Case Report: FDG-PET/CT findings in co-infection of visceral leishmaniasis and chronic hepatitis B.

Visceral leishmaniasis is an opportunistic infection in immunocompromised patients. Herein, we report a case of an adult male patient with a persistent fever of unknown origin, along with chronic hepatitis B. The patient underwent bone marrow aspiration twice, which revealed hemophagocytosis. Abdomen enhanced CT revealed splenomegaly with a persistent strengthening of multiple nodules, and hemangiomas were diagnosed. A subsequent 18-fluoro-deoxyglucose (18F-FDG) PET/CT scan, which was implemented to search for the reason for the fever, showed diffuse splenic disease uptake, and splenic lymphoma was considered as the diagnosis. His clinical symptoms improved after receiving hemophagocytic lymphohistiocytosis (HLH) chemotherapy. However, the patient was readmitted for fever again only 2 months later. Splenectomy surgery is performed to confirm the diagnosis and classification of lymphoma. Visceral leishmaniasis was eventually diagnosed in a spleen specimen and the third bone marrow biopsy. He received treatment with lipid amphotericin B and remained recurrence-free for 1 year. In this paper, we aim to provide detailed information that will help further our understanding of the clinical symptoms and radiographic findings of visceral leishmaniasis.

Evaluation of cardiovascular injury in dogs coinfected with visceral leishmaniasis and monocytic ehrlichiosis by echocardiographic examination and selected biomarker measurements.

Visceral Leishmaniasis (VL) and Monocytic Ehrlichiosis (ME), which are an important zoonotic diseases of dogs, causing multiple organ dysfunction and has a poor prognosis when not interfered. In this study, it was aimed to investigate the cardiovascular injury that develops in dogs that co­infected with VL and ME with cardiovascular biomarkers and echocardiographic parameters. The animal material of this study was consisted of 14 owned dogs in total; 7 diseased dogs which were determined to be co­infected with VL and ME according to the results of clinical examination and rapid test kits, and 7 healthy dogs, which were determined to be healthy as a result of the same examinations. As a result of echocardiographic examinations, decreased left ventricular cytolic and diastolic diameters (LVIDs, LVIDd), fractional shortening (FS) and increased ratio of left atrium to left aortic root diameter (LA/Ao) values were determined in the Co­infected Group compared with the Healthy Group. Also, as a result of biomarker analysis, higher cTnI) D­dimer and NT­proBNP levels were detected in the Co­infected Group. In conclusion, considering studies of dogs infected with VL and/or ME alone, it was concluded that similar cardiovascular injury develops in dogs co­infected with VL and ME.

Synovial fluid and radiographic evaluation of joints from dogs with visceral leishmaniasis.

BACKGROUND: Polyarthritis has been associated with canine visceral leishmaniasis (CanVL), and co-infection with Ehrlichia canis is common and may alter clinical manifestations. METHODS: A total of 89 dogs presenting CanVL were subdivided into two groups: (1) G1, consisting of 46 dogs seronegative to Ehrlichia spp., and (ii) G2, consisting of 43 dogs seropositive to Ehrlichia spp. Eight joints (carpal, tarsal, stifles and elbows) from each dog were evaluated by radiography and synovial fluid (SF) cytologic analysis. RESULTS: Overall, 74 of the 89 (83.1%) dogs presented joint abnormalities suggestive of osteoarthritis by radiography (G1: 40/46 [86.9%]; G2: 34/43 [79.0%]), with no statistically significant between-group difference. All dogs with abnormal joint X-ray images presented radiographic lesions bilaterally, independent of the characteristics of the lesion. Soft tissue swelling around the joint and joint space narrowing were more commonly observed in G1 than in G2 dogs. There was no significant between-group difference in terms of other radiographic abnormalities suggestive of osteoarthritis (evident trabecular pattern, subchondral bone sclerosis, osteolysis, osteolytic-proliferative lesions or bone proliferation). SF from 174/315 (55.2%) and 152/307 (49.5%) joints from G1 and G2 dogs, respectively, presented an inflammatory infiltrate, but there was no significant association between the presence of inflammatory infiltrate and group. There was also no statistical difference between groups in either of the evaluated joints in terms of the percentage of neutrophils or mononuclear cells. Leishmania spp. amastigotes were found in 69/315 (21.9%) joints from G1 dogs and in 100/307 (32.5%) joints from G2 dogs (Fisher's exact test, P = 0.002, odds ratio = 0.5, 95% confidence interval = 0.4-0.8). The neutrophilic infiltrate was significantly higher in joints with amastigote forms in both G1 (Mann-Whitney U-test, U(18) = 817, Z = -3.76, P = 0.0001) and G2 dogs (Mann-Whitney U-test, U(18) = 6543, Z = - 5.06, P < 0.0001). CONCLUSIONS: A high prevalence of arthritis in dogs with CanVL was found, and all dogs presented involvement in multiple joints. Although no difference was observed between groups in terms of the number of dogs with polyarthritis and the presence of an inflammatory infiltrate in SF, Leishmania spp. amastigotes were found more frequently in joints from G2 dogs. Further studies evaluating SF in dogs co-infected with L. infantum and E. canis should be performed to evaluate this finding.

Nódulos esplénicos como signo guía de leishmaniasis visceral en población infantil / Splenic nodules as guiding signs in pediatric population with visceral leishmaniasis

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Mapa de Evidências: Leishmaniose Visceral. Mapa de Evidencias: Leishmaniasis Visceral. Evidence Map: Visceral Leishmaniasis

O mapa de evidências Leishmaniose Visceral (LV) representa graficamente as evidências científicas disponíveis para prevenção e controle, tratamento, diagnóstico e prognóstico de LV, com a finalidade de identificar de lacunas no conhecimento e de prioridades para pesquisas futuras. Cada revisão sistemática incluída foi avaliada, caracterizada e categorizada pelo tipo de intervenção e por desfechos. As intervenções foram categorizadas em cinco grupos: I) Prevenção e Controle, II) Diagnóstico, III) Tratamento, IV) Prognóstico e V) Intervenções Combinadas. Os desfechos foram relacionados à LV (em geral), LV Humana, LV Canina ou Efeitos Adversos. Principais Achados: Para o grupo I-Prevenção e Controle, as intervenções mais avaliadas foram uso de mosquiteiros, coleira com inseticida, abate de cães e pulverização com inseticidas. O uso de mosquiteiros apresentou efeito positivo para mortalidade e redução da densidade dos vetores, porém parece não ter efeito para o desfecho soroconversão em humanos e cães. O abate de cães tem efeito inconclusivo para redução da incidência de LV em humanos e de soroconversão em cães e humanos. O uso de coleira com inseticida tem efeito potencialmente positivo para redução da incidência de LV em cães. A pulverização com inseticidas tem efeito positivo para redução da densidade dos vetores, mas parece não ter efeito sobre a soroconversão em humanos. Para o grupo II-Diagnóstico, os testes de aglutinação e o teste rápido com antígeno rK39 foram as intervenções mais avaliadas e que apresentaram desempenho positivo para detecção de casos de LV em humanos e cães. El mapa de evidencia de la Leishmaniasis Visceral (LV) presenta gráficamente la evidencia científica disponible para la prevención y control, tratamiento, diagnóstico y pronóstico de la LV, con el fin de identificar brechas en el conocimiento y prioridades para futuras investigaciones. Cada revisión sistemática incluida fue evaluada, caracterizada y categorizada por tipo de intervención y por hallazgos. Las intervenciones se clasificaron en 5 grupos: I) Prevención y control, II) Diagnóstico, III) Tratamiento, IV) Pronóstico y V) Intervenciones combinadas. Los hallazgos se relacionaron con LV (en general), LV humana, leishmaniasis visceral canina o efectos adversos. Principales resultados: Para el grupo I Prevención y Control, las intervenciones más evaluadas fueron el uso de mosquiteros, collar de perro con insecticida, sacrificio de perros y pulverización con insecticidas. El uso de mosquiteros tuvo un efecto positivo sobre la mortalidad y la reducción de la densidad de vectores, pero parece no tener efecto sobre el resultado de la seroconversión en humanos y perros. El sacrificio de perros tiene un efecto inconcluyente sobre la reducción de la incidencia de LV en humanos y la seroconversión en perros y humanos. El uso de un collar con insecticida tiene un efecto potencialmente positivo en la reducción de la incidencia de LV en perros. La pulverización con insecticidas tiene un efecto positivo en la reducción de la densidad del vector, pero parece no tener efecto en la seroconversión humana. Para el grupo II Diagnóstico las pruebas de aglutinación y la prueba rápida con antígeno rK39 fueron las intervenciones más evaluadas y mostraron un desempeño positivo para la detección de casos de LV en humanos y perros. Para el grupo III Tratamiento, la anfotericina B liposomal y el antimonial pentavalente fueron las intervenciones más evaluadas para la LV humana. Se destaca el efecto positivo de estas intervenciones para la curación de pacientes con LV, aunque el antimonial pentavalente se asocia con varios resultados adversos. El tratamiento de la LV canina tiene pocas opciones terapéuticas, pero la intervención antimonial pentavalente y la asociación de este fármaco con alopurinol se han identificado con un efecto positivo. Para el grupo IV, las variables más evaluadas asociadas a muerte fueron anemia, edema, hemorragias, ictericia, edad y coinfección por VIH. Los resultados para el grupo V Intervenciones combinadas siguen inconcluyentes. To identify gaps in evidence and to inform future research priorities, we present the Visceral Leishmaniasis (VL) Evidence Map to visually depict the scientific evidence available for prevention and control, treatment, diagnostic and prognosis of VL. Each included systematic review was evaluated, characterized, and categorized by the type of intervention and outcomes. Interventions were categorized into 4 groups: i) Prevention and Control, ii) Diagnostic, iii) Treatment, iv) Prognosis and v) Combined Interventions. Outcomes were related to VL (general), Human VL (HVL), Canine VL or Adverse effects. Main results: For i) prevention and control group, most interventions were regarding to bednets, insecticide-impregnated dog collars, dog culling and insecticidal spraying. The use of bednets was identified with a positive effect for sand fly mortality and associated with reduction of sand fly density, but it seemed to have no effect to seroconversion in humans and dogs. Dog culling presented an inconclusive effect for reduction of HVL incidence and for seroconversion in humans and dogs. The use of insecticide-impregnated dog collars had a potential positive effect for reduction of VL incidence in dogs. Insecticidal spraying demonstrated a positive effect for reduction of sand fly density, but it also seemed to have no effect for seroconversion in humans. For ii) diagnostic tools: agglutination tests and rK39 immunochromatographic test were the most evaluated interventions and presented positive performance to detect VL in humans and dogs. For iii) treatment: Liposomal Amphotericin B and Antimonial pentavalent were the most evaluated interventions for HVL. The retrieved results highlighted their positive effect for cure of VL patients, although Antimonial pentavalent had an association with many adverse effects. The treatment for CanVL had fewer therapeutic options, but the interventions with Antimonial pentavalent and its association with allopurinol were identified as a positive effect. For iv) prognosis group, the most evaluated variables associated with death were anaemia, oedema, hemorrhage, jaundice, age and HIV coinfection. The results for group iv) Combined Interventions remain inconclusive.

Visceral Hepatic Leishmaniasis in a Melanoma Patient in FDG-PET.

BACKGROUND: Leishmaniasis is caused by protozoans that depend on female phlebotomine sandflies as vectors. The natural habitat of these sandflies is changing due to climatic changes, affecting the immunocompromised population, as more patients get immunocompromised due to cancer therapy in the present time. CASE REPORT: We report the case of a 72-year-old patient with melanoma in whom we found visceral leishmaniasis mimicking hepatic metastasis in routine FDG-PET/CT. The patient was hospitalised due to fever and pancytopenia in the general hospital Steyr. The diagnosis was made by biopsy of the iliac crest with cytological study and polymerase chain reaction. After treatment with amphotericin B, the patient recovered and tests became negative, including FDG-PET/CT. Because of climate change and the increasing use of immunomodulatory medication, our awareness of such findings should grow. CONCLUSION: New pitfalls in diagnosis and surveillance of cancer patients because of altered environmental conditions and immunocompromised patients have to be taken into account.

Joint involvement in canine visceral leishmaniasis: Orthopedic physical examination, radiographic and computed tomographic findings.

This study aimed to evaluate the joint involvement in dogs with visceral leishmaniasis by means of orthopedic physical examination, radiographic and computed tomographic (CT) findings. Of the 46 evaluated dogs, an overall of 91.3 % presented joint (carpal, tarsal, elbows, and stifle) abnormalities, observed on physical examination, radiography and/or CT. In 67.3 % of the dogs orthopedic examination showed no abnormalities. Among the 31 dogs with normal orthopedic examination, 61.3 % showed radiographic and CT findings suggestive of osteoarthritis, 25.8 % presented normal radiographs with abnormalities evidenced only on CT, while 12.9 % presented normal radiographs and CT imaging. From the 15 dogs with abnormal orthopedic examination, 80 % had abnormal radiographic and CT findings suggestive of osteoarthritis, while 20 % presented normal radiographs with abnormalities evidenced only in their CT. Radiographic and CT findings included evident trabecular pattern, subchondral bone sclerosis, osteolysis, mixed bone lesions (osteolytic-proliferative lesions), soft tissue swelling around the joint (edema), joint space narrowing, bone proliferation, osteophytes, bone cyst and cartilage flap. Based on CT results the most affected joints, among those assessed, were the tarsal (80.9 %), followed by stifle (78.5 %), carpal (64.2 %), and elbows (54.7 %). Except by one dog that presented only one stifle joint compromised, the other three joints presented bilateral abnormalities in all dogs.

Abdominal ultrasound in the diagnostic work-up of visceral leishmaniasis and for detection of complications of spleen aspiration.

INTRODUCTION: Abdominal ultrasound (US) is increasingly used in the diagnostic work-up of infectious diseases, but studies on its diagnostic value in visceral leishmaniasis (VL) are lacking. US could help to identify complications of spleen aspiration (SA). We aimed to assess the diagnostic value of US and the evolution of findings after VL treatment; the incidence and degree of splenic injury; and the pain perceived during SA. METHODOLOGY/RESULT: We conducted a cross-sectional prospective study at the Leishmaniasis Research and Treatment Center, Gondar, Ethiopia between Oct 2017 and Dec 2018. We enrolled VL suspects undergoing tissue aspiration; US were conducted before and after SA, and at the end of VL treatment. Splenic injury was graded using the American association of surgery trauma injury scale (grade 1-4). The pain perceived during SA was graded using a visual analogue scale. Out of 392 VL suspects, 192 (49%) were confirmed VL cases. The median age was 25 years (IQR 21-30). Massive splenomegaly and hepatomegaly were the most common US findings. Splenic nodules were seen in 3.7% of the 190 VL cases and 1.5% of the 197 non-VL cases. Ascites was more common in VL (16.4%) than in non-VL cases (9.1%). The frequency of US abnormalities decreased with treatment. None of the US findings had sufficient sensitivity and specificity to justify its use as a diagnostic test. US detected splenic injury in four of the 318 patients who had post-SA US. All four patients remained clinically stable. Pain was perceived as moderate or severe in 51% of patients. CONCLUSION: The diagnostic value of abdominal US for VL was low but found useful to detect subclinical splenic injury. SA caries a risk of splenic injury and was perceived painful by most. Further research on less invasive diagnostic tools is needed.

Sonographic findings in visceral leishmaniasis - A narrative review.

BACKGROUND: Visceral leishmaniasis (VL) is predominantly a neglected tropical parasitic disease but may also be acquired by travellers. We aimed at summarizing knowledge on sonographic presentation of VL to better understand sonographic features of VL. METHODS: PubMed was searched for studies and case reports presenting original data on sonographic findings of VL, published before August 13th, 2019. Demographic, clinical, and sonographic data were extracted and summarized in a qualitative approach. RESULTS: A total of 36 publications were included in this review; 27 of these were case reports and the remainder were prospective or retrospective studies. No study reported systematic cross-sectional comparative imaging. Overall, publications reported on 512 patients with VL of whom 12 were reported HIV-infected. Spleno- and hepatomegaly were the most frequently reported findings. Further relevant and repeatedly reported findings were splenic and hepatic lesions, abdominal lymphadenopathy, pleural and pericardial effusion and ascites. Reported focal splenic lesions were heterogeneous in size, shape, and echogenicity. Several publications reported gradual diminution and resolution of sonographic findings with VL treatment. CONCLUSION: Available literature on sonographic findings of VL is limited. Available reports indicate that spleno- and hepatomegaly, free fluid, abdominal lymphadenopathy, and focal splenic lesions may be common sonographic features in patients with VL. Because of the apparent overlap of sonographic features of VL, extrapulmonary tuberculosis and other conditions, interpretation of sonographic findings needs to be made with particular caution.

Case Report: Visceral Leishmaniasis Falsely Diagnosed as Q Fever.

Visceral leishmaniasis (VL) is a systemic infection caused by the protozoal parasite Leishmania, spread via the bloodstream to the reticuloendothelial system, through the bite of the sand fly. It is endemic in parts of Africa, South America, Asia, and Europe, including the Mediterranean. Here, we describe a case of VL that was initially diagnosed as Q fever based on positive Coxiella burnetii serology and showed a partial response to doxycycline treatment.

Pulmonary involvement in human visceral leishmaniasis: Clinical and tomographic evaluation.

Visceral leishmaniasis (VL) is a severe, systemic and potentially lethal parasitosis. The lung, like any other organ, can be affected in VL, and interstitial pneumonitis has been described in past decades. This research aimed to bring more recent knowledge about respiratory impairment in VL, characterizing pulmonary involvement through clinical, radiographic and tomographic evaluation. This is an observational, cross-sectional study that underwent clinical evaluation, radiography and high-resolution computed tomography of the chest in patients admitted with the diagnosis of VL in a university service in Northeast Brazil, from January 2015 to July 2018. The sample consisted of 42 patients. Computed tomography was considered abnormal in 59% of patients. Images compatible with pulmonary interstitial involvement were predominant (50%). The most observed respiratory symptom was cough (33.3%), followed by tachypnea (14.1%). Chest radiography was altered in only four patients. VL is a disease characterized by systemic involvement and broad spectrum of clinical manifestations. The respiratory symptoms and tomographic alterations found show that the involvement of respiratory system in VL deserves attention because it is more common than previously thought. Chest X-ray may not reveal this impairment.

Evaluation of synergy between host and pathogen-directed therapies against intracellular Leishmania donovani.

Visceral leishmaniasis (VL) is associated with treatment complications due to the continued growth of resistant parasites toward currently available pathogen-directed therapeutics. To limit the emergence and combat resistant parasites there is a need to develop new anti-leishmanial drugs and alternative treatment approaches, such as host-directed therapeutics (HDTs). Discovery of new anti-leishmanial drugs including HDTs requires suitable in vitro assay systems. Herein, we modified and evaluated a series of resazurin assays against different life-stages of the VL causing parasite, Leishmania donovani to identify novel HDTs. We further analyzed the synergy of combinatorial interactions between traditionally used pathogen-directed drugs and HDTs for clearance of intracellular L. donovani. The inhibitory concentration at 50% (IC50) of the five evaluated therapies [amphotericin B (AMB), miltefosine, paromomycin, DNER-4, and AR-12 (OSU-03012)] was determined against promastigotes, extracellular amastigotes, and intracellular amastigotes of L. donovani via a resazurin-based assay and compared to image-based microscopy. Using the resazurin-based assay, all evaluated therapies showed reproducible anti-leishmanial activity against the parasite's different life-stages. These results were consistent to the traditional image-based technique. The gold standard of therapy, AMB, showed the highest potency against intracellular L. donovani, and was further evaluated for combinatorial effects with the HDTs. Among the combinations analyzed, pathogen-directed AMB and host-directed AR-12 showed a synergistic reduction of intracellular L. donovani compared to individual treatments. The modified resazurin assay used in this study demonstrated a useful technique to measure new anti-leishmanial drugs against both intracellular and extracellular parasites. The synergistic interactions between pathogen-directed AMB and host-directed AR-12 showed a great promise to combat VL, with the potential to reduce the emergence of drug-resistant strains.

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

OBJECTIVES: Visceral leishmaniasis (VL) is the most severe manifestation of the infection caused by the protozoan Leishmania, recently on increase in Italy and Spain. The aim of the study was to describe FDG uptake patterns in VL patients (pts) who underwent 18F-FDG PET/CT. METHODS: A retrospective monocentric study of pts who underwent FDG PET/CT between 2008 and 2017 and later diagnosed with VL was performed. Semi-quantitative parameters were calculated in FDG-positive lesions: SUVmax, SUVmax spleen/SUVmax liver ratio (SLR), SUVmax focal/diffuse spleen ratio (FDR). RESULTS: Overall, 23 pts were included. PET/CT was negative in 2 immunocompromised pts, positive in 21/23 (91%) [6 spleen only, 2 spleen + nodes, 7 spleen + bone marrow (BM), 4 spleen + BM + nodes, 1 spleen + BM + lung, 1 BM only + nodes, 2 nodes only]. Splenic involvement was demonstrated in 20/23 (87%) pts. Two different splenic patterns were observed: diffuse (13/20 pts, mean spleen SUVmax = 7.3 ± 4.2 [4.0-14.1], mean SLR = 2.2 ± 1.6 [1.3-6.7]) and focal over diffuse (7/20 pts, mean SUVmax = 12.6 ± 4.5 [9.5-20.5], mean SLR = 2.8 ± 0.8 [2.1-4.4], mean FDR = 2.1 ± 0.8 [1.2-3.6]). Extra-splenic FDG-avid findings were detected in 15/21 pts (65%): bone marrow in 13/15 (mean SUVmax = 4.0 ± 1.3 [2.8-6.0]), nodes in 67/15 and lung in 1/15. CONCLUSIONS: PET/CT demonstrated splenic FDG uptake in all immunocompetent VL pts; two splenic patterns (diffuse/focal over diffuse) were observed and indistinguishable from splenic involvement by other disorders. The most frequent extra-splenic FDG-positive sites were BM and lymph nodes. Considering the potential disease aggressiveness and recent outbreaks in north-eastern Italy, VL should be considered in the differential diagnosis of FDG-positive splenic findings in pts from endemic areas or reporting travels to endemic countries.

Verification and monitoring of visceral leishmaniasis in hamsters caused by Leishmania infantum, using non-invasive approaches involving ultrasound imaging and blood gases.

Hamsters are a suitable experimental model for visceral leishmaniasis (VL) because they mimic the features of the human disease. However, the infection after inoculation can only be verified after sacrifice of the animal or several months following infection, when obvious signs of the disease appear, compromising animal welfare in both cases. Unlike other studies, the present work used an inoculum of 5 × 108 promastigotes to induce Leishmania infantum infection, which are easier to produce than amastigotes, in in vitro culture. The infection in hamsters was detected using non-invasive methods such as ultrasound imaging (USG) and blood gases, in addition to alterations in hematological parameters and weight loss. USG imaging identified changes in the size and echogenicity of the spleen, liver, and kidney as early as week 9 (W9) after experimental inoculation. However, blood gases, specially lactate, was increased in response to the infection, with statistically significant differences between W9 and W0 (before infection) (p < 0.0001). The conventional hematological parameters showed progressive pancytopenia and weight loss of 15% and 10% in infected males and females respectively, at W9 versus W0 (p < 0.0001). Histological changes in the liver, kidney, and spleen correlated with changes detected by USG imaging and the number of parasites increased proportionately to the progression of infection, being higher at W24. In conclusion, USG imaging, lactate levels, hematocrit and hemoglobin parameters, along with weight loss allowed early detection of infection, which was then confirmed by the identification and quantification of parasites in the blood, liver, and spleen by qRT-PCR. In contrast, blood chemistry was not a useful tool in the early detection of VL infection because it did not correlate with alterations evident in other techniques. The use of non-invasive tools eliminates the need for animal sacrifice to confirm infection, thus reducing the number of animals required for a given study and eliminating the need to wait until the appearance of severe signs of infection, which affect animal welfare. These tools are therefore advantageous for use in preclinical studies, for studying pathogenesis as also for vaccine and drug development.

Cytokines: Key Determinants of Resistance or Disease Progression in Visceral Leishmaniasis: Opportunities for Novel Diagnostics and Immunotherapy.

Leishmaniasis is a parasitic disease of humans, highly prevalent in parts of the tropics, subtropics, and southern Europe. The disease mainly occurs in three different clinical forms namely cutaneous, mucocutaneous, and visceral leishmaniasis (VL). The VL affects several internal organs and is the deadliest form of the disease. Epidemiology and clinical manifestations of VL are variable based on the vector, parasite (e.g., species, strains, and antigen diversity), host (e.g., genetic background, nutrition, diversity in antigen presentation and immunity) and the environment (e.g., temperature, humidity, and hygiene). Chemotherapy of VL is limited to a few drugs which is expensive and associated with profound toxicity, and could become ineffective due to the parasites developing resistance. Till date, there are no licensed vaccines for humans against leishmaniasis. Recently, immunotherapy has become an attractive strategy as it is cost-effective, causes limited side-effects and do not suffer from the downside of pathogens developing resistance. Among various immunotherapeutic approaches, cytokines (produced by helper T-lymphocytes) based immunotherapy has received great attention especially for drug refractive cases of human VL. Therefore, a comprehensive knowledge on the molecular interactions of immune cells or components and on cytokines interplay in the host defense or pathogenesis is important to determine appropriate immunotherapies for leishmaniasis. Here, we summarized the current understanding of a wide-spectrum of cytokines and their interaction with immune cells that determine the clinical outcome of leishmaniasis. We have also highlighted opportunities for the development of novel diagnostics and intervention therapies for VL.

Preclinical candidate for the treatment of visceral leishmaniasis that acts through proteasome inhibition.

Visceral leishmaniasis (VL), caused by the protozoan parasites Leishmania donovani and Leishmania infantum, is one of the major parasitic diseases worldwide. There is an urgent need for new drugs to treat VL, because current therapies are unfit for purpose in a resource-poor setting. Here, we describe the development of a preclinical drug candidate, GSK3494245/DDD01305143/compound 8, with potential to treat this neglected tropical disease. The compound series was discovered by repurposing hits from a screen against the related parasite Trypanosoma cruzi Subsequent optimization of the chemical series resulted in the development of a potent cidal compound with activity against a range of clinically relevant L. donovani and L. infantum isolates. Compound 8 demonstrates promising pharmacokinetic properties and impressive in vivo efficacy in our mouse model of infection comparable with those of the current oral antileishmanial miltefosine. Detailed mode of action studies confirm that this compound acts principally by inhibition of the chymotrypsin-like activity catalyzed by the ß5 subunit of the L. donovani proteasome. High-resolution cryo-EM structures of apo and compound 8-bound Leishmania tarentolae 20S proteasome reveal a previously undiscovered inhibitor site that lies between the ß4 and ß5 proteasome subunits. This induced pocket exploits ß4 residues that are divergent between humans and kinetoplastid parasites and is consistent with all of our experimental and mutagenesis data. As a result of these comprehensive studies and due to a favorable developability and safety profile, compound 8 is being advanced toward human clinical trials.

A chronic bioluminescent model of experimental visceral leishmaniasis for accelerating drug discovery.

BACKGROUND: Visceral leishmaniasis is a neglected parasitic disease with no vaccine available and its pharmacological treatment is reduced to a limited number of unsafe drugs. The scarce readiness of new antileishmanial drugs is even more alarming when relapses appear or the occurrence of hard-to-treat resistant strains is detected. In addition, there is a gap between the initial and late stages of drug development, which greatly delays the selection of leads for subsequent studies. METHODOLOGY/PRINCIPAL FINDINGS: In order to address these issues, we have generated a red-shifted luminescent Leishmania infantum strain that enables long-term monitoring of parasite burden in individual animals with an in vivo limit of detection of 106 intracellular amastigotes 48 h postinfection. For this purpose, we have injected intravenously different infective doses (104-5x108) of metacyclic parasites in susceptible mouse models and the disease was monitored from initial times to 21 weeks postinfection. The emission of light from the target organs demonstrated the sequential parasite colonization of liver, spleen and bone marrow. When miltefosine was used as proof-of-concept, spleen weight parasite burden and bioluminescence values decreased significantly. CONCLUSIONS: In vivo bioimaging using a red-shifted modified Leishmania infantum strain allows the appraisal of acute and chronic stage of infection, being a powerful tool for accelerating drug development against visceral leishmaniasis during both stages and helping to bridge the gap between early discovery process and subsequent drug development.