Quantifying the Infectiousness of Post-Kala-Azar Dermal Leishmaniasis Toward Sand Flies

Portable smartphone-based molecular test for rapid detection of Leishmania spp

PURPOSE

Leishmaniasis, caused by the parasite of the genus Leishmania, is a neglected tropical disease which is endemic in more than 60 countries. In South-East Asia, Brazil, and East Africa, it mainly occurs as kala-azar (visceral leishmaniasis, VL), and subsequently as post kala-azar dermal leishmaniasis (PKDL) in a smaller portion of cases. As stated per WHO roadmap, accessibility to accurate diagnostic methods is an essential step to achieve elimination. This study aimed to test the accuracy of a portable minoo device, a small battery-driven, multi-use fluorimeter operating with isothermal technology for molecular diagnosis of VL and PKDL.

METHODS

Fluorescence data measured by the device within 20 min are reported back to the mobile application (or app) via Bluetooth and onward via the internet to a backend. This allows anonymous analysis and storage of the test data. The test result is immediately returned to the app displaying it to the user.

RESULTS

The limit of detection was 11.2 genome copies (95% CI) as determined by screening a tenfold dilution range of whole Leishmania donovani genomes using isothermal recombinase polymerase amplification (RPA). Pathogens considered for differential diagnosis were tested and no cross-reactivity was observed. For its diagnostic performance, DNA extracted from 170 VL and PKDL cases, comprising peripheral blood samples (VL, n = 96) and skin biopsies (PKDL, n = 74) from India (n = 108) and Bangladesh (n = 62), was screened. Clinical sensitivity and specificity were 88% and 91%, respectively.

CONCLUSION

Minoo devices can offer a convenient, cheaper alternative to other molecular diagnostics. Its easy handling makes it ideal for use in low-resource settings to identify parasite burden.

Amphotericin B Deoxycholate Treatment of Post-Kala-Azar Dermal Leishmaniasis in India

Post-kala-azar dermal leishmaniasis (PKDL) is widely prevalent in the endemic regions of India, but its treatment remains unsatisfactory. The WHO recommends a 12-week treatment with oral miltefosine, but its ocular toxicities are a serious concern. The late 1980s and early 1990s saw the use of sodium stibogluconate and amphotericin B (AmB) for a brief period. Both drugs had frequent adverse events and were expensive, and the duration of treatments was unacceptably long. This retrospective study evaluated, analyzed, and reported the outcomes of PKDL patients treated with a shorter course of AmB, the most effective antileishmanial drug. The hospital records of PKDL patients treated with AmB by 30 alternate-day infusions over 60 days (instead of conventional 60-80 infusions over 100-120 days) between September 2010 and August 2016 were reviewed. Only patients with confirmed parasitological diagnosis were included. Their records were studied for treatment-related adverse events, end-of-treatment parasitological status, and 12-month follow-up results. One hundred two patients were eligible for this study between September 2010 and August 2016. After therapy, 92/102 (90.2%) patients improved; 3 (2.9%) had to cease treatment owing to severe adverse effects, and one died of severe diarrhea unrelated to AmB. Six (5.9%) patients withdrew consent before the treatment was complete. At the 12-month evaluation, 89/102 (87.3%) patients attained a final cure. A 30-infusion regimen of AmB remains highly effective in PKDL. Without a shorter, safer, and more economical regimen for the treatment of PKDL, it should be used until a better regimen is available.

Skin pharmacokinetics of miltefosine in the treatment of post-kala-azar dermal leishmaniasis in South Asia

INTRODUCTION

Post-kala-azar dermal leishmaniasis (PKDL) arises as a dermal complication following a visceral leishmaniasis (VL) infection. Current treatment options for PKDL are unsatisfactory, and there is a knowledge gap regarding the distribution of antileishmanial compounds within human skin. The present study investigated the skin distribution of miltefosine in PKDL patients, with the aim to improve the understanding of the pharmacokinetics at the skin target site in PKDL.

METHODS

Fifty-two PKDL patients underwent treatment with liposomal amphotericin B (20 mg/kg) plus miltefosine (allometric dosing) for 21 days. Plasma concentrations of miltefosine were measured on study days 8, 15, 22 and 30, while a punch skin biopsy was taken on day 22. A physiologically based pharmacokinetic (PBPK) model was developed to evaluate the distribution of miltefosine into the skin.

RESULTS

Following the allometric weight-based dosing regimen, median miltefosine concentrations on day 22 were 43.73 µg/g (IQR: 21.94-60.65 µg/g) in skin and 33.29 µg/mL (IQR: 25.9-42.58 µg/mL) in plasma. The median individual concentration ratio of skin to plasma was 1.19 (IQR: 0.79-1.9). In 87% (45/52) of patients, skin exposure was above the suggested EC90 PK target of 10.6 mg/L associated with in vitro susceptibility. Simulations indicated that the residence time of miltefosine in the skin would be more than 2-fold longer than in plasma, estimated by a mean residence time of 604 versus 266 hours, respectively.

CONCLUSION

This study provides the first accurate measurements of miltefosine penetration into the skin, demonstrating substantial exposure and prolonged retention of miltefosine within the skin. These findings support the use of miltefosine in cutaneous manifestations of leishmaniasis. In combination with parasitological and clinical data, these results are critical for the future optimization of combination therapies with miltefosine in the treatment of PKDL.

Active Community-Based Case Finding of Endemic Leishmaniasis in West Bengal, India

INTRODUCTION

The ongoing visceral leishmaniasis (VL) elimination programme in India is targeting the elimination of the disease VL but not the pathogen. The persistence of hidden parasite pool may initiate a resurgence in suitable conditions. This study dealt with a novel approach to unearth such pathogen pool and their proper management to prevent the resurgence of VL.

MATERIALS AND METHODS

We deployed a new approach for detection of pathogen pool by following up the VL and post kala-azar dermal leishmaniasis patients treated during the last 10 years along with mass sero-surveillance within a radius of 500 m of recently treated individuals.

RESULTS

We followed up 72.6% (3026/4168) previously treated VL and post kala-azar dermal leishmaniasis patients and diagnosed 42 (1.4%) new and 38 (1.3%) recurrent post kala-azar dermal leishmaniasis. We detected 93 asymptomatic leishmanial infection, 8 VL and 1 post kala-azar dermal leishmaniasis by mass sero-surveillance.

CONCLUSION

Our three-step process including mapping and follow-up of previously treated cases, mass surveillance within 500 m of radius of known cases, and 6 monthly follow-on clinical and serological screening of asymptomatic cases, enabled detection of previously undetected cases of post kala-azar dermal leishmaniasis and VL. Recurrent post kala-azar dermal leishmaniasis deserves special attention regarding their treatment guideline. Early diagnosis and effective treatment of all leishmaniasis cases will hasten pathogen elimination and prevent resurgence of VL. This may help the policymakers to develop appropriate strategy for elimination of pathogen to prevent resurgence of VL.

Visceral Leishmaniasis-Human Immunodeficiency Virus-Coinfected Patients Are Highly Infectious to Sandflies in an Endemic Area in India

In an area endemic with Indian visceral leishmaniasis (VL), we performed direct xenodiagnosis to evaluate the transmission of Leishmania donovani from patients with VL-human immunodeficiency virus (HIV) coinfection to the vector sandflies, Phlebotomus argentipes. Fourteen patients with confirmed VL-HIV coinfection, with a median parasitemia of 42 205 parasite genome/mL of blood, were exposed to 732 laboratory-reared pathogen-free female P argentipes sandflies on their lower arms and legs. Microscopy revealed that 16.66% (122/732) of blood-fed flies were xenodiagnosis positive. Notably, 93% (13/14) of the VL-HIV group infected the flies, as confirmed by quantitative polymerase chain reaction and/or microscopy, and were 3 times more infectious than those who had VL without HIV.

A real-time PCR for quantification of parasite burden and its correlations with clinical characteristics and anti-rKRP42 IgG level in cutaneous leishmaniasis in Sri Lanka

In visceral and mucocutaneous leishmaniasis, humoral immune response can reflect disease severity and parasite burden. Cutaneous leishmaniasis (CL) in Sri Lanka is caused by a usually visceralizing parasite, Leishmania donovani. We assessed the parasite burden (relative quantity-RQ) in 190 CL patients using quantitative real-time PCR (qPCR-with primers designed for this study) and smear microscopy, then correlated it with clinical parameters and IgG response. RQ of parasite DNA was determined with human-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as the internal control. The qPCR sensitivity was tested with serially diluted DNA from cultured L. donovani parasites. Smears were assigned a score based on number of parasites per high power field. Data from previous studies were used for comparison and correlation; nested Internal Transcribed Spacer 1 (ITS1) PCR as reference standard (RS) and IgG antibody titers to the Leishmania rKRp42 antigen as the immune response. The qPCR amplified and quantified 86.8% of the samples while demonstrating a fair and significant agreement with ITS1-PCR and microscopy. Parasite burden by qPCR and microscopy were highly correlated (r = 0.76; p = 0.01) but showed no correlation with the IgG response (r = 0.056; p = 0.48). Corresponding mean RQs of IgG titers grouped by percentiles, showed no significant difference (p = 0.93). Mean RQ was higher in early lesions (p = 0.04), decreased with lesion size (p = 0.12) and slightly higher among papules, nodules and wet ulcers (p = 0.72). Our study established qPCR's efficacy in quantifying parasite burden in Sri Lankan CL lesions but no significant correlation was observed between the parasite burden and host IgG response to the Leishmania rKRP42 antigen.

A phase II, non-comparative randomised trial of two treatments involving liposomal amphotericin B and miltefosine for post-kala-azar dermal leishmaniasis in India and Bangladesh

BACKGROUND

In Southeast Asia, treatment is recommended for all patients with post-kala-azar dermal leishmaniasis (PKDL). Adherence to the first-line regimen, twelve weeks of miltefosine (MF), is low and ocular toxicity has been observed with this exposure period. We assessed the safety and efficacy of two shorter-course treatments: liposomal amphotericin B (LAmB) alone and combined with MF.

METHODOLOGY/PRINCIPAL FINDINGS

An open-label, phase II, randomized, parallel-arm, non-comparative trial was conducted in patients with parasitologically confirmed PKDL, 6 to ≤60 years. Patients were assigned to 20 mg/kg LAmB (total dose, in five injections over 15 days) alone or combined with allometric MF (3 weeks). The primary endpoint was definitive cure at 12 months, defined as complete resolution of papular and nodular lesions and >80% re-pigmentation of macular lesions. Definitive cure at 24 months was a secondary efficacy endpoint. 118/126 patients completed the trial. Definitive cure at 12 months was observed in 29% (18/63) patients receiving LAmB and 30% (19/63) receiving LAmB/MF (mITT), increasing to 58% and 66%, respectively, at 24 months. Most lesions had resolved/improved at 12 and 24 months for patients receiving LAmB (90%, 83%) and LAmB/MF (85%, 88%) by qualitative assessment. One death, unrelated to study drugs, was reported; no study drug-related serious adverse events were observed. The most frequent adverse drug reactions were MF-related vomiting and nausea, and LAmB-related hypokalaemia and infusion reactions. Most adverse events were mild; no ocular adverse events occurred.

CONCLUSIONS/SIGNIFICANCE

Both regimens are suitably safe and efficacious alternatives to long-course MF for PKDL in South Asia.

TRIAL REGISTRATION

CTRI/2017/04/008421.

The Hidden Hand of Asymptomatic Infection Hinders Control of Neglected Tropical Diseases: A Modeling Analysis

BACKGROUND

Neglected tropical diseases are responsible for considerable morbidity and mortality in low-income populations. International efforts have reduced their global burden, but transmission is persistent and case-finding-based interventions rarely target asymptomatic individuals.

METHODS

We develop a generic mathematical modeling framework for analyzing the dynamics of visceral leishmaniasis in the Indian sub-continent (VL), gambiense sleeping sickness (gHAT), and Chagas disease and use it to assess the possible contribution of asymptomatics who later develop disease (pre-symptomatics) and those who do not (non-symptomatics) to the maintenance of infection. Plausible interventions, including active screening, vector control, and reduced time to detection, are simulated for the three diseases.

RESULTS

We found that the high asymptomatic contribution to transmission for Chagas and gHAT and the apparently high basic reproductive number of VL may undermine long-term control. However, the ability to treat some asymptomatics for Chagas and gHAT should make them more controllable, albeit over relatively long time periods due to the slow dynamics of these diseases. For VL, the toxicity of available therapeutics means the asymptomatic population cannot currently be treated, but combining treatment of symptomatics and vector control could yield a quick reduction in transmission.

CONCLUSIONS

Despite the uncertainty in natural history, it appears there is already a relatively good toolbox of interventions to eliminate gHAT, and it is likely that Chagas will need improvements to diagnostics and their use to better target pre-symptomatics. The situation for VL is less clear, and model predictions could be improved by additional empirical data. However, interventions may have to improve to successfully eliminate this disease.

Monitoring the Long-Term Effectiveness of Miltefosine in Indian Post-Kala-Azar Dermal Leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL), the dermal sequel to visceral leishmaniasis (VL), is characterized by hypopigmented macules (macular) and/or papules and nodules (polymorphic). Post-kala-azar dermal leishmaniasis plays a significant role in disease transmission, emphasizing the need for monitoring chemotherapeutic effectiveness. Accordingly, this study aimed to quantify the parasite burden in PKDL patients after treatment with miltefosine by a quantitative polymerase chain reaction (qPCR). A Leishmania kinetoplastid gene-targeted qPCR was undertaken using DNA from skin biopsy specimens of patients with PKDL at three time points, i.e., at disease presentation (week 0, n = 157, group 1), upon completion of treatment (week 12, n = 39, group 2), and at any time point 6 months after completion of treatment (week ≥36, n = 54, group 3). A cycle threshold (Ct) <30 was considered the cutoff for positivity, and load was quantified as the number of parasites/µg genomic DNA (gDNA); cure was considered when samples had a Ct >30. The parasite load at disease presentation (group 1) was 10,769 (1,339-80,441)/µg gDNA (median [interquartile range]). In groups 2 and 3, qPCR results were negative in 35/39 cases (89.7%) and 48/54 cases (88.8%), respectively. In the 10/93 (10.8%) qPCR-positive cases, the parasite burdens in groups 2 and 3 were 2,420 (1,205-5,661)/µg gDNA and 22,195 (5,524-100,106)/µg gDNA, respectively. Serial monitoring was undertaken in 45 randomly selected cases that had completed treatment; all cases in groups 2 or 3 had a Ct >30, indicating cure. Overall, qPCR confirmed an 89.2% cure (as 83/93 cases showed parasite clearance), and the persistent qPCR positivity was attributed to nonadherence to treatment or unresponsiveness to miltefosine and remains to be investigated.

Post-kala-azar dermal leishmaniasis (PKDL) drug efficacy study landscape: A systematic scoping review of clinical trials and observational studies to assess the feasibility of establishing an individual participant-level data (IPD) platform

BACKGROUND

Post-kala-azar dermal leishmaniasis (PKDL) is a dermatosis which can occur after successful treatment of visceral leishmaniasis (VL) and is a public health problem in VL endemic areas. We conducted a systematic scoping review to assess the characteristics of published PKDL clinical studies, understand the scope of research and explore the feasibility and value of developing a PKDL individual patient data (IPD) platform.

METHODS

A systematic review of published literature was conducted to identify PKDL clinical studies by searching the following databases: PubMed, Scopus, Ovid Embase, Web of Science Core Collection, WHO Global Index Medicus, PASCAL, Clinicaltrials.gov, Ovid Global Health, Cochrane Database and CENTRAL, and the WHO International Clinical Trials Registry Platform. Only prospective studies in humans with PKDL diagnosis, treatment, and follow-up measurements between January 1973 and March 2023 were included. Extracted data includes variables on patient characteristics, treatment regimens, diagnostic methods, geographical locations, efficacy endpoints, adverse events and statistical methodology.

RESULTS

A total of 3,418 records were screened, of which 56 unique studies (n = 2,486 patients) were included in this review. Out of the 56 studies, 36 (64.3%) were from India (1983-2022), 12 (21.4%) from Sudan (1992-2021), 6 (10.7%) were from Bangladesh (1991-2019), and 2 (3.6%) from Nepal (2001-2007). Five (8.9%) studies were published between 1981-1990 (n = 193 patients), 10 (17.9%) between 1991-2000 (n = 230 patients), 10 (17.9%) between 2001-2010 (n = 198 patients), and 31 (55.4%) from 2011 onwards (n = 1,865 patients). Eight (14.3%) were randomised clinical trials, and 48 (85.7%) were non-randomised studies. The median post-treatment follow-up duration was 365 days (range: 90-540 days) in 8 RCTs and 360 days (range: 28-2,373 days) in 48 non-randomised studies. Disease diagnosis was based on clinical criterion in 3 (5.4%) studies, a mixture of clinical and parasitological methods in 47 (83.9%) and was unclear in 6 (10.7%) studies. Major drugs used for treatment were miltefosine (n = 636 patients), liposomal amphotericin B (L-AmB) (n = 508 patients), and antinomy regimens (n = 454 patients). Ten other drug regimens were tested in 270 patients with less than 60 patients per regimen.

CONCLUSIONS

Our review identified studies with very limited sample size for the three major drugs (miltefosine, L-AmB, and pentavalent antimony), while the number of patients combined across studies suggest that the IPD platform would be valuable. With the support of relevant stakeholders, the global PKDL community and sufficient financing, a PKDL IPD platform can be realised. This will allow for exploration of different aspects of treatment safety and efficacy, which can potentially guide future healthcare decisions and clinical practices.

Challenges for maintaining post elimination phase of visceral leishmaniasis control programme in India: A field-based study

BACKGROUND

India is going through the maintenance phase of VL elimination programme which may be threatened by the persistence of hidden parasite pools among asymptomatic leishmanial infection (ALI) and PKDL. The present work was designed to determine the burden of VL, PKDL, and ALI and to assess the role of treatment of ALI in maintaining post-elimination phase.

METHODS AND FINDING

The study was undertaken in Malda district, West Bengal, India during October 2016 to September 2021. Study areas were divided into 'Study' and 'Control' arms. VL and PKDL cases of both the arms were diagnosed by three active mass surveys with an interval of one year and treated as per National guideline. ALI of 'Study' arm was treated like VL. ALI of 'Control' arm was followed up to determine their fate. Fed sand-fly pools were analysed for parasitic DNA. No significant difference was noted between the incidence of VL and PKDL in both the arms. Incidence of ALI declined sharply in 'Study' arm but an increasing trend was observed in 'Control' arm. Significantly higher rate of sero-conversion was noted in 'Control' arm and was found to be associated with untreated ALI burden. Parasitic DNA was detected in 22.8% ALI cases and 2.2% sand-fly pools.

CONCLUSION

Persistence of a significant number of PKDL and ALI and ongoing transmission, as evidenced by new infection and detection of leishmanial DNA in vector sand-flies, may threaten the maintenance of post-elimination phase. Emphasis should be given for elimination of pathogen to prevent resurgence of VL epidemics.

Dermal microdialysis: A method to determine drug levels in the skin of patients with Post kala-azar dermal leishmaniasis (PKDL)

OBJECTIVES

Post-kala-azar-dermal leishmaniasis (PKDL) is an infectious skin disease that occurs as sequela of visceral leishmaniasis (VL) and causes cutaneous lesions on the face and other exposed body parts. While the first-line drug miltefosine is typically used for 28 days to treat VL, 12 weeks of therapy is required for PKDL, highlighting the need to evaluate the extent of drug penetration at the dermal site of infection. In this proof-of-concept study, we demonstrate the use of a minimally invasive sampling technique called microdialysis to measure dermal drug exposure in a PKDL patient, providing a tool for the optimization of treatment regimens.

METHODS AND MATERIALS

One PKDL patient receiving treatment with miltefosine (50 mg twice daily for 12 weeks) was recruited to this proof-of-concept study and consented to undergo dermal microdialysis. Briefly, a μDialysis Linear Catheter 66 for skin and muscle, a probe with a semi-permeable membrane, was inserted in the dermis. A perfusate (a drug-free physiological solution) was pumped through the probe at a low flow rate, allowing miltefosine present in the dermis to cross the membrane and be collected in the dialysates over time. Protein-free (dialysates) and total (blood and skin biopsies) drug concentrations were analysed using LC-MS/MS.

RESULTS

and conclusions: Using microdialysis, protein-free miltefosine drug concentrations could be detected in the infected dermis over time (Cmax ≈ 450 ng/ml). This clinical proof-of-concept study thus illustrates the potential of dermal microdialysis as a minimally invasive alternative to invasive skin biopsies to quantify drug concentrations directly at the pharmacological site of action in PKDL.

Epidemiological, serological, and entomological aspects of visceral leishmaniasis (VL) in suspected new VL foci in Bangladesh

The study aimed to explore epidemiological, serological, and entomological aspects of visceral leishmaniasis (VL) in suspected new VL foci and assess the knowledge, attitude, and practices of the community living in the alleged new VL foci. The study investigated new visceral leishmaniasis (VL) cases reported between 2019 and 2020 in four sub-districts (Dharmapasha, Hakimpur, Islampur and Savar) where we tested 560 members using the rK39 rapid test and conducted vector collections in six neighbouring houses of the index cases to assess sandfly density and distribution, examined sandflies' infection, and determined the spatial relationship with VL infection. Furthermore, we highlighted the importance of early detection, and community awareness in controlling the spread of the disease. The study screened 1078 people from 231 households in the four sub-districts for fever, history of visceral leishmaniasis (VL), and PKDL-like skin lesions. Among sub-districts, positivity rate for rK39 rapid test was highest (3.5 %) in Savar. Sandflies were present across all areas except in Dharmapasha, but all 21 collected female P. argentipes sandflies were negative for Leishmania parasite DNA. We found one person from Islampur with a history of VL, and one from Islampur and another one from Savar had PKDL. After the awareness intervention, more people became familiar with VL infection (91.2 %), and their knowledge concerning sandflies being the vector of the disease and the risk of having VL increased significantly (30.1 %). The study found no active case in the suspected new foci, but some asymptomatic individuals were present. As sandfly vectors exist in these areas, the National Kala-azar Elimination Programme (NKEP) should consider these areas as kala-azar endemic and initiate control activities as per national guidelines.

Vaccine value profile for leishmaniasis

Leishmania infections are global, occurring in 98 countries and all World Health Organization (WHO) regions with 600 million to 1 billion people at risk of infection. Visceral leishmaniasis is associated with almost 20,000 reported deaths annually, with children under 5 years of age being at the greatest risk of mortality. Amongst WHO-recognised Neglected Tropical Diseases (NTDs), leishmaniasis is one of the most important in terms of mortality and morbidity. With an increasing global burden of disease and a growing threat from climate change, urbanisation and drug resistance, there remains an imperative to develop leishmaniasis vaccines. New tools to understand correlates of protection and to assess vaccine efficacy are being developed to ease the transition into larger scale efficacy trials or provide alternate routes to licensure. Early indications suggest a diverse portfolio of manufacturers exists in endemic countries with an appetite to develop leishmaniasis vaccines. This Vaccine Value Profile (VVP) provides a high-level, comprehensive assessment of the currently available data to inform the potential public health, economic, and societal value of leishmaniasis vaccines. The leishmaniasis VVP was developed by a working group of subject matter experts from academia, public health groups, policy organizations, and non-profit organizations. All contributors have extensive expertise on various elements of the leishmaniasis VVP and have collectively described the state of knowledge and identified the current gaps. The VVP was developed using only existing and publicly available information.

Assessment of treatment outcomes of visceral leishmaniasis (VL) treated cases and impact of COVID-19 on VL management and control services in Bangladesh

BACKGROUND

COVID-19 has largely impacted the management of Visceral leishmaniasis (VL), like several other Neglected Tropical Diseases. The impact was particularly evident in Lower and Middle-Income countries where the already inadequate healthcare resources were diverted to managing the COVID-19 pandemic. Bangladesh achieved the elimination target for VL in 2016. To sustain this success, early diagnosis and treatment, effective vector control, and periodic surveillance are paramount. However, the specific control measures for VL in Bangladesh that were hampered during COVID-19 and their extent are unknown.

METHODS

This study aimed at identifying the gaps and challenges in the follow-up of treated VL patients by interviewing both the treated VL cases and their health service providers. We followed VL cases treated between 2019 and 2020 in five VL endemic subdistricts (upazilas) both retrospectively and prospectively to monitor clinical improvement, relapse, or other consequences. Moreover, interviews were conducted with the health service providers to assess the impact of COVID-19 on VL case detection, treatment, reporting, vector control operations, and logistic supply chain management.

RESULTS

There was no added delay for VL diagnosis; however, VL treatment initiation and reporting time increased almost two-fold due to COVID-19. Indoor Residual Spraying activity was significantly hampered due to a shortage of insecticides. Out of 44 enrolled and treated VL patients, two relapsed (4.5 %), two developed Para Kala-Azar Dermal Leishmaniasis (4.5 %), and three (6.8 %) Post Kala-Azar Dermal Leishmaniasis (PKDL). The health service providers highlighted patients` unwillingness to visit the hospital, financial constraints, and distance from the hospitals as the main reasons for missed follow-up visits (20.5 %). Building good communication in the community, awareness schemes, and incentive-based approaches were suggested as possible solutions to mitigate these problems.

CONCLUSION

Long-term follow-up is required for the early detection and management of VL relapse and PKDL cases. Effective vector control measures, capacity development, and identification of new VL hotspots are pivotal in the VL endemic regions to sustain the elimination goal.

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.

Post kala-azar dermal leishmaniasis in the Indian sub-continent: challenges and strategies for elimination

Visceral leishmaniasis (VL) is a severe and often fatal form of leishmaniasis caused by Leishmania donovani in the Indian sub-continent. Post Kala-azar Dermal Leishmaniasis (PKDL) is a late cutaneous manifestation of VL, typically occurring after apparent cure of VL, but sometimes even without a prior history of VL in India. PKDL serves as a significant yet neglected reservoir of infection and plays a crucial role in the transmission of the disease, posing a serious threat to the VL elimination program in the Indian sub-continent. Therefore, the eradication of PKDL should be a priority within the current VL elimination program aimed at achieving a goal of less than 1 case per 10,000 in the population at the district or sub-district levels of VL endemic areas. To accomplish this, a comprehensive understanding of the pathogenesis of PKDL is essential, as well as developing strategies for disease management. This review provides an overview of the current status of diagnosis and treatment options for PKDL, highlighting our current knowledge of the immune responses underlying disease development and progression. Additionally, the review discusses the impact of PKDL on elimination programs and propose strategies to overcome this challenge and achieve the goal of elimination. By addressing the diagnostic and therapeutic gaps, optimizing surveillance and control measures, and implementing effective intervention strategies, it is possible to mitigate the burden of PKDL and facilitate the successful elimination of VL in the Indian sub-continent.

Social determinants of visceral leishmaniasis elimination in Eastern Africa

Visceral leishmaniasis is a vector-borne, protozoan disease with severe public health implications. Following the successful implementation of an elimination programme in South Asia, there is now a concerted endeavour to replicate these efforts in Eastern Africa based on the five essential elimination pillars of case management, integrated vector management, effective surveillance, social mobilisation and operational research. This article highlights how key social determinants (SD) of health (poverty, sociocultural factors and gender, housing and clustering, migration and the healthcare system) operate at five different levels (socioeconomic context and position, differential exposure, differential vulnerability, differential outcomes and differential consequences). These SD should be considered within the context of increasing the success of the five-pillar elimination programme and reducing inequity in health.

Safety and Effectiveness of Miltefosine in Post-Kala-Azar Dermal Leishmaniasis: An Observational Study

Background

Post-kala-azar dermal leishmaniasis (PKDL) is a dermal complication of visceral leishmaniasis. Oral miltefosine (MF) is the first-line treatment for PKDL patients in South Asia. This study assessed the safety and effectiveness of MF therapy after 12 months of follow-up to explore more precise data.

Methods

In this observational study, 300 confirmed PKDL patients were enrolled. MF with the usual dose was administered to all patients for 12 weeks and followed up for 1 year. Clinical evolution was recorded systematically by photographs at screening and at 12 weeks, 6 months, and 12 months after treatment onset. Definitive cure consisted of disappearance of skin lesions with a negative PCR at 12 weeks or with >70% of lesions, disappearing or fading at 12-month follow-up. Patients with reappearing clinical features and any positive diagnostics of PKDL during the follow-up were considered as nonresponsive.

Results

Among 300 patients, 286 (95.3%) completed 12 weeks of treatment. The per-protocol cure rate at 12 months was 97%, but 7 patients relapsed and 51 (17%) were lost to 12-month follow-up, resulting in a final cure rate of only 76%. Eye-related adverse events were noted in 11 (3.7%) patients and resolved in most (72.7%) within 12 months. Unfortunately, 3 patients had persistent partial vision loss. Mild to moderate gastrointestinal side effects were seen in 28% patients.

Conclusions

Moderate effectiveness of MF was observed in the present study. A significant number of patients developed ocular complications, and thus MF for treatment for PKDL should be suspended and replaced with a safer alternative regimen.

Prevalence of post kala-azar dermal leishmaniasis (PKDL) and treatment seeking behavior of PKDL patients in Nepal

BACKGROUND

In Nepal, the burden of post kala-azar dermal leishmaniasis (PKDL) is not known since there is no active case detection of PKDL by the national programme. PKDL patients could pose a challenge to sustain visceral leishmaniasis (VL) elimination. The objective of this study was to determine the prevalence of PKDL and assess PKDL patients' knowledge on VL and PKDL, and stigma associated with PKDL.

METHODOLOGY/PRINCIPAL FINDINGS

Household surveys were conducted in 98 VL endemic villages of five districts that reported the highest number of VL cases within 2018-2021. A total of 6,821 households with 40373 individuals were screened for PKDL. Cases with skin lesions were referred to hospitals and examined by dermatologists. Suspected PKDL cases were tested with rK39 and smear microscopy from skin lesions. An integrated diagnostic approach was implemented in two hospitals with a focus on management of leprosy cases where cases with non-leprosy skin lesions were tested for PKDL with rK39. Confirmed PKDL patients were interviewed to assess knowledge and stigma associated with PKDL, using explanatory model interview catalogue (EMIC) with maximum score of 36. Among 147 cases with skin lesions in the survey, 9 (6.12%) were confirmed as PKDL by dermatologists at the hospital. The prevalence of PKDL was 2.23 per 10,000 population. Among these 9 PKDL cases, 5 had a past history of VL and 4 did not. PKDL cases without a past history of VL were detected among the "new foci", Surkhet but none in Palpa. None of the cases negative for leprosy were positive for PKDL. There was very limited knowledge of PKDL and VL among PKDL cases. PKDL patients suffered to some degree from social and psychological stigma (mean ± s.d. score = 17.89 ± 12.84).

CONCLUSIONS/SIGNIFICANCE

Strengthening the programme in PKDL case detection and management would probably contribute to sustenance of VL elimination. Awareness raising activities to promote knowledge and reduce social stigma should be conducted in VL endemic areas.

Does immune dysregulation contribute towards development of hypopigmentation in Indian post kala-azar dermal leishmaniasis?

Post kala-azar dermal leishmaniasis (PKDL), a sequel of apparently cured visceral leishmaniasis (VL) presents with papulonodular (polymorphic) or hypopigmented lesions (macular) and is the proposed disease reservoir. As hypopigmentation appears consistently in PKDL, especially the macular form, this study aimed to delineate immune factors that singly or in combination could contribute towards this hypopigmentation. At lesional sites, the presence of melanocytes and CD8⁺ T-cells was assessed by immunohistochemistry and mRNA expression of melanogenic markers (tyrosinase, tyrosinase-related protein-1 and MITF) by droplet digital PCR, while plasma levels of cytokines and chemokines were measured by a multiplex assay. In comparison with skin from healthy individuals, macular PKDL demonstrated a near total absence of Melan-A⁺ cells at dermal sites, while the polymorphic cases demonstrated a 3.2-fold decrease, along with a dramatic reduction in the expression of key enzymes related to the melanogenesis signalling pathway in both forms. The levels of circulating IFN-γ, IL-6, IL-2, IL-1β, TNF-α and IFN-γ-inducible chemokines (CXCL9/10/11) were elevated and was accompanied by an increased lesional infiltration of CD8⁺ T-cells. The proportion of CD8⁺ T-cells correlated strongly with plasma levels of IFN-γ (r = 0.8), IL-6 (r = 0.9, p < 0.05), IL-2 (r = 0.7), TNF-α (r = 0.9, p < 0.05) and IL-1β (r = 0.7), as also with CXCL9 (r = 0.5) and CXCL10 (r = 0.6). Taken together, the absence/reduction in Melan-A suggested hypopigmentation in PKDL was associated with the destruction of melanocytes, following the impairment of the melanogenesis pathway. Furthermore, the presence of CD8⁺ T-cells and an enhanced IFN-γ-associated immune milieu suggested the generation of a pro-inflammatory landscape that facilitated melanocyte dysfunction/destruction.

Challenges of using modelling evidence in the visceral leishmaniasis elimination programme in India

As India comes closer to the elimination of visceral leishmaniasis (VL) as a public health problem, surveillance efforts and elimination targets must be continuously revised and strengthened. Mathematical modelling is a compelling research discipline for informing policy and programme design in its capacity to project incidence across space and time, the likelihood of achieving benchmarks, and the impact of different interventions. To gauge the extent to which modelling informs policy in India, this qualitative analysis explores how and whether policy makers understand, value, and reference recently produced VL modelling research. Sixteen semi-structured interviews were carried out with both users- and producers- of VL modelling research, guided by a knowledge utilisation framework grounded in knowledge translation theory. Participants reported that barriers to knowledge utilisation include 1) scepticism that models accurately reflect transmission dynamics, 2) failure of modellers to apply their analyses to specific programme operations, and 3) lack of accountability in the process of translating knowledge to policy. Political trust and support are needed to translate knowledge into programme activities, and employment of a communication intermediary may be a necessary approach to improve this process.

A Composite Recombinant Salivary Proteins Biomarker for Phlebotomus argentipes Provides a Surveillance Tool Postelimination of Visceral Leishmaniasis in India

Incidence of visceral leishmaniasis (VL) in the Indian subcontinent (ISC) has declined by more than 95% since initiation of the elimination program in 2005. As the ISC transitions to the postelimination surveillance phase, an accurate measurement of human-vector contact is needed to assure long-term success. To develop this tool, we identified PagSP02 and PagSP06 from saliva of Phlebotomus argentipes, the vector of Leishmania donovani in the ISC, as immunodominant proteins in humans. We also established the absence of cross-reactivity with Phlebotomus papatasi saliva, the only other human-biting sand fly in the ISC. Importantly, by combining recombinant rPagSP02 and rPagSP06 we achieved greater antibody recognition and specificity than single salivary proteins. The receiver operating characteristics curve for rPagSP02 + rPagSP06 predicts exposure to Ph. argentipes bites with 90% specificity and 87% sensitivity compared to negative control sera (P >.0001). Overall, rPagSP02 + rPagSP06 provides an effective surveillance tool for monitoring vector control efforts after VL elimination.

Immune recovery-related patterns of post kala-azar dermal and ocular leishmaniasis in people living with HIV

OBJECTIVE

Post kala-azar dermal leishmaniasis (PKDL) is a rare complication of visceral leishmaniasis. We aimed at reporting PKDL cases in people living with HIV (PLHIV) and compare their characteristics based on whether PKDL occurred in the context of immune recovery under antiretroviral therapy (ART) or not.

DESIGN

National survey and literature review.

METHODS

We called for observations in France in October 2020 and performed a literature review from PubMed (Medline) and Web of Science up to December 2020. Two groups of patients were defined based on whether PKDL occurred in the context of immune recovery under ART (group 1) or not (group 2), and compared.

RESULTS

Three PLHIV with PKDL identified in France in the last decade were described and added to 33 cases from the literature. Compared with group 2 (16/36, 44.4%), patients from group 1 (20/36, 55.6%) originated more frequently from Europe (12/20, 60% vs. 2/16, 12.5%; P  = 0.0038), had higher median blood CD4 + cell counts (221/μl vs. 61/μl; P  = 0.0005) and increase under ART (122/μl, interquartile range 73-243 vs. 33/μl, interquartile range 0-53; P  = 0.0044), had less frequently concomitant visceral leishmaniasis (3/20, 15% vs. 8/12, 66.7%; P  = 0.006), and a trend to more frequent ocular involvement (7/20, 35% vs. 1/16, 6.25%; P  = 0.0531).

CONCLUSION

In PLHIV, PKDL occurs after a cured episode of visceral leishmaniasis as part of an immune restoration disease under ART, or concomitant to a visceral leishmaniasis relapse in a context of AIDS. For the latter, the denomination 'disseminated cutaneous lesions associated with visceral leishmaniasis' seems more accurate than PKDL.

Gauging the skin resident Leishmania parasites through a loop mediated isothermal amplification (LAMP) assay in post-kala-azar dermal leishmaniasis

Despite the availability of highly sensitive polymerase chain reaction (PCR)-based methods, the dearth of remotely deployable diagnostic tools circumvents the early and accurate detection of individuals with post-kala-azar dermal leishmaniasis (PKDL). Here, we evaluate a design-locked loop-mediated isothermal amplification (LAMP) assay to diagnose PKDL. A total of 76 snip-skin samples collected from individuals with probable PKDL (clinical presentation and a positive rK39 rapid diagnostic test (RDT)) were assessed by microscopy, qPCR, and LAMP. An equal number of age and sex-matched healthy controls were included to determine the specificity of the LAMP assay. The LAMP assay with a Qiagen DNA extraction (Q-LAMP) showed a promising sensitivity of 72.37% (95% CI: 60.91-82.01%) for identifying the PKDL cases. LAMP assay sensitivity declined when the DNA was extracted using a boil-spin method. Q-qPCR showed 68.42% (56.75-78.61%) sensitivity, comparable to LAMP and with an excellent agreement, whereas the microscopy exhibited a weak sensitivity of 39.47% (28.44-51.35%). When microscopy and/or qPCR were considered the gold standard, Q-LAMP exhibited an elevated sensitivity of 89.7% (95% CI: 78.83-96.11%) for detection of PKDL cases and Bayesian latent class modeling substantiated the excellent sensitivity of the assay. All healthy controls were found to be negative. Notwithstanding the optimum efficiency of the LAMP assay towards the detection of PKDL cases, further optimization of the boil-spin method is warranted to permit remote use of the assay.

Livestock and rodents within an endemic focus of Visceral Leishmaniasis are not reservoir hosts for Leishmania donovani

Leishmaniasis on the Indian subcontinent is thought to have an anthroponotic transmission cycle. There is no direct evidence that a mammalian host other than humans can be infected with Leishmania donovani and transmit infection to the sand fly vector. The aim of the present study was to evaluate the impact of sand fly feeding on other domestic species and provide clinical evidence regarding possible non-human reservoirs through experimental sand fly feeding on cows, water buffalo goats and rodents. We performed xenodiagnosis using colonized Phlebotomus argentipes sand flies to feed on animals residing in villages with active Leishmania transmission based on current human cases. Xenodiagnoses on mammals within the endemic area were performed and blood-fed flies were analyzed for the presence of Leishmania via qPCR 48hrs after feeding. Blood samples were also collected from these mammals for qPCR and serology. Although we found evidence of Leishmania infection within some domestic mammals, they were not infectious to vector sand flies. Monitoring infection in sand flies and non-human blood meal sources in endemic villages leads to scientific proof of exposure and parasitemia in resident mammals. Lack of infectiousness of these domestic mammals to vector sand flies indicates that they likely play no role, or a very limited role in Leishmania donovani transmission to people in Bihar. Therefore, a surveillance system in the peri-/post-elimination phase of visceral leishmaniasis (VL) must monitor absence of transmission. Continued surveillance of domestic mammals in outbreak villages is necessary to ensure that a non-human reservoir is not established, including domestic mammals not present in this study, specifically dogs.

Selective Anti-Leishmanial Strathclyde Minor Groove Binders Using an N-Oxide Tail-Group Modification

The neglected tropical disease leishmaniasis, caused by Leishmania spp., is becoming more problematic due to the emergence of drug-resistant strains. Therefore, new drugs to treat leishmaniasis, with novel mechanisms of action, are urgently required. Strathclyde minor groove binders (S-MGBs) are an emerging class of anti-infective agent that have been shown to have potent activity against various bacteria, viruses, fungi and parasites. Herein, it is shown that S-MGBs have potent activity against L. donovani, and that an N-oxide derivation of the tertiary amine tail of typical S-MGBs leads to selective anti-leishmanial activity. Additionally, using S-MGB-219, the N-oxide derivation is shown to retain strong binding to DNA as a 2:1 dimer. These findings support the further study of anti-leishmanial S-MGBs as novel therapeutics.

LEISH2b - A phase 2b study to assess the safety, efficacy, and immunogenicity of the Leishmania vaccine ChAd63-KH in post-kala azar dermal leishmaniasis

Background: The leishmaniases are neglected tropical diseases caused by various Leishmania parasite species transmitted by sand flies. They comprise a number of systemic and cutaneous syndromes including kala-azar (visceral leishmaniasis, VL), cutaneous leishmaniasis (CL), and post-kala-azar dermal leishmaniasis (PKDL). The leishmaniases cause significant mortality (estimated 20 - 50,000 deaths annually), morbidity, psychological sequelae, and healthcare and societal costs. Treatment modalities remain difficult. E.g., East African PKDL requires 20 days of intravenous therapy, and frequently relapsing VL is seen in the setting of HIV and immunodeficiency. We developed a new therapeutic vaccine, ChAd63-KH for VL / CL / PKDL and showed it to be safe and immunogenic in a phase 1 trial in the UK, and in a phase 2a trial in PKDL patients in Sudan.    Methods: This is a randomised double-blind placebo-controlled phase 2b trial to assess the therapeutic efficacy and safety of ChAd63-KH in patients with persistent PKDL in Sudan. 100 participants will be randomly assigned 1:1 to receive placebo or ChAd63-KH (7.5 x10 10vp i.m.) at a single time point. Follow up is for 120 days after dosing and we will compare the clinical evolution of PKDL, as well as the humoral and cellular immune responses between the two arms. Discussion: Successful development of a therapeutic vaccine for leishmaniasis would have wide-ranging direct and indirect healthcare benefits that could be realized rapidly. For PKDL patients, an effective therapeutic vaccination used alone   would have very significant clinical value, reducing the need for extensive hospitalization and chemotherapy. Combining vaccine with drug (immuno-chemotherapy) might significantly increase the effective life of new drugs, with lower dose / abbreviated regimens helping to limit the emergence of drug resistance. If therapeutic benefit of ChAd63-KH can be shown in PKDL further evaluation of the vaccine in other forms of leishmaniasis should be considered. Clinicaltrials.gov registration: NCT03969134.

Quantitative monitoring of experimental and human leishmaniasis employing amastigote-specific genes

The gold standard for diagnosis of leishmaniasis is the microscopic detection of amastigotes/Leishman Donovan (LD) bodies, but its moderate sensitivity necessitates the development of molecular approaches. This study aimed to quantify in experimental animal models and human leishmaniasis the expression of amastigote-specific virulence genes, A2 and amastin by droplet digital polymerase chain reaction (ddPCR). Total RNA was isolated from L. donovani-infected hamsters or murine peritoneal macrophages and lesional biopsies from patients with post kala-azar dermal leishmaniasis (PKDL). Following cDNA conversion, EvaGreen-based ddPCR was performed using specific primers for A2 or amastin and parasite load expressed in copies per μL. Assay was optimized and the specificity of amastigote-specific A2 and amastin was confirmed. In hepatic and splenic tissues of L. donovani-infected hamsters and peritoneal macrophages, ddPCR demonstrated a greater abundance of A2 than amastin. Treatment of L. donovani-infected peritoneal macrophages with conventional anti-leishmanials, miltefosine and amphotericin B translated into a dose-dependent reduction in copies per μL of A2 and amastin, and the extrapolated IC50 was comparable with results obtained by counting LD bodies in Giemsa-stained macrophages. Similarly, in dermal biopsies of patients with PKDL, A2 and amastin were detected. Overall, monitoring of A2 by ddPCR can be an objective measure of parasite burden and potentially adaptable into a high throughput approach necessary for drug development and monitoring disease progression when the causative species is L. donovani.

Visceral Leishmaniasis and the Skin: Dermal Parasite Transmission to Sand Flies

Visceral leishmaniasis is a parasitic disease with significant dermal tropism. The skin is an important site of infection contributing to parasite transmission to naïve sand flies, but understanding how parasitism of host skin and the related immune microenvironment supports or prevents skin parasite replication is now the focus of major investigation in the field of leishmaniasis research. Here, we review dermatoimmunology during visceral leishmaniasis (VL), dermal Leishmania parasite burden, and the role of skin parasitism in transmissibility to sand fly vectors. First, we discuss the epidemiology of VL amongst dogs, the primary zoonotic reservoir for human infection. We explore the association between spatial distribution and the burden of parasites in the skin in driving outward transmission. Factors associated with parasite persistence in the skin are examined. We discuss systemic immunity during VL and what is known about immunological correlates in the skin microenvironment. Finally, we touch on factors egested into the skin during Leishmania inoculation by sand flies. Throughout, we discuss factors associated with the early and chronic establishment of Leishmania parasites in the skin and the role of the dermal immune response.

Tackling Drug Resistance and Other Causes of Treatment Failure in Leishmaniasis

Leishmaniasis is a tropical infectious disease caused by the protozoan Leishmania parasite. The disease is transmitted by female sand flies and, depending on the infecting parasite species, causes either cutaneous (stigmatizing skin lesions), mucocutaneous (destruction of mucous membranes of nose, mouth and throat) or visceral disease (a potentially fatal infection of liver, spleen and bone marrow). Although more than 1 million new cases occur annually, chemotherapeutic options are limited and their efficacy is jeopardized by increasing treatment failure rates and growing drug resistance. To delay the emergence of resistance to existing and new drugs, elucidating the currently unknown causes of variable drug efficacy (related to parasite susceptibility, host immunity and drug pharmacokinetics) and improved use of genotypic and phenotypic tools to define, measure and monitor resistance in the field are critical. This review highlights recent progress in our understanding of drug action and resistance in Leishmania, ongoing challenges (including setbacks related to the COVID-19 pandemic) and provides an overview of possible strategies to tackle this public health challenge.

Impact of intensified control on visceral leishmaniasis in a highly-endemic district of Bihar, India: An interrupted time series analysis

Visceral leishmaniasis (VL) is declining in India and the World Health Organization’s (WHO) 2020 ‘elimination as a public health problem’ target has nearly been achieved. Intensified combined interventions might help reach elimination, but their impact has not been assessed. WHO’s Neglected Tropical Diseases 2021–2030 roadmap provides an opportunity to revisit VL control strategies. We estimated the combined effect of a district-wide pilot of intensified interventions in the highly-endemic Vaishali district, where cases fell from 3,598 in 2012–2014 to 762 in 2015–2017. The intensified control approach comprised indoor residual spraying with improved supervision; VL-specific training for accredited social health activists to reduce onset-to-diagnosis time; and increased Information Education & Communication activities in the community. We compared the rate of incidence decrease in Vaishali to other districts in Bihar state via an interrupted time series analysis with a spatiotemporal model informed by previous VL epidemiological estimates. Changes in Vaishali’s rank among Bihar’s endemic districts in terms of monthly incidence showed a change pre-pilot (3rd highest out of 33 reporting districts) vs. during the pilot (9th) (p<1e-10). The rate of decline in Vaishali’s incidence saw no change in rank at 11th highest, both pre-pilot & during the pilot. Counterfactual model simulations suggest an estimated median of 352 cases (IQR 234–477) were averted by the Vaishali pilot between January 2015 and December 2017, which was robust to modest changes in the onset-to-diagnosis distribution. Strengthening control strategies may have precipitated a substantial change in VL incidence in Vaishali and suggests this approach should be piloted in other highly-endemic districts.

Domestic mammals as reservoirs for Leishmania donovani on the Indian subcontinent: Possibility and consequences on elimination

Leishmania donovani is the causative agent of historically anthroponotic visceral leishmaniasis (VL) on the Indian subcontinent (ISC). L. donovani is transmitted by the sand fly species Phlebotomus argentipes. Our collaborative group and others have shown that sand flies trapped outside in endemic villages have fed on cattle and dogs in addition to people. Domestic animals are reservoirs for L. donovani complex spp., particularly L. infantum, in other endemic areas. Multiple studies using quantitative PCR or serological detection methods have demonstrated that goats, cattle, rats and dogs were diagnostically positive for L. donovani infection or exposure in eastern Africa, Bangladesh, Nepal and India. There is a limited understanding of the extent to which L. donovani infection of domestic animals drives transmission to other animals or humans on the ISC. Evidence from other vector-borne disease elimination strategies indicated that emerging infections in domestic species hindered eradication. The predominant lesson learned from these other situations is that non-human reservoirs must be identified, controlled and/or prevented. Massive efforts are underway for VL elimination on the Indian subcontinent. Despite these herculean efforts, residual VL incidence persists. The spectre of an animal reservoir complicating elimination efforts haunts the final push towards full VL control. Better understanding of L. donovani transmission on the Indian subcontinent and rigorous consideration of how non-human reservoirs alter VL ecology are critical to sustain elimination goals.

A profile of research on the parasitic trypanosomatids and the diseases they cause

The parasitic trypanosomatids cause lethal and debilitating diseases, the leishmaniases, Chagas disease, and the African trypanosomiases, with major impacts on human and animal health. Sustained research has borne fruit by assisting efforts to reduce the burden of disease and by improving our understanding of fundamental molecular and cell biology. But where has the research primarily been conducted, and which research areas have received the most attention? These questions are addressed below using publication and citation data from the past few decades.

Spatial Point Pattern Analysis Identifies Mechanisms Shaping the Skin Parasite Landscape in Leishmania donovani Infection

Increasing evidence suggests that in hosts infected with parasites of the Leishmania donovani complex, transmission of infection to the sand fly vector is linked to parasite repositories in the host skin. However, a detailed understanding of the dispersal (the mechanism of spread) and dispersion (the observed state of spread) of these obligatory-intracellular parasites and their host phagocytes in the skin is lacking. Using endogenously fluorescent parasites as a proxy, we apply image analysis combined with spatial point pattern models borrowed from ecology to characterize dispersion of parasitized myeloid cells (including ManR+ and CD11c+ cells) and predict dispersal mechanisms in a previously described immunodeficient model of L. donovani infection. Our results suggest that after initial seeding of infection in the skin, heavily parasite-infected myeloid cells are found in patches that resemble innate granulomas. Spread of parasites from these initial patches subsequently occurs through infection of recruited myeloid cells, ultimately leading to self-propagating networks of patch clusters. This combination of imaging and ecological pattern analysis to identify mechanisms driving the skin parasite landscape offers new perspectives on myeloid cell behavior following parasitism by L. donovani and may also be applicable to elucidating the behavior of other intracellular tissue-resident pathogens and their host cells.

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.

IgG3 and IL10 are effective biomarkers for monitoring therapeutic effectiveness in Post Kala-Azar Dermal Leishmaniasis

Background

The assessment of chemotherapeutic responses in Post Kala-azar Dermal Leishmaniasis (PKDL), especially its macular form is challenging, emphasizing the necessity for ‘test of cure’ tools. This study explored the diagnostic and prognostic potential of IgG subclasses and associated cytokines for monitoring the effectiveness of chemotherapy in PKDL.

Methods

Participants included PKDL cases at (a) disease presentation, (b) immediately at the end of treatment (12 weeks for Miltefosine or 3 weeks for Liposomal Amphotericin B, LAmB and (c) at any time point 6 months later, for estimating anti-leishmanial immunoglobulin (Ig, IgG, IgM, IgG1, IgG2 and IgG3) and cytokines (IL-10, IL-6).

Results

In PKDL, Ig levels were elevated, with IgG3 and IL-10 being the major contributors. Miltefosine decreased both markers substantially and this decrease was sustained for at least six months. In contrast, LAmB failed to decrease IgG3 and IL-10, as even after six months, their levels remained unchanged or even increased.

Conclusions

In PKDL, IgG3 and IL-10 proved to be effective predictors of responsiveness to chemotherapy and may be considered as a non invasive alternative for longitudinal monitoring.

Post Kala-azar Dermal Leishmaniasis (PKDL) is a dermal condition that occurs in East Africa and South Asia, the latter in 5–10% of patients after apparent cure from Visceral Leishmaniasis (VL). Till date, conventional knowledge in South Asia was that the polymorphic form of PKDL comprising of macules, papules and nodules was the predominant disease form, constituting 85–90%. However, since 2014, implementation of active-case surveillance led to unearthing of a large number of macular, hypopigmented cases, and was reported to contribute to nearly 50% of the disease burden. In particular, the macular form poses a diagnostic dilemma as microscopically parasites are difficult to identify in their lesions, and repigmentation occurs months after parasite clearance, emphasizing the need for developing non-invasive approaches for measurement of parasite burden. Till date, no formal clinical trial for treatment of PKDL has been undertaken where the parasite load was quantified and treatment remains empirical. This is primarily due to PKDL cases being unwilling to provide a repeat skin biopsy once their lesions have declined. Therefore, in cases where treatment failure occurs, it cannot be precisely identified, and could potentially lead to these cases becoming mobile disease reservoirs, thereby adversely impacting on the ongoing VL elimination programme. This study addressed this critical lacuna, where it was established that in both clinical types of PKDL, circulating levels of IgG3 and IL-10 can be considered as effective markers for monitoring treatment outcome. At disease presentation, the raised levels of IgG subclasses and associated cytokines (IL-10 and IL-6) declined following therapy with Miltefosine, the maximum decrease being with IgG3 along with IL-10; importantly, this decrease was sustained for at least six months. In contrast, LAmB failed to decrease the levels of immunoglobulins and associated cytokines even six months after completion of treatment; in fact the antibody levels either increased or remained unchanged. Taken together, this study has established the potential of IgG3 and IL10 as a non-invasive alternative for monitoring of chemotherapeutic responses in PKDL.

[Generalized old world leishmaniasis: first Moroccan case in an immunocompetent adult?]

BACKGROUND

Post-kala-azar dermal Leishmaniasis (PKDL) is a rare skin syndrome observed after treatment of visceral Leishmaniasis (VL) with pentavalent antimonial organic salts, never described in Morocco before. Here we report a case in an immunocompetent adult.

CASE

A 36-year-old-man from Tata in southern Morocco, with a history of visceral Leishmaniasis 2 years before and treated with meglumine antimoniate and amphotericin B with good clinical course, was hospitalized in dermatology for an erythematous papulo-nodular closet of the face. Six months ago, he presented oral mucosa involvement, then 3 months later, cutaneous lesions appeared on the face. The dermatological examination revealed a papulo-nodular erythematous closet extending to the nose and both cheeks, crusty and lupoid lesions on the forehead, around the eyes and chin, associated with an ulcerative and painless lesion on the heeL. The examination of the oral mucosa revealed an ulceration of the posterior third of the tongue and a papillomatous aspect of the soft palate. The skin biopsy and smear found some amastigote forms of Leishmania bodies. ITS1 PCR was positive (genus Leishmania). The HIV serology was negative. The diagnosis of PKDL was then evoked. The patient received intra-muscular injections of meglumine antimoniate with good progress.

CONCLUSION

To our knowledge, this is the first case of generalised leishmaniasis suggesting PKDL reported in a Moroccan immunocompetent adult.

Antiprotozoal agents: How have they changed over a decade?

Neglected tropical diseases are a diverse group of communicable diseases that are endemic in low- or low-to-middle-income countries located in tropical and subtropical zones. The number and availability of drugs for treating these diseases are low, the administration route is inconvenient in some cases, and most of them have safety, efficacy, or adverse/toxic reaction issues. The need for developing new drugs to deal with these issues is clear, but one of the most drastic consequences of this negligence is the lack of interest in the research and development of new therapeutic options among major pharmaceutical companies. Positive changes have been achieved over the last few years, although the overall situation remains alarming. After more than one decade since the original work reviewing antiprotozoal agents came to light, now it is time to question ourselves: How has the scenario for the treatment of protozoal diseases such as malaria, leishmaniasis, human African trypanosomiasis, and American trypanosomiasis changed? This review covers the last decade in terms of the drugs currently available for the treatment of these diseases as well as the clinical candidates being currently investigated.

Leishmania infantum xenodiagnosis from vertically infected dogs reveals significant skin tropism

BACKGROUND

Dogs are the primary reservoir for human visceral leishmaniasis due to Leishmania infantum. Phlebotomine sand flies maintain zoonotic transmission of parasites between dogs and humans. A subset of dogs is infected transplacentally during gestation, but at what stage of the clinical spectrum vertically infected dogs contribute to the infected sand fly pool is unknown.

METHODOLOGY/PRINCIPAL FINDINGS

We examined infectiousness of dogs vertically infected with L. infantum from multiple clinical states to the vector Lutzomyia longipalpis using xenodiagnosis and found that vertically infected dogs were infectious to sand flies at differing rates. Dogs with mild to moderate disease showed significantly higher transmission to the vector than dogs with subclinical or severe disease. We documented a substantial parasite burden in the skin of vertically infected dogs by RT-qPCR, despite these dogs not having received intradermal parasites via sand flies. There was a highly significant correlation between skin parasite burden at the feeding site and sand fly parasite uptake. This suggests dogs with high skin parasite burden contribute the most to the infected sand fly pool. Although skin parasite load and parasitemia correlated with one another, the average parasite number detected in skin was significantly higher compared to blood in matched subjects. Thus, dermal resident parasites were infectious to sand flies from dogs without detectable parasitemia.

CONCLUSIONS/SIGNIFICANCE

Together, our data implicate skin parasite burden and earlier clinical status as stronger indicators of outward transmission potential than blood parasite burden. Our studies of a population of dogs without vector transmission highlights the need to consider canine vertical transmission in surveillance and prevention strategies.

Role of wild rabbits as reservoirs of leishmaniasis in a non-epidemic Mediterranean hot spot in Spain

There is limited information regarding the role of wild mammals in the transmission dynamics of Leishmania infantum. A potential human leishmaniasis hot spot was detected in southern Spain that could not be explained solely by canine leishmaniasis prevalence. The aim of this work was to analyse the involvement of wild rabbits as the main factor affecting this Mediterranean hot spot. A survey of wild rabbits, dogs and sand flies was conducted in the human cases environment. A nearby region without clinical leishmaniasis cases was used as reference control. 51 wild rabbits shot by hunters were analysed by molecular techniques. 1100 sand flies were captured and morphologically identified. Blood collected from patients' relatives/ neighbours (n = 9) and dogs (n = 66) was used for molecular analysis and serology. In Mediterranean leishmaniasis hot spots such as Montefrío municipality (average incidence of 16.8 human cases per 100,000 inhabitants/year), wild rabbits (n = 40) support high L. infantum infection rates (100%) and heavy parasite burdens (average value: 503 parasites/mg) in apparently normal ear skin directly accessible to sand flies, enabling the existence of heavily parasitized Phlebotomus perniciosus females (12.5% prevalence). The prevalence of infection and median parasite load were very low among rabbits captured in Huéscar (n = 11), a human clinical leishmaniasis-free area for the last 18 years. P. perniciosus was the most abundant Phlebotomus species in all the domestic/peridomestic microhabitats sampled, both indoors and outdoors. Accordingly, leishmaniasis is clustering in space and time at this local scale represented by Montefrío due to the proximity of two competent host reservoirs (dogs and heavily parasitized wild rabbits) associated with overlapping sylvatic and domestic transmission cycles through the main vector, P. perniciosus. We highlight the usefulness of determining the prevalence of infection and parasite burden in wild rabbits as a control leishmaniasis measure with the advantage that the use of the ear offers.

Evaluation of molecular assays to detect Leishmania donovani in Phlebotomus argentipes fed on post-kala-azar dermal leishmaniasis patients

BACKGROUND

Post-kala-azar dermal leishmaniasis (PKDL) caused by Leishmania donovani (LD) is a skin disorder that often appears after treatment of visceral leishmaniasis (VL) patients. PKDL patients are potential reservoirs of LD parasites, which can initiate a new epidemic of anthroponotic VL. Therefore, host infectiousness to its sand fly vector is a critical factor for transmission, and its accurate estimation can facilitate control strategies. At present, conventional microscopy serves as the reference method to detect parasites in its vector. However, low sensitivity of microscopy can be a limiting factor.

METHODS

In this study, real-time quantitative PCR (LD-qPCR) and recombinase polymerase amplification (LD-RPA) assays were evaluated against microscopy for the detection of LD DNA extracted from live sand flies five days after controlled feeding on PKDL cases.

RESULTS

The sensitivity of LD-qPCR and LD-RPA assays were found to be 96.43 and 100%, respectively, against microscopy for the selected fed sand flies (n = 28), and an absolute specificity of both molecular tools for apparently unfed sand flies (n = 30). While the proportion of infectious cases among 47 PKDL patients was estimated as 46.81% as defined by microscopic detection of LD in at least one fed sand fly per case, LD-RPA assay evaluation of only the microscopy negative sand flies fed to those 47 PKDL cases estimated an even greater proportion of infectious cases (51.06%). In overall estimation of the infectious cases in retrospective manner, discordance in positivity rate was observed (p < 0.05) between LD-RPA (59.57%) assay and microscopy (46.81%), while LD-RPA had slightly better positivity rate than LD-qPCR (55.32%) as well.

CONCLUSIONS

Considering the sensitivity, cost, detection time, and field applicability, RPA assay can be considered as a promising single molecular detection tool for investigations pertaining to LD infections in sand flies and/or host infectiousness in PKDL, while it can also be useful in confirmation of microscopy negative sand fly samples.

Human leishmaniasis vaccines: Use cases, target population and potential global demand

The development of vaccines against one or all forms of human leishmaniasis remains hampered by a paucity of investment, at least in part resulting from the lack of well-evidenced and agreed estimates of vaccine demand. Starting from the definition of 4 main use cases (prevention of visceral leishmaniasis, prevention of cutaneous leishmaniasis, prevention of post-kala-azar dermal leishmaniasis and treatment of post-kala-azar dermal leishmaniasis), we have estimated the size of each target population, focusing on those endemic countries where incidence levels are sufficiently high to justify decisions to adopt a vaccine. We assumed a dual vaccine delivery strategy, including a wide age-range catch-up campaign before the start of routine immunisation. Vaccine characteristics and delivery parameters reflective of a target product profile and the likely duration of the clinical development effort were considered in forecasting the demand for each of the four indications. Over a period of 10 years, this demand is forecasted to range from 300-830 million doses for a vaccine preventing visceral leishmaniasis and 557-1400 million doses for a vaccine preventing cutaneous leishmaniasis under the different scenarios we simulated. In a scenario with an effective prophylactic visceral leishmaniasis vaccine, demand for use to prevent or treat post-kala-azar dermal leishmaniasis would be more limited (over the 10 years ~160,000 doses for prevention and ~7,000 doses for treatment). Demand would rise to exceed 330,000 doses, however, in the absence of an effective vaccine for visceral leishmaniasis. Because of the sizeable demand and potential for public health impact, a single-indication prophylactic vaccine for visceral or cutaneous leishmaniasis, and even more so a cross-protective prophylactic vaccine could attract the interest of commercial developers. Continuous refinement of these first-of-their kind estimates and confirmation of country willingness and ability to pay will be paramount to inform the decisions of policy makers and developers in relation to a leishmaniasis vaccine. Positive decisions can provide a much-needed contribution towards the achievement of global leishmaniasis control.

A review of the leishmanin skin test: A neglected test for a neglected disease

The leishmanin skin test (LST) has been used for decades to detect exposure and immunity to the parasite Leishmania, the causative agent of the neglected tropical disease leishmaniasis. In the LST, Leishmania antigen (leishmanin) is intradermally injected into the forearm. In an individual who has been previously infected, a delayed-type hypersensitivity (DTH) reaction results in a measurable induration at the site of the injection, indicating that previous exposure to Leishmania has resulted in the development of cell-mediated immunity. LST positivity is associated with long-lasting protective immunity against reinfection, most notably as reported for visceral leishmaniasis (VL). Despite efforts over the past few decades, leishmanin antigen is no longer produced under good manufacturing practice (GMP) conditions anywhere in the world. Consequently, the use of the LST in epidemiological studies has declined in favor of serological and molecular tests. In this review, we provide a historical overview of the LST and justification for the reintroduction of leishmanin. A GMP-grade leishmanin can be used to detect immunity in vivo by the LST and can be investigated for use in an interferon-γ release assay (IGRA), which may serve as an in vitro version of the LST. The LST will be a valuable tool for surveillance and epidemiological studies in support of the VL elimination programs and as a surrogate marker of immunity in vaccine clinical trials.

A clinical study to optimise a sand fly biting protocol for use in a controlled human infection model of cutaneous leishmaniasis (the FLYBITE study)

Background: Leishmaniasis is a globally important yet neglected parasitic disease transmitted by phlebotomine sand flies. With new candidate vaccines in or near the clinic, a controlled human challenge model (CHIM) using natural sand fly challenge would provide a method for early evaluation of prophylactic efficacy. Methods : We evaluated the biting frequency and adverse effects resulting from exposure of human volunteers to bites of either Phlebotomus papatasi or P. duboscqi, two natural vectors of Leishmania major. 12 healthy participants were recruited (mean age 40.2 ± 11.8 years) with no history of significant travel to regions where L. major-transmitting sand flies are prevalent. Participants were assigned to either vector by 1:1 allocation and exposed to five female sand flies for 30 minutes in a custom biting chamber. Bite frequency was recorded to confirm a bloodmeal was taken. Participant responses and safety outcomes were monitored using a visual analogue scale (VAS), clinical examination, and blood biochemistry. Focus groups were subsequently conducted to explore participant acceptability. Results: All participants had at least one successful sand fly bite with none reporting any serious adverse events, with median VAS scores of 0-1/10 out to day 21 post-sand fly bite. Corresponding assessment of sand flies confirmed that for each participant at least 1/5 sand flies had successfully taken a bloodmeal (overall mean 3.67±1.03 bites per participant). There was no significant difference between P. papatasi and P. duboscqi in the number of bites resulting from 5 sand flies applied to human participants (3.3±0.81 vs 3.00±1.27 bites per participant; p=0.56) .  In the two focus groups (n=5 per group), themes relating to positive participant-reported experiences of being bitten and the overall study, were identified. Conclusions: These results validate a protocol for achieving successful sand fly bites in humans that is safe, well-tolerated and acceptable for participants. Clinicaltrials.gov registration: NCT03999970 (27/06/2019).

Mechanisms of Immunopathogenesis in Cutaneous Leishmaniasis And Post Kala-azar Dermal Leishmaniasis (PKDL)

Leishmaniasis is a neglected tropical disease that affects 12 million people worldwide. The disease has high morbidity and mortality rates and is prevalent in over 80 countries, leaving more than 300 million people at risk of infection. Of all of the manifestations of this disease, cutaneous leishmaniasis (CL) is the most common form and it presents as ulcerating skin lesions that can self-heal or become chronic, leading to disfiguring scars. This review focuses on the different pathologies and disease manifestations of CL, as well as their varying degrees of severity. In particular, this review will discuss self-healing localized cutaneous leishmaniasis (LCL), leishmaniasis recidivans (LR), mucocutaneous leishmaniasis (MCL), anergic diffuse cutaneous leishmaniasis (ADCL), disseminated leishmaniasis (DL), and Post Kala-azar Dermal Leishmaniasis (PKDL), which is a cutaneous manifestation observed in some visceral leishmaniasis (VL) patients after successful treatment. The different clinical manifestations of CL are determined by a variety of factors including the species of the parasites and the host's immune response. Specifically, the balance between the pro and anti-inflammatory mediators plays a vital role in the clinical presentation and outcome of the disease. Depending upon the immune response, Leishmania infection can also transition from one form of the disease to another. In this review, different forms of cutaneous Leishmania infections and their immunology are described.

Asymptomatic Bordetella pertussis infections in a longitudinal cohort of young African infants and their mothers

Recent pertussis resurgence in numerous countries may be driven by asymptomatic infections. Most pertussis surveillance studies are cross-sectional and cannot distinguish asymptomatic from pre-symptomatic infections. Longitudinal surveillance could overcome this barrier, providing more information about the true burden of pertussis at the population level. Here we analyze 17,442 nasopharyngeal samples from a longitudinal cohort of 1320 Zambian mother/infant pairs. Our analysis has two elements. First, we demonstrate that the full range of IS481 qPCR CT values provides insight into pertussis epidemiology, showing concordance of low and high CT results over time, within mother/infant pairs, and in relation to symptomatology. Second, we exploit these full-range qPCR data to demonstrate a high incidence of asymptomatic pertussis, including among infants. Our results demonstrate a wider burden of pertussis infection than we anticipated in this population, and expose key limitations of threshold-based interpretation of qPCR results in infectious disease surveillance.

Mathematical modelling of the use of insecticide-treated nets for elimination of visceral leishmaniasis in Bihar, India

Visceral leishmaniasis (VL) is a deadly neglected tropical disease caused by a parasite Leishmania donovani and spread by female sand flies Phlebotomus argentipes. There is conflicting evidence regarding the role of insecticide-treated nets (ITNs) on the prevention of VL. Numerous studies demonstrated the effectiveness of ITNs. However, KalaNet, a large trial in Nepal and India did not support those findings. The purpose of this paper is to gain insight into the situation by mathematical modelling. We expand a mathematical model of VL transmission based on the KalaNet trial and incorporate the use of ITNs explicitly into the model. One of the major contributions of this work is that we calibrate the model based on the available epidemiological data, generally independent of the KalaNet trial. We validate the model on data collected during the KalaNet trial. We conclude that in order to eliminate VL, the ITN usage would have to stay above 96%. This is higher than the 91% ITNs use at the end of the trial which may explain why the trial did not show a positive effect from ITNs. At the same time, our model indicates that asymptomatic individuals play a crucial role in VL transmission.

Peptide-mediated leishmaniasis management strategy: Tachyplesin emerges as an effective anti-leishmanial peptide against Leishmania donovani

Visceral leishmaniasis is one of the neglected tropical diseases caused by an intracellular parasite, Leishmania donovani. Drug resistance, adverse side effects and long treatment regimes are important limitations in achieving the effective elimination of visceral leishmaniasis. In the absence of any vaccine, chemotherapy remains a viable treatment for leishmaniasis. For effective killing of leishmania parasite, the drug molecule needs to cross the cell membrane. In the present study, marine membrane-active peptide Tachyplesin has been used against Leishmania donovani. Further, the mechanism of action and importance of cysteine amino acids of Tachyplesin in anti-leishmanial activity has been assessed. The cargo-carrying ability of Tachyplesin in L. donovani has been established. Thus, dual-use of Tachyplesin as an anti-leishmanial peptide as well as a cargo delivery vehicle makes the marine peptide an attractive therapeutic target against visceral leishmaniasis.

Safety and immunogenicity of ChAd63-KH vaccine in post-kala-azar dermal leishmaniasis patients in Sudan

Post-kala-azar dermal leishmaniasis (PKDL) is a chronic, stigmatizing skin condition occurring frequently after apparent clinical cure from visceral leishmaniasis. Given an urgent need for new treatments, we conducted a phase IIa safety and immunogenicity trial of ChAd63-KH vaccine in Sudanese patients with persistent PKDL. LEISH2a (ClinicalTrials.gov: NCT02894008) was an open-label three-phase clinical trial involving sixteen adult and eight adolescent patients with persistent PKDL (median duration, 30 months; range, 6-180 months). Patients received a single intramuscular vaccination of 1 × 10¹⁰ viral particles (v.p.; adults only) or 7.5 × 10¹⁰ v.p. (adults and adolescents), with primary (safety) and secondary (clinical response and immunogenicity) endpoints evaluated over 42-120 days follow-up. AmBisome was provided to patients with significant remaining disease at their last visit. ChAd63-KH vaccine showed minimal adverse reactions in PKDL patients and induced potent innate and cell-mediated immune responses measured by whole-blood transcriptomics and ELISpot. 7/23 patients (30.4%) monitored to study completion showed >90% clinical improvement, and 5/23 (21.7%) showed partial improvement. A logistic regression model applied to blood transcriptomic data identified immune modules predictive of patients with >90% clinical improvement. A randomized controlled trial to determine whether these clinical responses were vaccine-related and whether ChAd63-KH vaccine has clinical utility is underway.