete spontaneous remission may occur in patients with overt, fully symptomatic VL. VL should therefore be considered in cases of self-resolving or relapsing episodes of fever of unknown origin. Confirmation should be based on both serological tests and specific PCR on a blood sample.

Quantitative PCR in epidemiology for early detection of visceral leishmaniasis cases in India

Introduction

Studies employing serological, DTH or conventional PCR techniques suggest a vast proportion of Leishmania infected individuals living in regions endemic for Visceral Leishmaniasis (VL) remain asymptomatic. This study was designed to assess whether quantitative PCR (qPCR) can be used for detection of asymptomatic or early Leishmania donovani infection and as a predictor of progression to symptomatic disease.

Methods

The study included 1469 healthy individuals living in endemic region (EHC) including both serology-positive and -negative subjects. TaqMan based qPCR assay was done on peripheral blood of each subject using kDNA specific primers and probes.

Results

A large proportion of EHC 511/1469 (34.78%) showed qPCR positivity and 56 (3.81% of 1469 subjects) had more than 1 calculated parasite genome/ml of blood. However, the number of individuals with parasite load above 5 genomes/ml was only 20 (1.36% of 1469). There was poor agreement between serological testing and qPCR (k = 0.1303), and 42.89% and 31.83% EHC were qPCR positive in seropositive and seronegative groups, respectively. Ten subjects had developed to symptomatic VL after 12 month of their follow up examination, of which eight were initially positive according to qPCR and among these, five had high parasite load.

Discussion

Thus, qPCR can help us to detect significant early parasitaemia, thereby assisting us in recognition of potential progressors to clinical disease. This test could facilitate early intervention, decreased morbidity and mortality, and possibly interruption of disease transmission.

Anthroponotic VL caused by Leishmania donovani in the Indian subcontinent accounts for 70% of the world burden of VL. Among the estimated 100,000 cases of VL acquired annually in India, 90% occur in the state of Bihar. Leishmania infection can result in either symptomatic or asymptomatic infection. L. donovani infection can also manifest as post-kala azar dermal leishmaniasis, a chronic cutaneous form thought to provide the reservoir for anthroponotic transmission of VL in regions endemic for this parasite species. We hypothesized that, in areas endemic for L. donovani, asymptomatic infections might also play a crucial role in disease transmission. This study describes use of quantitative PCR (qPCR) to determine the infection status in individuals living in an endemic region of India. We hypothesized that parasite load estimation by qPCR of peripheral blood cells among healthy individuals living in the endemic region might reveal the true frequency of infections through direct evidence of parasitemia. We reasoned this test would detect both asymptomatic non-progressors as well as asymptomatic individuals who will progress to fully symptomatic VL. Serologic testing by ELISA or DAT showed poor agreement with molecular detection of parasite DNA by qPCR, suggesting the tests differentiate between infection and immune response. Amongst ten healthy individuals who progressed to VL, only six were serologically positive whereas eight were initially qPCR positive, among whom five had high parasite loads in their blood. Thus, deployment of qPCR technique to estimate the presence and level of parasitemia in healthy individuals from Leishmania endemic regions may contribute to early case detection, thereby reducing morbidity and mortality. Consistent with the goals of the VL control and elimination program, this early intervention approach could help interrupt disease transmission.

Leishmaniasis

Leishmaniasis remains an important neglected tropical infection that affects children more than adults. Geographical variation exists in the distribution of the various Leishmania species. Although the majority of the disease burden is found in poor countries, leishmaniasis is also endemic in several countries within Southern Europe. Transmission is mediated by the sandfly and may follow an anthroponotic or zoonotic cycle that also varies by region. The expression of leishmaniasis depends on a complex interaction between the type of infecting species and the host immune response. Infection may be asymptomatic or may manifest as cutaneous disease that is pleiomorphic in presentation, muco-cutaneous disease or the visceral form that may be lethal if untreated. Molecular techniques aid diagnosis especially in cases where amastigotes are not visualised. The efficacy of treatment varies with the type of infecting species and resistance patterns. Preventive measures aimed at avoiding sandfly bites are effective in reducing acquisition of leishmaniasis and should be promoted for travellers visiting endemic regions. The persistent lack of a vaccine against human leishmaniasis is a result of the poor investment in this neglected parasitosis.

Serological survey of Leishmania infection in blood donors in Salvador, Northeastern Brazil

BACKGROUND

Visceral Leishmaniasis is endemic to Brazil, where it is caused by Leishmania infantum (syn. Leishmania chagasi). Following parasite inoculation, individuals may experience asymptomatic infection, raising the possibility of parasite transmission through the transfusion of contaminated blood products. In the present work, we evaluated the prevalence of asymptomatic Leishmania infection among blood donors in Salvador, northeastern Brazil.

METHODS

Peripheral blood was collected from 700 blood donors attending the Blood Bank of Bahia (HEMOBA/SESAB), from January to September 2010. We evaluated anti-Leishmania serology by ELISA, employing Soluble Leishmania Antigen (sensitivity 90% and specificity 95%). The presence of parasite DNA was determined by qPCR, targeting a single copy gene (G6PD), and by end-point PCR, targeting multiple targets, namely a segment located in the Leishmania rRNA locus (ITS) and the conserved region of kinetoplastid DNA (kDNA) minicircles.

RESULTS

The blood-donor population was comprised of 74.5% of males with a mean age of 34 years. Anti-Leishmania serology by ELISA was positive in 5.4% (38/700) individuals. One individual was also positive for Chagas' disease and another tested positive for Syphilis. Employing qPCR, parasite DNA was not found in any of 38 seropositive samples. However, by ITS PCR, 8/38 (21%) samples were positive and this positivity increased to 26/38 (68%) when we targeted kDNA amplification. Agreement between both techniques (ITS and kDNA PCR) was fair (kappa = 0.219).

CONCLUSIONS

These results indicate that asymptomatic infection is present among the blood donor population of Salvador, a finding that warrants a broader discussion regarding the need to implement specific screening strategies.

Immune regulation during chronic visceral leishmaniasis

Visceral leishmaniasis is a chronic parasitic disease associated with severe immune dysfunction. Treatment options are limited to relatively toxic drugs, and there is no vaccine for humans available. Hence, there is an urgent need to better understand immune responses following infection with Leishmania species by studying animal models of disease and clinical samples from patients. Here, we review recent discoveries in these areas and highlight shortcomings in our knowledge that need to be addressed if better treatment options are to be developed and effective vaccines designed.

Infection with Leishmania (Leishmania) infantum of 0 to 18-Month-old children living in a visceral leishmaniasis-endemic area in Brazil

The diagnosis of Leishmania (Leishmania) infantum infection in children from birth may serve as a reference for the early identification of cases that would progress to classical visceral leishmaniasis (VL) in endemic areas. This study prospectively evaluated newborns of mothers living in the municipality of Paracatu, Minas Gerais, Brazil. The infants were followed up at 6-month intervals by clinical examination, serological tests (immunofluorescence [IIF] and enzyme-linked immunosorbent assay with rK39 [ELISA-rK39]) and polymerase chain reaction (PCR) until they had completed 18 months of age. A total of 166 pregnant women were included to evaluate the possible transfer of antibodies or even congenital transmission. Twenty-two of the women tested positive by IIF, four by ELISA-rK39, and one by PCR. Three infants of the 25 women with some positive test results were also positive in the first test (one by IIF, one by ELISA-rK39, and the third by ELISA-rK39 and PCR). One hundred and sixty infants were included in the study; of these, 43 had at least one positive sample over time. However, agreement between tests was low. Follow-up of children with a positive result in the tests studied revealed no progression to classical disease within a period of 18 months. In contrast, two children with negative IIF, PCR, and ELISA-rK39 results developed classical VL at 9 and 12 months of age. In conclusion, a positive test result was variable and sometimes temporary and agreement between tests was low. Therefore, the early diagnosis of Leishmania infection was not associated with the early identification of cases that would progress to classical VL in the endemic area studied.

Clinical and parasitological protection in a Leishmania infantum-macaque model vaccinated with adenovirus and the recombinant A2 antigen

BACKGROUND

Visceral leishmaniasis (VL) is a severe vector-born disease of humans and dogs caused by Leishmania donovani complex parasites. Approximately 0.2 to 0.4 million new human VL cases occur annually worldwide. In the new world, these alarming numbers are primarily due to the impracticality of current control methods based on vector reduction and dog euthanasia. Thus, a prophylactic vaccine appears to be essential for VL control. The current efforts to develop an efficacious vaccine include the use of animal models that are as close to human VL. We have previously reported a L. infantum-macaque infection model that is reliable to determine which vaccine candidates are most worthy for further development. Among the few amastigote antigens tested so far, one of specific interest is the recombinant A2 (rA2) protein that protects against experimental L. infantum infections in mice and dogs.

METHODOLOGY/PRINCIPAL FINDINGS

Primates were vaccinated using three rA2-based prime-boost immunization regimes: three doses of rA2 plus recombinant human interleukin-12 (rhIL-12) adsorbed in alum (rA2/rhIL-12/alum); two doses of non-replicative adenovirus recombinant vector encoding A2 (Ad5-A2) followed by two boosts with rA2/rhIL-12/alum (Ad5-A2+rA2/rhIL12/alum); and plasmid DNA encoding A2 gene (DNA-A2) boosted with two doses of Ad5-A2 (DNA-A2+Ad5-A2). Primates received a subsequent infectious challenge with L. infantum. Vaccines, apart from being safe, were immunogenic as animals responded with increased pre-challenge production of anti-A2-specific IgG antibodies, though with some variability in the response, depending on the vaccine formulation/protocol. The relative parasite load in the liver was significantly lower in immunized macaques as compared to controls. Protection correlated with hepatic granuloma resolution, and reduction of clinical symptoms, particularly when primates were vaccinated with the Ad5-A2+rA2/rhIL12/alum protocol.

CONCLUSIONS/SIGNIFICANCE

The remarkable clinical protection induced by A2 in an animal model that is evolutionary close to humans qualifies this antigen as a suitable vaccine candidate against human VL.

Vaccines to prevent leishmaniasis

Leishmaniasis is a parasitic disease that encompasses a range of clinical manifestations affecting people in tropical and subtropical regions of the world. Epidemiological and experimental data indicate that protection from disease can be achieved in most people. In addition, we know how the host immune system must respond to infection in order to control parasite growth. However, there is still no vaccine for use in humans. Here, we review our understanding of host immunity following Leishmania infection and also discuss recent advances in the development of vaccines to prevent leishmaniasis, highlighting a new promising approach that targets the parasite hemoglobin receptor.