Asymptomatic Leishmania chagasi infection in relatives and neighbors of patients with visceral leishmaniasis

Asymptomatic Leishmania infection in humans: A systematic review

BACKGROUND

Leishmaniasis is a highly prevalent neglected tropical disease. It mainly presents as two forms: cutaneous and visceral leishmaniasis, the latter being the most severe form. However, asymptomatic cases of Leishmania infection result in an increase in the underreporting and transmission of the protozoan OBJECTIVES: In this study, articles on the incidence of asymptomatic Leishmania infection were systematically reviewed.

METHODS

The publications identified in the Medline/PubMed and Science Direct databases included 4568 articles. Inclusion, exclusion, and eligibility criterion analysis resulted in 83 articles being retained. These studies were mostly performed in Brazil (n = 26) and India (n = 15).

RESULTS

Several detection techniques have been used for diagnosis. Among the species found were L. infantum and L. donovani, which result in visceral leishmaniasis, and L. amazonensis, L. braziliensis, and L. panamensis. The incidence rates varied between the analyzed locations, largely due to sampling and the presence or absence of endemism in the regions. The largest populations analyzed were in two studies performed in India and Nepal. One of these studies evaluated 32,529 people and the incidence rate was 8.3% (n = 2702), while the other study evaluated 21,267 people and the incidence rate was 1.76% (n = 375). Only 14.28% of the studies investigated leishmaniasis in blood donors. Preexisting diseases have also been reported.

CONCLUSION

The findings of this systematic review present the incidence of cases of asymptomatic Leishmania infection worldwide, in addition to detailing the studies and offering information for researchers and health authorities to seek alternatives to reduce the number of leishmaniasis cases.

Estimation of Leishmania spp. infection in asymptomatic people from Muzaffarpur, Bihar, India by antigen-antibody and skin testing

Asymptomatic VL is a concern, considering the risk of transmission in highly endemic areas due to human-to-human transmission. The aim of this study was to report the sero-epidemiological prevalence in Bihar, India, a highly endemic area of VL, using the leishmanin skin test (LST) and the direct agglutination test (DAT). This was a cross-sectional study performed in Muzaffarpur, Bihar, India. Relatives of patients with VL were tested by LST and DAT. Other epidemiological data were evaluated and correlated with tests results. Forty individuals (either previous or current patients), and 109 household contacts were studied. There were 36% of male visceral leishmaniasis family members versus 17.57% of females visceral leishmaniasis family members, thus showing more males with symptomatic disease than females (p< 0.01). All visceral leishmaniasis cases had positive DAT tests, but only 37% of past cases were positive on the skin testing. Amongst healthy household contacts, 34% were DAT-positive, whilst 21% were LST-positive. The overall positivity for both assays combined was 44.8% and 23.8% were DAT-positive alone. The finding of high infection prevalence amongst asymptomatic individuals, and the estimation of those at greater risk for overt disease (DAT-positive alone) are important in the development of future disease control policies.

Can interruption/withdrawl of anti-retroviral therapy provide personalized immunotherapy against HIV-1?

We propose a treatment of HIV-1⁺ individuals designed to harness protective immunity, lead to viral containment, and so render the individual minimally infectious. A few HIV-infected individuals, 'elite controllers', generate a stable Th1, cytotoxic T lymphocyte response that contains the virus. Most infected individuals, in the absence of therapy, first generate a similarly protective response that evolves with time a Th2 component, associated with antibody production and loss of viral control. Cessation of anti-retroviral treatment after three years results in viral rebound in most, but about one in seven individuals contains the virus, so-called post-treatment controllers. We suggest an understanding, of how the Th1/Th2 phenotype of immune responses is controlled, can explain these different outcomes and leads us to propose a non-invasive, personalized strategy of immunotherapy. We propose that monitoring the relative prevalence of HIV-1 specific IgG₁ and IgG₂ antibodies can provide a biomarker for deciding when to interrupt/withdraw anti-retroviral therapy to optimally harness protective immunity.

Combined in vitro IL-12 and IL-15 stimulation promotes cellular immune response in dogs with visceral leishmaniasis

Domestic dogs are the main reservoir of Leishmania infantum, a causative agent of visceral leishmaniasis (VL). The number of human disease cases is associated with the rate of canine infection. Currently available drugs are not efficient at treating canine leishmaniasis (CanL) and months after the treatment most dogs show disease relapse, therefore the development of new drugs or new therapeutic strategies should be sought. In CanL, dogs lack the ability to mount a specific cellular immune response suitable for combating the parasite and manipulation of cytokine signaling pathway has the potential to form part of effective immunotherapeutic methods. In this study, recombinant canine cytokines (rcaIL-12, rcaIL-2, rcaIL-15 and rcaIL-7) and soluble receptor IL-10R1 (rcasIL-10R1), with antagonistic activity, were evaluated for the first time in combination (rcaIL-12/rcaIL-2, rcaIL-12/rcaIL-15, rcaIL-12/rcasIL-10R1, rcaIL-15/rcaIL-7) or alone (rcasIL-10R1) to evaluate their immunomodulatory capacity in peripheral blood mononuclear cells (PBMCs) from dogs with leishmaniasis. All the combinations of recombinant proteins tested were shown to improve lymphoproliferative response. Further, the combinations rcaIL-12/rcaIL-2 and rcaIL-12/rcaIL-15 promoted a decrease in programmed cell death protein 1 (PD-1) expression in lymphocytes. These same combinations of cytokines and rcaIL-12/rcasIL-10R1 induced IFN-γ and TNF-α production in PBMCs. Furthermore, the combination IL-12/IL-15 led to an increased in T-bet expression in lymphocytes. These findings are encouraging and indicate the use of rcaIL-12 and rcaIL-15 in future in vivo studies aimed at achieving polarization of cellular immune responses in dogs with leishmaniasis, which may contribute to the development of an effective treatment against CanL.

Dogs are the main reservoir of Leishmania infantum, a protozoan parasite that causes lethal systemic disease in human beings (Visceral Leishmaniasis, VL) and dogs (Canine Leishmaniasis, CanL). In dogs, the disease is often associated with extensive skin lesions. Curbing canine infection could help control human VL. Currently available drugs are not effective in treating CanL, and treated dogs frequently relapse, even when removed from an endemic area. Developing new drugs or alternative therapeutic strategies are essential for the proper treatment of CanL. Dogs that acquire the parasite can develop the disease or control the infection, depending on the body’s immune response. Cellular immune responses lead to infection control and prevent the disease from developing. Some proteins called cytokines, produced mainly by cells of the immune system, can favor the development of cellular immune responses. In this study, several recombinant cytokines and/or one cytokine blocking protein were tested, alone or in combination, for their ability to promote cellular immune response in dogs with leishmaniasis. One of the combinations of recombinant protein tested was the best at facilitating this cellular immune response. The findings reported here are encouraging and indicate the use of a combination of two recombinant cytokines (rcaIL-12/rcaIL-15) in future immunotherapeutic trials for CanL.

Asymptomatic human blood donors carriers of Leishmania infantum: Potential reservoirs for visceral leishmaniasis in northwestern Iran

BACKGROUND

Little is known regarding transfusion-transmitted leishmaniasis (TTL) and the real global incidence of visceral leishmaniasis (VL) among blood donors as carriers of Leishmania spp. in endemic VL foci including Iran. Recent epidemiological evidences indicate that blood donor may be harbor of Leishmania infantum (L. infantum) infection in Iran.

METHODS

The aim of the present study was to determine the prevalence of Leishmania infection among blood donors in a main endemic focus of VL in Iran using DAT and polymerase chain reaction (PCR) based methods Between July-September 2016, blood samples were collected from 600 apparently healthy blood donors from six blood donation centers and blood donation mobile unit in Ardabil Province, where VL cases had been recorded. Each of these samples was tested for anti-Leishmania antibodies, in direct agglutination test (DAT), and for L. infantum kDNA, the PCR-based assay.

RESULTS

Of 600 blood donors, which were examined, 23 (3.8%) blood donors were seropositive by DAT and of 23 seropositive subjects, 82.6% (19/23) were positive by PCR. All the seropositive cases were males except one of them was female.

CONCLUSIONS

Our findings showed that many asymptomatic human carriers of L. infantum live in the endemic regions of northwestern Iran and potentially act as reservoirs of infection; those must be considered carefully by arrangement VL control strategies in the country.

Asymptomatic leishmaniasis in kala-azar endemic areas of Malda district, West Bengal, India

Asymptomatic leishmaniasis may drive the epidemic and an important challenge to reach the goal of joint Visceral Leishmaniasis (VL) elimination initiative taken by three Asian countries. The role of these asymptomatic carriers in disease transmission, prognosis at individual level and rate of transformation to symptomatic VL/Post Kala-azar Dermal Leishmaniasis (PKDL) needs to be evaluated. Asymptomatic cases were diagnosed by active mass survey in eight tribal villages by detecting antileishmanial antibody using rK39 based rapid diagnostic kits and followed up for three years to observe the pattern of sero-conversion and disease transformation. Out of 2890 total population, 2603 were screened. Antileishmanial antibody was detected in 185 individuals of them 96 had a history of VL/PKDL and 89 without such history. Seventy nine such individuals were classified as asymptomatic leishmaniasis and ten as active VL with a ratio of 7.9:1. Out of 79 asymptomatic cases 2 were lost to follow up as they moved to other places. Amongst asymptomatically infected persons, disease transformation in 8/77 (10.39%) and sero-conversion in 62/77 (80.52%) cases were noted. Seven (9.09%) remained sero-positive even after three years. Progression to clinical disease among asymptomatic individuals was taking place at any time up to three years after the baseline survey. If there are no VL /PKDL cases for two or more years, it does not mean that the area is free from leishmaniasis as symptomatic VL or PKDL may appear even after three years, if there are such asymptomatic cases. So, asymptomatic infected individuals need much attention for VL elimination programme that has been initiated by three adjoining endemic countries.

A total of 79 asymptomatic VL cases were detected from two kala-azar endemic blocks of Malda districts of West Bengal by active mass screening. Follow study of the asymptomatic cases revealed that 10.39% cases transformed into disease and 9.09% cases remained as sero-positive even after three years. So progression to clinical disease among asymptomatic individuals was taking place at any time up to three years after the baseline survey. Therefore, in a given period if there are no cases of VL/PKDL for two or more years, it does not mean that the area is free from leishmaniasis as symptomatic VL or PKDL may appear even after three years, if there are such asymptomatic cases. So, asymptomatic infected individuals need much attention for VL elimination programme that has been initiated by three adjoining endemic countries.

The genetics of Leishmania virulence

The ability of Leishmania parasites to infect and persist in the antigen-presenting cell population of their mammalian hosts is dependent on their ability to gain entry to their host and host cells, to survive the mammalian cell environment, and to suppress or evade the protective immune response mechanisms of their hosts. A multitude of genes and their products have been implicated in each of these virulence-enhancing strategies to date, and we present an overview of the nature and known function of such virulence genes.

Factors associated with asymptomatic infection in family members and neighbors of patients with visceral leishmaniasis

This study analyzed factors associated with asymptomatic Leishmania chagasi infection in family members and neighbors of patients with visceral leishmaniasis (VL). A cross-sectional study was conducted with 361 individuals in the counties comprising Ilha de São Luís (São Luís Island) in Maranhão State, Brazil. The Montenegro skin test (MST) and serology by enzyme-linked immunosorbent assay (ELISA) were performed to detect infection. Odds ratios (OR) and prevalence ratios (PR) and their 95% confidence intervals (95%CI) were estimated by multilevel logistic regression and Poisson regression, respectively. The rates of positive reactions were 71.3% for MST and 9.7% for ELISA. The variable associated with infection according to MST was living in the same household as the index case (PR = 1.36; 95%CI: 1.03-1.78). According to ELISA, the statistically significant variables were: living in the county of Raposa (OR = 3.56; 95%CI: 1.24-10.19) and living in the same household as the index case (OR = 2.70; 95%CI: 1.19-6.08). Family members of individuals with LV are at increased risk of infection. Priority control measures should target these families.

Anti-leishmania infantum IgG antibody avidity in visceral leishmaniasis

IgG avidity tests are used to discriminate acute from chronic infections. There are few reports on the IgG avidity profile of patients with visceral leishmaniasis (VL). This study investigated the anti-Leishmania IgG avidity in patients with classic VL (n = 10), patients showing clinical cure after treatment (n = 18), and asymptomatic subjects with at least one positive Leishmania test (n = 20). All subjects were from areas in Brazil where VL is endemic. Serum samples were collected from each subject on two different occasions. IgG avidity was evaluated by Western blotting. The proportion of high-avidity antibodies was higher in all samples from patients with classic VL. In contrast, low-avidity antibodies predominated in subjects with a history of VL, including 13 cases (72.2%) in the first assessment and 14 (77.8%) in the second. Fifteen (75%) of the asymptomatic subjects presented a predominance of low-avidity antibodies in the first assessment, and the frequency of high-avidity antibodies increased over time in seven subjects (35%) of this group. Antibodies against the 14- and/or 16-kDa antigen fraction were detected in the first assessment in all patients with classic VL, in 10 (55.5%) treated patients, and in 10 (50%) asymptomatic subjects. These were high-avidity antibodies in most cases. In the asymptomatic group, an increase in IgG avidity against the 14- and/or 16-kDa antigen fraction was observed in three cases (15%). The results indicate distinct responses in infected and asymptomatic subjects, probably associated with the length of time after infection. In this respect, IgG avidity tests represent a new approach to better characterize asymptomatic VL.

Factors associated with visceral leishmaniasis in the americas: a systematic review and meta-analysis

Background

Still today, more than 30 years after the beginning of the process of visceral leishmaniasis' urbanization, there is little knowledge about the risk factors for its occurrence, despite their relevance to the control and understanding of disease dynamics. The present study is the first systematic review with meta-analysis about factors associated with Leishmania infantum infection in humans in the Americas.

Methods and Findings

After searching different databases, consultations to the reference lists of articles and to experts in the field, 51 studies were reviewed. Theoretical discussions or meta-analysis of p-values or of effect sizes were used to pool information about each variable. The Q test and the I² statistic were used to assess heterogeneities among the studies. Male sex was associated with visceral leishmaniasis in studies which used the leishmanin skin test for diagnosis and in those where the outcome was the clinical disease; the opposite occurred when serological diagnosis was applied. Younger individuals were less frequently infected than adults, but were more prone to illness. Although with different levels of evidence and of heterogeneity, the presence of dogs at home, higher dog seropositivity in nearby areas, lower socioeconomic status and highly vegetated areas were associated with L. infantum infection. This was not noticed for the presence of chickens in the house and with nutritional status. Susceptibilities to bias and limitations in the analysis and in the description of results were often identified in the studies analyzed.

Conclusions

Results showed the existence of consistent patterns for some of the factors analyzed and should be taken into account in developing more effective and well-targeted control measures. Studies must be conducted in new areas of the continent, with improved methodological quality and prioritizing the investigation of the patterns identified and their causes, as well as variables for which knowledge is poor.

Visceral leishmaniasis (VL) is the most severe clinical form of leishmaniasis. In the Americas, VL is a zoonosis caused by the protozoan parasite Leishmania infantum, an intracellular micro-organism transmitted to humans through the bite of female phlebotomine sand flies. The domestic dog is considered the main reservoir and human beings are dead-end hosts. The disease occurs in 12 countries of the New World and Brazil accounts for 90% of the reported cases. The factors associated with infection are only partially understood, making harder understanding the disease dynamics and the development of effective and well-targeted control measures. Our work is the first systematic review with meta-analysis about factors associated with human visceral leishmaniasis in the Americas. It provides an organization of the available information, the description of more accurate data on the role of each of the factors studied, the evaluation of possible causes of heterogeneity in the results of the studies as well as the analysis of the quality of publications and limitations in the existing knowledge. The results of this study might be useful in the definition of which and where target interventions should be delivered, and for guiding researchers towards the development of future studies of better methodological quality.

Molecular and serological markers of Leishmania donovani infection in healthy individuals from endemic areas of Bihar, India

OBJECTIVES

Recent epidemiological reports indicate that asymptomatic human infections with Leishmania donovani, the causative agent of visceral leishmaniasis or Kala-azar (KA), occur frequently in India. We explored markers of infection.

METHODS

Blood samples were collected from 286 healthy subjects from 16 villages in the Muzaffarpur district of Bihar. These individuals were classified into three groups: (i) persons with no history of KA and living in a house where no KA cases were previously reported, (ii) persons with no history of KA but living in a house where KA cases were diagnosed at the time of sampling or in the past, and (iii) successfully treated KA patients. Each sample was tested using a Leishmania-specific PCR to detect Leishmania DNA, and two serological tests to demonstrate anti-Leishmania antibodies: the Direct Agglutination Test and rK39 ELISA.

RESULTS

PCR positivity was similar among the three groups (20-25%). In contrast, among treated patients, the percentage of serologically positive individuals was roughly five times that of healthy individuals with no KA history, as measured with either test. Living in a house where KA had been reported did not affect seropositivity.

CONCLUSION

A significant proportion of asymptomatic infections of Leishmania exist in endemic regions. Using a combination of molecular and serological tests increases the capacity to detect infections at different stages. Further work is required to understand the kinetics of the markers.

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.

Evaluation of nephroprotective and immunomodulatory activities of antioxidants in combination with cisplatin against murine visceral leishmaniasis

Background

Most available drugs against visceral leishmaniasis are toxic, and growing limitations in available chemotherapeutic strategies due to emerging resistant strains and lack of an effective vaccine against visceral leishmaniasis deepens the crisis. Antineoplastic drugs like miltefosine have in the past been effective against the parasitic infections. An antineoplastic drug, cisplatin (cis-diamminedichloroplatinum II; CDDP), is recognized as a DNA-damaging drug which also induces alteration of cell-cycle in both promastigotes and amastigotes leading to cell death. First in vivo reports from our laboratory revealed the leishmanicidal potential of cisplatin. However, high doses of cisplatin produce impairment of kidney, which can be reduced by the administration of antioxidants.

Methodology/Principal Findings

The present study was designed to evaluate the antileishmanial effect of cisplatin at higher doses (5 mg and 2.5 mg/kg body weight) and its combination with different antioxidants (vitamin C, vitamin E and silibinin) so as to eliminate the parasite completely and reduce the toxicity. In addition, various immunological, hematological and biochemical changes induced by it in uninfected and Leishmania donovani infected BALB/c mice were investigated.

Conclusion/Significance

A significant reduction in parasite load, higher IgG2a and lower IgG1 levels, enhanced DTH responses, and greater concentration of Th1 cytokines (IFN-γ, IL-2) with a concomitant down regulation of IL-10 and IL-4 pointed towards the generation of the protective Th1 type of immune response. A combination of cisplatin with antioxidants resulted in successful reduction of nephrotoxicity by normalizing the enzymatic levels of various liver and kidney function tests. Reduction in parasite load, increase in Th1 type of immune responses, and normalization of various biochemical parameters occurred in animals treated with cisplatin in combination with various antioxidants as compared to those treated with the drug only. The above results are promising as antioxidants reduced the potential toxicity of high doses of cisplatin, making the combination a potential anti-leishmanial therapy, especially in resistant cases.

Leishmaniasis, a neglected tropical disease (NTD) caused by Leishmania, has been put on the World Health Organization agenda for eradication as a part of their Special Programme for Tropical Diseases Research. Visceral leishmaniasis (VL) is a life-threatening disease when no treatment is given. Most of the drugs still used to treat VL are often expensive, difficult to administer, have serious side effects, and several are becoming ineffective because of increasing parasite resistance. Cisplatin is a first-generation platinum-containing drug, used in the treatment of various solid tumors. We have for the first time characterized the in vivo effect of cisplatin in murine experimental visceral leishmaniasis, but at higher doses it is nephrotoxic. Considering the above findings, the present study was designed to evaluate the protective efficacy of the drug in combination with various antioxidants to reduce or prevent cisplatin-induced nephrotoxicity. Drug treatment induces a higher secretion of Th1 cytokines, diminution in parasite burden, and the supplementation of antioxidants which are antagonists of the toxicity helps in reducing the nephrotoxicity.

Asymptomatic carriage of Leishmania in family members of patients with visceral leishmaniasis in Central Tunisia

INTRODUCTION

In Tunisia, asymptomatic carriage of Leishmania is poorly documented.

OBJECTIVE

The aim of the present study was to estimate the frequency of asymptomatic infection among the family members of patients with patent visceral leishmaniasis by using the Western blotting kit based on 14 and 16kDa bands.

MATERIAL AND METHODS

We tested 94 sera collected from 24 patients with patent visceral leishmaniasis and 70 from their families' members.

RESULTS

The rate of seropositivity was 100% in the group of patients and 54.3% in the group of families' members. The analysis of the Western blotting patterns showed that the 33kDa, 24kDa and to a lesser extent the 22kDa band were very indicative of patent visceral leishmaniasis in contrast to asymptomatic infection where these bands were very rarely detected.

CONCLUSION

The results reported herein showed the high frequency of asymptomatic carriers of Leishmania among the families' members of visceral leishmaniasis cases and the usefulness of the Western blotting as a screening technique and in distinguishing between patent visceral leishmaniasis and the asymptomatic carriage of Leishmania.

Asymptomatic infection of visceral leishmaniasis in hyperendemic areas of Vaishali district, Bihar, India: a challenge to kala-azar elimination programmes

A cohort of 91 asymptomatic individuals with visceral leishmaniasis (VL) were identified during base line screening using recombinant 39-aminoacid antigen (rk-39) and polymerase chain reaction (PCR) conducted from December 2005 to June 2006 involving 997 individuals of two highly endemic villages of Vaishali district, Bihar. The point prevalence of asymptomatic infection was 98 per 1000 persons at baseline. There was no statistically significant difference between rk-39 and PCR positivity rate (P>0.05), even though PCR positivity alone was found significantly higher (4.2%) than rk-39 positivity alone (2.6%). The monthly follow-up of the asymptomatic cohort revealed a disease conversion rate of 23.1 per 100 persons within a year. There was a statistically significant difference in conversion of disease when individuals were positive by both tests as compared to single tests by rk-39 and PCR (P<0.01). Disease conversion rate in the subjects residing in households with a history of VL (62%, 13/21) was higher than those residing in the households without a history of VL (38%, 8/21). Most of the identified asymptomatic individuals were from low socio-economic strata similar to that of VL cases in general. Apart from rk-39, PCR may be considered for screening of asymptomatic Leishmania donovani infection in large-scale epidemiological studies. Screening of asymptomatic cases and their close follow-up to ascertain early detection and treatment of VL may be considered in addition to the existing VL control strategies.

Importance of worldwide asymptomatic carriers of Leishmania infantum (L. chagasi) in human

Leishmaniasis due to Leishmania infantum (syn. L. chagasi) infection is a zoonotic disease present mainly in Mediterranean basin, central Asia and Brazil. Besides a limited number of human cases of clinical visceral leishmaniasis, a great number of infections remains asymptomatic. In this review, the prevalence of asymptomatic carriers of L. infantum was evaluated worldwide using parasitological methods or indirect testing such as a skin test or serology. The consequences of the presence of asymptomatic carriers on parasite transmission by blood donation or the development of clinical visceral leishmaniasis in immunocompromised individuals and its possible role as reservoir are discussed.

Antileishmania immunological tests for asymptomatic subjects living in a visceral leishmaniasis-endemic area in Brazil

The objective of this study was to evaluate the behavior of different tests used for the diagnosis of visceral leishmaniasis (VL) in asymptomatic subjects living in an endemic area. No gold standard is available for the diagnosis of asymptomatic infection with Leishmania. In continuation of a previous study, 1,017 subjects living in a VL-endemic area were clinically reevaluated. Of these, 576 had at least one positive serological test in a first assessment. About 3 years after the first evaluation, none of the subjects had progressed to clinical VL. Among this group, 246 subjects were selected, and five serological tests (enzyme-linked immunosorbent assay p [ELISAp], ELISArK39, ELISArK26, indirect immunofluorescence test [IIFT] using L. amazonensis promastigote antigen, and an immunochromatographic test using rK39 antigen [TRALd]) and the Montenegro skin test (MST) were repeated. There was a significant increase in the number of subjects who tested positive in the MST, IIFT, ELISAp, and ELISArK39 in the second evaluation. For all tests, there were subjects who tested positive in the first evaluation and negative in the second evaluation. A positive result in the serological tests and MST in subjects from the endemic area studied did not indicate a risk of progression to VL and may only be temporary.

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

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

Asymptomatic infection in family contacts of patients with human visceral leishmaniasis in Três Lagoas, Mato Grosso do Sul State, Brazil

The Brazilian city of Três Lagoas, Mato Grosso do Sul State, has experienced an urban outbreak of visceral leishmaniasis since 2000. In 2002, due to the increase in the number of cases, 46 families with cases of visceral leishmaniasis were studied to verify the prevalence of asymptomatic infection in household contacts. Indirect immunofluorescence and ELISA showed a 36.4% positive infection rate. There were no cases of symptomatic disease among these contacts. There was no statistically significant difference in gender or age. Median age was 21 years, and the 10-19-year age bracket was the most heavily affected (23%). As for family characteristics, no differences were observed in schooling or family income; most families (58.7%) owned their homes, which were built of masonry (97.8%) and had adequate infrastructure. All the families reported what were probably phlebotomine sand flies in the peridomicile. In conclusion, asymptomatic visceral leishmaniasis infection is frequent and occurs in both males and females, regardless of age.

Visceral leishmaniasis is preventable in a highly endemic village in West Bengal, India

In 2004, following a cluster of kala-azar cases in Chatrakhali, West Bengal, India, we screened and treated this endemic village for leishmaniasis infection. In 2005, following new reports of kala-azar, we screened the village again and conducted a retrospective cohort study (exposure period: August 2004 to July 2005). We defined an incident case of leishmaniasis as a new seropositive sample (>or=1:1600 dilution in a direct agglutination test) in a person seronegative in 2004. We obtained information about potential risk factors and calculated the relative risk (RR) of infection for exposure to these factors. One hundred and fifty (20%) of the 751 residents acquired leishmaniasis in 1 year. Factors associated with infection included residing in homes with mud walls (RR 4.3), dampness in the home (RR 2.5), proximity to bodies of water (RR 2.5) and livestock ownership (RR 2.4). Sleeping dressed (RR 0.4), or under a bed net (RR 0.5) or in a cot (RR 0.6) were associated with a lower risk. High rates of infection indicated that transmission persisted in this community. Poor housing conditions were associated with a higher risk, while personal protection measures against vectors were effective. Major housing improvement and personal protection efforts are needed to protect this vulnerable population from leishmaniasis.

Development and evaluation ofLeishmania infantumrK26 ELISA for serodiagnosis of visceral leishmaniasis in Iran

The purpose of this study was to prepare recombinant K26 antigen fromLeishmania infantumand evaluate its performance by enzyme-linked immunosorbent assay (ELISA) test for serodiagnosis of visceral leishmaniasis (VL) in endemic regions of Iran. The results were compared with those obtained by direct agglutination test (DAT) and whole cell ELISA using crude parasite antigen. Of 93 sera from patients with confirmed VL, 90 sera were positive with rK26 ELISA (sensitivity=96·8%), whereas 85 sera were positive with DAT (sensitivity=91·4%) and 89 sera were positive with whole cell ELISA (sensitivity=95·7%). Of 130 subjects who either had other infectious diseases (n=30) or were healthy (n=100), rK26 ELISA were negative in all cases (specificity=100%), whereas DAT were negative in 116 cases (specificity=89·2%) and whole cell ELISA was negative in 114 cases (specificity=87·7%). The results of this study indicate that the rK26 ELISA is more sensitive and specific than conventional methods and could be used for reliable diagnosis of VL caused byLeishmania infantum.

Immune response to leishmania: paradox rather than paradigm

The leishmaniases are a group of diseases caused by protozoan parasites of the genus Leishmania. Various Leishmania species can cause human infection, producing a spectrum of clinical manifestations. It is estimated that 350 million people are at risk, with a global yearly incidence of 1-1.5 million for cutaneous and 500,000 for visceral leishmaniasis (VL). VL is a major cause of morbidity and mortality in East Africa and the Indian subcontinent. Coinfection with HIV enhances the risk of the disease. The only control measure currently available in India is case detection and treatment with antimonial drugs, which are expensive, not always available and cannot be self-administered. Newer drugs like oral miltefosine have not become widely available. Vector and reservoir control is difficult due to the elusive nature of the vector and the diversity of the animal reservoir. A detailed knowledge of immune response to the parasite would help in designing prophylactic and therapeutic strategies against this infection.

Diagnosing human asymptomatic visceral leishmaniasis in an urban area of the State of Minas Gerais, using serological and molecular biology techniques

A population-based cross-sectional study was set up in Sabará country, Southeastern Brazil, to identify asymptomatic human visceral leishmaniasis in an urban area of low disease prevalence. Blood was collected on filter paper (n=1,604 inhabitants) and examined by indirect immunofluorescent test, enzyme-linked immunosorbent assay and immunochromatographic strip test. The prevalence rates of infection ranged from 2.4 to 5.6% depending on the test used. One year later, venous blood was collected in a subset of 226 participants (102 seropositive and 124 seronegative). The tests performed were IFAT, ELISA, rk39-ELISA, polymerase chain reaction and hybridization with Leishmania donovani complex probe. No clinical signs or symptoms of leishmaniasis were observed. Using hybridization as a reference test, the sensitivity and specificity of serology were respectively: 24.8 and 71% (ELISA); 26.3 and 76.3% (rk-39); 30.1 and 63.4% (IFAT). Due to disagreements, different criteria were tested to define the infection and hybridization should be considered in epidemiological studies.

Risk factors for Leishmania chagasi infection in an urban area of Minas Gerais State

In order to understand the determinants of human infection by Leishmania chagasi in an urban area, a cross-sectional population based study was conducted using molecular and serologic methods to identify infection. Participants were interviewed using a pre-coded questionnaire. Two criteria were tested to identify risk factors: Model 1--including all participants positive in hybridization by Leishmania donovani complex probe; Model 2--including all participants positive for hybridization and at least one serologic test. In Model 1, the variables associated with infection were: ownership of birds, time spent outside house between 6:00-10:00 PM and garbage not collected. In Model 2, the variables associated with infection were: family with knowledge of the vector, garbage not collected, garbage not removed or buried, ownership of birds and eroded areas in the neighborhood. The risk factors identified were associated with household conditions, presence of animals and the likelihood of contact with phlebotomine sandflies.

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.

Subclinical form of the American visceral leishmaniasis

The subclinical form of visceral leishmaniasis (VL) shows nonspecific clinical manifestations, with difficulties being frequently met in its clinical characterization and diagnostic confirmation. Thus, the objective of the present study was to define the clinical-laboratory profile of this clinical form. A cohort study was conducted in the state of Maranhão, Brazil, from January/1998 to December/2000, with monthly follow-up of 784 children aged 0-5 years. Based on the clinical-laboratory parameters reported in the literature, four categories were established, with the children being classified (according to their clinical-evolutive behavior) as asymptomatic (N = 144), as having the subclinical form (N = 33) or the acute form (N = 12) or as subjects "without VL" (N = 595). Multiple discriminant analysis demonstrated that the combination of fever, hepatomegaly, hyperglobulinemia, and increased blood sedimentation rate (BSR) can predict the subclinical form of VL as long as it is not associated with splenomegaly or leukopenia. Subjects with the subclinical form did not show prolonged or intermittent evolution or progression to the acute form of VL. Subclinical cases have a profile differing from the remaining clinical forms of VL, being best characterized by the combination of fever, hepatomegaly, hyperglobulinemia, and increased BSR.

Serum cytokine profile in the subclinical form of visceral leishmaniasis

The factors determining the development or not of visceral leishmaniasis (VL) have not been completely identified, but a Leishmania-specific cellular immune response seems to play a fundamental role in the final control of infection. Few studies are available regarding the production of cytokines in the subclinical form of VL, with only the production of IFN-gamma and TNF-alpha known. The aim of the present study was to identify immunological markers for the oligosymptomatic or subclinical form of VL. A prospective cohort study was conducted on 784 children aged 0 to 5 years from an endemic area in the State of Maranhão, Brazil, between January 1998 and December 2001. During 30 consecutive months of follow-up, 33 children developed the oligosymptomatic form of the disease and 12 the acute form. During the clinical manifestations, serum cytokine levels were determined in 27 oligosymptomatic children and in nine patients with the acute form using a quantitative sandwich enzyme immunoassay. In the subclinical form of VL, variable levels of IL-2 were detected in 52.3% of the children, IL-12 in 85.2%, IFN-gamma in 48.1%, IL-10 in 88.9%, and TNF-alpha in 100.0%, with the last two cytokines showing significantly lower levels than in the acute form. IL-4 was not detected in oligosymptomatic individuals. Multiple discriminant analysis used to determine the profile or combination of cytokines predominating in the subclinical form revealed both a Leishmania resistance (Th1) and susceptibility (Th2) profile. The detection of both Th1 and Th2 cytokine profiles explains the self-limited evolution accompanied by the discrete alterations observed for the subclinical form of VL.

What information is needed to design effective vaccination against intracellular pathogens causing chronic disease?

An appreciation of global features of immune regulation may lead to vaccination strategies effective in a genetically diverse population against a number of intracellular pathogens that cause chronic disease. Such global strategies appear more straightforward than strategies requiring a detailed knowledge of the specificity of 'protective T-cells'. Global strategies may be effective against the virus, bacteria and protozoa that respectively cause AIDS, tuberculosis and the leishmaniases.

Predicting kala-azar disease manifestations in asymptomatic patients with latent Leishmania donovani infection by detection of antibody against recombinant K39 antigen

Clinically visceral leishmaniasis is suspected in only a fraction of infected persons, as the majority of these may not have clinical manifestations and remain asymptomatic. There is scanty information on diagnosing latent infections and predicting disease in asymptomatic persons. We therefore carried out a study on asymptomatic contacts of patients with visceral leishmaniasis and post-kala-azar dermal leishmaniasis by using methods for detection of antibody to recombinant K39 (rK39) antigen. A total of 240 patients with leishmaniasis and 150 asymptomatic contacts were tested for anti-rK39 immunoglobulin G (IgG) and IgA antibodies. Fifty-five asymptomatic persons were found to be seropositive. These individuals were monitored every 3 months for 1 year. On follow-up, 43.9% of the asymptomatic seropositive contacts developed kala-azar within the first 3 months, and a cumulative total of 69% developed kala-azar within 1 year. The rest remained asymptomatic and self-healed the infection. The sensitivity and specificity of rK39 enzyme-linked immunosorbent assay (ELISA) and dipstick tests were 100%, while an in-house-developed latex agglutination test had 80% sensitivity. The antibody profile showed that the IgG anti-rK39 antibodies reached a titer of up to 10(-6) within 6 months of infection, started declining thereafter, and completely disappeared in 2 to 3 years in successfully treated cases. Significant titers of IgA antibodies were detectable a little earlier than those of IgG antibodies and were undetectable after 6 months. The study showed that mass screening of family members and contacts by using anti-rK39 ELISA could be a highly reliable tool for early diagnosis and to plan prophylactic treatment of latently infected asymptomatic carriers to eradicate kala-azar.

Treatment of visceral leishmaniasis (kala-azar): a decade of progress and future approaches

In 1990, there was essentially one treatment regimen in use for visceral leishmaniasis (kala-azar) around the world: 20 to 28 days of daily injections of pentavalent antimony (Sb). During the past 10 years, however, new agents have been tested alone or in combination, in more than 50 studies carried out worldwide. This renewed clinical effort was spurred by a variety of factors, including the emergence of large-scale Sb unresponsiveness in India, where up to one-half of the world's cases of kala-azar now are found. As this new decade opens, the success of this clinical research effort is tangible: three additional, highly effective parenteral regimens now are available (amphotericin B, lipid formulations of amphotericin B, aminosidine), and an active oral agent, a long sought after objective in kala-azar, has been identified (miltefosine). This report reviews the evolution of treatment of visceral leishmaniasis, considers the interaction of the immune response and chemotherapy, highlights therapeutic successes and failures, examines advantages and disadvantages of current treatments, and looks at future therapeutic approaches to the management of this disseminated intracellular protozoal infection.

T cell response of asymptomatic Leishmania chagasi infected subjects to recombinant leishmania antigens

In areas of Leishmania chagasi transmission the ability to control leishmania infection is associated with IFN-gamma production. In visceral leishmaniasis down-regulation of T cell responses is mediated by interleukin-10 (IL-10). In this study we evaluated the lymphoproliferative response, IFN-gamma and IL-10 production on lymphocyte cultures stimulated with recombinant leishmania antigens in subjects with asymptomatic L. chagasi infection. There was a statistically significant difference in the lymphoproliferative response of the subjects with asymptomatic infection as compared to patients with visceral leishmaniasis and healthy subjects with respect to crude antigens (p<0.01), gp-63 (p<0.05) and hsp-70 (p<0. 01), as well as between asymptomatic L. chagasi infected subjects and patients with visceral leishmaniasis with respect to the response to all antigens tested. The IFN-gamma production observed in the group with asymptomatic infection with all the three recombinant antigens tested was higher (p<0.01) than that observed in patients with visceral leishmaniasis and in healthy subjects. Furthermore, in individuals with asymptomatic infection, IL-10 levels in cultures stimulated with recombinant antigens were very low. This study shows that lymphocytes from individuals with asymptomatic L. chagasi infection are able to recognize recombinant leishmania antigens with production of a cytokine that is associated with leishmania killing.