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

Spliced-Leader RNA as a Dynamic Marker for Monitoring Viable Leishmania Parasites During and After Treatment

Accurate detection of viable Leishmania parasites is critical for evaluating visceral leishmaniasis (VL) treatment response at an early timepoint. We compared the decay of kinetoplast DNA (kDNA) and spliced-leader RNA (SL-RNA) in vitro, in vivo, and in a VL patient cohort. An optimized combination of blood preservation and nucleic acid extraction improved efficiency for both targets. SL-RNA degraded more rapidly during treatment than kDNA, and correlated better with microscopic examination. SL-RNA quantitative polymerase chain reaction emerges as a superior method for dynamic monitoring of viable Leishmania parasites. It enables individualized treatment monitoring for improved prognoses and has potential as an early surrogate endpoint in clinical trials.

Simplified molecular diagnosis of visceral leishmaniasis: Laboratory evaluation of miniature direct-on-blood PCR nucleic acid lateral flow immunoassay

BACKGROUND

Diagnosis of visceral leishmaniasis (VL) in resource-limited endemic regions is currently based on serological testing with rK39 immunochromatographic tests (ICTs). However, rK39 ICT frequently has suboptimal diagnostic accuracy. Furthermore, treatment monitoring and detection of VL relapses is reliant on insensitive and highly invasive tissue aspirate microscopy. Miniature direct-on-blood PCR nucleic acid lateral flow immunoassay (mini-dbPCR-NALFIA) is an innovative and user-friendly molecular tool which does not require DNA extraction and uses a lateral flow strip for result read-out. This assay could be an interesting candidate for more reliable VL diagnosis and safer test of cure at the point of care.

METHODOLOGY/PRINCIPLE FINDINGS

The performance of mini-dbPCR-NALFIA for diagnosis of VL in blood was assessed in a laboratory evaluation and compared with the accuracy of rK39 ICTs Kalazar Detect in Spain and IT LEISH in East Africa. Limit of detection of mini-dbPCR-NALFIA was 650 and 500 parasites per mL of blood for Leishmania donovani and Leishmania infantum, respectively. In 146 blood samples from VL-suspected patients from Spain, mini-dbPCR-NALFIA had a sensitivity of 95.8% and specificity 97.2%, while Kalazar Detect had a sensitivity of 71.2% and specificity of 94.5%, compared to a nested PCR reference. For a sample set from 58 VL patients, 10 malaria patients and 68 healthy controls from Ethiopia and Kenya, mini-dbPCR-NALFIA had a pooled sensitivity of 87.9% and pooled specificity of 100% using quantitative PCR as reference standard. IT LEISH sensitivity and specificity in the East African samples were 87.9% and 97.4%, respectively.

CONCLUSIONS/SIGNIFICANCE

Mini-dbPCR-NALFIA is a promising tool for simplified molecular diagnosis of VL and follow-up of treated patients in blood samples. Future studies should evaluate its use in endemic, resource-limited settings, where mini-dbPCR-NALFIA may provide an accurate and versatile alternative to rK39 ICTs and aspirate microscopy.

Molecular monitoring of treatment efficacy in human visceral leishmaniasis

BACKGROUND

Focused efforts of the visceral leishmaniasis elimination program have led to a drastic decline in cases, and the present challenge is disease monitoring, which this study aimed to assess.

METHODS

A Leishmania kinetoplastid-targeted qPCR quantified parasite load at disease presentation, and following treatment completion (n=49); an additional 80 cases were monitored after completion of treatment.

RESULTS

The parasite load at disease presentation was 13 461.00 (2560.00-37764.00)/µg gDNA, which upon completion of treatment reduced in 47 of 49 cases to 1(1-1)/µg gDNA, p<0.0001. In 80 cases that presented >2 months post-treatment, their parasite burden similarly decreased to 1(1-1)/µg gDNA except in 6 of 80 cases, which were qPCR positive.

CONCLUSION

In 129 cases of visceral leishmaniasis, qPCR by quantification of parasite burden proved effective for monitoring treatment.

Visceral Leishmaniasis in a Twin Pregnancy: A Case Report and Review of the Literature

Visceral leishmaniasis (VL), often referred to as kala-azar, is quite rare in developed countries during pregnancy. Only few studies have evaluated its impact on perinatal outcome. It is caused primarily by Leishmania donovani or Leishmania infantum and presents with a wide spectrum of clinical manifestations from cutaneous ulcers to multisystem disease. Differential diagnosis is challenging as symptoms and signs are insidious, mimicking other diseases. Misdiagnosis can result in severe adverse perinatal outcomes, even maternal/neonatal death. Early treatment with liposomal amphotericin-B (LAmB) is currently the first choice with adequate effectiveness. We report a rare case of VL in a twin pregnancy with onset at the second trimester, presenting with periodic fever with rigors, right flank pain, and gradual dysregulation of all three cell lines. The positive rK39 enzyme-linked immunosorbent assay test confirmed the diagnosis. Treatment with LAmB resulted in clinical improvement within 48 h and in the delivery of two late-preterm healthy neonates with no symptoms or signs of vertical transmission. The one-year follow-up, of the mother and the neonates, was negative for recurrence. To our knowledge, this is the first reported case of VL in a twin pregnancy, and consequently treatment and perinatal outcome are of great importance.

Leishmania blood parasite dynamics during and after treatment of visceral leishmaniasis in Eastern Africa: A pharmacokinetic-pharmacodynamic model

BACKGROUND

With the current treatment options for visceral leishmaniasis (VL), recrudescence of the parasite is seen in a proportion of patients. Understanding parasite dynamics is crucial to improving treatment efficacy and predicting patient relapse in cases of VL. This study aimed to characterize the kinetics of circulating Leishmania parasites in the blood, during and after different antileishmanial therapies, and to find predictors for clinical relapse of disease.

METHODS

Data from three clinical trials, in which Eastern African VL patients received various antileishmanial regimens, were combined in this study. Leishmania kinetoplast DNA was quantified in whole blood with real-time quantitative PCR (qPCR) before, during, and up to six months after treatment. An integrated population pharmacokinetic-pharmacodynamic model was developed using non-linear mixed effects modelling.

RESULTS

Parasite proliferation was best described by an exponential growth model, with an in vivo parasite doubling time of 7.8 days (RSE 12%). Parasite killing by fexinidazole, liposomal amphotericin B, sodium stibogluconate, and miltefosine was best described by linear models directly relating drug concentrations to the parasite elimination rate. After treatment, parasite growth was assumed to be suppressed by the host immune system, described by an Emax model driven by the time after treatment. No predictors for the high variability in onset and magnitude of the immune response could be identified. Model-based individual predictions of blood parasite load on Day 28 and Day 56 after start of treatment were predictive for clinical relapse of disease.

CONCLUSION

This semi-mechanistic pharmacokinetic-pharmacodynamic model adequately captured the blood parasite dynamics during and after treatment, and revealed that high blood parasite loads on Day 28 and Day 56 after start of treatment are an early indication for VL relapse, which could be a useful biomarker to assess treatment efficacy of a treatment regimen in a clinical trial setting.

The status of combination therapy for visceral leishmaniasis: an updated review

For the past 15 years, trials of combination therapy options for visceral leishmaniasis have been conducted with the aim of identifying effective, and safe treatment regimens that were shorter than existing monotherapy regimens and could also prevent or delay the emergence of drug resistance. Although first-line treatment currently relies on combination therapy in east Africa, this is not true in Latin America owing to disappointing trial results, with lower than expected efficacy seen for the combination treatment group. By contrast, several effective combination therapy regimens have been identified through trials on the Indian subcontinent; yet, first-line therapy is still AmBisome monotherapy as the drug is part of a free donation programme and is highly effective in this region. Achieving a short all-oral combination treatment will require new chemical entities, several of which are currently under evaluation. Future studies should systematically include pharmacological substudies to ensure optimal dosing for all patient groups. To achieve maximal impact of new combination treatments, mechanisms to ensure drug availability and access after trials should be established. Enhancing the longevity of current and novel treatments will require effective systems for early detection of emerging drug resistance.

Safety and efficacy of paromomycin/miltefosine/liposomal amphotericin B combinations for the treatment of post-kala-azar dermal leishmaniasis in Sudan: A phase II, open label, randomized, parallel arm study

BACKGROUND

Treatment for post-kala-azar dermal leishmaniasis (PKDL) in Sudan is currently recommended only for patients with persistent or severe disease, mainly because of the limitations of current therapies, namely toxicity and long hospitalization. We assessed the safety and efficacy of miltefosine combined with paromomycin and liposomal amphotericin B (LAmB) for the treatment of PKDL in Sudan.

METHODOLOGY/PRINCIPAL FINDINGS

An open-label, phase II, randomized, parallel-arm, non-comparative trial was conducted in patients with persistent (stable or progressive disease for ≥ 6 months) or grade 3 PKDL, aged 6 to ≤ 60 years in Sudan. The median age was 9.0 years (IQR 7.0-10.0y) and 87% of patients were ≤12 years old. Patients were randomly assigned to either daily intra-muscular paromomycin (20mg/kg, 14 days) plus oral miltefosine (allometric dose, 42 days)-PM/MF-or LAmB (total dose of 20mg/kg, administered in four injections in week one) and oral miltefosine (allometric dose, 28 days)-LAmB/MF. The primary endpoint was a definitive cure at 12 months after treatment onset, defined as clinical cure (100% lesion resolution) and no additional PKDL treatment between end of therapy and 12-month follow-up assessment. 104/110 patients completed the trial. Definitive cure at 12 months was achieved in 54/55 (98.2%, 95% CI 90.3-100) and 44/55 (80.0%, 95% CI 70.2-91.9) of patients in the PM/MF and AmB/MF arms, respectively, in the mITT set (all randomized patients receiving at least one dose of treatment; in case of error of treatment allocation, the actual treatment received was used in the analysis). No SAEs or deaths were reported, and most AEs were mild or moderate. At least one adverse drug reaction (ADR) was reported in 13/55 (23.6%) patients in PM/MF arm and 28/55 (50.9%) in LAmB/MF arm, the most frequent being miltefosine-related vomiting and nausea, and LAmB-related hypokalaemia; no ocular or auditory ADRs were reported.

CONCLUSIONS/SIGNIFICANCE

The PM/MF regimen requires shorter hospitalization than the currently recommended 60-90-day treatment, and is safe and highly efficacious, even for patients with moderate and severe PKDL. It can be administered at primary health care facilities, with LAmB/MF as a good alternative. For future VL elimination, we need new, safe oral therapies for all patients with PKDL.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03399955, https://clinicaltrials.gov/study/NCT03399955 ClinicalTrials.gov ClinicalTrials.gov.

Clinical performance of a quantitative pan-genus Leishmania Real-time PCR assay for diagnosis of cutaneous and visceral leishmaniasis

Leishmaniasis is a complex vector-borne disease caused by various Leishmania species, affecting humans and animals. Current diagnostic methods have limitations, leading to potential misdiagnosis. Therefore, there is an urgent need for specific and sensitive diagnostic tools. We evaluated the sensitivity of a quantitative real-time PCR (qPCR) assay targeting the 18S gene in diverse clinical sample matrices. The assay showed a wide dynamic range and a limit of detection (LoD) of 1 parasite equivalent per milliliter (eq-p/mL) for all tested species. It exhibited high specificity for Leishmania DNA, with no amplification against other microorganisms. When applied to samples from patients with visceral and cutaneous leishmaniasis, the qPCR assay provided results that matched the reference methods and allowed estimation of parasite burdens. This assay holds promise for diagnosing and monitoring leishmaniasis by offering high sensitivity, specificity, and the ability to estimate parasitemia. Further studies are needed to enhance Leishmania molecular diagnostics and expand their coverage for improved clinical impact.

Leishmania Animal Models Used in Drug Discovery: A Systematic Review

Many different animal models are in use for drug development for leishmaniasis, but a universal model does not exist. There is a plethora of models, and this review assesses their design, quality, and limitations, including the attention paid to animal welfare in the study design and execution. A systematic review was performed following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines of available literature after the year 2000 describing animal models for leishmaniasis. The risk of bias was determined using the SYstematic Review Centre for Laboratory animal Experimentation (SYRCLE) risk of bias assessment tool. A total of 10,980 records were initially identified after searching the databases PubMed, EMBASE, LILACS, and SciELO. Based on the application of predetermined exclusion and inclusion criteria, a total of 203 papers describing 216 animal experiments were available for full analysis. Major reasons for exclusion were a lack of essential study information or appropriate ethical review and approval. Mice (82.8%; an average of 35.9 animals per study) and hamsters (17.1%; an average of 7.4 animals per study) were the most frequently used animals, mostly commercially sourced, in the included studies. All studies lacked a formal sample size analysis. The promastigote stages of L. amazonensis or L. major were most frequently used to establish experimental infections (single inoculum). Animal welfare was poorly addressed in all included studies, as the definition of a human end-point or consideration of the 3Rs (Replacement, Reduction, Refinement) was hardly addressed. Most animals were euthanized at the termination of the experiment. The majority of the studies had an unknown or high risk of bias. Animal experiments for drug development for leishmaniasis mainly poorly designed and of low quality, lack appropriate ethical review, and are deficient in essential information needed to replicate and interpret the study. Importantly, aspects of animal welfare are hardly considered. This underpins the need to better consider and record the details of the study design and animal welfare.

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.

Blood parasite load by qPCR as therapeutic monitoring in visceral leishmaniasis patients in Brazil: a case series study

Background:

This study aimed to describe the kinetics of Leishmania parasite load determined using kinetoplast DNA (kDNA)-based quantitative polymerase chain reaction (qPCR) in visceral leishmaniasis (VL) patients.

Methods:

Parasite load in blood was assessed by qPCR at five time points, up to 12 months post-diagnosis. Sixteen patients were followed up.

Results:

A significant reduction in the parasite load was observed after treatment (P < 0.0001). One patient had an increased parasite load 3 months post-treatment and relapsed clinically at month six.

Conclusions:

We have described the use of kDNA-based qPCR in the post-treatment follow-up of VL cases.

Immunological factors, but not clinical features, predict visceral leishmaniasis relapse in patients co-infected with HIV

Visceral leishmaniasis (VL) has emerged as a clinically important opportunistic infection in HIV patients, as VL/HIV co-infected patients suffer from frequent VL relapse. Here, we follow cohorts of VL patients with or without HIV in Ethiopia. By the end of the study, 78.1% of VL/HIV-but none of the VL patients-experience VL relapse. Despite a clinically defined cure, VL/HIV patients maintain higher parasite loads, lower BMI, hepatosplenomegaly, and pancytopenia. We identify three immunological markers associated with VL relapse in VL/HIV patients: (1) failure to restore antigen-specific production of IFN-γ, (2) persistently lower CD4+ T cell counts, and (3) higher expression of PD1 on CD4+ and CD8+ T cells. We show that these three markers, which can be measured in primary hospital settings in Ethiopia, combine well in predicting VL relapse. The use of our prediction model has the potential to improve disease management and patient care.

Precision Medicine in Control of Visceral Leishmaniasis Caused by L. donovani

Precision medicine and precision global health in visceral leishmaniasis (VL) have not yet been described and could take into account how all known determinants improve diagnostics and treatment for the individual patient. Precision public health would lead to the right intervention in each VL endemic population for control, based on relevant population-based data, vector exposures, reservoirs, socio-economic factors and other determinants. In anthroponotic VL caused by L. donovani, precision may currently be targeted to the regional level in nosogeographic entities that are defined by the interplay of the circulating parasite, the reservoir and the sand fly vector. From this 5 major priorities arise: diagnosis, treatment, PKDL, asymptomatic infection and transmission. These 5 priorities share the immune responses of infection with L. donovani as an important final common pathway, for which innovative new genomic and non-genomic tools in various disciplines have become available that provide new insights in clinical management and in control. From this, further precision may be defined for groups (e.g. children, women, pregnancy, HIV-VL co-infection), and eventually targeted to the individual level.

An update on the clinical pharmacology of miltefosine in the treatment of leishmaniasis

Miltefosine is an alkylphosphocholine agent with a broad spectrum of antiparasitic properties. For over two decades, miltefosine has remained the only oral drug licensed and used in the treatment of the neglected tropical disease, leishmaniasis. The last extensive review of the pharmacology of miltefosine was published in 2012. Additional data on the clinical pharmacokinetics (PK) and pharmacodynamics (PD) of miltefosine have become available in the last decade, and there are ongoing and future studies in this area. Miltefosine PK are characterized by slow absorption and elimination, resulting in accumulation of drug in plasma until the end of treatment. Several recent studies established exposure-response relationships for various regimens of miltefosine in the treatment of visceral and cutaneous leishmaniasis, leading to the identification of PK parameters predictive of clinical relapse and outcome. This review provides an update on the most recent developments in the area of clinical pharmacology of miltefosine, including a discussion of the current dosing regimens.

Loop-Mediated Isothermal Amplification Allows Rapid, Simple and Accurate Molecular Diagnosis of Human Cutaneous and Visceral Leishmaniasis Caused by Leishmania infantum When Compared to PCR

Loop-mediated isothermal amplification allows the rapid, sensitive and specific amplification of DNA without complex and expensive equipment. We compared the diagnostic performance of Loopamp™ Leishmania Detection Kit (Eiken Chemical Co., Ltd., Tokyo, Japan) with conventional and real-time polymerase chain reaction (PCR) for human cutaneous and visceral leishmaniasis caused by L. infantum. A total of 230 DNA samples from cutaneous (CL) and visceral (VL) leishmaniasis cases and controls from Spain, characterized by Leishmania nested PCR (LnPCR) were tested by: (i) the Loopamp™ Leishmania Detection Kit (Loopamp), run on Genie III real-time fluorimeter (OptiGene, UK); and (ii) real-time quantitative PCR (qPCR). The Loopamp test returned 98.8% (95% confidence interval—CI: 96.0–100.00) sensitivity and specificity of 97.7% (95% CI: 92.2–100) on VL samples, and 100% (95% CI: 99.1–100) sensitivity and 100.0% (95% CI: 98.8–100.0) specificity on CL samples. The Loopamp time-to-positivity (Tp) obtained by real-time fluorimetry showed excellent concordance (C = 97.91%) and strong correlation (r = 0.799) with qPCR’s cycle threshold (Ct). The performance of Loopamp is comparable to that of LnPCR and qPCR in the diagnosis of cutaneous and visceral leishmaniasis due to L. infantum. The excellent correlation between the Tp and Ct should be further investigated to determine the accuracy of Loopamp to quantify parasite load in tissues.