Evaluation of serological markers to monitor the disease status of Indian post kala-azar dermal leishmaniasis

In vitro growth of Leishmania parasites from biopsy samples of suspected cutaneous and visceral leishmaniasis cases in Sri Lanka: An observational study

Sri Lanka reports a large focus of Leishmania donovani caused cutaneous leishmaniasis (CL). Subsequent emergence of visceral leishmaniasis (VL) was also reported recently. Expansion of the on-going disease outbreak and many complexities indicate urgent need to enhance early case detection methods. In vitro cultivation (IVC) of parasites causing visceral leishmaniasis (VL) is important for disease confirmation and to obtain sufficient quantities of parasites required in many scientific studies. IVC is carried out as a useful second line investigation for direct microscopy negative patients with CL in this setting. Along with the emergence of VL, current study was carried out to evaluate in vitro growth of local VL parasites and to identify their differences associated with in vitro growth characteristics. Routine parasitological diagnostic methods, i.e., light microscopy (LM), polymerase chain reaction (PCR) were used for confirmation of suspected cases. Lesion samples from 125 suspected CL cases and bone marrow or splenic aspirations from 125 suspected VL patients were used to inoculate IVCs. Media M199 (about 70 μl) supplemented with 15-20% of heat inactivated fetal bovine serum was used for initial culturing procedures in capillaries. Capillary cultures were monitored daily. Total of 44 different compositions/conditions were used for evaluating in vitro growth of VL causing parasite. Daily records on parasite counts, morphological appearance (size, shape, and wriggly movements) were maintained. In vitro transformation of Leishmania promastigotes to amastigotes and outcome of the attempts on recovery of live Leishmania from culture stabilates was also compared between CL and VL parasites. Proportion of cultures showing a transformation of promastigotes were 40/45 (88.9%) and 4/10 (40.0%) for CL and VL respectively. In the transformed cultures, parasites showing typical shape, size and movement patterns were less in VL (1/4, 25.0%) compared to CL (28/40, 70.0%). CL cultures showed a growth up to mass culturing level with mean duration of two weeks while it was about five weeks for VL cultures. Proportion of cultures that reached a parasite density of 1 × 106 cells/ml (proceeded to mass cultures) was significantly low in VL (4/10, 40%) as compared to CL (28/40, 70.0%). None of media compositions/conditions were successful for mass culturing of VL parasites while all of them were shown to be useful for growing CL strains. Also in vitro transformation to amastigote form and recovering of culture stabilates were not successful compared to CL. There were clear differences between in vitro growth of Leishmania parasites causing local CL and VL. Further studies are recommended for optimization of in vitro culturing of VL parasite which will be invaluable to enhance case detection in future.

Serological studies on rK39 negative Visceral Leishmaniasis in an endemic focus of Leishmania donovani induced Cutaneous Leishmaniasis

Sri Lanka reports a focus of L. donovani induced cutaneous leishmaniasis (CL). Our more recent parasite and clinical studies and historical evidence point towards long term existence of Leishmania in the country, indicating a possible evolution leading to antigenic heterogenicity as well. In-house enzyme-linked immunosorbent assay (ELISA) that was developed during phase 1 study indicated >80% sero-positivity in local CL, while visceral leishmaniasis (VL) remained very rare with majority being negative when tested with rK39 assay. A novel serological tool was developed and sero-positivity of VL was assessed for the first time. The assay showed 100.0% sensitivity and 98.3% specificity for detection of VL. Samples were showed less positivity with established direct agglutination test (DAT) and rK39 strip test. The assay was less expensive than that of established rapid diagnostic tests (RDTs), culture and PCR assays. This assay may be useful in diagnosing clinical VL infections, detection of light microscopy (LM) negative patients, tracking post treatment stages, field screening of asymptomatic cases and in further serological studies.

RG203KR Mutations in SARS-CoV-2 Nucleocapsid: Assessing the Impact Using a Virus-Like Particle Model System

Since its origin in late 2019, the SARS-CoV-2 virus has been constantly mutating and evolving. Current studies mostly employ spike protein (S) pseudovirus systems to determine the effects of mutations on the infectivity and immunogenicity of variants.

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.

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.

Utility of Blood as the Clinical Specimen for the Molecular Diagnosis of Post-Kala-Azar Dermal Leishmaniasis

The countries in the Indian subcontinent have reported a dramatic decline in visceral leishmaniasis (VL) cases. However, the presence of the parasite reservoir in the form of post-kala-azar dermal leishmaniasis (PKDL), a dermal sequel of VL, is a hurdle in attaining VL elimination. Presently employed clinical specimens for the diagnosis of PKDL include skin biopsy specimens and slit skin smears. In this study, the use of blood as a clinical specimen was investigated in different manifestations of PKDL in India. This is a bicentric study (National Institute of Pathology, Indian Council of Medical Research [ICMR], New Delhi, and Institute of Medical Sciences [IMS], Banaras Hindu University, Varanasi), with 215 participants (120 PKDL patients and 95 controls). Highly sensitive quantitative real-time PCR (Q-PCR) and field-deployable loop-mediated isothermal amplification (LAMP) were employed using blood samples for diagnosis. Promising sensitivities of 77.50% (95% confidence interval [CI], 69.24 to 84.05%) for Q-PCR and 70.83% (95% CI, 62.16 to 78.22%) for LAMP were obtained for the diagnosis of PKDL. Further, enhanced sensitivities of 83.33% (95% CI, 71.28 to 90.98%) and 77.78% (95% CI, 65.06 to 86.80%) for Q-PCR and LAMP, respectively, were recorded for the detection of macular cases. The study revealed an inverse correlation between the parasite load estimated in slit and blood samples, thereby favoring the use of blood for the diagnosis of the macular variant, which may be missed due to scant parasite loads in the slit. This study is the first to propose the promising potential of blood as a clinical specimen for accurate diagnosis of PKDL, which would aid in fast-tracking VL elimination.

Molecular Tracking of the Leishmania Parasite

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

Post Kala-Azar Dermal Leishmaniasis: Clinical Features and Differential Diagnosis

Post kala-azar dermal leishmaniasis (PKDL) is a mucocutaneous disease usually seen in apparently cured, inadequately treated or untreated cases of visceral leishmaniasis and is endemic to many parts of India, Nepal, Bangladesh, and eastern Africa (Sudan, Ethiopia, Kenya). The disease usually manifests as a variable combination of hypopigmented patches, erythematous succulent papulo-plaques, and nodular lesions on the face and upper body and sometimes extending on the extremities, genitalia, and tongue. Atypical morphology and presentations are not uncommon, especially in endemic areas, which include photosensitivity, verrucous, hypertrophic, xanthomatous, and ulcerative lesions. Recognition of spectrum of mucocutaneous changes helps physicians in early initiation of treatment and in reducing disease transmission in the community. The differential diagnosis depends on the pattern of manifestations, but lepromatous leprosy is the closest mimicker. Since PKDL does not cause significant morbidity, at least initially, but the affected patients continue to act as a reservoir of the disease, active case detection is required to identify cases early to control the disease transmission in the community.

The importance of T cell-derived cytokines in post-kala-azar dermal leishmaniasis

Infection with the same species of Leishmania (L)donovani causes different manifestations including visceral leishmaniasis (VL) and post kala-azar dermal leishmaniasis (PKDL), indicating that the host-related immunological parameters perform a decisive role in the pathogenesis of diseases. As PKDL is a reservoir of the parasite, a better understanding of the host immune responses is necessary to restrict the L. donovani transmission. The proper local production of Th1 cell-related cytokines (including IFN-γ, TNF-α and IL-12), Th17 cell-derived cytokines (such as IL-17A, IL-17F and IL-22), and CD8⁺ cytotoxic T lymphocyte (CTL)-derived IFN-γ are protective against PKDL. However, dominant production of regulatory CD4⁺ T cell-derived cytokines (such as IL-10 and TGF-β), Th2 cell-derived cytokines (such as IL-4/IL-13), M2 macrophage-derived cytokines (such as IL-4 and IL-10), keratinocyte-derived IL-10, regulatory CD8⁺ T cell-derived IL-10, and dendritic cell-derived IL-10, IL-27 and IL-21 can contribute to the parasite persistence and PKDL development. Understanding of the T cell-related cytokine network within PKDL lesions gives rise to novel insights concerning the role of each cytokine in the protection or susceptibility to disease. Manipulation of the cytokine network can be considered as an interesting immunotherapeutic strategy for the treatment of L. donovani-mediated PKDL.

Prevalidation of an ELISA for Detection of a New Clinical Entity: Leishmania donovani-Induced Cutaneous Leishmaniasis

Human leishmaniasis which is considered a neglected tropical parasitic disease presents in three main clinical forms (i.e., cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), and visceral leishmaniasis (VL)) that are mainly determined by its causative species. Leishmania donovani, the most virulent and visceralizing parasite, is increasingly reported to cause CL in many countries in the world. Although CL is generally not considered to evoke a humoral immune response except for a nonrobust and a variable response in minority of cases, VL is associated with a clear strong humoral response. However, humoral response in L. donovani-induced CL has not been well evaluated before. A suitable serology-based assay is an essential primary step in such a study. An indirect enzyme-linked immunosorbent assay (ELISA) based on Leishmania promastigote crude antigen (Ag) was designed and optimized in order to utilize in further serological studies on this new clinical entity. Optimization included quantification of crude Ag, checkerboard titration method for determination of optimal concentrations for coating Ag, human sera and secondary antibody (Ab) with suitable coating buffer, blocking buffer, and incubating temperatures. The selected coating buffer was 0.02 M phosphate buffer, pH 6.8, and the blocking buffer was 2% fetal bovine serum with 0.01 M phosphate-buffered saline. At least 1 μg of crude Ag was required for coating the ELISA plate, while 1 : 1000 serum was used as primary Ab. The optimized concentration of secondary Ab was 1 : 64000 which might be altered according to manufacturer recommendations. The assay specificity was pre-evaluated using sera (n = 20 from each category) from confirmed CL patients and controls (other skin diseases which mimic CL, other systemic diseases that mimic VL, nonendemic healthy controls, and endemic healthy controls). This procedure described an optimization procedure of an ELISA technique for detection of anti-Leishmania antibodies in patients with L. donovani caused CL.

Quantification of Soluble or Insoluble Fractions of Leishmania Parasite Proteins in Microvolume Applications: A Simplification to Standard Lowry Assay

Protein quantification is often an essential step in any research field that involves proteins. Although the standard Lowry assay and its modifications are most abundantly used in protein quantification, the existing methods are rigid or often demonstrate nonlinearity between protein concentration and color intensity. A method for fast and accurate qualitative and/or quantitative determination of total soluble/insoluble proteins or micro-well plate immobilized proteins isolated from Leishmania parasites in microvolumes was described in the current study. Improvements in cost-effective techniques are necessary to increase the research outputs in resource-limited settings. This method is a modification to the established Lowry assay for protein quantification. Concentrations of unknown samples were calculated using a standard curve prepared using a standard series of bovine serum albumin (BSA). The optimized reagents were 2 N NaOH (sodium hydroxide), 2% Na₂CO₃ (sodium carbonate), 1% CuSO₄ (copper sulfate), 2% KNaC₄H₄O₆ (potassium sodium tartrate), and 2 N Folin and Ciocalteu's phenol. This modified protein assay was sensitive for quantifying Leishmania proteins in a total crude extract or in a soluble fraction within the approximate range of 10–500 μg/ml (1–50 μg/assay) and showed a linearity between color intensity and concentration of the protein. This is an easier, fast, and accurate method for quantifying proteins with microvolumes in a cost-effective manner for routine use in research laboratories in resource-limited settings.

A Leishmania infantum hypothetical protein evaluated as a recombinant protein and specific B-cell epitope for the serodiagnosis and prognosis of visceral leishmaniasis

The serodiagnosis of visceral leishmaniasis (VL) presents problems related to the sensitivity and/or specificity of the tests. In this context, more refined antigens should be identified and applied for the improvement of disease diagnosis. In the present study, DNA with an encoding of a Leishmania infantum hypothetical protein, LiHyC, was cloned, and the recombinant protein was expressed, purified, and evaluated for the serodiagnosis of canine and human VL. In addition, a specific B-cell epitope present in the LiHyC sequence was predicted; the peptide was both synthetized and evaluated in the ELISA experiments. For comparison, commercial diagnostic kits were used against positive (VL hosts) and negative (healthy hosts) samples. Results showed that the recombinant protein (rLiHyC) and synthetic peptide (PeptC) were highly sensitive and specific to diagnose canine and human VL, with 100% sensitivity and specificity, while no false-positive or false-negative result was detected. When the DPP® CVL kit was used to identify canine samples, 44 and 52 of the 60 L. infantum-infected animals, without or with clinical signals of disease, respectively, were identified, while eight and four samples were considered as false-negatives, respectively. For human VL, an IT LEISH® kit was used, and 33 of the 40 VL patients were identified, while seven samples were considered to be false-negatives. Post-therapeutic serological follow-up testing sera samples from treated and untreated VL patients showed a significant drop in the anti-PeptC and anti-rLiHyC antibody levels, thus suggesting the feasibility to use the recombinant protein and/or synthetic peptide in future studies as diagnostic and/or prognostic markers for VL.

Immune Responses in Post Kala-azar Dermal Leishmaniasis

Kala-azar, commonly known as visceral leishmaniasis (VL), is a neglected tropical disease that has been targeted in South Asia for elimination by 2020. Presently, the Kala-azar Elimination Programme is aimed at identifying new low-endemic foci by active case detection, consolidating vector control measures, and decreasing potential reservoirs, of which Post Kala-azar Dermal Leishmaniasis (PKDL) is considered as the most important. PKDL is a skin condition that occurs after apparently successful treatment of VL and is characterized by hypopigmented patches (macular) or a mixture of papules, nodules, and/or macules (polymorphic). To achieve this goal of elimination, it is important to delineate the pathophysiology so that informed decisions can be made regarding the most appropriate and cost-effective approach. We reviewed the literature with regard to PKDL in Asia and Africa and interpreted the findings in establishing a potential correlation between the immune responses and pathophysiology. The overall histopathology indicated the presence of a dense, inflammatory cellular infiltrate, characterized by increased expression of alternatively activated CD68+ macrophages, CD8+ T cells showing features of exhaustion, CD20+ B cells, along with decreased CD1a+ dendritic cells. Accordingly, this review is an update on the overall immunopathology of PKDL, so as to provide a better understanding of host-parasite interactions and the immune responses generated which could translate into availability of markers that can be harnessed for assessment of disease progression and improvement of existing treatment modalities.

In-situ immune profile of polymorphic vs. macular Indian Post Kala-azar dermal leishmaniasis

Post Kala-azar Dermal Leishmaniasis (PKDL), a sequel of apparently cured Visceral Leishmaniasis presents in South Asia with papulonodular (polymorphic) or hypomelanotic lesions (macular). Till date, the polymorphic variant was considered predominant, constituting 85–90%. However, following active-case surveillance, the proportion of macular PKDL has increased substantially to nearly 50%, necessitating an in-depth analysis of this variant. Accordingly, this study aimed to delineate the cellular infiltrate in macular vis-à-vis polymorphic PKDL. To study the overall histopathology, hematoxylin and eosin staining was performed on lesional sections and phenotyping by immunohistochemistry done in terms of dendritic cells (CD1a), macrophages (CD68), HLA-DR, T-cells (CD8, CD4), B-cells (CD20) and Ki67 along with assessment of the status of circulating homing markers CCL2, CCL7 and CXCL13. In polymorphic cases (n = 20), the cellular infiltration was substantial, whereas in macular lesions (n = 20) it was mild and patchy with relative sparing of the reticular dermis. Although parasite DNA was identified in both variants by ITS-1 PCR, the parasite load was significantly higher in the polymorphic variant and Leishman-Donovan bodies were notably minimally present in macular cases. Both variants demonstrated a decrease in CD1a⁺ dendritic cells, HLA-DR expression and CD4⁺ T-cells. In macular cases, the proportion of CD68⁺ macrophages, CD8⁺ T-cells and CD20⁺ B-cells was 4.6 fold, 17.0 fold and 1.6 fold lower than polymorphic cases. The absence of Ki67 positivity and increased levels of chemoattractants suggested dermal homing of these cellular subsets. Taken together, as compared to the polymorphic variant, patients with macular PKDL demonstrated a lower parasite load along with a lesser degree of cellular infiltration, suggesting differences in host-pathogen interactions, which in turn can impact on their disease transmitting potential and responses to chemotherapy.

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Comparative analysis of immunopathology of polymorphic vs. macular PKDL.

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Dense lymphohistiocytic infiltrate in polymorphic PKDL.

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Mild and patchy cellular infiltration in macular PKDL with minimal Leishman Donovan bodies.

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Decreased presence of CD1a, HLA-DR and CD4⁺ T-cells in both variants.

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The presence of CD8⁺, CD68⁺and CD20⁺ cells in polymorphic>>>macular PKDL.

Biomarkers in Post-kala-azar Dermal Leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL) follows visceral leishmaniasis (VL, kala-azar) in 10–60% of cases. It is characterized by an asymptomatic skin rash, usually starting in the face and consisting of macules, papules, or nodules. Diagnosis is difficult in the field and is often made clinically. There is an extensive differential diagnosis, and parasitological confirmation is preferred particularly when drug treatment is considered. The response to treatment is difficult to assess as this may be slow and lesions take long to heal, thus possibly exposing patients unnecessarily to prolonged drug treatment. Biomarkers are needed; these may be parasitological (from microscopy, PCR), serological (from blood, or from the lesion), immunological (from blood, tissue), pathological (from cytology in a smear, histology in a biopsy), repeated clinical assessment (grading, photography), or combinations. In this paper, we will review evidence for currently used biomarkers and discuss promising developments.

Sex-Related Differences in Immune Response and Symptomatic Manifestations to Infection with Leishmania Species

Worldwide, an estimated 12 million people are infected with Leishmania spp. and an additional 350 million are at risk of infection. Leishmania are intracellular parasites that cause disease by suppressing macrophage microbicidal responses. Infection can remain asymptomatic or lead to a spectrum of diseases including cutaneous, mucocutaneous, and visceral leishmaniasis. Ultimately, the combination of both pathogen and host factors determines the outcome of infection. Leishmaniasis, as well as numerous other infectious diseases, exhibits sex-related differences that cannot be explained solely in terms of environmental exposure or healthcare access. Furthermore, transcriptomic evidence is revealing that biological sex is a variable impacting physiology, immune response, drug metabolism, and consequently, the progression of disease. Herein, we review the distribution, morbidity, and mortality among male and female leishmaniasis patients. Additionally, we discuss experimental findings and new avenues of research concerning sex-specific responses in cutaneous and visceral leishmaniasis. The limitations of current therapies and the emergence of drug-resistant parasites underscore the need for new treatments that could harness the host immune response. As such, understanding the mechanisms driving the differential immune response and disease outcome of males versus females is a necessary step in the development of safer and more effective treatments against leishmaniasis.

Visceral Leishmaniasis IgG1 Rapid Monitoring of Cure vs. Relapse, and Potential for Diagnosis of Post Kala-Azar Dermal Leishmaniasis

Background: There is a recognized need for an improved diagnostic test to assess post-chemotherapeutic treatment outcome in visceral leishmaniasis (VL) and to diagnose post kala-azar dermal leishmaniasis (PKDL). We previously demonstrated by ELISA and a prototype novel rapid diagnostic test (RDT), that high anti-Leishmania IgG1 is associated with post-treatment relapse versus cure in VL.

Methodology: Here, we further evaluate this novel, low-cost RDT, named VL Sero K-SeT, and ELISA for monitoring IgG1 levels in VL patients after treatment. IgG1 levels against L. donovani lysate were determined. We applied these assays to Indian sera from cured VL at 6 months post treatment as well as to relapse and PKDL patients. Sudanese sera from pre- and post-treatment and relapse were also tested.

Results: Of 104 paired Indian sera taken before and after treatment for VL, when deemed clinically cured, 81 (77.9%) were positive by VL Sero K-SeT before treatment; by 6 months, 68 of these 81 (84.0%) had a negative or reduced RDT test line intensity. ELISAs differed in positivity rate between pre- and post-treatment (p = 0.0162). Twenty eight of 33 (84.8%) Indian samples taken at diagnosis of relapse were RDT positive. A comparison of Indian VL Sero K-SeT data from patients deemed cured and relapsed confirmed that there was a significant difference (p < 0.0001) in positivity rate for the two groups using this RDT. Ten of 17 (58.8%) Sudanese sera went from positive to negative or decreased VL Sero K-SeT at the end of 11–30 days of treatment. Forty nine of 63 (77.8%) PKDL samples from India were positive by VL Sero K-SeT.

Conclusion: We have further shown the relevance of IgG1 in determining clinical status in VL patients. A positive VL Sero K-SeT may also be helpful in supporting diagnosis of PKDL. With further refinement, such as the use of specific antigens, the VL Sero K-SeT and/or IgG1 ELISA may be adjuncts to current VL control programmes.

Vaccination with a CD4+ and CD8+ T-cell epitopes-based recombinant chimeric protein derived from Leishmania infantum proteins confers protective immunity against visceral leishmaniasis

Vaccination seems to be the best approach to control visceral leishmaniasis (VL). Resistance against infection is based on the development of a Th1 immune response characterized by the production of interferons-γ (IFN-γ), interleukin-12 (IL-12), granulocyte-macrophage-colony-stimulating factor (GM-CSF), and tumor necrosis factor-α (TNF-α), among others. A number of antigens have been tested as potential targets against the disease; few of them are able to stimulate human immune cells. In the present study, 1 prediction of MHC class I and II molecules-specific epitopes in the amino acid sequences of 3 Leishmania proteins: 1 hypothetical, prohibitin, and small glutamine-rich tetratricopeptide repeat-containing proteins, was performed using bioinformatics tools, and a T-cell epitopes-based recombinant chimeric protein was constructed, synthetized and purified to be evaluated in invitro and in vivo experiments. The purified protein was tested regarding its immunogenicity in peripheral blood mononuclear cells (PBMCs) from healthy subjects and VL patients, as well as to its immunogenicity and protective efficacy in a murine model against Leishmania infantum infection. Results showed a Th1 response based on high IFN-γ and low IL-10 levels derived from in chimera-stimulated PBMCs in both healthy subjects and VL patients. In addition, chimera and/or saponin-immunized mice presented significantly lower parasite burden in distinct evaluated organs, when compared to the controls, besides higher levels of IFN-γ, IL-2, IL-12, and GM-CSF, and an IgG2a isotype-based humoral response. In addition, the CD4⁺ and CD8⁺ T-cell subtypes contributed to IFN-γ production in the protected animals. The results showed the immunogenicity in human cells and the protective efficacy against L. infantum in a murine model, and well indicate that this recombinant chimera can be considered as a promising strategy to be used against human disease.

Identification of atypical dermal leishmaniasis resolved by restriction fragment length polymorphism

This case report series alerts to the atypical manifestations of dermal leishmaniasis in an area endemic for post kala-azar dermal leishmaniasis, the sequel to visceral leishmaniasis. We have reported two cases with multiple skin lesions, wherein the rK39 strip test, polymerase chain reaction and parasite load confirmed the presence of Leishmania parasites. The causative parasite was identified as Leishmania major by restriction fragment length polymorphism of the ribosomal DNA Internal Transcribed Spacer-1, overruling the clinical suspicion of post kala-azar dermal leishmaniasis. The third case presented with fever and extensive hypopigmented patches in the upper extremities; parasites were identified in blood and skin by polymerase chain reaction and typed by restriction fragment length polymorphism as Leishmania donovani, establishing this as a case of visceral leishmaniasis concomitant with dermal leishmaniasis, secondary to dissemination of viscerotropic L. donovani. The present case series emphasizes the importance of molecular tools to identify the Leishmania species in order to ensure appropriate treatment.

Evaluation of a Leishmania hypothetical protein administered as DNA vaccine or recombinant protein against Leishmania infantum infection and its immunogenicity in humans

Visceral leishmaniasis (VL) is a fatal disease when acute and untreated. The treatment against this disease is long and presents toxicity and/or high costs. Moreover, parasite resistance has been increasing. Therefore, alternative control measures to avoid the spread of disease should be considered. It is accepted that the development of the T helper (Th)1 immune response, based on the production of pro-inflammatory cytokines, is required for the control of parasites. Although recombinant protein-based vaccines have been tested against VL, they require supplementation with immune adjuvants. In addition, there is a scarcity of studies that comparatively evaluate the efficacy of the immunogens when administered by different delivery systems in mammalian hosts. In the present study, a Leishmania hypothetical protein, LiHyR, was cloned and evaluated by immunization as a plasmid deoxyribonucleic acid (DNA) vaccine or in a recombinant format plus saponin against Leishmania infantum infection. Results showed that both vaccination regimens induced a Th1 cell-based immunity, since high levels of interferon-gamma (IFN-γ), interleukin (IL)-2, IL-12, granulocyte-macrophage colony-stimulating factor (GM-CSF), and tumor necrosis factor alpha (TNF-α) were found, and were associated with the low production of IL-4, IL-10, and anti-parasite immunoglobulin (IgG)1 isotype. In addition, significant reductions in the parasite load were found in the evaluated organs of the DNA LiHyR or rLiHyR/saponin-vaccinated animals. No significant difference was achieved between groups vaccinated with DNA or the recombinant protein. The antigen proved to be also immunogenic in human peripheral blood mononuclear cells (PBMCs) collected from healthy subjects and from untreated and treated VL patients. A higher IgG2 isotype was also found in sera samples of these subjects, thus demonstrating its possible use as a human vaccine. This study demonstrates the protective efficacy of a new Leishmania protein against VL, when it is administered as a DNA vaccine or a recombinant protein plus saponin, and points out its use as a human vaccine against disease.

Identification of immune biomarkers related to disease progression and treatment efficacy in human visceral leishmaniasis

Visceral leishmaniasis (VL) is a potentially fatal disease, in which the treatment based on chemotherapy is considered toxic. The cure of disease is associated with the life-long Th1-type immunity against the infection. The Th1-related cytokines production by peripheral blood mononuclear cells (PBMCs) seems to be crucial for host control of parasite load and clinical cure. In the current study, we used five proteins (IgE-dependent histamine-releasing factor [HRF], LiHyD, LiHyV, LiHyT and LiHyp6) recently shown to be antigenic and/or immunogenic in the canine VL, aiming to evaluate the antigen-specific antibody levels and cytokine production in PBMCs culture supernatants collected from VL patients before and after anti-VL treatment. In the results, when PBMCs were exposed to rHRF, rLiHyD and rLiHyT, higher IFN-γ and lower IL-10 levels were observed in all patients that were treated and clinically cured. Analysis of specific antibody subclasses was in line with in vitro cellular response, since a higher IgG2 production was found in the treated and cured patients, when compared to the IgG1 subclass levels. In addition, evaluating the diagnostic efficacy of the recombinant molecules, the rHRF, rLiHyD and rLiHyT proteins showed the best results in the serology assays to identify all VL patients, as well as these antigens were not recognized by antibodies in sera from non-infected subjects or those with leishmaniasis-related diseases. Our results corroborate the view that clinical cure of VL is associated with a sustained Th1-related response, and indicate the potential use of rHRF, rLiHyD and rLiHyT as immune biomarkers of VL treatment.

The immunology of post-kala-azar dermal leishmaniasis (PKDL)

Post-kala-azar dermal leishmaniasis (PKDL) is a common complication of visceral leishmaniasis (VL) caused by Leishmania donovani. Because of its possible role in transmission it is considered a public health problem in VL endemic areas. The clinical features include a skin rash consisting of macules, papules or nodules in an otherwise healthy individual; this presentation is determined by the immune response towards parasites in the skin that probably persisted from the previous VL episode. The immune response in VL, cured VL and PKDL is the result of changes in the cytokine profile that only in part can be captured under the Th1 and Th2 dichotomy. Regulatory T cells and Th 17 cells also play a role. VL is characterized by an absent immune response to Leishmania with a predominantly Th2 type of response with high levels of IL-10; after successful treatment the patient will be immune with in vitro features of a Th1 type of response and in vivo a positive leishmanin skin test. PKDL takes an intermediate position with a dissociation of the immune response between the skin and the viscera, with a Th2 and Th1 type of response, respectively. It is likely that immune responses determine the different epidemiological and clinical characteristics of PKDL in Asia and Africa; various risk factors for PKDL may influence this, such as incomplete and inadequate treatment of VL, parasite resistance and genetic factors. It should be noted that PKDL is a heterogeneous and dynamic condition and patients differ with regard to time of onset after visceral leishmaniasis (VL), chronicity, extent and appearance of the rash including related immune responses, all of which may vary over time. Better understanding of these immune responses may offer opportunities for manipulation including combined chemotherapy and immunotherapy for VL to prevent PKDL from occurring and similarly in the treatment of chronic or treatment resistant PKDL cases.

A male preponderance in patients with Indian post kala-azar dermal leishmaniasis is associated with increased circulating levels of testosterone

BACKGROUND

Post kala-azar dermal leishmaniasis (PKDL) is a neglected parasitic disease that occurs after apparent cure from visceral leishmaniasis (VL) and poses a challenge for elimination of VL, being its proposed reservoir. Several epidemiological studies have proposed that sex hormones may account for the increased susceptibility of males towards infectious diseases, including leishmaniasis; however, the role of testosterone and sex bias, if any, in PKDL has not been evaluated.

METHODS

The study population included 87 patients with PKDL and 39 with VL; levels of testosterone were measured by competitive enzyme-linked immunosorbent assay along with their levels of antileishmanial immunoglobulin and IgG. The association of testosterone, if any, was then correlated with age, gender, humoral response, lesional profile, disease duration, and lag period.

RESULTS

A male predominance was evident in PKDL, not in VL; importantly, this male bias was predominant postpubertal, strongly indicative of an association between sex hormone and disease progression. Male patients with PKDL had significantly higher levels of testosterone, which regressed significantly with miltefosine, not with sodium antimony gluconate. Additionally, a significant correlation was found between plasma testosterone and antileishmanial IgG.

CONCLUSION

Taken together, our study has established a male dominance in PKDL, which showed a strong association with testosterone. This information should be taken into consideration for disease monitoring and control.

Systematic review of biomarkers to monitor therapeutic response in leishmaniasis

Recently, there has been a renewed interest in the development of new drugs for the treatment of leishmaniasis. This has spurred the need for pharmacodynamic markers to monitor and compare therapies specifically for visceral leishmaniasis, in which the primary recrudescence of parasites is a particularly long-term event that remains difficult to predict. We performed a systematic review of studies evaluating biomarkers in human patients with visceral, cutaneous, and post-kala-azar dermal leishmaniasis, which yielded a total of 170 studies in which 53 potential pharmacodynamic biomarkers were identified. In conclusion, the large majority of these biomarkers constituted universal indirect markers of activation and subsequent waning of cellular immunity and therefore lacked specificity. Macrophage-related markers demonstrate favorable sensitivity and times to normalcy, but more evidence is required to establish a link between these markers and clinical outcome. Most promising are the markers directly related to the parasite burden, but future effort should be focused on optimization of molecular or antigenic targets to increase the sensitivity of these markers. In general, future research should focus on the longitudinal evaluation of the pharmacodynamic biomarkers during treatment, with an emphasis on the correlation of studied biomarkers and clinical parameters.

IgG1 as a potential biomarker of post-chemotherapeutic relapse in visceral leishmaniasis, and adaptation to a rapid diagnostic test

Background

Visceral leishmaniasis (VL), caused by protozoa of the Leishmania donovani complex, is a widespread parasitic disease of great public health importance; without effective chemotherapy symptomatic VL is usually fatal. Distinction of asymptomatic carriage from progressive disease and the prediction of relapse following treatment are hampered by the lack of prognostic biomarkers for use at point of care.

Methodology/Principal Findings

All IgG subclass and IgG isotype antibody levels were determined using unpaired serum samples from Indian and Sudanese patients with differing clinical status of VL, which included pre-treatment active VL, post-treatment cured, post-treatment relapsed, and post kala-azar dermal leishmaniasis (PKDL), as well as seropositive (DAT and/or rK39) endemic healthy controls (EHCs) and seronegative EHCs. L. donovani antigen-specific IgG1 levels were significantly elevated in relapsed versus cured VL patients (p<0.0001). Using paired Indian VL sera, consistent with the known IgG1 half-life, IgG1 levels had not decreased significantly at day 30 after the start of treatment (p = 0.8304), but were dramatically decreased by 6 months compared to day 0 (p = 0.0032) or day 15 (p<0.0001) after start of treatment. Similarly, Sudanese sera taken soon after treatment did not show a significant change in the IgG1 levels (p = 0.3939). Two prototype lateral flow immunochromatographic rapid diagnostic tests (RDTs) were developed to detect IgG1 levels following VL treatment: more than 80% of the relapsed VL patients were IgG1 positive; at least 80% of the cured VL patients were IgG1 negative (p<0.0001).

Conclusions/Significance

Six months after treatment of active VL, elevated levels of specific IgG1 were associated with treatment failure and relapse, whereas no IgG1 or low levels were detected in cured VL patients. A lateral flow RDT was successfully developed to detect anti-Leishmania IgG1 as a potential biomarker of post-chemotherapeutic relapse.

Visceral leishmaniasis (VL) is a systemic disease with highest prevalence in South Asia, East Africa, and Brazil. VL is caused by protozoan (unicellular) parasites of the Leishmania donovani complex, transmitted to humans when an infected sandfly takes a bloodmeal. Within the human host, the parasites replicate within cells, particularly of bone marrow and spleen. Without effective treatment, symptomatic VL is usually fatal. As outlined in a recent World Health Organisation report, the development of new diagnostic tools to test for successful cure after chemotherapy is a research priority. In this work we investigated the association of clinical status of VL patients (active pre-treatment, and those deemed cured or relapsed post-treatment) with subclasses of the IgG antibody response made to L. donovani infection. We show that high levels of subclass IgG1 are found in pre-treatment and relapsed patients, but are very much lower in patients deemed to be cured. We further show that the decrease in IgG1 is detectable in patients 6 months after successful treatment, and that this detection method can be adapted to a rapid diagnostic test format requiring minimal technical expertise. Thus we believe that IgG1 levels are potentially a biomarker of post-chemotherapeutic monitoring.

Post Kala-Azar dermal leishmaniasis following treatment with 20 mg/kg liposomal amphotericin B (Ambisome) for primary visceral leishmaniasis in Bihar, India

Background

The skin disorder Post Kala-Azar Dermal Leishmaniasis (PKDL) occurs in up to 10% of patients treated for visceral leishmaniasis (VL) in India. The pathogenesis of PKDL is not yet fully understood. Cases have been reported in India following therapy with most available treatments, but rarely in those treated with liposomal amphotericin B (Ambisome). Between July 2007 and August 2012 with the support of the Rajendra Memorial Research Institute (RMRI), Médecins Sans Frontières (MSF) supported a VL treatment programme in Bihar, India—an area highly endemic for Leishmania donovani—in which 8749 patients received 20 mg/kg intravenous Ambisome as first-line treatment. This study describes the characteristics of patients who returned to the MSF supported treatment programme with PKDL.

Methods and Principal Findings

Over a 5-year period, Ambisome was administered to 8749 patients with laboratory-confirmed VL (clinical signs, rK39 positive, with/without parasite confirmation) in four intravenous doses of 5 mg/kg to a total of 20 mg/kg, with a high initial-cure rate (99.3%) and low default rate (0.3%). All patients received health education highlighting the possibility and symptoms of developing PKDL, and advice to return to the MSF programme if these symptoms developed. This is an observational retrospective cohort study of the programme outcomes. Of the 8311 patients completing treatment for their first episode of VL, 24 (0.3%) returned passively to the programme complaining of symptoms subsequently confirmed as PKDL, diagnosed from clinical history, appearance consistent with PKDL, and slit-skin smear examination. Of the 24 patients, 89% had macular lesions, with a median time (interquartile range) to development of 1.2 (0.8–2.2) years following treatment. Comparison of the demographic and clinical characteristics of the VL patients treated with Ambisome who later developed PKDL, with those of the remaining cohort did not identify any significant risk factors for PKDL. However, the time to developing PKDL was significantly shorter with Ambisome than in a subset of patients presenting to the programme with PKDL following previous sodium stibogluconate treatment for VL.

Conclusions

In this large cohort of patients with VL in Bihar who were treated with 20 mg/kg Ambisome, PKDL following treatment appears to be infrequent with no predictive risk factors. The shorter median time to developing symptoms of PKDL compared with that after conventional VL treatments should be taken into account when counseling patients treated with regimens including Ambisome.

Visceral leishmaniasis (VL), also known as Kala-azar, is caused by the parasite L.donovani. Half of cases worldwide occur in India, with up to 90% of these in Bihar state. Post Kala-azar dermal leishmaniasis (PKDL) is a difficult to treat skin condition that develops in up to 10% of VL cases following treatment in the Indian subcontinent. Although often mild, PKDL can be severe and disfiguring. Patients are otherwise healthy. PKDL is considered a reservoir of L.donovani and requires treating to support disease elimination. Between 2007–2012, 8311 patients diagnosed with a first episode of VL completed treatment with 20 mg/kg intravenous liposomal amphotericin B (Ambisome) in a Médecins Sans Frontières (MSF) programme supported by the Rajendra Memorial Research Institute (RMRI) in Bihar. Ambisome is a safe and effective treatment that is recommended by the WHO for first-line use in the Indian subcontinent; although not yet included in the Indian guidelines. PKDL has been described following all VL treatments, but so far in only two patients treated with Ambisome. Here, we describe 24 patients treated with Ambisome who returned to the MSF treatment programme with confirmed PKDL. We found no risk factors for PKDL following treatment; however, the average time to development of PKDL was much shorter than that seen following older treatments.