Browsing by Author "Om Prakash Singh"

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A molecular signature for CD8+ T cells from visceral leishmaniasis patients
(Blackwell Publishing Ltd, 2019) Bhawana Singh; Shashi Bhushan Chauhan; Rajiv Kumar; Siddharth Sankar Singh; Susanna Ng; Fiona Amante; Fabian de Labastida Rivera; Om Prakash Singh; Madhukar Rai; Susanne Nylen; Shyam Sundar; Christian Engwerda
CD8+ T-cell function is compromised in chronic diseases such as visceral leishmaniasis (VL). However, little is known about the changes in gene expression that cause CD8+ T-cell dysfunction during VL. We used targeted transcriptional profiling of peripheral blood CD8+ T cells from VL patients pre- and post-anti-parasitic drug treatment, and compared them with the same cell population from healthy endemic controls to assess their activation, differentiation and functional status during disease. We found a predominance of downregulated immune genes in CD8+ T cells from VL patients. However, genes encoding several notable immune checkpoint molecules, including LAG-3, TIM-3 and CTLA-4, cytolytic molecules, such as granzymes A, B and H and perforin, as well as SOCS3, STAT1, JAK2 and JAK3 cytokine signalling genes were found to be increasingly expressed by VL patient CD8+ T cells. Additional studies confirmed increased expression of the inhibitory receptors LAG3 and TIM3 on VL patient CD8+ T cells, thereby identifying these molecules as potential targets to improve antigen-specific CD8+ T-cell responses during disease. © 2019 John Wiley & Sons Ltd
Abnormal b-cell subset and blimp-1-mediated humoral responses associated with visceral leishmaniasis pathogenesis
(American Society of Tropical Medicine and Hygiene, 2019) Bhawana Singh; Om Prakash Singh; Neetu Singh; Siddharth Sankar Singh; Shyam Sundar
B-cells have a spectrum of functions ranging from antibody production to antigen presentation and have additional vital roles in immune mechanisms. There is rudimentary knowledge about the role of B-cells in intracellular infections with contradictory findings. We explored the role of B-cell dysfunctions in visceral leishmaniasis (VL) pathogenesis in terms of the phenotypic and functional properties of B-cells during the course of disease. This study was performed on blood and splenic aspirates (SA) of VL cases pre- and post-treatment. Whole blood was used for flow cytometric studies for determining the profiles of B-cells at different time-points of treatment. Peripheral blood mononuclear cells were used for magnetic purification of B-cells, for transcriptional studies by real-time polymerase chain reaction (RT-PCR). Serum/plasma was used for direct agglutination test for determining parasite-specific antibodies and SAwere usedfor scoringthepresence ofparasitebymicroscopic examination. Flowcytometric studiesdepicteddecreased B-cell percentages during the entire course of disease and attainment of exhaustive phenotypewith tissue-likememory cell markers, indicative of B-cell dysfunctions in VL. In addition, B-cells had compromised abilities of antigen processing and presentation and altered levels of B-lymphocyte-induced maturation protein-1 (Blimp-1). Blimp-1 expression goes hand in hand with B-cell maturation antigen and transmembrane activator and calcium modulator (TACI) and cyclophilin ligand interactor, suggestive of its role in promoting plasma cell survival and antibody production. Elevated level of VL-specific antibody titre was directly correlated with exhausted phenotype and also with disease severity during VL. This study indicated for impaired B-cell functions during chronic infection which may lead to pathological consequences in human VL. © 2019 by The American Society of Tropical Medicine and Hygiene.
An Insight Into Systemic Immune Response in Leishmania donovani Mediated Atypical Cutaneous Leishmaniasis in the New Endemic State of Himachal Pradesh, India
(Frontiers Media S.A., 2022) Lovlesh Thakur; Priyanka Madaan; Aklank Jain; Vinay Shankar; Ajeet Negi; Shashi Bhushan Chauhan; Shyam Sundar; Om Prakash Singh; Manju Jain
Leishmaniasis continues to afflict known and newer endemic sites despite global efforts towards its control and elimination. In this regard, the emergence of newer endemic sites with unusual disease formats is recognized wherein Leishmania donovani complex classically known to cause visceral disease is demonstrated to cause cutaneous manifestation. In this context, atypical cutaneous leishmaniasis (CL) cases caused by L. donovani genetic variants from the newer endemic state of Himachal Pradesh (HP) in India are beginning to be understood in terms of parasite determinants. The atypical CL manifestation further needs to be explored to define host immune correlates with a possible role in driving the unusual disease progression. In the given study, we performed comprehensive systemic-immune profiling of the atypical CL patients from the study area in HP, India, in comparison with the classical visceral leishmaniasis (VL) patients from the northeast region of India. The systemic immune response was studied using ELISA-based assessment of Th1, Th2, Th17, Treg, and Th22 specific plasma cytokine expression pattern and parasite-specific total serum IgG/IgG subclasses. The specified immune correlates are known to exhibit heterogeneous association with the different infecting parasite species, infection load, and co-lateral host immunopathology in classical CL and VL. In the atypical CL patient group, altered expression of IL-10 emerged as the key finding that could potentially fine-tune the Th1/Th17/Th22 effector cytokine axis towards a localized cutaneous manifestation. A reduced expression of IL-10 along with a high IFN-γ/IL-10 ratio as a readout of effective parasite killing defined atypical cutaneous outcome. In contrast, high circulatory IL-10 levels and a depressed IFN-γ/IL-10 ratio were seen in classical VL patients in line with an ineffective parasite-killing cytokine response. Overall, the study highlights new knowledge on host immune correlates in terms of cytokine expression pattern and IgG subclasses that underline atypical disease manifestation such that L. donovani, a generally visceralizing parasite species cause skin localized cutaneous lesions. Copyright © 2022 Thakur, Madaan, Jain, Shankar, Negi, Chauhan, Sundar, Singh and Jain.
Anti-interleukin-10 unleashes transcriptional response to leishmanial antigens in visceral leishmaniasis patients
(Oxford University Press, 2021) Om Prakash Singh; Genevieve Syn; Susanne Nylén; Christian Engwerda; David Sacks; Mary E. Wilson; Rajiv Kumar; Jaya Chakravarty; Shyam Sundar; Jenefer M. Blackwell; Michaela Fakiola
Visceral leishmaniasis (VL; Leishmania donovani) cases produce interferon-γand tumor necrosis factor in response to soluble leishmanial antigen (SLA) in whole-blood assays. Using transcriptional profiling, we demonstrate the impact of interleukin-10 (IL-10), a cytokine implicated in VL, on this response. SLA stimulation identified 28 differentially expressed genes (DEGs), 17/28 in a single network with TNF as hub. SLA plus anti-IL-10 produced 454 DEGs, 292 in a single network with TNF, IFNG, NFKBIA, IL6, and IL1B as hubs in concert with a remarkable chemokine/cytokine storm. Our data demonstrate the singular effect of IL-10 as a potent immune modulator in VL. © 2020 The Author(s) 2020. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.
Assessing L. donovani Skin Parasite Load: A Proof of Concept Study of a Microbiopsy Device in an Indian Setting
(Frontiers Media S.A., 2021) Kristien Cloots; Om Prakash Singh; Abhishek Kumar Singh; Gert Van der Auwera; Prashant Kumar; Mallikarjuna Rao Gedda; Tulika Kumari Rai; Epco Hasker; Shyam Sundar; Marleen Boelaert
Background: In the endgame of the elimination initiative of visceral leishmaniasis (VL) on the Indian subcontinent, one of the main questions remaining is whether asymptomatically infected individuals also contribute to transmission. We piloted a minimally invasive microbiopsy device that could help answer this question. While the potential of this device has been previously illustrated in Ethiopia, no such information is available for the setting of the Indian subcontinent. In this proof of concept study we aimed to assess 1) to what extent skin parasite load obtained with the new microbiopsy device correlates with disease status, 2) to what extent skin parasite load correlates with blood parasite load in the same subject, and 3) to what extent the skin parasite load obtained from different sampling sites on the body correlates with one another. Methods: We performed a pilot study in Bihar, India, including 29 VL patients, 28 PKDL patients, 94 asymptomatically infected individuals, 22 endemic controls (EC), and 28 non-endemic controls (NEC). Presence of infection with L. donovani in the blood was assessed using Direct Agglutination Test, rK39 ELISA, Whole Blood Analysis measuring IFN-γ and qPCR. A skin sample was collected with the microbiopsy device on two different locations on the body. PKDL patients provided a third skin sample from the edge of a PKDL lesion. Parasite load in the skin was measured by qPCR. Findings: We found a clear correlation between the skin parasite load obtained with the microbiopsy device and disease status, with both higher skin parasite loads and higher proportions of positive skin samples in VL and PKDL patients compared to asymptomatics, EC, and NEC. No clear correlation between skin parasite load and blood parasite load was found, but a moderate correlation was present between the skin parasite load in arm and neck samples. In addition, we found four positive skin samples among asymptomatic individuals, and 85% of PKDL lesions tested positive using this microbiopsy device. Conclusions: In line with previous pilot studies, our results from an Indian setting suggest that the microbiopsy device provides a promising tool to measure skin parasite load, and – if validated by xenodiagnosis studies – could facilitate much needed larger scale studies on infectiousness of human subgroups. In addition, we advocate further evaluation of this device as a diagnostic tool for PKDL. © Copyright © 2021 Cloots, Singh, Singh, Van der Auwera, Kumar, Gedda, Rai, Hasker, Sundar and Boelaert.
Asymptomatic leishmania infection: A new challenge for leishmania control
(University of Chicago Press, 2014) Om Prakash Singh; Epco Hasker; David Sacks; Marleen Boelaert; Shyam Sundar
Visceral leishmaniasis (VL) is a serious parasitic disease, causing high morbidity and mortality in the developing world. The pathogenesis of VL is complex, and the clinical presentation ranges from asymptomatic infection to severe and fatal disease. Despite a wealth of research on the full-blown "clinical VL" syndrome, asymptomatic leishmania infections remain poorly understood. Asymptomatic infection could present a major challenge for control programs if its infectiousness is confirmed. In this viewpoint, we highlight the crucial knowledge gaps as well as the obstacles in research on asymptomatic leishmanial infection. Research in this area is essential for the development of more-effective VL control strategies. © 2014 The Author.
Carboxymethyl chitosan modified lipid nanoformulations as a highly efficacious and biocompatible oral anti-leishmanial drug carrier system
(Elsevier B.V., 2022) Aakriti Singh; Ganesh Yadagiri; Manorma Negi; Anurag Kumar Kushwaha; Om Prakash Singh; Shyam Sundar; Shyam Lal Mudavath
Herein, carboxymethyl chitosan (CMC) grafted lipid nanoformulations were facilely prepared by thin-film hydration method as a highly efficient biocompatible anti-leishmanial carrier encapsulating amphotericin B (AmB). Nanoformulations were characterized for their physicochemical characteristics wherein TEM analysis confirmed the spherical structure, whereas FTIR analysis revealed the conjugation of CMC onto nanoformulations and confirmed the free state of AmB. Furthermore, the wettability study confirmed the presence of CMC on the surface of nanoformulations attributed to the enhanced hydrophilicity. Surface hydrophilicity additionally contributes towards consistent mucin retention ability for up to 6 h, superior mucoadhesiveness, and hence enhanced bioavailability. The proposed nanoformulations with high encapsulation and drug loading properties displayed controlled drug release in the physiological microenvironment. In vitro, antileishmanial results showed an astounding 97% inhibition in amastigote growth. Additionally, in vivo studies showed that treatment with nanoformulations significantly reduced the liver parasitic burden (93.5%) without causing any toxicity when given orally. © 2022 Elsevier B.V.
Coalition of Biological Agent (Melatonin) with Chemotherapeutic Agent (Amphotericin B) for Combating Visceral Leishmaniasis via Oral Administration of Modified Solid Lipid Nanoparticles
(American Chemical Society, 2023) Shabi Parvez; Ganesh Yadagiri; Kanika Arora; Aaqib Javaid; Anurag Kumar Kushwaha; Om Prakash Singh; Shyam Sundar; Shyam Lal Mudavath
In this study, 2-hydroxypropyl-β-cyclodextrin (HPβCD) grafted solid lipid nanoparticle (SLN)-based bioconjugate was synthesized and used for administering a combination of melatonin (Mel) and amphotericin B (AmB) orally for effective visceral leishmaniasis (VL) treatment. The formulations (HPCD-Mel-AmB SLN) were synthesized by the emulsion solvent evaporation method. HPCD-Mel-AmB SLN showed a high loading capacity and a high entrapment efficiency of AmB (% DL = 9.0 ± 0.55 and % EE = 87.9 ± 0.57) and Mel (% DL = 7.5 ± 0.51 and % EE = 63 ± 6.24). The cumulative percent release of AmB and Mel was 66.10 and 73.06%, respectively, up to 72 h. Time-dependent cellular uptake was noticed for HPCD-Mel-AmB SLN for 4 h. Further, HPCD-Mel-AmB SLN did not show any toxic effects on J774A.1 macrophages and Swiss albino mice. HPCD-Mel-AmB SLN (10 mg/kg ×5 days, p.o.) has significantly diminished (98.89%) the intracellular parasite load in liver tissues of L. donovani-infected BALB/c mice, subsequently highlighting the role of melatonin toward an effective strategy in combating leishmanial infection. Therefore, these results indicated that administration of HPCD-Mel-AmB SLN improve the therapeutic index of the first-line drug in addition to the introduction of biological agent and would be a promising therapeutic candidate for effective VL therapy. In the present study, the objective is to test the efficacy of the chemotherapeutic approach in combination with a biological immunomodulatory agent against leishmanial infection using in vitro and in vivo studies. This information suggests that melatonin could be an efficacious and potent antileishmanial agent. © 2023 American Chemical Society. All rights reserved.
Color Doppler Ultrasound Indices as Predictors of Propranolol Response in Infantile Hemangioma: A Prospective Study
(Springer, 2024) Vaibhav Pandey; Rathindra Nath Bera; Amit Nandan Dhar Diwedi; Om Prakash Singh; Preeti Tiwari
Objective: To evaluate the utility of color Doppler ultrasonography in assessing infantile hemangioma response to treatment with oral propranolol. Method: A prospective study was conducted between January, 2016 and December, 2022, wherein children with symptomatic (ulceration, bleeding, pain and scarring) infantile hemangioma were given oral propranol (2 mg/kg per day in three divided doses) as outpatient therapy. The clinical response was assessed three months post-initiation of treatment (intermediate clinical response) and three months post-completion of treatment (final clinical response, FCR). The primary outcome measurement was a clinical and radiological response (resistivity index (RI), pulsatility index (PI) and peak systolic velocity) to treatment. The secondary outcomes assessed were the complications related to treatment. Result: Out of 601 patients who were started on propranolol, 99 developed severe adverse effects and were excluded from analysis. At FCR assessment, out of 502 participants, 64.3% (n = 323) showed excellent response, 17.7% (n = 89) showed partial, and 17.9% (n = 90) were non-responders. A significant increase in RI and PI values was noted in all children following propranolol treatment for six months. An increase > 7.5% in RI could identify responders with 92% sensitivity, 91% specificity and area under the curve (AUC) of 0.963. An increase of > 11.5% in PI could identify responders with 86% sensitivity, 91% specificity and AUC of 0.896. Patients initially showing no response but later becoming excellent responders had significantly higher RI and PI values. Conclusion: Color Doppler ultrasonography is a valuable tool in predicting the treatment outcome of infantile hemangioma using propranolol. © Indian Academy of Pediatrics 2024.
Comparative Efficacy of Autologous Blood and Dextrose Prolotherapy in the Management of Temporomandibular Joint Hypermobility: A Rabbit Model Study
(Springer, 2025) Preeti Tiwari; Amit Nandan Dwivedi; T. P. Chaturvedi; Rahul Patel; Om Prakash Singh; Bitan Naik; Nishtha Chauhan
Introduction: Temporomandibular joint (TMJ) hypermobility affects broad demographic, challenging the efficacy of traditional treatments. The aim of this study is to investigate therapeutic potential of autologous blood injections (ABI) vs dextrose prolotherapy in rabbit model, through detailed histopathological & radiological analyses. Material and Methods: After ethical approval from the institutional committee, a hypermobile joint model was established in rabbits through surgery affirmed by MRI. Subsequently, rabbits were randomly divided into two groups i.e. ABI and dextrose solution. In each group, one joint was designated as control, treated with saline. Following surgical induction of TMJ hypermobility, treatments were administered, & outcome was assessed through histological examination for fibrosis grading & CD68 staining for macrophage infiltration. Results: The ABI group exhibited a higher fibrosis grade (> 75% in 50% of joints) & stronger CD68 staining, indicating a significant fibrotic response & macrophage infiltration compared to dextrose group. In contrast, control joints displayed no fibrosis grades & negative CD68 staining. Conclusion: The study highlights both ABI & dextrose prolotherapy elicit significant fibrotic responses in treating TMJ hypermobility, indicating their therapeutic mechanisms. ABI in particular, triggers more marked inflammatory reaction, underscoring its potential efficacy. Further evaluation is essential to understand its clinical significance and applicability in managing TMJ disorders. © The Association of Oral and Maxillofacial Surgeons of India 2025.
Contact glow discharge electrolysis: a study of its chemical yields in aqueous inert-type electrolytes
(1994) Susanta K. Sengupta; Om Prakash Singh
A study of the chemical yields of contact glow discharge electrolysis (CGDE) at the anode in aqueous inert electrolytes at various quantities of electricity, applied voltages and electrolyte compositions shows that, for the passage of each mole of electrons, 0.25 mol of O2 and more than 1.0 mol of both H2 and H2O2 plus O2 are produced at the anode when the glow discharges there are fully grown. Non-faradaic yields may originate in two reaction zones: the anolyte near the plasma where liquid water molecules are broken up into H2O2, O2 and H2, and the plasma around the anode where gas phase dissociation of water molecules into H2 and O2 occurs. The former is important for anodic CGDE. Hickling's radiolytic mechanism has been applied to interpret the chemical results of the liquid phase reaction zone. A comparative study of the chemical yields of anodic and cathodic CGDE indicates that the breakup of water molecules occurs entirely in the plasma during cathodic CGDE, but primarily in the liquid anolyte and partly in the plasma during the anodic phenomenon. © 1994.
Contact glow discharge electrolysis: a study of its onset and location
(1991) Susanta K. Sengupta; Om Prakash Singh
At sufficiently high voltages a normal electrolysis switches over to a phenomenon called contact glow discharge electrolysis (CGDE) in which glow discharges take place across a gaseous envelope over either the anode or the cathode. A critical investigation on the influence of the relative anode-cathode dimensions, the relative anolyte-catholyte surface tension, the nature of the electrolyte constituents, and the polarity of the electrode on the onset and location of CGDE in aqueous media has been carried out. The mechanism of the growth of a stable vapour envelope on an electrode underneath an electrolyte during normal electrolysis has been examined in the light of the theory of hydrodynamic instabilities. Overall analysis of the results has led to the following conclusions: (a) vaporization, and not gas evolution at an electrode, is the prime requisite for the growth of CGDE in the aqueous phase; (b) an electrode-electrolyte area where the conditions help both easier vaporization and easier onset of hydrodynamic instabilities would be the location of CGDE; and (c) the nature of the glow discharges at an anode is quite different from that at a cathode. © 1991.
Correction to: The NK cell granule protein NKG7 regulates cytotoxic granule exocytosis and inflammation (Nature Immunology, (2020), 21, 10, (1205-1218), 10.1038/s41590-020-0758-6)
(Nature Research, 2024) Susanna S. Ng; Fabian De Labastida Rivera; Juming Yan; Dillon Corvino; Indrajit Das; Ping Zhang; Rachel Kuns; Shashi Bhushan Chauhan; Jiajie Hou; Xian-Yang Li; Teija C. M. Frame; Benjamin A. McEnroe; Eilish Moore; Jinrui Na; Jessica A. Engel; Megan S. F. Soon; Bhawana Singh; Andrew J. Kueh; Marco J. Herold; Marcela Montes de Oca; Siddharth Sankar Singh; Patrick T. Bunn; Amy Roman Aguilera; Mika Casey; Matthias Braun; Nazanin Ghazanfari; Shivangi Wani; Yulin Wang; Fiona H. Amante; Chelsea L. Edwards; Ashraful Haque; William C. Dougall; Om Prakash Singh; Alan G. Baxter; Michele W. L. Teng; Alex Loukas; Norelle L. Daly; Nicole Cloonan; Mariapia A. Degli-Esposti; Jude Uzonna; William R. Heath; Tobias Bald; Siok-Keen Tey; Kyohei Nakamura; Geoffrey R. Hill; Rajiv Kumar; Shyam Sundar; Mark J. Smyth; Christian R. Engwerda
Correction to: Nature Immunologyhttps://doi.org/10.1038/s41590-020-0758-6, published online 24 August 2020. The Chief Editor is correcting this article at the request of the corresponding author, Christian Engwerda. An investigation by QIMR Berghofer Medical Research Institute found that the original Figs. 7e, 7h (upper panel) and 8a and Extended Data Fig. 5b (EO771 data only) were based on experiments for which no evidence of their conduct or primary data could be confirmed. As such, the data from the underlying experiments are believed to have been fabricated or are unreliable, respectively. The four panels have been removed from Figs. 7 and 8 and Extended Data Fig. 5 (see Supplementary Information for a list of edits and original article for comparison). The major finding of the paper that NKG7 regulates cytotoxic granule exocytosis and inflammation remains unaffected. No concerns have been raised regarding other data in the paper. © The Author(s), under exclusive licence to Springer Nature America, Inc. 2024.
Current challenges in treatment options for visceral leishmaniasis in India: A public health perspective
(BioMed Central Ltd., 2016) Om Prakash Singh; Bhawana Singh; Jaya Chakravarty; Shyam Sundar
Visceral leishmaniasis (VL) is a serious parasitic disease causing considerable mortality and major disability in the Indian subcontinent. It is most neglected tropical disease, particularly in terms of new drug development for the lack of financial returns. An elimination campaign has been running in India since 2005 that aim to reduce the incidence of VL to below 1 per 10,000 people at sub-district level. One of the major components in this endeavor is reducing transmission through early case detection followed by complete treatment. Substantial progress has been made during the recent years in the area of VL treatment, and the VL elimination initiatives have already saved many lives by deploying them effectively in the endemic areas. However, many challenges remain to be overcome including availability of drugs, cost of treatment (drugs and hospitalization), efficacy, adverse effects, and growing parasite resistance. Therefore, better emphasis on implementation research is urgently needed to determine how best to deliver existing interventions with available anti-leishmanial drugs. It is essential that the new treatment options become truly accessible, not simply available in endemic areas so that they may promote healing and save lives. In this review, we highlight the recent advancement and challenges in current treatment options for VL in disease endemic area, and discuss the possible strategies to improve the therapeutic outcome. © 2016 Singh et al.
Cytokine Responses to Novel Antigens in an Indian Population Living in an Area Endemic for Visceral Leishmaniasis
(2012) Om Prakash Singh; Carmel B. Stober; Abhishek Kr. Singh; Jenefer M. Blackwell; Shyam Sundar
Background: There are no effective vaccines for visceral leishmaniasis (VL), a neglected parasitic disease second only to malaria in global mortality. We previously identified 14 protective candidates in a screen of 100 Leishmania antigens as DNA vaccines in mice. Here we employ whole blood assays to evaluate human cytokine responses to 11 of these antigens, in comparison to known defined and crude antigen preparations. Methods: Whole blood assays were employed to measure IFN-γ, TNF-α and IL-10 responses to peptide pools of the novel antigens R71, Q51, L37, N52, L302.06, J89, M18, J41, M22, M63, M57, as well as to recombinant proteins of tryparedoxin peroxidase (TRYP), Leishmania homolog of the receptor for activated C kinase (LACK) and to crude soluble Leishmania antigen (SLA), in Indian patients with active (n = 8) or cured (n = 16) VL, and in modified Quantiferon positive (EHC+ve, n = 20) or modified Quantiferon negative (EHC-ve, n = 9) endemic healthy controls (EHC). Results: Active VL, cured VL and EHC+ve groups showed elevated SLA-specific IFN-γ, but only active VL patients produced IL-10 and EHC+ve did not make TNF-α. IFN-γ to IL-10 and TNF-α to IL-10 ratios in response to TRYP and LACK antigens were higher in cured VL and EHC+ve exposed individuals compared to active VL. Five of the eleven novel candidates (R71, L37, N52, J41, and M22) elicited IFN-γ and TNF-α, but not IL-10, responses in cured VL (55-87.5% responders) and EHC+ve (40-65% responders) subjects. Conclusions: Our results are consistent with an important balance between pro-inflammatory IFNγ and TNFγ cytokine responses and anti-inflammatory IL-10 in determining outcome of VL in India, as highlighted by response to both crude and defined protein antigens. Importantly, cured VL patients and endemic Quantiferon positive individuals recognise 5 novel vaccine candidate antigens, confirming our recent data for L. chagasi in Brazil, and their potential as cross-species vaccine candidates. © 2012 Singh et al.
Detection of Immunoglobulin G1 against rK39 Improves Monitoring of Treatment Outcomes in Visceral Leishmaniasis
(Oxford University Press, 2019) Guy Mollett; Bruno C. Bremer Hinckel; Tapan Bhattacharyya; Tegwen Marlais; Om Prakash Singh; Pascal Mertens; Andrew K. Falconar; Sayda El-Safi; Shyam Sundar; Michael A. Miles
Background: Visceral leishmaniasis (VL), caused by the Leishmania donovani complex, is a fatal, neglected tropical disease that is targeted for elimination in India, Nepal, and Bangladesh. Improved diagnostic tests are required for early case detection and for monitoring the outcomes of treatments. Previous investigations using Leishmania lysate antigen demonstrated that the immunoglobulin (Ig) G1 response is a potential indicator of a patient's clinical status after chemotherapy. Methods: IgG1 or IgG enzyme-linked immunosorbent assays (ELISAs) with rK39 or lysate antigens and novel IgG1 rK39 rapid diagnostic tests (RDTs) were assessed with Indian VL serum samples from the following clinical groups: paired pre-and postchemotherapy (deemed cured); relapsed; other infectious diseases; and endemic, healthy controls. Results: With paired pre-and post-treatment samples (n = 37 pairs), ELISAs with rK39-and IgG1-specific conjugates gave a far more discriminative decrease in post-treatment antibody responses when compared to IgG (P <. 0001). Novel IgG1 rK39 RDTs provided strong evidence for decreased IgG1 responses in patients who had successful treatment (P <. 0001). Furthermore, both IgG1 rK39 RDTs (n = 38) and ELISAs showed a highly significant difference in test outcomes between cured patients and those who relapsed (n = 23; P <. 0001). RDTs were more sensitive than corresponding ELISAs. Conclusions: We present strong evidence for the use of IgG1 in monitoring treatment outcomes in VL, and the first use of an IgG1-based RDT using the rK39 antigen for the discrimination of post-treatment cure versus relapse in VL. Such an RDT may have a significant role in monitoring patients and in targeted control and elimination of this devastating disease. © 2018 The Author(s) 2018. Published by Oxford University Press for the Infectious Diseases Society of America.
Determinants for progression from asymptomatic infection to symptomatic visceral leishmaniasis: A cohort study
(Public Library of Science, 2018) Jaya Chakravarty; Epco Hasker; Sangeeta Kansal; Om Prakash Singh; Paritosh Malaviya; Abhishek Kumar Singh; Ankita Chourasia; Toolika Singh; Medhavi Sudarshan; Akhil Pratap Singh; Bhawana Singh; Rudra Pratap Singh; Bart Ostyn; Michaela Fakiola; Albert Picado; Joris Menten; Jenefer M. Blackwell; Mary E. Wilson; David Sacks; Marleen Boelaert; Shyam Sundar
Background: Asymptomatic Leishmania donovani infections outnumber clinical presentations, however the predictors for development of active disease are not well known. We aimed to identify serological, immunological and genetic markers for progression from L. donovani infection to clinical Visceral Leishmaniasis (VL). Methods: We enrolled all residents >2 years of age in 27 VL endemic villages in Bihar (India). Blood samples collected on filter paper on two occasions 6–12 months apart, were tested for antibodies against L. donovani with rK39-ELISA and DAT. Sero converters, (negative for both tests in the first round but positive on either of the two during the second round) and controls (negative on both tests on both occasions) were followed for three years. At the start of follow-up venous blood was collected for the following tests: DAT, rK39- ELISA, Quantiferon assay, SNP/HLA genotyping and L.donovani specific quantitative PCR. Results: Among 1,606 subjects enrolled,17 (8/476 seroconverters and 9/1,130 controls) developed VL (OR 3.1; 95% CI 1.1–8.3). High DAT and rK39 ELISA antibody titers as well as positive qPCR were strongly and significantly associated with progression from seroconversion to VL with odds ratios of 19.1, 30.3 and 20.9 respectively. Most VL cases arose early (median 5 months) during follow-up. Conclusion: We confirmed the strong association between high DAT and/or rK39 titers and progression to disease among asymptomatic subjects and identified qPCR as an additional predictor. Low predictive values do not warrant prophylactic treatment but as most progressed to VL early during follow-up, careful oberservation of these subjects for at least 6 months is indicated. © 2018, Public Library of Science. All rights reserved. https://creativecommons.org/publicdomain/zero/1.0/.
Developments in diagnosis of visceral leishmaniasis in the elimination era
(Hindawi Publishing Corporation, 2015) Om Prakash Singh; Shyam Sundar
Visceral leishmaniasis (VL) is the most devastating parasitic infection worldwide causing high morbidity and mortality. Clinical presentation of VL ranges from asymptomatic or subclinical infection to severe and complicated symptomatic disease. A major challenge in the clinical management of VL is the weakness of health systems in disease endemic regions. People affected by VL mostly present to primary health care centers (PHCs), often late in their therapeutic itinerary. PHC physicians face a major challenge: they do not deal with a single disease issue but with patients presenting with complaints pointing to several diagnostic possibilities. Risk exists when some patients having less clinical manifestations are misdiagnosed. Therefore, field based accurate, sensitive, and cost effective rapid diagnostic tools that can detect disease in its mildest form are essential for effective control and reaching the goal of VL elimination. In this review, we discuss the current status and challenges of various diagnostic tools for the diagnosis of VL and assess their application in resource poor settings. © 2015 Om Prakash Singh and Shyam Sundar.
Diagnosis of Visceral Leishmaniasis in an Elimination Setting: A Validation Study of the Diagnostic Algorithm in India
(Multidisciplinary Digital Publishing Institute (MDPI), 2022) Kristien Cloots; Om Prakash Singh; Abhishek Kumar Singh; Anurag Kumar Kushwaha; Paritosh Malaviya; Sangeeta Kansal; Epco Hasker; Shyam Sundar
Visceral leishmaniasis (VL) is on the verge of elimination on the Indian subcontinent. Nonetheless, the currently low VL-incidence setting brings along new challenges, one of which is the validity of the diagnostic algorithm, based on a combination of suggestive clinical symptoms in combination with a positive rK39 Rapid Diagnostic Test (RDT). With this study, we aimed to assess the positive predictive value of the diagnostic algorithm in the current low-endemic setting in India by re-assessing newly diagnosed VL patients with a qPCR analysis on venous blood as the reference test. In addition, we evaluated the specificity of the rK39 RDT by testing non-VL cases with the rK39 RDT. Participants were recruited in Bihar and Uttar Pradesh, India. VL patients diagnosed based on the diagnostic algorithm were recruited through six primary health care centers (PHCs); non-VL cases were identified through a door-to-door survey in currently endemic, previously endemic, and non-endemic clusters, and tested with rK39 RDT, as well as—if positive—with qPCR on peripheral blood. We found that 95% (70/74; 95% CI 87–99%) of incident VL cases diagnosed at the PHC level using the current diagnostic algorithm were confirmed by qPCR. Among 15,422 non-VL cases, 39 were rK39 RDT positive, reflecting a specificity of the test of 99.7% (95% CI 99.7–99.8%). The current diagnostic algorithm combining suggestive clinical features with a positive rK39 RDT still seems valid in the current low-endemic setting in India. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.
Diagnostic techniques for visceral leishmaniasis: An overview of methods used in East Africa
(Elsevier Inc., 2025) Vincent Obino Orucho; Ankit Gupta; Rael Jepkogei Masai; Erick Nyakundi Ondari; Om Prakash Singh; Benuel Nyagaka; Angamuthu Selvapandiyan
Leishmanias is a parasitic infection caused by a protozoan belonging to the genus Leishmania and transmitted by sand fly, Phlebotomus fly in the old world and Lutzomyia in the New world. The disease is prevalent in the tropics, subtropics, and Southern Europe, where it affects about 1.5 million to 2 million people annually. India, Bangladesh, Sudan, South Sudan, Brazil and Ethiopia account for up to 90% of all the VL cases. While Leishmania cases in Asia are declining, cases in East Africa especially in Somalia, Sudan, South Sudan, Ethiopia and Kenya have been increasing. The rise in East African cases is partially attributed to ongoing armed conflicts especially in Somalia, Sudan and Southern Sudan, which has displaced people and increased their exposure to sand fly bites. Migration from endemic to non-endemic regions, misdiagnosis, famine, malnutrition, climate change and an increase in HIV cases are other contributing factors. The clinical diagnosis of Leishmania in East Africa combines the patient's clinical signs with either serological or parasitological test, with rK39 strip and microscopy being the major methods used. Diagnosis of the condition remains challenging, as current techniques have limitations, including the inability to detect parasites in tissue, the need for specialized expertise, prohibitive costs of testing equipment, low antibody titers, and the risk of misdiagnosis due to co-infections with diseases such as HIV, tuberculosis, malaria and typhoid. Various techniques, including serological and molecular parasitological methods, have been employed in attempts to address these challenges, but with limited success. This article therefore, reviews some of the techniques that have been used in Leishmania diagnosis in East Africa and discusses other available new techniques with aim of overcoming the current challenges. © 2024 Elsevier Inc.