Detection of Leishmania in the blood of early kala-azar patients with the aid of the polymerase chain reaction

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.

A review of non-invasive samples and tools in kala-azar diagnosis and test of cure

The recurrence of visceral leishmaniasis (VL), also called kala-azar (KA), in endemic regions of tropical countries like India, is primarily attributed to asymptomatic VL, post-kala azar dermal leishmaniasis (PKDL), and human immunodeficiency virus (HIV) co-infection. To effectively manage VL cases and elimination targets, an early and rapid diagnosis as well as accurate field surveillance is highly essential. The traditional sampling methods like bone marrow (BM), spleen, and lymph node (LN) tissue aspirations are invasive, painful, tedious, and prone to nosocomial infections, require skilled persons and hospital facilities, and are not feasible in rural areas. Therefore, there is an urgent requirement for the adoption of a patient-friendly, non-invasive, non-hospitalized sampling procedure that ensures an effective VL diagnosis. This review aims to meticulously evaluate the most recent scientific research that focuses on the precision, feasibility, and applicability of non-invasive sampling (NIS) and techniques for the diagnosis and test of cure of VL, particularly in resource-limited settings. Apart from that, the non-invasive techniques (NIT) that have shown promising results while monitoring VL treatment response and relapse are also reviewed. The limitations associated with NIT and possible improvements in this regard are discussed as well to improve the diagnosis and management of VL.

Diagnosis of Visceral Leishmaniasis in an Elimination Setting: A Validation Study of the Diagnostic Algorithm in India

Visceral leishmaniasis (VL) is on the verge of elimination on the Indian subcontinent. Nonetheless, the currently low VL-incidence setting brings along new challenges, one of which is the validity of the diagnostic algorithm, based on a combination of suggestive clinical symptoms in combination with a positive rK39 Rapid Diagnostic Test (RDT). With this study, we aimed to assess the positive predictive value of the diagnostic algorithm in the current low-endemic setting in India by re-assessing newly diagnosed VL patients with a qPCR analysis on venous blood as the reference test. In addition, we evaluated the specificity of the rK39 RDT by testing non-VL cases with the rK39 RDT. Participants were recruited in Bihar and Uttar Pradesh, India. VL patients diagnosed based on the diagnostic algorithm were recruited through six primary health care centers (PHCs); non-VL cases were identified through a door-to-door survey in currently endemic, previously endemic, and non-endemic clusters, and tested with rK39 RDT, as well as—if positive—with qPCR on peripheral blood. We found that 95% (70/74; 95% CI 87–99%) of incident VL cases diagnosed at the PHC level using the current diagnostic algorithm were confirmed by qPCR. Among 15,422 non-VL cases, 39 were rK39 RDT positive, reflecting a specificity of the test of 99.7% (95% CI 99.7–99.8%). The current diagnostic algorithm combining suggestive clinical features with a positive rK39 RDT still seems valid in the current low-endemic setting in India.

Real Time PCR-based diagnosis of human visceral leishmaniasis using urine samples

Diagnosis of visceral leishmaniasis (VL) through the detection of its causative agents namely Leishmania donovani and L. infantum is traditionally based on immunochromatographic tests, microscopy of bone marrow, spleen aspirates, liver or lymph node and differential diagnosis. While the first process has low specificity, the later one carries the risk of fatal hemorrhage. Over the last decade, multiple Polymerase Chain Reaction (PCR) based diagnosis has been developed using blood and urine sample with a varying degree of sensitivity and specificity, an issue worth improving for precision diagnosis. Earlier, we reported a PCR-based diagnosis of L. donovani in peripheral blood using a novel set of PCR primers with absolute specificity. Using the same set of primers and PCR conditions, here we describe diagnosis of L. donovani from urine, for a non-invasive, rapid and safe diagnosis. Diagnosis of VL was carried out using urine samples collected from clinically diagnosed VL patients (n = 23) of Bangladesh in Real Time PCR. Test results were validated by comparing blood samples from the same set of patients. Sensitivity and specificity of this diagnosis was analyzed using retrospective bone marrow samples, collected earlier from confirmed VL patients (n = 19). The method showed 100% sensitivity in detecting L. donovani in urine and corresponding blood and retrospective bone marrow samples, as well as 100% specificity in control groups. A Real Time PCR-based molecular detection system using urine sample is hereafter presented what could be a, non-invasive approach for VL detection with precision and perfection.

Molecular Diagnosis of Leishmaniasis: Quantification of Parasite Load by a Real-Time PCR Assay with High Sensitivity

Real-time PCR was developed to quantify Leishmania infantum kinetoplast DNA and optimized to achieve a sensitivity of 1 parasite/mL. For this purpose, we cloned the conserved kDNA fragment of 120 bp into competent cells and correlated them with serial dilutions of DNA extracted from reference parasite cultures calculating that a parasite cell contains approximately 36 molecules of kDNA. This assay was applied to estimate parasite load in clinical samples from visceral, cutaneous leishmaniasis patients and infected dogs and cats comparing with conventional diagnosis. The study aimed to propose a real-time PCR for the detection of Leishmania DNA from clinical samples trying to solve the diagnostic problems due to the low sensitivity of microscopic examination or the low predictive values of serology and resolve problems related to in vitro culture. The quantitative PCR assay in this study allowed detection of Leishmania DNA and quantification of considerably low parasite loads in samples that had been diagnosed negative by conventional techniques. In conclusion, this quantitative PCR can be used for the diagnosis of both human, canine and feline Leishmaniasis with high sensitivity and specificity, but also for evaluating treatment and the endpoint determination of leishmaniasis.

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.

Molecular Diagnosis of Visceral Leishmaniasis

Visceral leishmaniasis (VL), a deadly parasitic disease, is a major public health concern globally. Countries affected by VL have signed the London Declaration on Neglected Tropical Diseases and committed to eliminate VL as a public health problem by 2020. To achieve and sustain VL elimination, it will become progressively important not to miss any remaining cases in the community who can maintain transmission. This requires accurate identification of symptomatic and asymptomatic carriers using highly sensitive diagnostic tools at the primary health service setting. The rK39 rapid diagnostic test (RDT) is the most widely used tool and with its good sensitivity and specificity is the first choice for decentralized diagnosis of VL in endemic areas. However, this test cannot discriminate between current, subclinical, or past infections and is useless for diagnosis of relapses and as a prognostic (cure) test. Importantly, as the goal of elimination of VL as a public health problem is approaching, the number of people susceptible to infection will increase. Therefore, correct diagnosis using a highly sensitive diagnostic test is crucial for applying appropriate treatment and management of cases. Recent advances in molecular techniques have improved Leishmania detection and quantification, and therefore this technology has  become increasingly relevant due to its possible application in a variety of clinical sample types. Most importantly, given current problems in identifying asymptomatic individuals because of poor correlation between the main methods of detection, molecular tests are valuable for VL elimination programs, especially to monitor changes in burden of infection in specific communities. This review provides a comprehensive overview of the available VL diagnostics and discusses the usefulness of molecular methods in the diagnosis, quantification, and species differentiation as well as their clinical applications.

Exploring prognosis in chronic relapsing visceral leishmaniasis among HIV-infected patients: Circulating Leishmania DNA

BACKGROUND

Visceral leishmaniasis (VL) affecting HIV-infected patients is considered a challenging condition because of its high mortality and relapse rates. The approach of this condition is still surrounded by many uncertainties, especially regarding the criteria to institute and discontinue secondary prophylaxis for VL. The aim of this study was to evaluate the Leishmania parasitism kinetic assessed by polymerase chain reaction (PCR) as a possible tool in the prognostic assessment in a context in which patients are receiving highly active antiretroviral therapy and secondary prophylaxis.

METHODS

A prospective observation of Leishmania-HIV-co infected patients was performed and two groups with distinct clinical prognosis unpredicted by their CD4 count at the moment of VL diagnosis and not related to their HIV load control were confirmed.

RESULTS

Relapsing (R) and non-relapsing (NR) patients had similar antiviral therapy use rates, CD4 lymphocyte count medians and HIV load levels at VL-diagnosis. At the 12-month follow-up, R-patients presented a significantly lower CD4 lymphocyte count than NR-patients, without difference in HIV load control. The time between HIV and VL diagnoses was longer in the R than NR-group. Comparison between Kaplan-Meier relapse-free survival curves (time to relapse) using a log rank test showed that patients presenting circulating Leishmania DNA had a significantly higher risk of clinical VL relapse within 4 months after a positive test (p=0.001).

CONCLUSIONS

These results reinforce that a negative PCR could be a useful tool to support prophylaxis interruption among patients with CD4 counts above 200cells/mm³ and that a positive PCR suggests imminent VL relapse.

A Correlative Study of Splenic Parasite Score and Peripheral Blood Parasite Load Estimation by Quantitative PCR in Visceral Leishmaniasis

Parasitological diagnosis of visceral leishmaniasis (VL) by splenic smear is highly sensitive, but it is associated with the risk of severe hemorrhage. In this study, the diagnosis of VL using quantitative PCR (qPCR) in peripheral blood was evaluated in 100 patients with VL. Blood parasitemia ranged from 5 to 93,688 leishmania parasite genomes/ml of blood and positively correlated with splenic score (P<0.0001; r2=0.58). Therefore, quantification of parasite genomes by qPCR can replace invasive procedures for diagnostic and prognostic evaluations.

Molecular tools for diagnosis of visceral leishmaniasis: systematic review and meta-analysis of diagnostic test accuracy

Molecular methods have been proposed as highly sensitive tools for the detection of Leishmania parasites in visceral leishmaniasis (VL) patients. Here, we evaluate the diagnostic accuracy of these tools in a meta-analysis of the published literature. The selection criteria were original studies that evaluate the sensitivities and specificities of molecular tests for diagnosis of VL, adequate classification of study participants, and the absolute numbers of true positives and negatives derivable from the data presented. Forty studies met the selection criteria, including PCR, real-time PCR, nucleic acid sequence-based amplification (NASBA), and loop-mediated isothermal amplification (LAMP). The sensitivities of the individual studies ranged from 29 to 100%, and the specificities ranged from 25 to 100%. The pooled sensitivity of PCR in whole blood was 93.1% (95% confidence interval [CI], 90.0 to 95.2), and the specificity was 95.6% (95% CI, 87.0 to 98.6). The specificity was significantly lower in consecutive studies, at 63.3% (95% CI, 53.9 to 71.8), due either to true-positive patients not being identified by parasitological methods or to the number of asymptomatic carriers in areas of endemicity. PCR for patients with HIV-VL coinfection showed high diagnostic accuracy in buffy coat and bone marrow, ranging from 93.1 to 96.9%. Molecular tools are highly sensitive assays for Leishmania detection and may contribute as an additional test in the algorithm, together with a clear clinical case definition. We observed wide variety in reference standards and study designs and now recommend consecutively designed studies.

Parasite load estimation by qPCR differentiates between asymptomatic and symptomatic infection in Indian visceral leishmaniasis

Using quantitative PCR (qPCR), we differentiated asymptomatic and symptomatic Indian Leishmania donovani infection. qPCR on blood of 40 visceral leishmaniasis, 130 endemic, and 40 non-endemic healthy controls showed 500 times less (P < .0001) parasitemia in asymptomatic compared to the symptomatic ones and threshold of 5 parasite genome/mL for the clinical disease.

USE OF THE POLYMERASE CHAIN REACTION FOR THE DIAGNOSIS OF ASYMPTOMATIC Leishmania INFECTION IN A VISCERAL LEISHMANIASIS-ENDEMIC AREA

The diagnosis of asymptomatic infection with Leishmania (Leishmania) chagasi has become more important over recent years. Expansion of visceral leishmaniasis might be associated with other routes of transmission such as transfusion, congenital or even vector transmission, and subjects with asymptomatic infection are potential reservoirs. Moreover, the identification of infection may contribute to the management of patients with immunosuppressive conditions (HIV, transplants, use of immunomodulators) and to the assessment of the effectiveness of control measures. In this study, 149 subjects living in a visceral leishmaniasis endemic area were evaluated clinically and submitted to genus-specific polymerase chain reaction (PCR), serological testing, and the Montenegro skin test. Forty-nine (32.9%) of the subjects had a positive PCR result and none of them developed the disease within a follow-up period of three years. No association was observed between the results of PCR, serological and skin tests. A positive PCR result in subjects from the endemic area did not indicate a risk of progression to visceral leishmaniasis and was not associated with a positive result in the serological tests.

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.

Diagnosis of Indian visceral leishmaniasis by nucleic acid detection using PCR

Background

PCR based diagnosis for Visceral Leishmaniasis (VL), despite numerous published primers, remains far from being applied in the field. The present study was planned to design a Leishmania specific diagnostic assay and to evaluate its sensitivity and specificity on a sample size, which to the best of our knowledge is the largest ever screened in one study.

Methods

Leishmania specific primers were developed using 18S rRNA gene and their sensitivity was evaluated on 500 parasitologically confirmed patients with VL and 25 Post Kala-azar Dermal Leishmaniasis (PKDL) patients. Specificity was calculated on 250 healthy endemic controls, 250 healthy non endemic controls and 250 non leishmanial diseases like malaria.

Results

Our PCR assay had a sensitivity of 87.8% (95%CI: 84.1–89.8) using 200 µL of patient's peripheral-blood. Specificity was absolute in non-endemic healthy controls and in subjects with different diseases while in endemic controls it was 84% (95%CI: 78.9–88.0). Its overall specificity was 94.6% (95%CI-92.8–96.1).

Conclusions

The PCR assay developed is sensitive enough to detect the 18S rRNA gene in an amount equivalent to a single parasite or less in a one million human cell environment. The high sensitivity of this PCR diagnostic test with relatively non-invasive peripheral blood sampling method opens up the possibility of its deployment in field for the routine diagnosis of VL.

Diagnosis of visceral leishmaniasis

Leishmaniasis is a vector-borne disease with up to 350 million people at risk of infection worldwide. Among its different clinical manifestations, visceral is the most severe form. Since clinical features of visceral leishmaniasis (VL) mimic several other common diseases, accurate diagnosis is crucial as the treatment is associated with significant toxicity. Invasive and risky techniques involving demonstration of the parasites in stained preparations from splenic and bone marrow aspirate is still the gold standard for VL diagnosis. Serological tests using rK39 in ELISA or rapid immunochromatographic format, Direct Agglutination Test (DAT), immunoblotting have issues related to a significant proportion of asymptomatic individuals being positive with these tests and their inability to diagnose relapses as these remain positive for several months to years after cure. PCR is the most common molecular technique successfully used for diagnosis and differentiation of species. Through this review we focus extensively on the comparative utilities of the various diagnostic tools currently available for VL, describing in depth their advantages and disadvantages, addressing the recent advances attained in the field. A simple, rapid, non invasive, accurate and cost effective marker of active VL, which can be used in field conditions, is necessary to improve diagnosis of VL.

Polymerase chain reaction of peripheral blood as a tool for the diagnosis of visceral leishmaniasis in children

The diagnosis of visceral leishmaniasis (VL) generally requires the use of invasive tests for the collection of infected tissue (aspirates of bone marrow, spleen, liver or lymph nodes). This difficulty has led to the search for safer and less painful techniques to confirm the occurrence of the disease in children. Polymerase chain reaction (PCR) is a method that is advantageous in that it allows the use of peripheral blood samples for diagnosis. This paper reports the utilisation of PCR on peripheral blood samples to diagnose VL in 45 children in Mato Grosso do Sul, Brazil. This technique is compared with methods carried out using tissue collected by invasive procedures, including direct microscopy, culture and detection of Leishmania DNA by PCR in bone marrow aspirates. The results show that PCR of peripheral blood provides great sensitivity (95.6%) that is similar to that from the PCR of bone marrow aspirates (91.1%) and higher than that achieved with microscopy (80%) or culture (26.7%) methods. PCR of peripheral blood proved to be a suitable tool for the diagnosis of VL in children because it is highly sensitive and safe, with tissue collection being less invasive than in traditional tests.

An epitope-specific PCR test for diagnosis of Leishmania donovani infections

The carboxy-terminal region of recombinant heat shock protein 70 of Leishmania donovani has been shown to have an immunodominant epitope. We designed a PCR assay using a new set of primers encompassing the gene sequence from 457bp to 927bp, which amplified a segment of the L. donovani genome in a species-specific manner. The assay was sensitive enough to detect 0.5pg of parasite DNA, which increased 10-fold (0.05pg) when an internal probe (583-609bp) was used in the Southern blot. The assay was able to detect parasite DNA from the liver and spleen of L. donovani-infected hamsters as well as lesion aspirates from parasitologically confirmed post-kala-azar dermal leishmaniasis (PKDL) and bone marrow aspirates from visceral leishmaniasis (VL) patients. No amplification was seen with axenically cultured promastigotes of L. infantum, L. tropica, L. major, L. mexicana, L. aethiopica or other intracellular organisms such as Entamoeba histolytica, Mycobacterium tuberculosis, Plasmodium vivax or human peripheral blood mononuclear cells. This PCR provides a specific tool for the diagnosis of VL and PKDL with simultaneous species identification.

A urine-based polymerase chain reaction method for the diagnosis of visceral leishmaniasis in immunocompetent patients

In the Mediterranean basin and Middle East, including Iran, visceral leishmaniasis (VL), also known as kala-azar, is caused by Leishmania donovani infantum. For the first time, the use of urine samples for the diagnosis of VL in immunocompetent patients has been used in this study. Based on its high sensitivity and specificity, as well as simplicity, this approach can serve as a valuable tool in the diagnosis of VL. We studied 60 urine samples from 60 individuals, 30 of which were patients with VL confirmed by parasitology, serology, or molecular methods, 5 were from healthy individuals, and 25 were from patients with cutaneous leishmaniasis, malaria, brucellosis, and hydatid cyst. Out of 30 samples from confirmed VL immunocompetent patients, 29 were positive (sensitivity, 96.8%) by polymerase chain reaction (RV1 and RV2 primers), and all the remaining 30 samples either from healthy individuals or patients with other diseases were negative (specificity, 100%). High sensitivity, specificity, and simplicity of the test can serve as a valuable tool in the diagnosis of VL.

Clinical use of polymerase chain reaction performed on peripheral blood and bone marrow samples for the diagnosis and monitoring of visceral leishmaniasis in HIV-infected and HIV-uninfected patients: a single-center, 8-year experience in Italy and review of the literature

BACKGROUND

To overcome some of the limitations of conventional microbiologic techniques, polymerase chain reaction (PCR)-based assays are proposed as useful tools for the diagnosis of visceral leishmaniasis.

PATIENTS AND METHODS

A comparative study using conventional microbiologic techniques (i.e., serologic testing, microscopic examination, and culture) and a Leishmania species-specific PCR assay, using peripheral blood and bone marrow aspirate samples as templates, was conducted during an 8-year period. The study cohort consisted of 594 Italian immunocompetent (adult and pediatric) and immunocompromised (adult) patients experiencing febrile syndromes associated with hematologic alterations and/or hepatosplenomegaly. Identification of the infecting protozoa at the species level was directly obtained by PCR of peripheral blood samples, followed by restriction fragment-length polymorphism analysis of the amplified products, and the results were compared with those of isoenzyme typing of Leishmania species strains from patients, which were isolated in vitro.

RESULTS

Sixty-eight patients (11.4%) had a confirmed diagnosis of visceral leishmaniasis. Eleven cases were observed in human immunodeficiency virus (HIV)-uninfected adults, 20 cases were observed in HIV-infected adults, and the remaining 37 cases were diagnosed in HIV-uninfected children. In the diagnosis of primary visceral leishmaniasis, the sensitivities of the Leishmania species-specific PCR were 95.7% for bone marrow aspirate samples and 98.5% for peripheral blood samples versus sensitivities of 76.2%, 85.5%, and 90.2% for bone marrow aspirate isolation, serologic testing, and microscopic examination of bone marrow biopsy specimens, respectively. None of 229 healthy blood donors or 25 patients with imported malaria who were used as negative control subjects had PCR results positive for Leishmania species in peripheral blood samples (i.e., specificity of Leishmania species-specific PCR, 100%). PCR and restriction fragment-length polymorphism analysis for Leishmania species identification revealed 100% concordance with isoenzyme typing in the 19 patients for whom the latter data were available.

CONCLUSIONS

PCR assay is a highly sensitive and specific tool for the diagnosis of visceral leishmaniasis in both immunocompetent and immunocompromised patients and can be reliably used for rapid parasite identification at the species level.

Evaluation of PCR for diagnosis of Indian kala-azar and assessment of cure

This study was done to evaluate PCR with Ld1 primers for the diagnosis of Indian visceral leishmaniasis (VL) and to assess its role in prediction of the disease outcome. The PCR assay was performed with DNA isolated from the peripheral blood of parasitologically confirmed cases of VL before the initiation of treatment, just after the end of treatment, and at 3 and 6 months of follow-up. The pretreatment PCR result was positive for 100 of 101 patients (sensitivity, 99%; confidence interval [CI], 94 to 100%). None of the 150 negative controls tested were PCR positive (specificity, 100%; CI, 96.8 to 100%). Of 60 patients who were treated at our center, 51 (85%; CI, 73 to 93%) became negative immediately after treatment and continued to be negative at 3 and 6 months of follow-up. At the 3-month follow-up, two of the remaining nine patients were PCR positive, making 58 (96.7%; CI, 87 to 100%) patients PCR negative. At the 6-month follow-up, all patients became PCR negative. One patient who was PCR negative immediately after the end of treatment relapsed 11 months later. This limited prospective study with VL patients suggests that the PCR assay is a highly sensitive and specific (99% and 100%, respectively) tool for the diagnosis of VL. In the majority of patients, it can identify a successful disease outcome; however, its translation into the field setting remains a major challenge.

A novel semiquantitative fluorescence-based multiplex polymerase chain reaction assay for rapid simultaneous detection of bacterial and parasitic pathogens from blood

A multiplex polymerase chain reaction assay was developed for the rapid simultaneous detection of category A select bacterial agents (Bacillus anthracis and Yersinia pestis) and parasitic pathogens (Leishmania species) in blood using the Cepheid Smart Cycler platform. B. anthracis (Sterne) and Yersinia. pseudotuberculosis were used in the assay for optimization for B. anthracis and Y. pestis, respectively. The specificity of the target amplicons [protective antigen gene of B. anthracis and rRNA genes of other pathogens or human (internal control)] was evaluated by staining the amplicons with SYBR Green I and determining their individual melting temperatures (T(m)). As a novel approach for pathogen semiquantitation, the Tm peak height of the amplicon was correlated with a known standard curve of pathogen-spiked samples. This assay was able to detect DNA in blood spiked with less than 50 target cells/ml for all of the pathogens. The sensitivity of this assay in blood was 100% for the detection of Leishmania donovani from leishmaniasis patients and B. anthracis (Sterne) from symptomatic mice. The time necessary for performing this assay including sample preparation was less than 1.5 hours, making this a potentially useful method for rapidly diagnosing and monitoring the efficacy of drugs or vaccines in infected individuals.

A new PCR-ELISA for diagnosis of visceral leishmaniasis in blood of HIV-negative subjects

The PCR-ELISA represents a promising advance for diagnosis of visceral leishmaniasis (VL) in blood samples. However, the method has been validated mostly with HIV-positive patients who are known to have high levels of parasitaemia. We developed a new PCR-ELISA assay for specific detection of Leishmania in patients' blood and validated it in Nepalese subjects with clinically suspected VL, almost all of whom were HIV-negative. For blood samples, PCR-ELISA was more sensitive (83.9%) than conventional PCR (73.2%), and demonstrated 100% and 87.2% specificity when using healthy controls who had never travelled to a VL-endemic area and controls from a VL-endemic area as references, respectively. We have demonstrated the ability of PCR-ELISA to detect parasites in blood of HIV-negative patients. The method could be used for epidemiological as well as clinical purposes, as it reduces the need for traumatic bone marrow sampling and risky spleen aspiration.

Cross-reaction of sera from patients with various infectious diseases with Leishmania infantum

OBJECTIVE

To compare and evaluate the application of indirect fluorescent antibody (IFA) and counterimmunoelectrophoresis (CIEP) for laboratory identification of visceral leishmaniasis.

MATERIALS AND METHODS

Serum samples from patients with malaria (Plasmodium vivax, n = 86; Plasmodium falciparum, n = 38), brucellosis (n = 26), tuberculosis (n = 31) and typhoid fever (n = 35) were examined for the presence of antibody to Leishmaniainfantum antigen using IFA and CIEP tests.

RESULTS

Using IFA, false-positive results were malaria (P. vivax 19.8%, P. falciparum 13.2%), tuberculosis (6.4%), brucellosis (3.8%), and typhoid fever (2.8%). Using CIEP, a lower percentage of false-positives was observed only among malaria patients (P. vivax 2.3%, P. falciparum 2.6%). Serum samples from patients with other infectious diseases were negative in the CIEP test.

CONCLUSION

Based on the results of this study, the CIEP technique is recommended for immunodiagnosis of visceral leishmaniasis, especially in regions where malaria, brucellosis and tuberculosis are prevalent.

Parasite detection in patients with post kala-azar dermal leishmaniasis in India: a comparison between molecular and immunological methods

AIMS

To evaluate the sensitivity and specificity of serological, immunohistochemical, and molecular methods in the diagnosis of post kala-azar dermal leishmaniasis (PKDL).

METHODS

Twenty five patients with confirmed PKDL and 25 controls were included in the study. G2D10, a monoclonal antibody against Leishmania, was used for the immunohistochemical (IHC) staining of lesion sections to visualise anti-Leishmania donovani antibodies. The diagnostic usefulness of IHC was compared with enzyme linked immunosorbent assay (ELISA) with a recombinant (rk39) antigen, and a species specific polymerase chain reaction (PCR) assay, amplifying a kinetoplast minicircle DNA sequence.

RESULTS

IHC detected 22 of 25 PKDL cases, giving a sensitivity of 88%. The diagnostic sensitivity of both the ELISA and PCR tests was higher (96%). All of the 25 controls examined were negative in PCR, indicating 100% specificity of the test, whereas ELISA showed 96% specificity.

CONCLUSIONS

IHC with G2D10 significantly enhances the sensitivity of detection of PKDL over routine haematoxylin and eosin staining. ELISA with a recombinant antigen is an economical and practical assay. PCR is the most sensitive and specific diagnostic method for PKDL. The tests described would facilitate the recognition of patients with PKDL, enabling timely treatment, which would contribute greatly to the control of kala-azar.

Detection of circulating Leishmania chagasi DNA for the non-invasive diagnosis of human infection

A polymerase chain reaction (PCR) assay for the detection of Leishmania spp. DNA in peripheral blood was optimized and evaluated for the diagnosis of human visceral leishmaniasis (VL) in Brazil during May 2001 to December 2002. Optimization of the technique resulted in a detection limit of 1.65 fg of purified L. (L.) chagasi DNA, equivalent to 1.65 x 10(-2) parasites. Leishmania DNA was detected in the blood of 48 of 53 patients with parasitologically-confirmed VL, which corresponds to a sensitivity of 91%. No DNA was detected in the peripheral blood of 15 healthy, non-exposed volunteers, giving a specificity of 100%. We conclude that detection of parasite DNA in peripheral blood offers a non-invasive, sensitive and rapid method for the detection of VL caused by L. (L.) chagasi.

Development of a PCR-based method for diagnosis of Leishmania in blood samples

Visceral Leishmaniasis (VL) cases reported in Mediterranean countries and in Northern Europe are becoming increasingly frequent. The past few years several studies have shown Polymerase Chain Reaction to be more effective than the classical methods for the diagnosis of VL in clinical samples. The purpose of this study was the development of a simple, specific and sensitive PCR-based assay for the detection of Leishmania in blood samples. A specific pair of oligonucleotides was designed using conserved sequences of the ssu-rRNA Leishmania infantum gene. Of the 53 blood samples of patients suspected for leishmaniasis that were processed with the newly designed oligonucleotides, 13 were successfully diagnosed positive. The results were confirmed with sequencing and restriction fragment length polymorphism. The lower detection limit of the reported assay was 10 parasites per ml in all seeded samples tested and considered highly satisfactory for diagnosis of Leishmaniasis in blood samples.

Development of an assay for quantification of linkage-specific O-acetylated sialoglycans on erythrocytes; its application in Indian visceral leishmaniasis

We have developed a noninvasive approach for the quantification of linkage-specific 9-O-acetylated sialoglycans on mammalian erythrocytes using a lectin, Achatinin-H, whose lectinogenic epitope has previously been defined as 9-O-acetylated sialoglycoconjugates (9-O-AcSGs) alpha 2-->6 linked to subterminal GalNAc. Titration and checkerboard analysis were performed to optimize the assay using rabbit, rat and human erythrocytes that contain differing amounts of this glycotope. Assay specificity was established by decreased binding of erythrocytes to immobilised Achatinin-H when pre-incubated with excess lectin. The intra-assay coefficient of variation (CV) for rat and human erythrocytes was 8.6-9.2% and 11.1-13.0%, respectively. The inter-assay CV for rat and human erythrocytes was 9.9-10.1% and 15.2-16.6%, respectively. In previous studies, we have identified an enhanced presence of cell surface 9-O-AcSGs on the erythrocytes of patients with visceral leishmaniasis (VL) [Am. J. Trop. Med. Hyg. 58 (1998) 551]. Our assay when evaluated on erythrocytes from VL patients (n=30) showed a fourfold increase in lectin binding as compared to endemic controls. The mean +/- S.E.M. of the A(405) nm value was 1.14 +/- 0.04 vs. 0.23 +/- 0.03, respectively (p<0.0001). Following effective chemotherapy, a significant reduction of this glycotope on the erythrocytes of VL patients indicates that this assay has both a diagnostic and prognostic potential. Taken together, we conclude that this antigen-based assay is a specific and reproducible method for monitoring the disease status of VL patients and could be used in retrospective and prospective trials.

Molecular biological applications in the diagnosis and control of leishmaniasis and parasite identification

Molecular biology is increasingly relevant to the diagnosis and control of infectious diseases. Information on DNA sequences has been extensively exploited for the development of polymerase chain reaction-based assays for the diagnosis of leishmaniasis and the identification of parasite species. It has also led to the use of cloned antigen for serodiagnosis. It is expected that the sequencing of the Leishmania major genome and the genomes of other Leishmania species will enable important progress in further improving diagnosis and control. The ability to use genome data to clone and sequence genes, which, when expressed, provide antigens for vaccine development, will increase the possibilities for rational vaccine development. Moreover, DNA on its own will provide the basis for the development of DNA vaccines that may overcome some of the problems encountered with protein-based vaccines. One of the greatest threats to parasite control is the development of drug resistance in parasites. Knowing the molecular basis of drug resistance and the ability to monitor its development with sensitive and specific DNA-based assays for 'resistance alleles' may aid maintaining the effectiveness of available anti-Leishmania drugs. Finally, techniques such as microarrays and nucleic acid sequence-based amplification will eventually allow rapid screening for specific parasite genotypes and assist in diagnostic and epidemiological studies.

A nested polymerase chain reaction (Ln-PCR) for diagnosing and monitoring Leishmania infantum infection in patients co-infected with human immunodeficiency virus

We investigated a Leishmania-specific nested polymerase chain reaction (Ln-PCR) for the diagnosis and treatment monitoring of L. infantum infections in patients co-infected with human immunodeficiency virus (HIV). Peripheral blood and bone marrow samples from 89 HIV patients in Spain suspected of having leishmaniasis were examined by different diagnostic techniques (Ln-PCR, microscopy, NNN culture and indirect fluorescent antibody test). The sensitivity of Ln-PCR compared with microscopy and culture of bone marrow was 95.45% using blood and 100% when using bone marrow. 38 of these patients with confirmed leishmaniasis were entered in a chemotherapy trial (reported elsewhere), and samples from them were collected before treatment, one month after treatment ended and during follow-up (1-20 months), and examined similarly. Ln-PCR was shown to be a good method for testing efficacy of treatment and for predicting relapses after treatment (relapses were predicted on average 5 months earlier than when using classical diagnostic techniques). We suggest that Ln-PCR (especially using peripheral blood) should be the technique of choice for diagnosis, monitoring the success of treatment, and predicting relapses in patients with HIV and suspected or confirmed L. infantum infection.

Visceral leishmaniasis in India: promises and pitfalls of a PCR-based blood test

Traditional methods of diagnosing visceral leishmaniasis (kala-azar) in India suffer from a number of disadvantages. Amplification of multicopy nuclear genes and messenger ribonucleic acid of Leishmania by the polymerase chain reaction (PCR) was evaluated as an alternative assay under various clinical conditions. PCR of peripheral blood has the highest absolute sensitivity among all the available procedures, and is particularly useful for detecting parasites in early infections, post kala-azar dermal leishmaniasis, concurrent infections and immunocompromised cases, but is not so reliable for late infections. PCR of immunopurified blood mononuclear cells indicated the association of parasites with monocytes as well as non-monocyte cell types.

A nested polymerase chain reaction for diagnosis and follow-up of human visceral leishmaniasis patients using blood samples

A nested polymerase chain reaction (PCR) assay for the diagnosis of human visceral leishmaniasis (VL) due to Leishmania infantum infection was developed using primers selected from the parasite's genomic deoxyribonucleic acid (DNA). The assay, which is based on the use of leucocytes separated from blood samples by Ficoll-Paque centrifugation, was compared with culture in vitro. Blood samples were collected from 17 patients in Spain with a history of clinical VL, 15 of whom were also infected with human immunodeficiency virus (HIV) (13 samples during the VL episode and 31 samples during post-treatment monitoring) and one sample was collected from each of 28 patients with HIV infection and fever but no history of VL. The nested PCR using blood detected all the cases of parasitologically confirmed, clinically active VL, while culture detected 92%. The nested PCR detected Leishmania DNA in 18% of the HIV-infected patients with fever and no history of VL, none of whom gave a positive culture. Follow-up examination of the VL patients by nested PCR and culture demonstrated the persistence of L. infantum in blood for a long time after treatment.

Parasitological and immunological follow-up of American tegumentary leishmaniasis patients

A long-term evaluation of human American tegumentary leishmaniasis patients was conducted to detect immunological and/or parasitological indicators associated with cure or protection against leishmaniasis. Cutaneous leishmaniasis (CL) and mucosal leishmaniasis (ML) patients from endemic areas of Leishmania braziliensis infection in Brazil were studied during the active disease, at the end of therapy, and up to 10 years after the end of therapy. For immunological studies, lymphocyte proliferative responses, phenotypic characterization of CD4+ and CD8+ T cells reactive to L. braziliensis and cytokine production in vitro were assayed. In CL, with its tendency for healing lesions, at or shortly after the completion of therapy the ratio of CD4+ to CD8+ T cells was approximately one and production of interferon gamma (IFN gamma) remained roughly constant. In ML, these apparently beneficial CD4+/CD8+ ratios and cytokine patterns appeared later. The long-term memory T cell responses were associated with preferential induction of CD4+ subpopulations and IFN gamma production that probably led to protection against relapses or reinfection. Deoxyribonucleic acid (DNA) was isolated from peripheral blood and oligonucleotides that amplify the conserved region of the minicircle molecules of Leishmania were used in a 'hot-start' polymerase chain reaction (PCR). Leishmania DNA was found in about one-quarter of the patients with active disease as well as in individuals who had received chemotherapy. The PCR was also positive in one-third of the individuals with a positive skin test but no past or present history of leishmaniasis. The well-modulated T cell response leading to long-term protection observed in CL patients could result from a favourable host genetic background and/or a particular parasite genotype, leading to a beneficial T cell immune response even in the presence of parasite antigens. The possibility of parasite persistence after clinical cure suggests that the immune response can control, but not fully eliminate, the infection. It could prevent the parasite from causing disease, maintaining a leishmanial antigen-specific response and hampering reinfection.

Comparison of six PCR methods using peripheral blood for detection of canine visceral leishmaniasis

The objectives of this study were to compare the sensitivities and reliabilities of different PCR methods for the diagnosis and epidemiological study of canine visceral leishmaniasis (CVL) using dog blood. We chose to work with peripheral blood, as this type of sampling is noninvasive, straightforward, and easy to repeat. Six PCR methods were compared: three primer pairs target genomic DNA, and the other three target kinetoplast (mitochondrial) DNA. Sensitivity, specificity, reproducibility, and ease of interpretation without hybridization were evaluated for each method. The assessment was first performed using artificial samples. All methods could detect less than one parasite per reaction tube. However, the sensitivities varied among the different methods by a factor of 500 on purified cultivated parasites and by a factor of 10,000 on seeded dog blood samples (i.e., from 10 to 10(-3) parasite per ml of blood for the latter). Only four methods were found sufficiently reliable for the diagnosis of CVL. They were tested on 37 dogs living in an area of endemicity and grouped according to clinical status and specific serology. Only the two methods targeting kinetoplast DNA (K13A-K13B and RV1-RV2) could detect the parasite in 100% of symptomatic infected dogs. Similarly, all seropositive dogs were found PCR positive by these methods versus 62% by the genomic-DNA-based methods. Finally, these kinetoplast-based methods proved clearly superior to the others in the detection of Leishmania in asymptomatic dogs. Our data allow the discussion of the advantages and drawbacks of highly sensitive versus moderately sensitive PCR methods in diagnosis and prevalence studies of CVL.

QBC for the diagnosis of human and canine american visceral leishmaniasis: preliminary data

"Quantitative Buffy Coat" (QBC) is a direct and fast fluorescent method used for the identification of blood parasites. Since Leishmania chagasi circulates in blood, we decided to test it in American visceral leishmaniasis (AVL). Bone marrow (BM) and peripheral blood (PB) of 49 persons and PB of 31 dogs were analyzed. QBC was positive in BM of 11/11 patients with AVL and in 1/6 patients with other diseases. Amastigotes were identified in PB of 18/22 patients with AVL and in none without AVL. The test was positive in 30 out of the 31 seropositive dogs and in 28/28 dogs with Leishmania identified in other tissues. QBC is a promising method for diagnosis of human AVL, and possibly for the exam of PB of patients with AVL/AIDS, for the control of the cure and for the identification of asymptomatic carriers. Because it is fast and easy to collect and execute, QBC should be evaluated for programs of reservoir control.

Development of a species-specific PCR assay for detection of Leishmania donovani in clinical samples from patients with kala-azar and post-kala-azar dermal leishmaniasis

We have developed a PCR assay that is capable of amplifying kinetoplast DNA (kDNA) of Leishmania donovani in a species-specific manner among Old World leishmanias. With Indian strains and isolates of L. donovani the assay was sensitive enough to detect kDNA in an amount equivalent to a single parasite or less. The extreme sensitivity of the assay was reflected in its ability to detect parasite DNA from small volumes of peripheral blood of patients with kala-azar (KA) and from skin lesions from patients with post-KA dermal leishmaniasis (PKDL). A total of 107 clinical leishmaniasis samples were analyzed. Of these 102 (95.3%) were positive by PCR. The test provided a diagnosis of KA with 96% sensitivity using patient whole-blood samples instead of bone marrow or spleen aspirates that are obtained by invasive procedures. The assay was also successful in the diagnosis of 45 of 48 PKDL cases (93.8%). Cross-reactions with pathogens prevalent in the area of endemicity, viz., Mycobacterium tuberculosis, Mycobacterium leprae, and Plasmodium spp., could be ruled out. Eighty-one control samples, including dermal scrapings from healthy portions of skin from patients with PKDL were all negative. Two of twenty controls from the area of endemicity were found positive by PCR assay; however, there was a good possibility that these two were asymptomatic carriers since they were serologically positive for KA. Thus, this PCR assay represents a tool for the diagnosis of KA and PKDL in Indian patients in a noninvasive manner, with simultaneous species identification of parasites in clinical samples.

Comparison of various sample preparation methods for PCR diagnosis of visceral leishmaniasis using peripheral blood

We have compared various sample preparation methods for the PCR diagnosis of visceral leishmaniasis (VL) using peripheral blood samples and tested the influence of these protocols upon sensitivity. Four methods of lysis-DNA extraction were used with two types of blood samples: whole blood (WB) and buffy coat (BC). Comparisons were first carried out with seeded samples at various parasite concentrations. At high concentrations (> or = 1,000 parasites/ml), there were no significant differences in PCR sensitivity among the methods tested. At concentrations of < or = 100 parasites/ml, proteinase K (PK)-based methods proved clearly superior to guanidine-EDTA-based methods. Moreover, a 10-fold increase in sensitivity was observed for BC over that for WB. Thus, the best sensitivity was obtained with the BC prepared with PK-based methods. With this combination, the PCR reliably detected 10 parasites/ml but was inconsistent when the sample contained 1 parasite/ml of blood. The methods that yielded the highest sensitivities were evaluated with seven dogs and four human VL patients. Again, the utilization of the BC prepared with PK-based methods gave the best results. The optimization of each step of the assay (sample preparation, DNA extraction, and PCR conditions) yielded a highly sensitive tool for the diagnosis of VL using patient blood, thus avoiding more invasive diagnostic procedures and allowing the detection of low parasitemia during posttherapeutic follow-up.

Visceral leishmaniasis control: a public health perspective

Visceral leishmaniasis (VL), also known as kala-azar, is a vector-borne disease caused by a protozoan of the Leishmania donovani complex. A phlebotomine sandfly transmits the parasite from person to person or via an animal reservoir. VL is a severe, debilitating disease, characterized by prolonged fever, splenomegaly, hypergammaglobulinaemia and pancytopenia. Patients become gradually ill over a period of a few months, and nearly always die if untreated. Case-fatality ratios are high even in treated patients. Worldwide an estimated 500,000 VL cases occur each year. This study reviews clinical, epidemiological and public health aspects of the disease and shows how critical adequate case detection is for the success of VL control. Examination of the issue of VL diagnosis with respect to the global challenges in VL control leads to the observation that a sound diagnostic-therapeutic algorithm for the health services in endemic areas is badly needed. Serological tests could be an alternative to parasitological diagnosis and the direct agglutination test (DAT) was found to fulfil many criteria for a 'field test', including cost effectiveness. Although research needs on vaccine and better drugs continue to be high on the agenda, a VL test-treatment strategy based on currently available highly sensitive serological tests, such as the DAT, should be introduced in the health services in endemic areas.

Sequencing a specific kinetoplast DNA fragment of Leishmania donovani for polymerase chain reaction amplification in diagnosis of leishmaniasis in bone marrow and blood samples

A set of oligonucleotide primers I and II was developed by analyzing the specificity of a cloned kinetoplast DNA (kDNA) fragment of Leishmania donovani and sequencing the fragment. Polymerase chain reaction (PCR) was conducted with the primers to amplify a minicircle kDNA fragment (297 bp) to detect L. donovani in the bone marrow (22 samples), whole blood (16 samples), and serum (17 samples) of 22 patients with visceral leishmaniasis. All of 22 patients were diagnosed by microscopic identification. Control samples of bone marrow, whole blood, and serum were obtained from patients with leukemia and from healthy volunteers. In addition, 12 dogs were infected with L. donovani promastigotes for the PCR test. The total number of patients positive by PCR testing was 95.5% (21/22), with 91.0% (20/22) from the bone marrow, 68.8% (11/16) from the blood, and 29.4% (5/17) from the sera. Similar results were obtained in infected dogs. No amplification products were seen in control samples from humans or dogs. Our results suggest that PCR may be useful in detecting kDNA in the bone marrow and blood of patients with visceral leishmaniasis.

Optimized PCR using patient blood samples for diagnosis and follow-up of visceral Leishmaniasis, with special reference to AIDS patients

We developed a highly sensitive PCR method that enables the diagnosis and posttherapeutic follow-up of visceral leishmaniasis with patient blood. The PCR assay was thoroughly optimized by successive procedural refinements to increase its sensitivity and specificity. It was compared to in vitro cultivation as well as to direct examination of bone marrow and to serology. Two hundred thirty-seven patients presenting with clinical signs compatible with visceral leishmaniasis were included in the study. Thirty-six were diagnosed as having Mediterranean visceral leishmaniasis (MVL). Twenty-three of them, including 19 AIDS patients, were monitored during and after treatment over a period from 2 weeks to 3 years. Our PCR assay proved more sensitive than in vitro cultivation, direct examination, and serology for all patients. It is simple and can be adapted to routine hospital diagnostic procedures. For the primary diagnosis of MVL, the sensitivity of PCR versus that of cultivation was 97 versus 55% with peripheral blood and 100 versus 81% with bone marrow samples. Regarding posttherapeutic follow-up, overall, 48% of positive samples were detected by PCR only. Seven patients presented with a clinical relapse during the study; six relapses were detected at first by PCR only, sometimes a few weeks before the reappearance of signs or symptoms. We conclude that an optimized and well-mastered PCR assay with a peripheral blood sample is sufficient to provide a secure diagnosis for all immunocompromised patients and most immunocompetent patients. We also suggest systematic posttherapeutic monitoring by PCR with peripheral blood for immunocompromised patients.

Leishmania donovani: development and characterisation of a kinetoplast DNA probe and its use in the detection of parasites

The polymerase chain reaction is used increasingly widely for the diagnosis of both cutaneous and visceral leishmaniasis and for the identification of asymptomatic carriers in the population in endemic disease areas. The use of complex-specific hybridisation probes in conjunction with the polymerase chain reaction increases the specificity as well as the sensitivity of the diagnostic procedure as it discriminates between different infecting Leishmania species. A minicircle kinetoplast DNA probe, B4 Rsa, which hybridizes to all members of the Leishmania (L.) donovani complex has been identified and characterised. It is a segment of a minicircle highly conserved in Bangladeshi and Indian L. (L.) donovani isolates.

Diagnostic and prognostic potential of a competitive enzyme-linked immunosorbent assay for leishmaniasis in India

A Leishmania donovani species-specific monoclonal antibody (monoclonal antibody D2) was evaluated for its diagnostic and prognostic potential by a competitive enzyme-linked immunosorbent assay (C-ELISA) in sera from Indian patients with visceral leishmaniasis (VL) and seven patients with post-kala-azar dermal leishmaniasis (PKDL). These results were compared with those obtained by microscopy with Giemsa-stained tissue smears and a direct enzyme-linked immunosorbent assay (direct ELISA) with crude parasite antigen. Of 121 patients with clinically diagnosed VL examined, 103 (85.1%) were positive and 11 (9.1%) were negative by all three methods. An additional 7 (5.8%) who were negative by microscopy were positive by both C-ELISA and direct ELISA. Seven PKDL patients were also examined and were found to be positive by all three methods. Analysis of the chemotherapeutic response to sodium antimony gluconate of these 110 serologically positive VL patients showed that 57 (51.8%) were drug responsive and 53 (48.2%) were drug resistant. The C-ELISA with sera from 20 longitudinally monitored VL patients before and after chemotherapy showed a significant decrease in percent inhibition of monoclonal antibody D2 in drug-responsive patients. However, in drug-unresponsive patients, the percent inhibition of D2 was unchanged or was slightly increased. Our results therefore indicate (i) the applicability of L. donovani species-specific monoclonal antibody D2 for sensitive and specific serodiagnosis by C-ELISA, (ii) that the C-ELISA is more sensitive than microscopy, especially for early diagnosis, (iii) that L. donovani is still the main causative agent of VL, irrespective of the chemotherapeutic response, and (iv) that the C-ELISA can be used to evaluate the success of drug treatment.

Identification of antibodies directed against O-acetylated sialic acids in visceral leishmaniasis: its diagnostic and prognostic role

A significantly increased O-acetylated sialic acid (O-AcSA) binding fraction was purified from serum of visceral leishmaniasis (VL) patients by affinity chromatography on immobilized bovine submaxillary mucin (BSM) and found to be immunoglobulin in origin. The serodiagnostic and prognostic potential of BSM as a capture antigen was established by ELISA with no cross reactivity with coendemic diseases like malaria, tuberculosis, leprosy, chagas disease and cutaneous leishmaniasis; however, a strong cross reactivity was present with trypanosomiasis patients. In 56 clinically diagnosed VL patients, the BSM-ELISA was compared with diagnosis by microscopy using Giemsa stained tissue smears and direct ELISA using crude parasite antigen (parasite-ELISA); 49/56(87.5%) and 5/56(9.0%) were positive and negative respectively by all 3 methods. The BSM-ELISA failed to diagnose 2/56(3.5%) patients which were biopsy and parasite-ELISA positive. The prognostic potential of the BSM-ELISA in 18 longitudinally monitored VL patients before and after conventional antimonial treatment showed a significant decrease in anti O-AcSA titres in drug responsive patients whereas anti O-AcSA levels persisted in drug unresponsive patients. The IgG subclass distribution of antibodies directed against O-AcSA showed increased IgG2 levels in VL patients as compared to healthy controls. The BSM-based ELISA holds great promise as a serodiagnostic and prognostic assay for VL.

Evaluation of PCR for diagnosis of visceral leishmaniasis

An evaluation of Leishmania PCR was performed with bone marrow, lymph node, and blood samples from 492 patients, 60 positive controls, and 90 negative controls. Results were compared with microscopy results for Giemsa-stained smears. PCR and microscopy of lymph node and bone marrow aspirates from patients with microscopically confirmed visceral leishmaniasis (VL) were equally sensitive. However, in patients clinically suspected of having VL and in whom parasites could not be demonstrated by microscopy, PCR was positive for 12 of 23 (52.2%) lymph node aspirates and 8 of 12 (66.7%) bone marrow aspirates, thus confirming the clinical diagnosis of VL. With PCR on filter paper, Leishmania DNA was detected in the blood of 33 of 47 (70%) patients with confirmed VL and in 2 of 11 (19%) patients suspected of having VL. Positive PCR results were more frequently found for blood samples on filter paper than for samples stored in EDTA. In conclusion, PCR is a more sensitive method than microscopy for the detection of Leishmania in lymph node and bone marrow aspirates, being especially useful for the confirmation of cases of suspected VL. Blood from a finger prick may be used for the initial PCR screening of people suspected of having VL. If the PCR of blood is negative, one should perform PCR with lymph node and/or bone marrow material, because PCR with these materials is more often positive.

Leishmania and human immunodeficiency virus coinfection: the first 10 years

Over 850 Leishmania-human immunodeficiency virus (HIV) coinfection cases have been recorded, the majority in Europe, where 7 to 17% of HIV-positive individuals with fever have amastigotes, suggesting that Leishmania-infected individuals without symptoms will express symptoms of leishmaniasis if they become immunosuppressed. However, there are indirect reasons and statistical data demonstrating that intravenous drug addiction plays a specific role in Leishmania infantum transmission: an anthroponotic cycle complementary to the zoonotic one has been suggested. Due to anergy in patients with coinfection, L. infantum dermotropic zymodemes are isolated from patient viscera and a higher L. infantum phenotypic variability is seen. Moreover, insect trypanosomatids that are currently considered nonpathogenic have been isolated from coinfected patients. HIV infection and Leishmania infection each induce important analogous immunological changes whose effects are multiplied if they occur concomitantly, such as a Th1-to-Th2 response switch; however, the consequences of the viral infection predominate. In fact, a large proportion of coinfected patients have no detectable anti-Leishmania antibodies. The microorganisms share target cells, and it has been demonstrated in vitro how L. infantum induces the expression of latent HIV-1. Bone marrow culture is the most useful diagnostic technique, but it is invasive. Blood smears and culture are good alternatives. PCR, xenodiagnosis, and circulating-antigen detection are available only in specialized laboratories. The relationship with low levels of CD4+ cells conditions the clinical presentation and evolution of disease. Most patients have visceral leishmaniasis, but asymptomatic, cutaneous, mucocutaneous, diffuse cutaneous, and post-kala-azar dermal leishmaniasis can be produced by L. infantum. The digestive and respiratory tracts are frequently parasitized. The course of coinfection is marked by a high relapse rate. There is a lack of randomized prospective treatment trials; therefore, coinfected patients are treated by conventional regimens. Prophylactic therapy is suggested to be helpful in preventing relapses.

Peripheral blood mononuclear cells of patients with Indian visceral leishmaniasis suppress natural killer cell activity in vitro

Peripheral blood mononuclear cells (PBMC) of patients with Indian visceral leishmaniasis (VL) suppressed the natural killer cell (NK) activity of normal human PBMC in vitro in a dose-dependent manner. Adherent monocytes, but not the non-adherent lymphocytes of VL patients suppressed NK activity through soluble mediators. The level of suppression seen in different patients was variable.