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.

Immunotherapy Combining Mimotopes Selected by Phage Display Plus Amphotericin B Is Effective for Treatment Against Visceral Leishmaniasis.

The treatment for visceral leishmaniasis (VL) causes toxicity in patients, entails high cost and/or leads to the emergence of resistant strains. No human vaccine exists, and diagnosis presents problems related to the sensitivity or specificity of the tests. Here, we tested two phage clones, B1 and D11, which were shown to be protective against Leishmania infantum infection in a murine model as immunotherapeutics to treat mice infected with this parasite species. The phages were used alone or with amphotericin B (AmpB), while other mice received saline, AmpB, a wild-type phage (WTP) or WTP/AmpB. Results showed that the B1/AmpB and D11/AmpB combinations induced polarised Th1-type cellular and humoral responses, which were primed by high levels of parasite-specific IFN-γ, IL-12, TNF-α, nitrite and IgG2a antibodies, which reflected in significant reductions in the parasite load in distinct organs of the animals when analyses were performed 1 and 30 days after the treatments. Reduced organic toxicity was also found in these animals, as compared with the controls. In conclusion, preliminary data suggest the potential of the B1/AmpB and D11/AmpB combinations as immunotherapeutics against L. infantum infection.

A Case Series of Hemophagocytic Lymphohistiocytosis: An Atypical Presentation of Visceral Leishmaniasis.

Visceral leishmaniasis (VL) is a parasitic vector-borne disease endemic in Armenia. Its complications include hemophagocytic lymphohistiocytosis (HLH), which is a potentially fatal syndrome if misdiagnosed or left untreated. Higher clinical caution is required for the prompt diagnosis of HLH since the clinical findings associated with systemic inflammation overlap with those of many other pathological conditions, such as sepsis or Kawasaki disease. This study aims to provide an overview of the most common presentations that should prompt consideration of HLH. We described a case series of three pediatric patients with VL who developed HLH during antiparasitic treatment and received total doses of 40 mg/kg of liposomal amphotericin B for complete elimination of the pathogen.

Apolipoprotein E Is Upregulated in Blood and Circulating Monocytes of Indian Patients With Visceral Leishmaniasis.

Apolipoprotein E (ApoE) has been associated with several diseases including Parkinson's disease, Alzheimer's and multiple sclerosis. ApoE also has documented immunomodulatory functions. We investigated gene expression in circulating monocytes and in bone marrows of patients with visceral leishmaniasis (VL) living in an endemic area in Bihar, India, and contrasted these with control healthy subjects or other diagnostic bone marrows from individuals in the same region. Samples from VL patients were obtained prior to initiating treatment. Our study revealed significant upregulated expression of the apoE transcript in patients with VL. Furthermore, the levels of ApoE protein were elevated in serum samples of subjects with VL compared with healthy endemic controls. These observations may provide clues regarding the complex interactions between lipid metabolism and immunoregulation of infectious and inflammatory diseases.

Synthetic Peptides Selected by Immunoinformatics as Potential Tools for the Specific Diagnosis of Canine Visceral Leishmaniasis.

Diagnosing canine visceral leishmaniasis (CVL) in Brazil faces challenges due to the limitations regarding the sensitivity and specificity of the current diagnostic protocol. Therefore, it is urgent to map new antigens or enhance the existing ones for future diagnostic techniques. Immunoinformatic tools are promising in the identification of new potential epitopes or antigen candidates. In this study, we evaluated peptides selected by epitope prediction for CVL serodiagnosis in ELISA assays. Ten B-cell epitopes were immunogenic in silico, but two peptides (peptides No. 45 and No. 48) showed the best performance in vitro. The selected peptides, both individually and in combination, were highly diagnostically accurate, with sensitivities ranging from 86.4% to 100% and with a specificity of approximately 90%. We observed that the combination of peptides showed better performance when compared to peptide alone, by detecting all asymptomatic dogs, showing lower cross-reactivity in sera from dogs with other canine infections, and did not detect vaccinated animals. Moreover, our data indicate the potential use of immunoinformatic tools associated with ELISA assays for the selection and evaluation of potential new targets, such as peptides, applied to the diagnosis of CVL.

Canine Visceral Leishmaniasis: A Histological and Immunohistochemical Study of Fibropoiesis in Chronic Interstitial Pneumonitis.

We studied some fibrotic aspects of chronic interstitial pneumonitis in the lungs of dogs infected with Leishmania infantum. The lungs of eleven naturally infected dogs, twelve experimentally infected with two distinct strains of L. infantum (BH401 and BH46), and six uninfected (controls) dogs, were analyzed by histological, parasitological, and immunohistochemical studies. Conventional histology (HE), collagen deposition (Gomori's silver staining for reticulin collagen fibers), and immunohistochemistry for myofibroblast characterization were carried out based on the cellular expression of alpha-smooth muscle actin, vimentin, cytokeratin, E-cadherin, snail antigen homologue 1 (SNAI1) (Snail), and the cytokine expression of transforming growth factor-beta (TGF-ß). Parasitological screening was carried out using conventional polymerase chain reaction (PCR) and the immunohistochemical reaction of streptavidin-peroxidase for visualizing Leishmania amastigotes. Dogs naturally infected with L. infantum and experimentally infected with L. infantum BH401 strains showed intense interstitial pneumonitis characterized by thickening of the alveolar septa as a consequence of an intense diffuse and focal (plaques) chronic exudate of mononuclear cells associated with fibrogenesis. The expression of alpha-actin, vimentin, and TGF-ß was higher in the lung interstitium of all infected dogs than in the other two groups (BH46 strain and controls). Moreover, in both the naturally and experimentally infected dog (BH401 strain) groups, the expression of Snail was moderate to intense in contrast to the other groups. Based on these immunohistochemical results, we concluded that mesenchymal cells are active in promoting changes in the extracellular matrix in the lungs of dogs naturally and experimentally infected with L. infantum, but it depends on the virulence of the parasite.

Anatomical Vascular Differences and Leishmania-Induced Vascular Morphological Changes Are Associated with a High Parasite Load in the Skin of Dogs Infected with Leishmania infantum.

Canine visceral leishmaniasis (CVL), caused by the protozoan Leishmania infantum, affects several organs, including the skin. Dogs are considered the major domestic reservoir animals for leishmaniasis, and through their highly parasitized skin, they can serve as a source of infection for sandfly vectors. Therefore, studies of the skin parasite-host relationship can contribute to the understanding of the infectious dissemination processes of parasites in the dermis and help to identify targets for diagnosis and treatment. Thus, the aim of this study was to evaluate the association of anatomical vascular differences and Leishmania-induced vascular morphological changes with clinical signs and parasite load by analyzing the ear and abdominal skin from dogs naturally infected with L. infantum. Paired samples of ear and abdominal skin from L. infantum-positive dogs (n = 26) were submitted for histological and immunohistochemistry analyses. The ear skin samples showed a more intense and more diffusely distributed granulomatous inflammatory reaction, a higher number and larger diameter of blood vessels, increased parasite load, higher expression of VEGF+ (vascular endothelial growth factor) and MAC 387+ (calprotectin) recently infiltrating cells, and more intense collagen disruption compared to the abdominal skin samples. Intracellular amastigotes were observed in blood vessels and inside endothelial cells and were diffusely distributed throughout the dermis in the ear skin samples. The NOS2/MAC387+ cell ratio was lower in the ear skin samples than in those of the abdomen, suggesting that in the ear dermis, the inflammatory infiltrate was less capable of producing NO and thereby control the parasite load. Together, these findings indicate how parasites and immune cells are distributed in the skin and suggest an important role for dermal vascularization in cellular influx and thereby in parasite dissemination through the skin of naturally infected dogs.

Case Report: Visceral Leishmaniasis Falsely Diagnosed as Viral Hepatitis C Without Febrile Symptoms.

Background: Visceral leishmaniasis (VL), also known as kala-azar, is caused by an intracellular parasite transmitted to humans by the bite of a sand fly, and with the source of the infection mainly being dogs. The main features of the disease are irregular fever, weight loss, hepatosplenomegaly and anaemia. Diagnosis relies mainly on bone marrow aspiration tests to find Leishman-Donovan(LD) bodies. And we report the case without febrile symptoms and hepatitis C virus antibody was probably false positive. Case Presentation: The case was a 74-year-old male residing in Yangquan City, Shanxi Province, a VL endemic area. He presented with generalised malaise, hepatosplenomegaly and scarring pigmentation on the skin as a result of scratching. Laboratory tests showed pancytopenia, positive hepatitis C virus antibody (HCV-Ab), positive direct anti-human globulin test (DAT), positive anti-cardiolipin antibody IgG, IgM (+), and increased immunoglobulin IgG. Symptomatic treatments such as hepatoprotection and blood transfusion were given, but the patient's symptoms still persisted and his spleen and liver further enlarged. Further repeat tests were performed and found to be negative for hepatitis C virus antibodies and antigens. The patient was eventually found to be infected with Leishmania protozoa by rk39 rapid diagnostic test and metagenomic next-generation sequencing(mNGS). And the patient quickly relieved after one course of treatment with sodium stibogluconate. Conclusion: Patients with VL may cause abnormalities in the immune system, leading to false positives for various antibodies without clear febrile symptoms, resulting in misdiagnosis or delayed diagnosis. It is important to consider VL in cases where there is a significant hepatosplenomegaly with a relevant epidemiological history. If the diagnosis cannot be confirmed through bone marrow aspiration and the patient is not suitable for splenic aspiration, the rk39 test can be used for initial exclusion and further verified through mNGS.

Spatio-Temporal Analysis and Clinical-Epidemiological Characterization of Visceral Leishmaniasis in Maranhão, Brazil, from 2009 to 2020.

This study was carried out to identify the spatial distribution and characterize the clinical-epidemiological profile of Visceral Leishmaniasis (VL) in Maranhão state, Brazil, from 2009 to 2020. This descriptive ecological study collected sociodemographic and clinical data of VL cases from the Brazilian Notifiable Diseases Information System database. A spatial autocorrelation analysis (Moran statistics) was performed. From 2009 to 2020, 5699 cases of VL were reported, with incidence of 6.5 cases/100,000 and prevalence of 7.1 cases/100,000. The temporal analysis showed a significant growth in incidence from 2009 to 2018, followed by a significant decrease between 2019 and 2020. The Moran map shows hotspots of high values in the central-west and central-east regions, and hotspots of low values in the northern region of Maranhão. The profile of patients affected by VL comprises males (OR = 1.8; IC95% = 1.72-1.92), aged under 14 years, brown, and with incomplete elementary schooling. The main symptoms reported were fever, fatigue, and edema. The main diagnostic method was laboratory. The mortality rate was 6.8%, and co-infection with HIV was reported by 8.5% of patients. The results of this study indicated the increase in incidence and lethality, as well as the expansion, of leishmaniasis in the state of Maranhão.

Comparative Study of Colorimetric In Situ Hybridization and Quantitative Real-Time Polymerase Chain Reaction for Diagnosis of Infection by Leishmania infantum in Dogs in Formalin-Fixed and Paraffin-Embedded Skin.

The zoonotic visceral leishmaniasis is caused by the protozoan Leishmania infantum and dogs are reservoirs for this parasite. For the diagnosis of Leishmania at the species level in dogs in formalin-fixed, paraffin-embedded skin (FFPES) samples, colorimetric in situ hybridization (CISH) and quantitative real-time polymerase chain reaction (qPCR) are options, but their sensitivities are not well established. Therefore, the aim of this study was to determine the sensitivity of these two techniques in FFPES for the diagnosis of the L. infantum infection in dogs using culture as the reference standard. The FFPES of 48 dogs with cutaneous infection by L. infantum confirmed by culture and by multilocus enzyme electrophoresis were examined by CISH and qPCR using specific probes for L. infantum. The sensitivities of qPCR, CISH and their combination were, respectively, 77.0%, 58.0% and 83.3%. The sensitivities of qPCR in dogs with and without clinical signs were, respectively, 74.2% and 82.4%. The sensitivities of CISH in dogs with and without clinical signs were, respectively, 61.3% and 52.9%. The CISH and qPCR showed satisfactory sensitivities for the diagnosis of L. infantum in the FFPES of dogs, even in dogs without clinical signs, and their combination increases the sensitivity for this diagnosis.

A panel of recombinant Leishmania donovani cell surface and secreted proteins identifies LdBPK_323600.1 as a serological marker of symptomatic infection.

Visceral leishmaniasis is a deadly infectious disease and is one of the world's major neglected health problems. Because the symptoms of infection are similar to other endemic diseases, accurate diagnosis is crucial for appropriate treatment. Definitive diagnosis using splenic or bone marrow aspirates is highly invasive, and so, serological assays are preferred, including the direct agglutination test (DAT) or rK39 strip test. These tests, however, are either difficult to perform in the field (DAT) or lack specificity in some endemic regions (rK39), making the development of new tests a research priority. The availability of Leishmania spp. genomes presents an opportunity to identify new diagnostic targets. Here, we use genome data and a mammalian protein expression system to create a panel of 93 proteins consisting of the extracellular ectodomains of the Leishmania donovani cell surface and secreted proteins. We use these panel and sera from murine experimental infection models and natural human and canine infections to identify new candidates for serological diagnosis. We observed a concordance between the most immunoreactive antigens in different host species and transmission settings. The antigen encoded by the LdBPK_323600.1 gene can diagnose Leishmania infections with high sensitivity and specificity in patient cohorts from different endemic regions including Bangladesh and Ethiopia. In longitudinal sampling of treated patients, we observed reductions in immunoreactivity to LdBPK_323600.1 suggesting it could be used to diagnose treatment success. In summary, we have identified new antigens that could contribute to improved serological diagnostic tests to help control the impact of this deadly tropical infectious disease. IMPORTANCE: Visceral leishmaniasis is fatal if left untreated with patients often displaying mild and non-specific symptoms during the early stages of infection making accurate diagnosis important. Current methods for diagnosis require highly trained medical staff to perform highly invasive biopsies of the liver or bone marrow which pose risks to the patient. Less invasive molecular tests are available but can suffer from regional variations in their ability to accurately diagnose an infection. To identify new diagnostic markers of visceral leishmaniasis, we produced and tested a panel of 93 proteins identified from the genome of the parasite responsible for this disease. We found that the pattern of host antibody reactivity to these proteins was broadly consistent across naturally acquired infections in both human patients and dogs, as well as experimental rodent infections. We identified a new protein called LdBPK_323600.1 that could accurately diagnose visceral leishmaniasis infections in humans.

Visceral Leishmaniasis Masquerading as Drug-Induced Pancytopenia in Lung Cancer Patients.

Maintenance chemotherapy is a standard treatment in patients with non-progressive advance staged IV non-squamous non-small cell lung cancer after induction therapy. Here, we report the case of a 53-year-old man undergoing a maintenance monotherapy with pemetrexed who presented prolonged pancytopenia despite filgrastim injections. A bone marrow aspiration revealed a macrophage activation syndrome with Leishmania amastigotes. A Polymerase Chest Reaction testing confirmed the diagnosis of visceral leishmaniasis. Treatment with liposomal amphotericin B was started. Oncologists should bear in mind that visceral leishmaniasis in endemic areas can potentially induce severe and prolonged pancytopenia in immunosuppressed patients, during chemotherapy in particular.

Demographic characteristics and prevalence of asymptomatic Leishmania donovani infection in migrant workers working in an endemic area in Northwest Ethiopia.

Introduction: Visceral leishmaniasis (VL), a neglected tropical disease that causes substantial morbidity and mortality, is a serious health problem in Ethiopia. Infections are caused by Leishmania (L.) donovani parasites. Most individuals remain asymptomatic, but some develop VL, which is generally fatal if not treated. We identified the area of Metema-Humera in Northwest Ethiopia as a setting in which we could follow migrant workers when they arrived in an endemic area. The demographic characteristics of this population and factors associated with their risk of asymptomatic infection are poorly characterised. Methods: We divided our cohort into individuals who visited this area for the first time (first comers, FC) and those who had already been in this area (repeat comers, RC). We followed them from the beginning (Time 1, T1) to the end of the agricultural season (Time 2, T2), performing tests for sand fly bite exposure (anti-sand fly saliva antibody ELISA) and serology for Leishmania infection (rK39 rapid diagnostic test and the direct agglutination test) at each time point and collecting information on risk factors for infection. Results: Our results show that most migrant workers come from non-endemic areas, are male, young (median age of 20 years) and are farmers or students. At T1, >80% of them had been already exposed to sand fly bites, as shown by the presence of anti-saliva antibodies. However, due to seasonality of sand flies there was no difference in exposure between FC and RC, or between T1 and T2. The serology data showed that at T1, but not at T2, a significantly higher proportion of RC were asymptomatic. Furthermore, 28.6% of FC became asymptomatic between T1 and T2. Over the duration of this study, one FC and one RC developed VL. In multivariable logistic regression of asymptomatic infection at T1, only age and the number of visits to Metema/Humera were significantly associated with asymptomatic infection. Conclusion: A better understanding of the dynamics of parasite transmission and the risk factors associated with the development of asymptomatic infections and potentially VL will be essential for the development of new strategies to prevent leishmaniasis.

Seroprevalence of visceral leishmaniasis among pregnant women in Jahrom city in Fars province, southern Iran.

Background: Visceral leishmaniasis (VL) is a public health issue in endemic countries with poor sanitation facilities. In this study, the seroprevalence rate and associated risk factors of VL were investigated during September 2020 to February 2021 in pregnant women referred to Ostad Mottahari and Peymanieh hospitals in Jahrom county, Fars province, southern Iran. Material and methods: A total of 220 serum samples of pregnant women were assessed for the presence of Anti-Leishmania infantum antibodies by direct agglutination antigen (DAT). The associated risk factors were obtained using questionnaires. Results: The overall seroprevalence of VL in pregnant women was 12.72% (28/220). Considering the antibody titer, titer 1:1600 was detected in 23 samples, titer 1:3200 in 4 samples, and titer 1:6400 in one sample. All 5 women with titer >3200 had mild fever. As such, there was a statistically significant difference regarding the age (≥39 years old with p-value: 0.01). Conclusions: We recommend an appropriate health education program for pregnant women and serological screening of VL before pregnancy in endemic cities. Moreover, we believed a need for more epidemiological studies for better understand the status of VL in pregnant women.

Visceral Leishmaniasis (VL) Clinical Presentation, Laboratory Findings, Treatment Options and Outcome.

Background: Black disease, also known as visceral leishmaniasis (VL), is a parasitic illness caused by various Leishmania species. The risk of morbidity and mortality increases with delayed diagnosis and treatment. Early VL diagnosis and fast appropriate treatment are critical issues in endemic areas. Methods: This study was a retrospective cross-sectional study to investigate the diagnostic and therapeutic course of patients admitted with the diagnosis of VL in the Children's Medical Center (CMC) Hospital, Tehran, Iran. All cases of VL in patients under the age of 18 hospitalized between the years 2012 to 2022 were enrolled. Results: Twenty-seven patients were enrolled with an average age of 28.13 months with the majority of females (51.8%). Common clinical signs were fever (96.2%) and splenomegaly (92.59%). However, lymphadenopathy was rare. The largest number of patients was from Tehran Province, followed by Ardabil, Khuzestan, Gilan, and Alborz provinces. The most common hematological abnormalities were anemia (85.1%) and thrombocytopenia (44.4%). In accordance with the treatment strategy, liposomal amphotericin B and amphotericin B deoxycholate were given to 11 and 5 patients, respectively. Eleven of them received glucantime. The average length of hospitalization for liposomal amphotericin B was 15.36 ± 12.49 days. In comparison with glucantime (18.38 ±10.26 days) and amphotericin B deoxycholate (20.20± 6.18 days), liposomal amphotericin B group hospitalization was shorter than others were. Conclusion: VL should be included in the differential diagnosis of any child who presents with fever, splenomegaly, and anemia. Concerning the treatment strategy in this study, liposomal amphotericin B had more efficiency and shorter hospitalization duration.

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.

Mathematical modeling and stability analysis of the novel fractional model in the Caputo derivative operator: A case study.

The fundamental goal of this research is to suggest a novel mathematical operator for modeling visceral leishmaniasis, specifically the Caputo fractional-order derivative. By utilizing the Fractional Euler Method, we were able to simulate the dynamics of the fractional visceral leishmaniasis model, evaluate the stability of the equilibrium point, and devise a treatment strategy for the disease. The endemic and disease-free equilibrium points are studied as symmetrical components of the proposed dynamical model, together with their stabilities. It was shown that the fractional calculus model was more accurate in representing the situation under investigation than the classical framework at α = 0.99 and α = 0.98. We provide justification for the usage of fractional models in mathematical modeling by comparing results to real-world data and finding that the new fractional formalism more accurately mimics reality than did the classical framework. Additional research in the future into the fractional model and the impact of vaccinations and medications is necessary to discover the most effective methods of disease control.

The spleen is the graveyard of CD4+ cells in patients with immunological failure of visceral leishmaniasis and AIDS.

BACKGROUND: Visceral leishmaniasis (VL), or kala-azar, is a common comorbidity in patients with AIDS in endemic areas. Many patients continue to experiences relapses of VL despite virological control, but with immunological failure. These patients remain chronically symptomatic with hypersplenism, for example with anemia, leukopenia, and thrombocytopenia, and are at risk of severe co-infection due to low CD4+ count. Therefore, in this study, splenectomized patients with VL and HIV infection were investigated to understand why the CD4+ count fails to recover in these patients, evaluating the importance of spleen mass for hypersplenism and immunological failure. METHODS: From a retrospective open cohort of 13 patients who had previously undergone splenectomy as salvage therapy for relapsing VL, 11 patients with HIV infection were investigated. This study compared the patients' complete blood cell count (CBC) and CD4+ and CD8+ cell counts before and after splenectomy with respect to spleen weight. RESULTS: CBC was substantially improved after splenectomy, indicating hypersplenism. However, to the best of our knowledge, this is the first study to show that spleen mass is strongly and negatively correlated with CD4+ cell count (ρ = -0.71, P = 0.015). CONCLUSIONS: This finding was unexpected, as the spleen is the most extensive lymphoid tissue and T-lymphocyte source. After reviewing the literature and reasoning, we hypothesized that the immunological failure was secondary to CD4+ loss initially by apoptosis in the spleen induced by productive HIV infection and, subsequently, by pyroptosis sustained by parasitic infection in spleen macrophages.

Estimating the proportion of relapse following treatment of Visceral Leishmaniasis: meta-analysis using Infectious Diseases Data Observatory (IDDO) systematic review.

Background: Occurrences of relapse after 6-months post-treatment has been reported in recent Visceral Leishmaniasis (VL) efficacy studies. A meta-analysis was carried out to quantify the proportion of relapses observed at and beyond 6-months using the Infectious Diseases Data Observatory (IDDO) systematic review (SR) database. Methods: Studies in the IDDO SR database (1983-2021; 160 studies) were eligible for inclusion if follow-up was at least 6-months, relapse was clearly reported, and patients with HIV coinfections were excluded. Meta-analysis of single proportion was undertaken and the estimates were reported with 95% confidence intervals (CI). Findings: Overall, 131 studies enrolling 27,687 patients were included; 1193 patients relapsed. In the Indian sub-continent (ISC), relapse estimates at 6-months was 4.5% [95% CI: 2.6%-7.5%; I2 = 66.2%] following single dose liposomal amphotericin B (L-AmB) and 1.5% [95% CI: 0.7%-3.3%; I2 = 0%] for L-AmB in a combination therapy. In East Africa (EA), corresponding estimates were 3.8% [95% CI: 1.3%-10.9%; I2 = 75.8%] following pentavalent antimony (PA), and 13.0% [95% CI: 4.3%-33.6%; I2 = 0%] for PA + paromomycin. From 21 studies with follow-up longer than 6-months, 0.6% [95% CI: 0.2%-1.8%; I2 = 0%] of patients relapsed after 6-months and estimated 27.6% [95% CI: 11.2%-53.4%; I2 = 12%] of relapses would have been missed by a 6-month follow-up. Interpretation: The estimated relapse proportion ranged from 0.5% to 4.5% in ISC and 3.8%-13.0% in EA with the currently recommended drugs. Over one-quarter of relapses would be missed with 6-months follow-up suggesting a longer follow-up may be warranted. Funding: Wellcome Trust (ref: 208378/Z/17/Z).

New Approaches to the Prevention of Visceral Leishmaniasis: A Review of Recent Patents of Potential Candidates for a Chimeric Protein Vaccine.

The development of prophylactic vaccines is important in preventing and controlling diseases such as visceral leishmaniasis (VL), in addition to being an economic measure for public health. Despite the efforts to develop a vaccine against human VL caused by Leishmania infantum, none is available, and the focus has shifted to developing vaccines against canine visceral leishmaniasis (CVL). Currently, commercially available vaccines are targeted at CVL but are not effective. Different strategies have been applied in developing and improving vaccines, such as using chimeric proteins to expand vaccine coverage. The search for patents can be a way of tracking vaccines that have the potential to be marketed. In this context, the present work presents a summary of immunological aspects relevant to VL vaccine development with a focus on the composition of chimeric protein vaccines for CVL deposited in patent banks as an important approach for biotechnological development. The resulting data could facilitate the screening and selection of antigens to compose vaccine candidates with high performance against VL.