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

Molecular Diagnosis of Leishmaniasis in Spain: Development and Validation of Ready-To-Use Gel-Form Nested and Real-Time PCRs To Detect Leishmania spp

Leishmaniasis is an endemic parasitic disease in at least 98 countries. In Spain, it is considered a zoonosis caused by Leishmania infantum, with an annual incidence of 0.62 cases/100,000 inhabitants. The predominant clinical manifestations are the cutaneous (CL) and visceral forms (VL), and the diagnosis is performed by parasitological, serological, and molecular tests. At the WHO Collaborating Center for Leishmaniasis (WHOCCLeish), routine diagnostic tests are based on a nested PCR (Ln-PCR), culture, and serological tests. To simplify our PCR protocol, we aimed to develop and validate a ready-to-use nested gel-form PCR (LeishGelPCR) and a duplex real-time PCR (qPCR) that allowed simultaneous detection of Leishmania and mammalian DNA as an internal control (Leish-qPCR). Clinical validation was performed in 200 samples from the WHOCCLeish collection; 92 and 85 out of 94 and 87 samples were positive by LeishGelPCR and Leish-qPCR, respectively, showing a sensitivity of 98% in both approaches. The specificity was 100% for LeishGelPCR and 98% for Leish-qPCR. The limits of detection of both protocols were similar (0.5 and 0.2 parasites/reaction). Parasite loads in VL and CL forms were similar, although high loads were observed when invasive samples were tested. In conclusion, LeishGelPCR and Leish-qPCR showed excellent performance in the diagnosis of leishmaniasis. These new forms of 18S rRNA gene PCR are equivalent to Ln-PCR and can be introduced in the algorithm for CL and VL diagnosis. IMPORTANCE Although the gold standard for diagnosis of leishmaniasis is the microscopic observation of amastigotes, molecular techniques are becoming a cost-efficient alternative. Currently, PCR is a routine resource that is used in many reference microbiology laboratories. In this article, we have described two ways to improve the reproducibility and usability of the molecular detection of Leishmania spp. These new approaches could be introduced even in middle- and low-resource laboratories; one is a ready-to-use gel-form system of a nested PCR and the other is a real-time PCR. We show why molecular diagnosis is the best methodology to confirm a clinical suspicion of leishmaniasis with higher sensitivity than traditional methods, thus facilitating early diagnosis and timely treatment of human leishmaniasis.

Molecular Detection of Neglected Tropical Diseases: The Case for Automated Near-Point-of-Care Diagnosis of Leishmaniasis

Neglected tropical diseases affect those in poorer nations disproportionately across the globe. One example of these, leishmaniasis, is a debilitating and potentially fatal parasitic infection. Molecular detection of this disease can provide accurate and fast diagnosis, and with near point-of-care technologies, detection can be provided in many health-care settings. Traditionally, the perceived limitations to such detection methods have hindered their provision to resource-limited nations, but new technologies and techniques are helping to overcome these perceptions. The current pandemic offers an opportunity to maintain and develop further advances, ensuring molecular diagnostics are accessible to all.

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.

Blood Parasite Load as an Early Marker to Predict Treatment Response in Visceral Leishmaniasis in Eastern Africa

BACKGROUND

To expedite the development of new oral treatment regimens for visceral leishmaniasis (VL), there is a need for early markers to evaluate treatment response and predict long-term outcomes.

METHODS

Data from 3 clinical trials were combined in this study, in which Eastern African VL patients received various antileishmanial therapies. Leishmania kinetoplast DNA was quantified in whole blood with real-time quantitative polymerase chain reaction (qPCR) before, during, and up to 6 months after treatment. The predictive performance of pharmacodynamic parameters for clinical relapse was evaluated using receiver-operating characteristic curves. Clinical trial simulations were performed to determine the power associated with the use of blood parasite load as a surrogate endpoint to predict clinical outcome at 6 months.

RESULTS

The absolute parasite density on day 56 after start of treatment was found to be a highly sensitive predictor of relapse within 6 months of follow-up at a cutoff of 20 parasites/mL (area under the curve 0.92, specificity 0.91, sensitivity 0.89). Blood parasite loads correlated well with tissue parasite loads (ρ = 0.80) and with microscopy gradings of bone marrow and spleen aspirate smears. Clinical trial simulations indicated a > 80% power to detect a difference in cure rate between treatment regimens if this difference was high (> 50%) and when minimally 30 patients were included per regimen.

CONCLUSIONS

Blood Leishmania parasite load determined by qPCR is a promising early biomarker to predict relapse in VL patients. Once optimized, it might be useful in dose finding studies of new chemical entities.

Diversity and Within-Host Evolution of Leishmania donovani from Visceral Leishmaniasis Patients with and without HIV Coinfection in Northern Ethiopia

Visceral leishmaniasis (VL) is a fatal disease and a growing public health problem in East Africa, where Ethiopia has one of the highest VL burdens. The largest focus of VL in Ethiopia is driven by high prevalence in migrant agricultural workers and associated with a high rate of coinfection with HIV. This coinfection makes VL more difficult to treat successfully and is associated with a high rate of relapse, with VL/HIV patients frequently experiencing many relapses of VL before succumbing to this infection. We present genome-wide data on Leishmania donovani isolates from a longitudinal study of cohorts of VL and VL/HIV patients reporting to a single clinic in Ethiopia. Extensive clinical data allow us to investigate the influence of coinfection and relapse on the populations of parasites infecting these patients. We find that the same parasite population is responsible for both VL and VL/HIV infections and that, in most cases, disease relapse is caused by recrudescence of the population of parasites that caused primary VL. Complex, multiclonal infections are present in both primary and relapse cases, but the infrapopulation of parasites within a patient loses genetic diversity between primary disease presentation and subsequent relapses, presumably due to a population bottleneck induced by treatment. These data suggest that VL/HIV relapses are not caused by genetically distinct parasite infections or by reinfection. Treatment of VL does not lead to sterile cure, and in VL/HIV, the infecting parasites are able to reestablish after clinically successful treatment, leading to repeated relapse of VL. IMPORTANCE Visceral leishmaniasis (VL) is the second largest cause of deaths due to parasite infections and a growing problem in East Africa. In Ethiopia, it is particularly associated with migrant workers moving from regions of nonendemicity for seasonal agricultural work and is frequently found as a coinfection with HIV, which leads to frequent VL relapse following treatment. Insight into the process of relapse in these patients is thus key to controlling the VL epidemic in Ethiopia. We show that there is little genetic differentiation between the parasites infecting HIV-positive and HIV-negative VL patients. Moreover, we provide evidence that relapses are caused by the initially infecting parasite population and that treatment induces a loss of genetic diversity in this population. We propose that restoring functioning immunity and improving antiparasitic treatment may be key in breaking the cycle of relapsing VL in VL/HIV patients.

Leishmaniasis in the United States: Emerging Issues in a Region of Low Endemicity

Leishmaniasis, a chronic and persistent intracellular protozoal infection caused by many different species within the genus Leishmania, is an unfamiliar disease to most North American providers. Clinical presentations may include asymptomatic and symptomatic visceral leishmaniasis (so-called Kala-azar), as well as cutaneous or mucosal disease. Although cutaneous leishmaniasis (caused by Leishmania mexicana in the United States) is endemic in some southwest states, other causes for concern include reactivation of imported visceral leishmaniasis remotely in time from the initial infection, and the possible long-term complications of chronic inflammation from asymptomatic infection. Climate change, the identification of competent vectors and reservoirs, a highly mobile populace, significant population groups with proven exposure history, HIV, and widespread use of immunosuppressive medications and organ transplant all create the potential for increased frequency of leishmaniasis in the U.S. Together, these factors could contribute to leishmaniasis emerging as a health threat in the U.S., including the possibility of sustained autochthonous spread of newly introduced visceral disease. We summarize recent data examining the epidemiology and major risk factors for acquisition of cutaneous and visceral leishmaniasis, with a special focus on implications for the United States, as well as discuss key emerging issues affecting the management of visceral 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 Tracking of the Leishmania Parasite

With the Visceral Leishmaniasis/Kala-azar Elimination Program in South Asia in its consolidation phase, the focus is mainly on case detection, vector control, and identifying potential sources of infection. Accordingly, emphasis is presently on curbing transmission, which is potentially achievable by identification and elimination of potential reservoirs. The strongest contenders for being the disease reservoir are cases of Post Kala-azar Dermal Leishmaniasis (PKDL) which occurs in a minor proportion of individuals apparently cured of Visceral Leishmaniasis (VL). The demonstration of parasites in tissue aspirates despite being a risky and invasive process is the gold standard for diagnosis of VL, but is now being replaced by serological tests e.g., rK39 strip test and direct agglutination test. However, these antibody based tests are limited in their ability to diagnose relapses, detect cases of PKDL, and monitor effectiveness of treatment. Accordingly, detection of antigen or nucleic acids by polymerase chain reaction has been successfully applied for monitoring of parasite kinetics. This review article provides updated information on recent developments regarding the available antibody or antigen/nucleic acid based biomarkers for longitudinal monitoring of patients with VL or PKDL and emphasizes the need for availability of studies pertaining to quantification of treatment response or relapse.

Recent advances and new strategies in Leishmaniasis diagnosis

Leishmaniasis is a set of complex and multifaceted syndromes, with different clinical manifestations, caused by different species of the genus Leishmania spp. that can be characterized by at least four syndromes: visceral leishmaniasis (VL, also known as kala-azar), post-kala-azar dermal leishmaniasis (PKDL), cutaneous leishmaniasis (CL), and mucocutaneous leishmaniasis (MCL). Among the most serious clinical forms, VL stands out, which causes the death of around 59,000 people annually. Fast and accurate diagnosis in VL is essential to reduce the disease's morbidity and mortality. There are a large number of diagnostic tests for leishmaniasis, however they do cross-react with other protozoa and their sensitivity changes according to the clinical form of the disease. Thus, it is essential and necessary to provide a diagnosis that is sufficiently sensitive to detect asymptomatic infected individuals and specific to discriminate individuals with other infectious and parasitic diseases, thus enabling more accurate diagnostic tools than those currently used. In this context, the aim of this review is to summarize the conventional diagnostic tools and point out the new advances and strategies on visceral and cutaneous leishmaniasis diagnosis.

Visceral leishmaniasis: a practical strategy for quantitative molecular diagnosis in naturally infected dogs

The diagnosis of canine visceral leishmaniasis (CVL) has been a problem for public health services due to the variety of clinical signs similar to other diseases and low sensitivity and specificity of available tests. In this sense, our main objective was to develop a simple, rapid, and accurate quantitative real-time PCR (qPCR) diagnosis for CVL. Thus, low-invasive samples from bone marrow (BM), popliteal lymph nodes (PLN), and conjunctival swabs (CS) were selected from negative and VL-positive dogs, using as gold standard, immunological and parasitological tests performed with different tissues. Oligonucleotides for Leishmania infantum kDNA were designed and the limit of quantification and amplification efficiency of the qPCR were determined using tissue-specific standards produced with DNA from those different tissues, mixed with DNA from a known amount of L. infantum promastigotes. Endogenous control was used to validate a comparative Ct method, and tissue parasite concentrations were estimated by comparison with tissue-specific reference standard samples. The overall analysis of the qPCR data suggests the following ranking for tissue choice: PLN > BM > CS. Finally, we have concluded that this molecular approach simplifies and accelerates the quantitative diagnostic process because it is easy to perform, requiring no DNA dosing or standard curve application, and it shows good diagnostic parameters, especially when using popliteal lymph node samples.

Semi-Quantitative, Duplexed qPCR Assay for the Detection of Leishmania spp. Using Bisulphite Conversion Technology

Leishmaniasis is caused by the flagellated protozoan Leishmania, and is a neglected tropical disease (NTD), as defined by the World Health Organisation (WHO). Bisulphite conversion technology converts all genomic material to a simplified form during the lysis step of the nucleic acid extraction process, and increases the efficiency of multiplex quantitative polymerase chain reaction (qPCR) reactions. Through utilization of qPCR real-time probes, in conjunction with bisulphite conversion, a new duplex assay targeting the 18S rDNA gene region was designed to detect all Leishmania species. The assay was validated against previously extracted DNA, from seven quantitated DNA and cell standards for pan-Leishmania analytical sensitivity data, and 67 cutaneous clinical samples for cutaneous clinical sensitivity data. Specificity was evaluated by testing 76 negative clinical samples and 43 bacterial, viral, protozoan and fungal species. The assay was also trialed in a side-by-side experiment against a conventional PCR (cPCR), based on the Internal transcribed spacer region 1 (ITS1 region). Ninety-seven percent of specimens from patients that previously tested positive for Leishmania were positive for Leishmania spp. with the bisulphite conversion assay, and a limit of detection (LOD) of 10 copies per PCR was achieved, while the LOD of the ITS1 methodology was 10 cells/1000 genomic copies per PCR. This method of rapid, accurate and simple detection of Leishmania can lead to improved diagnosis, treatment and public health outcomes.

18F-FDG PET/CT in visceral leishmaniasis: uptake patterns in the context of a multiannual outbreak in Northern Italy

OBJECTIVES

Visceral leishmaniasis (VL) is the most severe manifestation of the infection caused by the protozoan Leishmania, recently on increase in Italy and Spain. The aim of the study was to describe FDG uptake patterns in VL patients (pts) who underwent 18F-FDG PET/CT.

METHODS

A retrospective monocentric study of pts who underwent FDG PET/CT between 2008 and 2017 and later diagnosed with VL was performed. Semi-quantitative parameters were calculated in FDG-positive lesions: SUVmax, SUVmax spleen/SUVmax liver ratio (SLR), SUVmax focal/diffuse spleen ratio (FDR).

RESULTS

Overall, 23 pts were included. PET/CT was negative in 2 immunocompromised pts, positive in 21/23 (91%) [6 spleen only, 2 spleen + nodes, 7 spleen + bone marrow (BM), 4 spleen + BM + nodes, 1 spleen + BM + lung, 1 BM only + nodes, 2 nodes only]. Splenic involvement was demonstrated in 20/23 (87%) pts. Two different splenic patterns were observed: diffuse (13/20 pts, mean spleen SUVmax = 7.3 ± 4.2 [4.0-14.1], mean SLR = 2.2 ± 1.6 [1.3-6.7]) and focal over diffuse (7/20 pts, mean SUVmax = 12.6 ± 4.5 [9.5-20.5], mean SLR = 2.8 ± 0.8 [2.1-4.4], mean FDR = 2.1 ± 0.8 [1.2-3.6]). Extra-splenic FDG-avid findings were detected in 15/21 pts (65%): bone marrow in 13/15 (mean SUVmax = 4.0 ± 1.3 [2.8-6.0]), nodes in 67/15 and lung in 1/15.

CONCLUSIONS

PET/CT demonstrated splenic FDG uptake in all immunocompetent VL pts; two splenic patterns (diffuse/focal over diffuse) were observed and indistinguishable from splenic involvement by other disorders. The most frequent extra-splenic FDG-positive sites were BM and lymph nodes. Considering the potential disease aggressiveness and recent outbreaks in north-eastern Italy, VL should be considered in the differential diagnosis of FDG-positive splenic findings in pts from endemic areas or reporting travels to endemic countries.

Maternal Leishmania infantum infection status has significant impact on leishmaniasis in offspring

Visceral Leishmaniasis is a deadly disease caused by Leishmania infantum, endemic in more than 98 countries across the globe. Although the most common means of transmission is via a sand fly vector, there is growing evidence that vertical transmission may be critical for maintaining L. infantum infection within the reservoir, canine, population. Vertical transmission is also an important cause of infant morbidity and mortality particularly in sub-Saharan Africa. While vertical transmission of visceralizing species of Leishmania has been reported around the globe, risk factors associated with this unique means of Leishmania transmission have not been identified therefore interventions regarding this means of transmission have been virtually non-existent. Furthermore, the basic reproductive number, (R0), or number of new L. infantum infections that one infected mother or dam can cause has not been established for vertical transmission, also hampering the ability to assess the impact of this means of transmission within reservoir of human hosts. Canine Leishmaniosis (CanL) is enzootic within a U.S. hunting dog population. CanL is transmitted within this population via transplacental transmission with no reported vector transmission, despite many repeated attempts to find infected sand flies associated with these dogs and kennels. This population with predominantly, if not solely, vertical transmission of L. infantum was used to evaluate the critical risk factors for vertical transmission of Leishmania and establish the R0 of vertical L. infantum infection. Evaluation of 124 animals born to eighteen dams diagnostically positive for infection with L. infantum showed that there was a 13.84x greater chance of being positive for L. infantum within their lifetime if the mother was also positive within her lifetime (RR: 13.84, 95% CI: 3.54-54.20, p-value: <0.0001). The basic reproductive number for vertically transmitted L. infantum within this cohort was 4.12. These results underscore that there is a high risk of L. infantum infection to transmit from mother to offspring. Targeted public health interventions and control efforts that address vertical transmission of L. infantum are necessary in endemic countries to eliminate visceral leishmaniasis.

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.

Combining epidemiology with basic biology of sand flies, parasites, and hosts to inform leishmaniasis transmission dynamics and control

Quantitation of the nonlinear heterogeneities in Leishmania parasites, sand fly vectors, and mammalian host relationships provides insights to better understand leishmanial transmission epidemiology towards improving its control. The parasite manipulates the sand fly via production of promastigote secretory gel (PSG), leading to the “blocked sand fly” phenotype, persistent feeding attempts, and feeding on multiple hosts. PSG is injected into the mammalian host with the parasite and promotes the establishment of infection. Animal models demonstrate that sand flies with the highest parasite loads and percent metacyclic promastigotes transmit more parasites with greater frequency, resulting in higher load infections that are more likely to be both symptomatic and efficient reservoirs. The existence of mammalian and sand fly “super-spreaders” provides a biological basis for the spatial and temporal clustering of clinical leishmanial disease. Sand fly blood-feeding behavior will determine the efficacies of indoor residual spraying, topical insecticides, and bed nets. Interventions need to have sufficient coverage to include transmission hot spots, especially in the absence of field tools to assess infectiousness. Interventions that reduce sand fly densities in the absence of elimination could have negative consequences, for example, by interfering with partial immunity conferred by exposure to sand fly saliva. A deeper understanding of both sand fly and host biology and behavior is essential to ensuring effectiveness of vector interventions.

We review recent research that sheds light on the quantitative biology of leishmanial transmission between sand flies and mammalian hosts and use these insights to better understand transmission, the observed epidemiology of the disease, and their implications in choice of control strategy. Using animal models, we show how the parasite-induced processes manipulate sand fly blood-feeding behavior and the infectious metacyclic dose to promote host infection and to differentially regulate the onward transmission potential of individual vectors and hosts. The existence of subpopulations of mammalian and sand fly “super-spreaders” provides a biological basis for the spatial and temporal clustering of clinical leishmanial disease. While tools are unavailable to distinguish these individuals in mixed populations, blanket interventions will be necessary to ensure inclusion of transmission hot spots. Interventions that reduce sand fly densities without elimination could interfere with vector—host dynamics and conferred partial immunity to host populations.

Real-time PCR in detection and quantitation of Leishmania donovani for the diagnosis of Visceral Leishmaniasis patients and the monitoring of their response to treatment

Sustained elimination of Visceral Leishmaniasis (VL) requires the reduction and control of parasite reservoirs to minimize the transmission of Leishmania donovani infection. A simple, reproducible and definitive diagnostic procedure is therefore indispensable for the early and accurate detection of parasites in VL, Relapsed VL (RVL) and Post Kala-azar Dermal Leishmaniasis (PKDL) patients, all of whom are potential reservoirs of Leishmania parasites. To overcome the limitations of current diagnostic approaches, a novel quantitative real-time polymerase chain reaction (qPCR) method based on Taqman chemistry was devised for the detection and quantification of L. donovani in blood and skin. The diagnostic efficacy was evaluated using archived peripheral blood buffy coat DNA from 40 VL, 40 PKDL, 10 RVL, 20 cured VL, and 40 cured PKDL along with 10 tuberculosis (TB) cases and 80 healthy endemic controls. Results were compared to those obtained using a Leishmania-specific nested PCR (Ln-PCR). The real time PCR assay was 100% (95% CI, 91.19-100%) sensitive in detecting parasite genomes in VL and RVL samples and 85.0% (95% CI, 70.16-94.29%) sensitive for PKDL samples. In contrast, the sensitivity of Ln-PCR was 77.5% (95% CI, 61.55-89.16%) for VL samples, 100% (95%CI, 69.15-100%) for RVL samples, and 52.5% (95% CI, 36.13-68.49%) for PKDL samples. There was significant discordance between the two methods with the overall sensitivity of the qPCR assay being considerably higher than Ln-PCR. None of the assay detected L. donovani DNA in buffy coats from cured VL cases, and reduced infectious burdens were demonstrated in cured PKDL cases who remained positive in 7.5% (3/40) and 2.5% (1/40) cases by real-time PCR and Ln-PCR, respectively. Both assays were 100% (95% CI, 95.98-100) specific with no positive signals in either endemic healthy control or TB samples. The real time PCR assay we developed offers a molecular tool for accurate detection of circulating L. donovani parasites in VL, PKDL and RVL patients, as well as being capable of assessing response to treatment. As such, this real time PCR assay represents an important contribution in efforts to eliminate VL.

Detection of high Leishmania infantum loads in Phlebotomus perniciosus captured in the leishmaniasis focus of southwestern Madrid region (Spain) by real time PCR

Since 2010 a human leishmaniasis outbreak has been notified in southwestern Madrid region that still remains active. Entomological surveys have been carried out in the affected area in order to obtain information about species diversity, distribution, and density of sand flies. Moreover, molecular identification of blood meal preferences of sand flies and molecular detection of Leishmania infantum has been performed. In this work, we optimized a real time PCR assay in order to determine parasite loads in unfed and blood-fed Phlebotomus perniciosus female sand flies caught in the focus area. Results showed elevated parasite loads in nearly 70% of the studied positive sand flies. Furthermore, significantly higher parasite loads were observed in females without blood in their guts. In conclusion, high L. infantum loads found in P. perniciosus sand flies from the Madrid focus support the exceptional characteristics of this outbreak.

Causes and consequences of higher Leishmania infantum burden in patients with kala-azar: a study of 625 patients

BACKGROUND

An infected host's Leishmania infantum load in blood is considered to be an estimate of his or her total parasite burden. Therefore, the measurement of blood parasite burden is important in the identification of factors involved in parasite control.

METHODS

Quantitative polymerase chain reaction was performed on blood samples from 625 patients with kala-azar consecutively admitted to a reference hospital in Teresina, Brazil. Primers were used to amplify a segment of kDNA using the TaqMan system. Non-parametric statistical tests were applied.

RESULTS

The median blood parasite burden was 499.2 amastigote equivalents (AE)/ml. Children <1 year old (yo) had a high parasite burden, which dropped sharply after the first year of life (192.8, AE/ml at 1 < 2 yo) and remained lower until adolescence. Following adolescence, the parasite burden increased with age, peaking among elderly individuals. Men had a higher parasite burden than women. HIV-infected patients had a much higher parasite burden than non-infected patients. The parasite burden of children under 5 years with acute moderate to severe malnourishment (weight-for-age and body mass index z-scores <-2) was almost three times greater than that of better-nourished children. The parasite burden identified in deceased patients was more than twice that of surviving patients; those with a higher risk of death, sepsis, pneumonia and jaundice also had increased parasite burdens. All of these differences were statistically significant at P-values <0.05.

CONCLUSIONS

These data indicate that the parasite burden in patients with kala-azar was associated with age- and gender-associated factors and with HIV infection status. Acute malnutrition could be either a cause or a consequence of a higher parasite burden. An individual's parasite burden influences his or her clinical profile, disease severity and mortality risk. The best explanation for the presence of a higher parasite burden in individuals with these immunoregulatory conditions and severe disease is the occurrence of acquired immunosuppression followed by heightened innate immunity.

Single locus genotyping to track Leishmania donovani in the Indian subcontinent: Application in Nepal

Background

We designed a straightforward method for discriminating circulating Leishmania populations in the Indian subcontinent (ISC). Research on transmission dynamics of visceral leishmaniasis (VL, or Kala-azar) was recently identified as one of the key research priorities for elimination of the disease in the ISC. VL in Bangladesh, India, and Nepal is caused by genetically homogeneous populations of Leishmania donovani parasites, transmitted by female sandflies. Classical methods to study diversity of these protozoa in other regions of the world, such as microsatellite typing, have proven of little use in the area, as they are not able to discriminate most genotypes. Recently, whole genome sequencing (WGS) so far identified 10 different populations termed ISC001-ISC010.

Methodology / Principle findings

As an alternative to WGS for epidemiological or clinical studies, we designed assays based on PCR amplification followed by dideoxynucleotide sequencing for identification of the non-recombinant genotypes ISC001 up to ISC007. These assays were applied on 106 parasite isolates collected in Nepal between 2011 and 2014. Combined with data from WGS on strains collected in the period 2002–2011, we provide a proof-of-principle for the application of genotyping to study treatment outcome, and differential geographic distribution.

Conclusions / Significance

Our method can aid in epidemiological follow-up of visceral leishmaniasis in the Indian subcontinent, a necessity in the frame of the Kala-azar elimination initiative in the region.

Visceral Leishmaniasis (VL) or Kala-azar is a life-threatening neglected tropical disease that annually affects half a million people worldwide. In the Indian subcontinent (India, Nepal, Bangladesh), the disease is caused by infection with the protozoan parasite Leishmania donovani, which is transmitted by female sand flies. Currently, the Kala-azar elimination program aims at reducing the number of VL cases in the region to less than 1 in 10.000 at upazila, sub-district and district level in Bangladesh, India, and Nepal respectively. In support of this program, tools for tracking L. donovani populations are essential, because these allow monitoring geographic spread over time. However, the parasite populations in the region are highly homogeneous, requiring sequencing of the entire genome to gather sufficient information for discriminating them. Because whole genome sequencing (WGS) is impractical for large-scale use, we designed a simple alternative to identify the WGS-genotypes. Our method is based on PCR amplification followed by sequencing of one particular locus, diagnostic of each population. We provide proof-of-principle that our method can be used to track parasite populations over time, and to correlate them with clinical parameters. We believe that our assay can support the Kala-azar control efforts in the Indian subcontinent.

Inflammatory chemokines and their receptors in human visceral leishmaniasis: Gene expression profile in peripheral blood, splenic cellular sources and their impact on trafficking of inflammatory cells

Chemokines play an important role in determining cellular composition at inflammatory sites, and as such, influence disease outcome. In this study, we investigated the expression profile and splenic cellular source of various inflammatory chemokines and their receptors in human visceral leishmaniasis (VL). The expression of chemokines or their receptors was measured at the gene and protein level by employing real time qPCR and a cytometric bead array assay, respectively. In addition, the cellular source of chemokines and their receptors in the spleen was identified employing gene expression analyses in sequentially selected cell subsets. We identified elevated expression of CXCL10, CXCL9, CXCL8, and decreased CCL2 from VL patients. Further, we found reduced expression of the chemokine receptors CXCR1, CXCR2, CXCR3 and CCR2, but increased expression of CCR7 on VL PBMC, compared to endemic healthy controls. Additionally, splenic monocytes were found to be the major source of CXCL10, CXCL9 and CCR2, whereas T cells were the main source of CXCR3 and CCR7. We also report a strong association between plasma IFN-γ and CXCL-10, CXCL-9 levels. Enhanced parasite burden positively correlates with increased expression of CXCL10, CXCL9, IFN-γ and IL-10. Overall our result indicates that VL patients have an elevated inflammatory chemokine milieu which correlated with disease severity. However, expression of their chemokine receptors was significantly impaired, which may have contributed to reduced frequencies of blood monocytes and neutrophils in peripheral blood. In contrast, enhanced expression of CCR7 was associated with increased numbers of activated T cells in circulation. These findings highlight the importance of chemokines for recruitment of various cell populations in VL, and the knowledge gained may help in global understandings of the complex interaction between chemokines and pathological processes, and therefore will contribute towards the design of novel chemokine based immunological therapies against VL.

Effectiveness of Short-Course Meglumine Antimoniate (Glucantime®) for Treatment of Visceral Leishmaniasis: A 13-Year, Multistage, Non-Inferiority Study in Iran

The World Health Organization's (WHO) recommendation is 28-day course of meglumine antimoniate (Glucantime^®, Sanofi Aventis, France) for the treatment of visceral leishmaniasis (VL). The aim of this study was to evaluate the effectiveness of a shorter duration of treatment in regions with low level of resistance to Glucantime. During 13 years, this study was conducted in three phases on 392 patients. In the pilot first phase, we performed splenic punctures in seven patients to assess the correlation between the changes in the parasite load during treatment with Glucantime and defervescence. With defervescence, parasite density was dramatically dropped (P = 0.014), propounding defervescence as a marker of parasitological response. On the basis of the results, we conducted a randomized trial on 75 patients, comparing the efficacy of continuation of Glucantime therapy for 1, 2, or 3 weeks after defervescence. The treatment course of 1 week after defervescence (mean = 11.7 days) was non-inferior to that of 3 weeks (final cure rate, 96% versus 100%; P = 0.023). The third phase was a retrospective cohort study of 302 patients treated either with the WHO's regimen or for 7 days after defervescence (intervention group). Relapse was detected in 8.3% patients of the intervention group and in 5% patients following the WHO's regimen (P = 0.006 for non-inferiority). The final duration of treatment in intervention group was significantly shorter than standard course (13.3 ± 2.6 versus 28 days; P < 0.001). In summary, treatment of VL with Glucantime for 1 week after defervescence was non-inferior to and appears to be an acceptable alternative to the standard 28-day course for patients in Iran who show a response to antimonial therapy.

A new quantitative PCR method for the detection of Anaplasma platys in dogs based on the citrate synthase gene

Anaplasma platys is an obligate intracellular bacterium that primarily affects dogs, but it can also infect humans. Our study aimed to standardize a quantitative real-time (q)PCR method using the citrate synthase gene (gltA) as a specific target for A. platys detection in naturally infected dogs. Primers (gltA84F and gltA84R) and probe (PLATYSp) were designed to amplify an 84-bp fragment based on the gltA gene sequences of A. platys available in GenBank. A total of 186 dog blood samples originating from the Brazilian state of Rio de Janeiro were tested by qPCR. Additionally, the same samples were tested by cytology and a nested (n)PCR that targeted the 16S ribosomal DNA to determine the performance of our qPCR method compared to these existing techniques. Among the samples tested with qPCR, 17.2% were considered positive, significantly more than detected by nPCR (14.0%). Under optical microscopy, inclusions were observed in platelets of 25.3% of the samples, and among these samples, only 33.9% were identified as positive for A. platys using qPCR. The qPCR technique proved to be more specific than cytology and to have superior sensitivity to nPCR for detecting A. platys in dogs. The development of this new qPCR method contributes to the advancement of research involving A. platys Furthermore, it can be used to quantify the presence of this bacterium to evaluate the treatment of infected animals, or even as a more sensitive and specific tool for situations indicating possible clinical disease but with negative cytology.

Development of real-time PCR assays for evaluation of immune response and parasite load in golden hamster (Mesocricetus auratus) infected by Leishmania (Viannia) braziliensis

Background

Cutaneous leishmaniasis (CL) is a neglected disease with a broad spectrum of clinical manifestations, ranging from small cutaneous nodules to severe mucosal tissue destruction. Leishmania (Viannia) braziliensis is the main species attributed to CL in the Americas. However, studies of experimental infection are limited in the murine model due to the self-resolutive pattern of the disease. Previously, our group demonstrated that the hamster model reproduces many of the clinical and histopathological features observed in humans. Herein, we standardized a RT-qPCR gene expression assay to evaluate a panel of immunological markers and a qPCR assay in order to quantify with high sensitivity and reproducibility the parasite load in skin lesions.

Methods

Hamsters were intradermally infected in the footpad with 10⁵ promastigotes of L. (V.) braziliensis and 110 days post-infection skin lesions and popliteal lymph nodes were removed for RNA and DNA extraction, both from the same tissue fragment. Gene expression of IFN-ɣ, IL-10, TGF-β TNF, IL-4, IL-6, iNOS and arginase were measured using non-infected animal tissue as a calibrator. Parasite load was quantified from DNA extracted from lesions by qPCR targeting Leishmania kDNA and normalized by hamster GAPDH, using a SYBR Green-based absolute quantification methodology.

Results

A relative quantification RT-qPCR assay was standardized for the evaluation of mRNA levels from skin and lymph node samples of golden hamsters, with PCR efficiencies ranging from 92.3 to 116.4 %. In uninfected animals, higher basal mRNA levels in lymph nodes were observed for IFN-ɣ, TGF-β, TNF and IL-4 (111.4 ± 92.2; 5.6 ± 1.2; 5.3 ± 1.7; and 60.3 ± 26.8, respectively) in comparison to skin. In golden hamsters infected with L. (V.) braziliensis, an increase in the expression of all immunological markers evaluated was observed, ranging from 2.7 ± 0.2 for TGF-β to 1018.5 ± 809.0 for iNOS in skin lesions, and 2.4 ± 1.6 for TGF-β to 600.2 ± 666.4 for iNOS in popliteal lymph nodes. Interestingly, significantly higher levels of IFN-ɣ, TNF and IL-10 mRNA were observed in skin in comparison to lymph nodes, while a lower significant level of arginase mRNA was observed in skin. In parallel, parasite loads were quantified by qPCR from the skin lesions of infected animals, ranging from 27.0 to 6647.0, with a median of 553.4 (416.7–1504.0) parasites/mg skin equivalents, whereas lesion size varied from 0.3 to 3.1 mm. Despite the tendency of larger lesions to present higher parasite load, the correlation observed was not statistically significant.

Conclusions

In this study, we describe for the first time a sensitive, reproducible and cheaper molecular assay to quantify from the same tissue fragment the gene expression of immunological markers and the parasite load in skin lesions, observing a mixed profile of immune response in the hamster model infected by L. (V.) braziliensis.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1647-6) contains supplementary material, which is available to authorized users.