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Background: Which cell populations that determine the fate of bacteria in infectious granulomas remain unclear. Leprosy, a granulomatous disease with a strong genetic predisposition, caused by Mycobacterium leprae infection, exhibits distinct sub-types with varying bacterial load and is considered an outstanding disease model for studying host-pathogen interactions., Methods: We performed single-cell RNA and immune repertoire sequencing on 11 healthy controls and 20 patients with leprosy, and integrated single-cell data with genome-wide genetic data on leprosy. Multiplex immunohistochemistry, and in vitro and in vivo infection experiments were conducted to confirm the multimodal omics findings., Findings: Lepromatous leprosy (L-LEP) granulomas with high bacterial burden were characterised by exhausted CD8 + T cells, and high RGS1 expression in CD8 + T cells was associated with L-LEP. By contrast, tuberculoid leprosy (T-LEP) granulomas with low bacterial burden displayed enrichment in resident memory IFNG + CD8 + T cells (CD8 + Trm) with high GNLY expression. This enrichment was potentially attributable to the communication between IL1B macrophages and CD8 + Trm via CXCL10-CXCR3 signalling. Additionally, IL1B macrophages in L-LEP exhibited anti-inflammatory phenotype, with high APOE expression contributing to high bacterial burden. Conversely, IL1B macrophages in T-LEP were distinguished by interferon-γ induced GBP family genes., Interpretation: The state of IL1B macrophages and functional CD8 + T cells, as well as the relationship between them, is crucial for controlling bacterial persistence within granulomas. These insights may indicate potential targets for host-directed immunotherapy in granulomatous diseases caused by mycobacteria and other intracellular bacteria., Funding: The Key research and development program of Shandong Province (2021LCZX07), Natural Science Foundation of Shandong Province (ZR2023MH046), Youth Science Foundation Cultivation Funding Plan of Shandong First Medical University (Shandong Academy of Medical Sciences) (202201-123), National Natural Science Foundation of China (82471800, 82230107, 82273545, 82304039), the China Postdoctoral Science Foundation (2023M742162), Shandong Province Taishan Scholar Project (tspd20230608), Joint Innovation Team for Clinical & Basic Research (202410), Central guidance for local scientific and technological development projects of Shandong Province (YDZX2023058)., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

The diagnosis of pure neural leprosy is more challenging because patients share characteristics with other common pathologies, such as ulnar compression, which should be taken into consideration for differential diagnosis. In this study, we identify ulnar nerve conduction characteristics to aid in the differential diagnosis of ulnar neuropathy (UN) in leprosy and that of non-leprosy etiology. In addition, we include putative markers to better understand the inflammatory process that may occur in the nerve. Data were extracted from a database of people affected by leprosy (leprosy group) diagnosed with UN at leprosy diagnosis. A non-leprosy group of patients diagnosed with mechanical neuropathy (compressive, traumatic) was also included. Both groups were submitted to clinical, neurological, neurophysiological and immunological studies. Nerve enlargement and sensory impairment were significantly higher in leprosy patients than in patients with compressive UN. Bilateral impairment was significantly higher in the leprosy group than in the non-leprosy group. Leprosy reactions were associated to focal demyelinating lesions at the elbow and to temporal dispersion (TD). Clinical signs such as sensory impairment, nerve enlargement and bilateral ulnar nerve injury associated with eletrodiagnostic criteria such as demyelinating finds, specifically temporal dispersion, could be tools to help us decided on the best conduct in patients with elbow ulnar neuropathy and specifically decide if we should perform a nerve biopsy for diagnosis of pure neural leprosy., Competing Interests: No authors have competing interests.

Leprosy is an infectious disease that may present different clinical forms depending on host immune response to Mycobacterium leprae. Mannose-binding lectin (MBL) is an acute phase protein associated with the pathophysiology of leprosy. Some studies have shown that there is a correlation between serum levels of MBL and polymorphisms in its gene associated with susceptibility per se and to different clinical forms. The aim of this study was to conduct a systematic review of publications in the literature that studied the association of MBL with leprosy. Databases were searched until December 2020 (PROSPERO: CRD42020158458), and additional searches were conducted scanning the reference lists of the articles. Two independent reviewers assessed the study quality using the Newcastle-Ottawa Quality Assessment Scale. Finally, 10 eligible articles were included in the study. The overall results indicated that both low MBL serum levels and polymorphisms in the structural or promoter region of its gene seem to be associated as protective factors against the development of severe forms. The results suggest that MBL may play a role in the clinical progression of leprosy., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The respiratory tract is considered the main port of entry of Mycobacterium leprae , the causative agent of leprosy. However, the great majority of individuals exposed to the leprosy bacillus will never manifest the disease due to their capacity to develop protective immunity. Besides acting as a physical barrier, airway epithelium cells are recognized as key players by initiating a local innate immune response that orchestrates subsequent adaptive immunity to control airborne infections. However, to date, studies exploring the interaction of M. leprae with the respiratory epithelium have been scarce. In this work, the capacity of  M. leprae  to immune activate human alveolar epithelial cells was investigated, demonstrating that M. leprae -infected A549 cells secrete significantly increased IL-8 that is dependent on NF-κB activation. M. leprae was also able to induce IL-8 production in human primary nasal epithelial cells. M. leprae -treated A549 cells also showed higher expression levels of human β-defensin-2 (hβD-2), MCP-1, MHC-II and the co-stimulatory molecule CD80. Furthermore, the TLR-9 antagonist inhibited both the secretion of IL-8 and NF-κB activation in response to M. leprae , indicating that bacterial DNA sensing by this Toll-like receptor constitutes an important innate immune pathway activated by the pathogen. Finally, evidence is presented suggesting that extracellular DNA molecules anchored to Hlp, a histone-like protein present on the M. leprae surface, constitute major TLR-9 ligands triggering this pathway. The ability of M. leprae to immune activate respiratory epithelial cells herein demonstrated may represent a very early event during infection that could possibly be essential to the generation of a protective response., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2021 Dias, Silva, Silva, Linhares, Santos, Vivarini, Marques, Rosa, Lopes, Berrêdo-Pinho and Pessolani.)

The enzyme IDO-1 is involved in the first stage of tryptophan catabolism and has been described in both microbicidal and tolerogenic microenvironments. Previous data from our group have shown that IDO-1 is differentially regulated in the distinctive clinical forms of leprosy. The present study aims to investigate the mechanisms associated with IDO-1 expression and activity in human monocyte-derived dendritic cells (mDCs) after stimulation with irradiated Mycobacterium leprae and its fractions. M. leprae and its fractions induced the expression and activity of IDO-1 in human mDCs. Among the stimuli studied, irradiated M. leprae and its membrane fraction (MLMA) induced the production of proinflammatory cytokines TNF and IL-6 whereas irradiated M. leprae and its cytosol fraction (MLSA) induced an increase in IL-10. We investigated if TLR2 activation was necessary for IDO-1 induction in mDCs. We observed that in cultures treated with a neutralizing anti-TLR2 antibody, there was a decrease in IDO-1 activity and expression induced by M. leprae and MLMA. The same effect was observed when we used a MyD88 inhibitor. Our data demonstrate that coculture of mDCs with autologous lymphocytes induced an increase in regulatory T (Treg) cell frequency in MLSA-stimulated cultures, showing that M. leprae constituents may play opposite roles that may possibly be related to the dubious effect of IDO-1 in the different clinical forms of disease. Our data show that M. leprae and its fractions are able to differentially modulate the activity and functionality of IDO-1 in mDCs by a pathway that involves TLR2, suggesting that this enzyme may play an important role in leprosy immunopathogenesis., (© 2020 The Authors. Journal of Leukocyte Biology published by Wiley Periodicals LLC on behalf of Society for Leukocyte Biology.)

Mycobacterium leprae (M. leprae) is the etiological agent of leprosy, and the skin lesions of lepromatous leprosy are filled with numerous foamy or xanthomatous histiocytes that are parasitized by M. leprae. Lipids are an important nutrient for the intracellular survival of M. leprae. In this study, we attempted to determine the intracellular lipid composition and underlying mechanisms for changes in host cell lipid metabolism induced by M. leprae infection. Using high-performance thin-layer chromatography (HPTLC), we demonstrated specific induction of triacylglycerol (TAG) production in human macrophage THP-1 cells following M. leprae infection. We then used [14C] stearic acid tracing to show incorporation of this newly synthesized host cell TAG into M. leprae. In parallel with TAG accumulation, expression of host glycerol-3-phosphate acyltransferase 3 (GPAT3), a key enzyme in de novo TAG synthesis, was significantly increased in M. leprae-infected cells. CRISPR/Cas9 genome editing of GPAT3 in THP-1 cells (GPAT3 KO) dramatically reduced accumulation of TAG following M. leprae infection, intracellular mycobacterial load, and bacteria viability. These results together suggest that M. leprae induces host GPAT3 expression to facilitate TAG accumulation within macrophages to maintain a suitable environment that is crucial for intracellular survival of these bacilli., Competing Interests: The authors have declared that no competing interests exist.

Leprosy is an infectious disease caused by Mycobacterium leprae that affects the skin and nerves. The nerve damage in leprosy may be related to alterations in transcriptional factors, such as Krox-20, Oct-6, Sox-10. Thirty skin biopsies in leprosy patients and 15 non-leprosy skin biopsies were evaluated using RT-qPCR to assess Krox-20, Oct-6, and Sox-10 and these data was related with S-100 immunohistochemistry. Changes in gene expression were observed in the skin and dermal nerves of leprosy patients in Oct-6 and Sox-10. When comparing Oct-6 with S-100 IHC as diagnostic tests for leprosy, Oct-6 showed a sensitivity of 73.3%, and specificity of 100%, while S-100 IHC showed a sensitivity of 96.6% and specificity of 100%. Our data suggest Oct-6 could be an auxiliary biomarker specific to detecting changes in dermal nerves in leprosy and thus useful to health workers and pathologists with no expertise to observe nerve injuries in leprosy., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Leprosy is a chronic infectious disease caused by Mycobacterium leprae (M. leprae). In lepromatous leprosy (LL), skin macrophages, harboring extensive bacterial multiplication, gain a distinctive foamy appearance due to increased intracellular lipid load. To determine the mechanism by which M. leprae modifies the lipid homeostasis in host cells, an in vitro M. leprae infection system, using human macrophage precursor THP-1 cells and M. leprae prepared from the footpads of nude mice, was employed. RNA extracted from skin smear samples of patients was used to investigate host gene expressions before and after multidrug therapy (MDT). We found that a cluster of peroxisome proliferator-activated receptor (PPAR) target genes associated with adipocyte differentiation were strongly induced in M. leprae-infected THP-1 cells, with increased intracellular lipid accumulation. PPAR-δ and PPAR-γ expressions were induced by M. leprae infection in a bacterial load-dependent manner, and their proteins underwent nuclear translocalization after infection, indicating activation of PPAR signaling in host cells. Either PPAR-δ or PPAR-γ antagonist abolished the effect of M. leprae to modify host gene expressions and inhibited intracellular lipid accumulation in host cells. M. leprae-specific gene expressions were detected in the skin smear samples both before and after MDT, whereas PPAR target gene expressions were dramatically diminished after MDT. These results suggest that M. leprae infection activates host PPAR signaling to induce an array of adipocyte differentiation-associated genes, leading to accumulation of intracellular lipids to accommodate M. leprae parasitization. Certain PPAR target genes in skin lesions may serve as biomarkers for monitoring treatment efficacy., Competing Interests: The authors have declared that no competing interests exist.

Th17 cells play vital role during pathogenesis of leprosy reactions. Previously, we have reported that IL-23 is involved in Th17 cells differentiation. Subsequently, our group also showed that IL-6 induces Th17 cell differentiation along with TGF-β in leprosy reactions. Here, we next asked the question that whether IL-6 or IL-23 induced Th17 cells are different in nature? In this study, Type 1 Reactions (T1R) showed significantly (p < 0.001) higher percentage of IL-17A producing CD4 + IL6R + T cells as compared to non-reaction (NR) patients. Furthermore, recombinant IL-6, IL-23 and TGF-β promoted IL-17A secretion by CD4 + IL6R + T cells. Subsequently, IL-6R and IL-23R blocking experiments showed significantly (p < 0.002) down regulated IL-17A in T1R reaction as compared to NR leprosy patients. The present study for the first time establishes that pathogenic Th17 cells produce IL-17 in an IL-6 dependent manner in leprosy T1R reactions. Thus, present approaches that specifically target Th17 cells and/or the cytokines that promote their development, such as IL-6, TGF-β and IL-23A may provide more focused treatment strategies for the management of Mycobacterium leprae and its reactions.

Leprosy is a chronic bacterial disease caused by Mycobacterium leprae . Cytokines are known to play vital role as a peacekeeper during inflammatory and other immunocompromised conditions such as leprosy. This study has tried to bridge the gap of information on cytokine gene polymorphisms and its potential role in the pathogenesis of leprosy. Interleukin-10 (IL-10) is an immunosuppressive cytokine, found to be elevated in leprosy that accounted for the suppression of host's immune system by regulating the functions of other immune cells. T helper cells and T regulatory (Tregs) cells are the major source of IL-10 in lepromatous leprosy patients. In this study, we have documented the association of IL-10 cytokine gene polymorphism with the disease progression. A total of 132 lepromatous leprosy patients and 120 healthy controls were analyzed for IL-10 cytokine gene polymorphisms using PCR-SSP assay and flow cytometry was used to analyze IL-10 secretion by CD4 and Tregs in various genotype of leprosy patients. The frequencies of IL-10 (-819) TT and IL-10 (-1082) GG genotypes were significantly higher in leprosy patients as compared to healthy controls. This observation advocates that these genotypes were associated with the susceptibility and development of the disease. In addition, flow cytometry analysis demonstrated an increased number of IL-10 producing CD4 and Treg cells in IL-10 (819) TT genotype compared to CT and CC genotypes. These observations were further supported by immunohistochemical studies. Therefore, we can conclude that IL-10 cytokine gene polymorphisms by affecting its production can determine the predilection and progression of leprosy in the study population., (Copyright © 2020 Tarique, Naz, Saini, Suhail, Shankar, Khanna and Sharma.)

The aim of this study was to evaluate the expression of human leukocyte antigen G (HLA-G) in leprosy. Biopsy and serum samples were collected from 18 patients presenting with leprosy and from healthy controls. Samples were analyzed using immunohistochemistry and ELISA techniques. HLA-G expression was observed in biopsy samples of all patients. The healthy control samples were consistently negative for HLA-G expression. Control plasma samples displayed significantly higher HLA-G expression than those from the patients (p < 0.01). These results are the first demonstration of the expression of HLA-G in leprosy.

Gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) have several biomedical applications. However, the effective usage of these two nanoparticles is impeded due to limited understanding of their interaction with proteins including small heat shock proteins (sHSPs). Specifically, no evidences of interaction of these two nanoparticles with HSP18 (an antigenic protein) which is an important factor for the growth and survival of M. leprae (the causative organism of leprosy) are available in the literature. Here, we report for the first time evidences of "HSP18-AuNPs/AgNPs interaction" and its impact on the structure and chaperone function of HSP18. Interaction of citrate-capped AuNPs/AgNPs (~20 nm diameter) to HSP18 alters the secondary and tertiary structure of HSP18 in a distinctly opposite manner; while "HSP18-AuNPs interaction" leads to oligomeric association, "HSP18-AgNPs interaction" results in oligomeric dissociation of the protein. Surface hydrophobicity, thermal stability, chaperone function of HSP18 and survival of thermally stressed E. coli harbouring HSP18 are enhanced upon AuNPs interaction, while all of them are reduced upon interaction with AgNPs. Altogether, our study reveals that HSP18 is an important drug target in leprosy and its chaperone function may possibly plays a vital role in the growth and survival of M. leprae pathogen in infected hosts., Competing Interests: Declaration of competing interest The authors declare that they have no conflicts of interest with the contents of this article., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Leprosy continues to be the belligerent public health hazard for the causation of high disability and eventual morbidity cases with stable prevalence rates, even with treatment by the on-going multidrug therapy (MDT). Today, dapsone (DDS) resistance has led to fear of leprosy in more unfortunate people of certain developing countries. Herein, DDS was chemically conjugated with five phytochemicals independently as dapsone-phytochemical conjugates (DPCs) based on azo-coupling reaction. Possible biological activities were verified with computational chemistry and quantum mechanics by molecular dynamics simulation program before chemical synthesis and spectral characterizations viz., proton-HNMR, FTIR, UV and LC-MS. The in vivo antileprosy activity was monitored using the 'mouse-foot-pad propagation method', with WHO recommended concentration 0.01% mg/kg each DPC for 12 weeks, and the host-toxicity testing of the active DPC4 was seen in cultured-human-lymphocytes in vitro. One-log bacilli cells in DDS-resistant infected mice footpads decreased by the DPC4, and no bacilli were found in the DDS-sensitive mice hind pads. Additionally, the in vitro host toxicity study also confirmed that the DCP4 up to 5,000 mg/L level was safety for oral administration, since a minor number of dead cells were found in red color under a fluorescent microscope. Several advanced bioinformatics tools could help locate the potential chemical entity, thereby reducing the time and resources required for in vitro and in vitro tests. DPC4 could be used in place of DDS in MDT, evidenced from in vivo antileprosy activity and in vitro host toxicity study.

Introduction: Leprosy is an infectious disease caused by Mycobacterium leprae , a debilitating disease that affects the skin and peripheral nerves. It is possible that tissue changes during infection with leprosy are related to alterations in the activity of the Notch signaling pathway, an innate signaling pathway in the physiology of the skin and peripheral nerves. Methods: This is a descriptive observational study. Thirty skin biopsies from leprosy patients and 15 from individuals with no history of this disease were evaluated. In these samples, gene expressions of cellular components associated with the Notch signaling pathway, Hes-1, Hey-1, Runx-1 Jagged-1, Notch-1 , and Numb , were evaluated using q-PCR, and protein expression was evaluated using immunohistochemistry of Runx-1 and Hes-1. Results: Changes were observed in the transcription of Notch signaling pathway components; Hes-1 was downregulated and Runx-1 upregulated in the skin of infected patients. These results were confirmed by immunohistochemistry, where reduction of Hes-1 expression was found in the epidermis, eccrine glands, and hair follicles. Increased expression of Runx-1 was found in inflammatory cells in the dermis of infected patients; however, it is not related to tissue changes. With these results, a multivariate analysis was performed to determine the causes of transcription factor Hes-1 reduction. It was concluded that tissue inflammation was the main cause. Conclusions: The tissue changes found in the skin of infected patients could be associated with a reduction in the expression of Hes-1, a situation that would promote the survival and proliferation of M. leprae in this tissue., (Copyright © 2020 Serrano-Coll, Ospina, Salazar-Peláez and Cardona-Castro.)

Background: Leprosy is an infectious-contagious disease caused by Mycobacterium leprae that remain endemic in 105 countries. This neglected disease has a wide range of clinical and histopathological manifestations that are related to the host inflammatory and immune responses. More recently, the inflammasome has assumed a relevant role in the inflammatory response against microbiological agents. However, the involvement of inflammasome in leprosy remains poorly understood., Objectives: The aim is to associate biomarkers of inflammasome with the different immunopathological forms of leprosy., Methods: We performed an observational, cross-sectional, and comparative study of the immunophenotypic expression of inflammasome-associated proteins in immunopathological forms of leprosy of 99 skin lesion samples by immunohistochemistry. The intensity and percentage of NLRP3, Caspase-1, Caspases-4/5, interleukin-1β and interleukin-18 immunoreactivities in the inflammatory infiltrate of skin biopsies were evaluated., Findings: Strong expression of NLRP3 and inflammatory Caspases-4/5 were observed in lepromatous leprosy (lepromatous pole). In addition, were observed low expression of caspase-1, interleukin-1β, and interleukin-18 in tuberculoid and lepromatous leprosy. The interpolar or borderline form showed immunophenotype predominantly similar to the lepromatous pole., Main Conclusions: Our results demonstrate that the NLRP3 inflammasome is inactive in leprosy, suggesting immune evasion of M. leprae.

A population pharmacokinetic (PPK) model to describe the pharmacokinetics of thalidomide in different patient populations was developed using data pooled from healthy subjects and patients with Hansen's disease, human immunodeficiency virus (HIV), and multiple myeloma (MM). The analysis data set had a total of 164 evaluable subjects who received various doses (50 to 400 mg) of oral thalidomide in single- and/or multiple-dose regimens. The plasma thalidomide concentrations were adequately described by a linear 1-compartment PPK model with first-order absorption and first-order elimination. Inclusion of MM as a covariate on apparent clearance (CL/F) accounted for 4.4% of the interindividual variability (IIV) of CL/F. Body weight as a covariate on CL/F and apparent volume of distribution (V/F) also improved model fitting slightly, accounting for 7.2% and 20% of IIV, respectively. Although inclusion of body weight and MM as covariates of CL/F and body weight on V/F improved the goodness of fit of the model in a statistically significant manner, the impact of this difference in CL/F is not considered clinically relevant. Other factors such as age, sex, race, creatinine clearance, and alanine transaminase had no effect on thalidomide pharmacokinetics. MM, HIV, and Hansen's disease have no clinically relevant effect on thalidomide disposition relative to healthy volunteers., (© 2019, The American College of Clinical Pharmacology.)

New approaches are needed to control leprosy, but understanding of the biology of the causative agent Mycobacterium leprae remains rudimentary, principally because the pathogen cannot be grown in axenic culture. Here, we applied 13 C isotopomer analysis to measure carbon metabolism of M. leprae in its primary host cell, the Schwann cell. We compared the results of this analysis with those of a related pathogen, Mycobacterium tuberculosis , growing in its primary host cell, the macrophage. Using 13 C isotopomer analysis with glucose as the tracer, we show that whereas M. tuberculosis imports most of its amino acids directly from the host macrophage, M. leprae utilizes host glucose pools as the carbon source to biosynthesize the majority of its amino acids. Our analysis highlights the anaplerotic enzyme phosphoenolpyruvate carboxylase required for this intracellular diet of M. leprae , identifying this enzyme as a potential antileprosy drug target. IMPORTANCE Leprosy remains a major problem in the world today, particularly affecting the poorest and most disadvantaged sections of society in the least developed countries of the world. The long-term aim of research is to develop new treatments and vaccines, and these aims are currently hampered by our inability to grow the pathogen in axenic culture. In this study, we probed the metabolism of M. leprae while it is surviving and replicating inside its primary host cell, the Schwann cell, and compared it to a related pathogen, M. tuberculosis , replicating in macrophages. Our analysis revealed that unlike M. tuberculosis , M. leprae utilized host glucose as a carbon source and that it biosynthesized its own amino acids, rather than importing them from its host cell. We demonstrated that the enzyme phosphoenolpyruvate carboxylase plays a crucial role in glucose catabolism in M. leprae Our findings provide the first metabolic signature of M. leprae in the host Schwann cell and identify novel avenues for the development of antileprosy drugs., (Copyright © 2019 Borah et al.)

Leprosy, once considered as poor man's disease may cause severe neurological complications and physical disabilities. Classification of leprosy depends upon the cell mediated and humoral immune responses of the host, from tuberculoid to lepromatous stage. Current therapy to prevent the disease is not only very lengthy but also consists of expensive multiple antibiotics in combination. Treatment and the duration depend on the bacillary loads, from six months in paucibacillary to a year in multibacillary leprosy. Although as per WHO recommendations, these antibiotics are freely available but still out of reach to patients of many rural areas of the world. In this review, we have focused on the nutritional aspect during the multi-drug therapy of leprosy along with the role of nutrition, particularly malnutrition, on susceptibility of Mycobacterium leprae and development of clinical symptoms. We further discussed the diet plan for the patients and how diet plans can affect the immune responses during the disease., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Leprosy reactions are acute immunological events that occur during the evolution of chronic infectious disease causing neural damage and disabilities. A study using blood samples of 17 leprosy reaction patients and 17 reaction-free was carried out by means of associations between antigens, receptors, and expression of cytokines, using path analysis providing new insights into the immunological mechanisms involved in triggering leprosy reactions. Toll-like receptors (TLR) such as TLR1 and TLR2, presented balanced expression in the reaction-free multibacillary (MB) group (TLR1: 1.01 ± 0.23, TLR2: 1.22 ± 0.18; p = 0.267). On the other hand, downgrading type 1 reaction (T1R) (TLR1: 1.24 ± 0.17, TLR2: 2.88 ± 0.37; p = 0.002) and erythema nodosum leprosum (ENL) (TLR1: 1.93 ± 0.17, TLR2: 2.81 ± 0.15; p = 0.004) revealed an unbalance in relation to the expression of these receptors. When the path analysis was approached, it was noted that interleukin 10 (IL-10) expression showed a dependence relation with phenolic glycolipid I (PGL-I) in downgrading T1R (direct effect = 0.503 > residual effect = 0.364), whereas in ENL, such relationship occurred with lipoarabinomannan (LAM) (direct effect = 0.778 > residual effect = 0.280). On the contrary, in the reaction-free leprosy group, interferon-gamma (IFN- γ ) levels were dependent on the association between TLR2 and TLR1 (0.8735). The high TLR2 expression associated with IL-10 levels, in the leprosy reaction groups, may be hypothetically related to the formation of TLR2/2 homodimers and/or TLR2/6 heterodimers linked to evasion mechanisms in downgrading reactions and pathophysiology of ENL., Competing Interests: The authors declare no financial or commercial conflict of interest., (Copyright © 2019 Douglas Eulálio Antunes et al.)

Reversal reactions (RRs) in leprosy are characterized by a reduction in the number of bacilli in lesions associated with an increase in cell-mediated immunity against the intracellular bacterium Mycobacterium leprae, the causative pathogen of leprosy. To identify the mechanisms that contribute to cell-mediated immunity in leprosy, we measured changes in the whole blood-derived transcriptome of patients with leprosy before, during and after RR. We identified an 'RR signature' of 1017 genes that were upregulated at the time of the clinical diagnosis of RR. Using weighted gene correlated network analysis (WGCNA), we detected a module of 794 genes, bisque4, that was significantly correlated with RR, of which 434 genes were part of the RR signature. An enrichment for both IFN-γ and IFN-β downstream gene pathways was present in the RR signature as well as the RR upregulated genes in the bisque4 module, including those encoding proteins of the guanylate binding protein (GBP) family that contributes to antimicrobial responses against mycobacteria. Specifically, GBP1, GBP2, GBP3 and GBP5 mRNAs were upregulated in the RR peripheral blood transcriptome, with GBP1, GBP2 and GBP5 mRNAs also upregulated in the RR disease lesion transcriptome. These data indicate that RRs involve a systemic upregulation of IFN-γ downstream genes including GBP family members as part of the host antimicrobial response against mycobacteria., Competing Interests: The authors have declared that no competing interests exist.

Type-1 reactions (T1R) are pathological inflammatory episodes and main contributors to nerve damage in leprosy. Here, we evaluate the genewise enrichment of rare protein-altering variants in 7 genes where common variants were previously associated with T1R. We selected 474 Vietnamese leprosy patients of which 237 were T1R-affected and 237 were T1R-free matched controls. Genewise enrichment of nonsynonymous variants was tested with both kernel-based (sequence kernel association test [SKAT]) and burden methods. Of the 7 genes tested 2 showed statistical evidence of association with T1R. For the LRRK2 gene an enrichment of nonsynonymous variants was observed in T1R-free controls ( P SKAT-O = 1.6 × 10 -4 ). This genewise association was driven almost entirely by the gain-of-function variant R1628P ( P = 0.004; odds ratio = 0.29). The second genewise association was found for the Parkin coding gene PRKN (formerly PARK2 ) where 7 rare variants were enriched in T1R-affected cases ( P SKAT-O = 7.4 × 10 -5 ). Mutations in both PRKN and LRRK2 are known causes of Parkinson's disease (PD). Hence, we evaluated to what extent such rare amino acid changes observed in T1R are shared with PD. We observed that amino acids in Parkin targeted by nonsynonymous T1R-risk mutations were also enriched for mutations implicated in PD ( P = 1.5 × 10 -4 ). Hence, neuroinflammation in PD and peripheral nerve damage due to inflammation in T1R share overlapping genetic control of pathogenicity., Competing Interests: The authors declare no conflict of interest., (Copyright © 2019 the Author(s). Published by PNAS.)

Schwann cells (SCs) critically maintain the plasticity of the peripheral nervous system. Peripheral nerve injuries and infections stimulate SCs in order to retrieve homeostasis in neural tissues. Previous studies indicate that Mycobacterium leprae (ML) regulates the expression of key factors related to SC identity, suggesting that alterations in cell phenotype may be involved in the pathogenesis of neural damage in leprosy. To better understand whether ML restricts the plasticity of peripheral nerves, the present study sought to determine the expression of Krox-20, Sox-10, c-Jun and p75NTR in SC culture and mice sciatic nerves, both infected by ML Thai-53 strain. Primary SC cultures were stimulated with two different multiplicities of infection (MOI 100:1; MOI 50:1) and assessed after 7 and 14 days. Sciatic nerves of nude mice (NU-Foxn1 nu ) infected with ML were evaluated after 6 and 9 months. In vitro results demonstrate downregulation of Krox-20 and Sox-10 along with the increase in p75NTR-immunolabelled cells. Concurrently, sciatic nerves of infected mice showed a significant decrease in Krox-20 and increase in p75NTR. Our results corroborate previous findings on the interference of ML in the expression of factors involved in cell maturation, favouring the maintenance of a non-myelinating phenotype in SCs, with possible implications for the repair of adult peripheral nerves., (© 2019 The Authors. International Journal of Experimental Pathology © 2019 International Journal of Experimental Pathology.)

Background: Leprosy is an ideal human disease to study T cell regulation as patients show correlation between cytokine skewed Th1-Th2 responses and clinical forms of the disease. The Role of transcription factors on the modulation of Th1 and Th2 responses by M. leprae antigens has not been adequately studied. In the present study, we studied the effect of M. leprae antigens on transcription factors STAT-4, STAT-6 and CREB and their correlation with Th1/Th2 cell mediated immune responses in leprosy., Methods: Leprosy patients of both categories of tuberculoid leprosy (BT/TT) and lepromatous leprosy (BL/LL) were selected from the OPD of NJ1L & OMD, (ICMR), Agra and healthy individuals (H) were chosen from the staff and students working in the institute. Peripheral blood mononuclear cells (PBMCs) of the study subjects were stimulated with M. leprae antigens (WCL, MLSA, and PGL-1). Sandwich ELISA was done in the culture supernatants of healthy and leprosy patients to detect IL-4, IL-10 and IFN-γ. Further, expression of IFN-γ and IL-4 and activation of STAT4, STAT6 and CREB transcription factors in CD4 + T cell with or without stimulation of M. leprae antigens was investigated by flow cytometry., Results: Lepromatous leprosy patients showed significantly lower IFN-γ and higher IL-4 levels in culture supernatant and significantly low expression of IFN-γ and higher expression of IL-4 by CD4 + T cells than healthy individuals with or without antigenic stimulation. Antigenic stimulation significantly increased IL-10 in BL/LL patients but not in BT/TT patients or healthy individuals. PGL-1 stimulation led to significantly higher activation of STAT-6 in BT/TT and BL/LL patients in comparison to healthy individuals. All the three antigens led to activation of CREB in healthy and BT/TT patients but not in BL/LL patients., Conclusion: Our findings show that M. leprae antigens differentially modulate activation of T cell transcription factors STAT-4/STAT-6 and CREB. These transcription factors are well known to regulate Th1 and Th2 mediated immune response which in turn could play vital role in the clinical manifestations of leprosy. These observations may help to determine how these T cell transcription factors affect the development of immune dysfunction and whether these new pathways have a role in immunomodulation in intracellular diseases like leprosy and TB.

Mycobacterium leprae causes leprosy, a dermatoneurological disease which affects the skin and peripheral nerves. One of several cellular structures affected during M. leprae infection is the endoplasmic reticulum (ER). Infection by microorganisms can result in ER stress and lead to the accumulation of unfolded or poorly folded proteins. To restore homeostasis in the cell, the cell induces a series of signaling cascades known as the unfolded protein response called UPR (unfolded protein response). The present work is aimed at investigating the in situ expression of these markers in cutaneous lesions of clinical forms of leprosy and establish possible correlation expression patterns and types of lesion. A total of 43 samples from leprosy patients were analyzed by immunohistochemistry with monoclonal antibodies against GRP78/BiP, PERK, IRE1 α , and ATF6. A statistically significant difference between the indeterminate, tuberculoid, and lepromatous clinical forms was detected, with high expression of GRP78/BiP, PERK, IRE1 α , and ATF6 in tuberculoid forms (TT) when compared to lepromatous leprosy (LL) and indeterminate (I) leprosy. These results represent the first evidence of ER stress in samples of skin lesions from leprosy patients. We believe that they will provide better understanding of the complex pathogenesis of the disease and facilitate further characterization of the cascade of molecular events elicited during infection.

Background: Since macrophages are one of the major cell types involved in the Mycobacterium leprae immune response, roles of the M1 and M2 macrophage subpopulations have been well defined. However, the role of M4 macrophages in leprosy or other infectious diseases caused by mycobacteria has not yet been clearly characterized. This study aimed to investigate the presence and potential role of M4 macrophages in the immunopathology of leprosy., Methods: We analyzed the presence of M4 macrophage markers (CD68, MRP8, MMP7, IL-6, and TNF-α) in 33 leprosy skin lesion samples from 18 patients with tuberculoid leprosy and 15 with lepromatous leprosy by immunohistochemistry., Results: The M4 phenotype was more strongly expressed in patients with the lepromatous form of the disease, indicating that this subpopulation is less effective in the elimination of the bacillus and consequently is associated with the evolution to one of the multibacillary clinical forms of infection., Conclusion: M4 macrophages are one of the cell types involved in the microbial response to M. leprae and probably are less effective in controlling bacillus replication, contributing to the evolution to the lepromatous form of the disease.

Background: Leprosy reactions appear episodically in leprosy patients, which lead to high inflammation, morbidity and peripheral nerve damage. The role of Th17 cell has been well studied in leprosy reactions but the role of γδ or unconventional T cells which is an other major source of IL-17 in many diseases, not studied in leprosy reactional episodes., Objective: The aim of the present study to elucidate the role of γδ T cells in leprosy reactions., Methodology: A total of 40 untreated non-reaction and reactions patients were recruited. PBMCs were isolated and stimulated with M. leprae sonicated antigen (MLSA) for 48 h and immuno-phenotyping was done using flow cytometry. Moreover, γδ T cells were isolated by Magnetic beads technology and mRNA expression of IL-17, IFN-γ, TGF-β and FOXP3 were analyzed by real-time PCR (qPCR) and cytokine was estimated in the culture supernatant by ELISA., Results: γδ T cells were significantly increased in both Reversal reaction (RR) and Erythema nodosum leprosum (ENL) reaction patients. These cells produced significant amount of IL-17 and IFN-γ. Furthermore, CD3 + TCRγδ + T cells expressed transient FOXP3 with a low amount of TGF-β in both reactions as compared to stable patients. Moreover, low TGF-β producing TCR-γδ cells were associated with low phosphorylation of STAT5A., Conclusion: This study will add to our understanding of the immunological features that mediate and regulate the pathogenesis of leprosy and may helpful to reduce the immuno-pathogenesis of leprosy reaction by targeting these cells., (Copyright © 2018 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.)

Mycobacterium leprae, an obligate intracellular bacillus, infects Schwann cells (SCs), leading to peripheral nerve damage, the most severe leprosy symptom. In the present study, we revisited the involvement of phenolic glycolipid I (PGL I), an abundant, private, surface M. leprae molecule, in M. leprae-SC interaction by using a recombinant strain of M. bovis BCG engineered to express this glycolipid. We demonstrate that PGL I is essential for bacterial adhesion and SC internalization. We also show that live mycobacterium-producing PGL I induces the expression of the endocytic mannose receptor (MR/CD206) in infected cells in a peroxisome proliferator-activated receptor gamma (PPARγ)-dependent manner. Of note, blocking mannose recognition decreased bacterial entry and survival, pointing to a role for this alternative recognition pathway in bacterial pathogenesis in the nerve. Moreover, an active crosstalk between CD206 and the nuclear receptor PPARγ was detected that led to the induction of lipid droplets (LDs) formation and prostaglandin E2 (PGE2), previously described as fundamental players in bacterial pathogenesis. Finally, this pathway was shown to induce IL-8 secretion. Altogether, our study provides evidence that the entry of live M. leprae through PGL I recognition modulates the SC phenotype, favoring intracellular bacterial persistence with the concomitant secretion of inflammatory mediators that may ultimately be involved in neuroinflammation., Competing Interests: The authors have declared that no competing interests exist.

Neurotrophins are a family of proteins that regulate different aspects of biological development and neural function and are of great importance in neuroplasticity. This group of proteins has multiple functions in neuronal cells, as well as in other cellular populations. Nerve growth factor (NGF) is a neurotrophin that is endogenously produced during development and maturation by multiple cell types, including neurons, Schwann cells, oligodendrocytes, lymphocytes, mast cells, macrophages, keratinocytes, and fibroblasts. These cells produce proNGF, which is transformed by proteolytic cleavage into the biologically active NGF in the endoplasmic reticulum. The present review describes the role of NGF in the pathogenesis of leprosy and its correlations with different clinical forms of the disease and with the phenomena of regeneration and neural injury observed during infection. We discuss the involvement of NGF in the induction of neural damage and the pathophysiology of pain associated with peripheral neuropathy in leprosy. We also discuss the roles of immune factors in the evolution of this pathological process. Finally, we highlight avenues of investigation for future research to broaden our understanding of the role of NGF in the pathogenesis of leprosy. Our analysis of the literature indicates that NGF plays an important role in the evolution and outcome of Mycobacterium leprae infection. The findings described here highlight an important area of investigation, as leprosy is one of the main causes of infection in the peripheral nervous system.

Mast cells (MCs) have important immunoregulatory roles in skin inflammation. Annexin A1 (ANXA1) is an endogenous anti-inflammatory protein that can be expressed by mast cells, neutrophils, eosinophils, monocytes, epithelial and T cells. This study investigated MCs heterogeneity and ANXA1 expression in human dermatoses with special emphasis in leprosy. Sixty one skin biopsies from 2 groups were investigated: 40 newly diagnosed untreated leprosy patients (18 reaction-free, 11 type 1 reaction/T1R, 11 type 2 reaction/T2R); 21 patients with other dermatoses. Tryptase/try+ and chymase/chy + phenotypic markers and toluidine blue stained intact/degranulated MC counts/mm 2 were evaluated. Try + /chy + MCs and ANXA1 were identified by streptavidin-biotin-peroxidase immunostaining and density was reported. In leprosy, degranulated MCs outnumbered intact ones regardless of the leprosy form (from tuberculoid/TT to lepromatous/LL), leprosy reactions (reactional/reaction-free) and type of reaction (T1R/T2R). Compared to other dermatoses, leprosy skin lesions showed lower numbers of degranulated and intact MCs. Try + MCs outnumbered chy + in leprosy lesions (reaction-free/reactional, particularly in T2R), but not in other dermatoses. Compared to other dermatoses, ANXA1 expression, which is also expressed in mast cells, was higher in the epidermis of leprosy skin lesions, independently of reactional episode. In leprosy, higher MC degranulation and differential expression of try + /chy + subsets independent of leprosy type and reaction suggest that the Mycobacterium leprae infection itself dictates the inflammatory MCs activation in skin lesions. Higher expression of ANXA1 in leprosy suggests its potential anti-inflammatory role to maintain homeostasis preventing tissue and nerve damage., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

For those with leprosy, the extent of host infection by Mycobacterium leprae and the progression of the disease depend on the ability of mycobacteria to shape a safe environment for its replication during early interaction with host cells. Thus, variations in key genes such as those in pattern recognition receptors ( NOD2 and TLR1 ), autophagic flux ( PARK2, LRRK2 , and RIPK2 ), effector immune cytokines ( TNF and IL12 ), and environmental factors, such as nutrition, have been described as critical determinants for infection and disease progression. While parkin-mediated autophagy is observed as being essential for mycobacterial clearance, leprosy patients present a prominent activation of the type I IFN pathway and its downstream genes, including OASL, CCL2 , and IL10 . Activation of this host response is related to a permissive phenotype through the suppression of IFN-γ response and negative regulation of autophagy. Finally, modulation of host metabolism was observed during mycobacterial infection. Both changes in lipid and glucose homeostasis contribute to the persistence of mycobacteria in the host. M. leprae -infected cells have an increased glucose uptake, nicotinamide adenine dinucleotide phosphate generation by pentose phosphate pathways, and downregulation of mitochondrial activity. In this review, we discussed new pathways involved in the early mycobacteria-host interaction that regulate innate immune pathways or metabolism and could be new targets to host therapy strategies.

Mycobacterium leprae has a reduced genome size due to the reductive evolution over a long period of time. Lipid metabolism plays an important role in the life cycle and pathogenesis of this bacterium. In comparison to 26 lip genes (Lip A-Z) of M. tuberculosis, M. leprae retained only three orthologs indicating their importance in its life cycle. ML0314c (LipU) is one of them. It is conserved throughout the mycobacterium species. Bioinformatics analysis showed the presence of an α/β hydrolase fold and 'GXSXG' characteristic of the esterases/lipases. The gene was expressed in E. coli and purified to homogeneity. It showed preference towards short chain esters with pNP-acetate as the preferred substrate. The enzyme showed optimal activity at 45°C and pH8.0. ML0314c protein was stable between temperatures ranging from 20 to 60°C and pH5.0-8.0, i.e., relatively acidic and neutral conditions. The active site residues predicted bioinformatically were confirmed to be Ser168, Glu267, and His297 by site directed mutagenesis. E-serine, DEPC and Tetrahydrolipstatin (THL) completely inhibited the activity of ML0314c. The protein was localized in cell wall and extracellular medium. Several antigenic epitopes were predicted in ML0314c. Protein elicited strong humoral immune response in leprosy patients, whereas, a reduced immune response was observed in the relapsed cases. No humoral response was observed in treatment completed patients. Overexpression of ml0314c in the surrogate host M. smegmatis showed marked difference in the colony morphology and growth rate. In conclusion, ML0314c is a secretary carboxyl esterase that could modulate the immune response in leprosy patients., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Leprosy is a chronic infectious disease caused by Mycobacterium leprae mainly affecting skin and peripheral nerves. Leprosy has a broad range of clinical manifestations that range from mild (tuberculoid leprosy) to severe (lepromatous leprosy) forms, and are highly dependent on the host's immune response. Among the immune response elements involved in the pathogenesis of leprosy are the Toll-like receptors (TLRs), vitamin D receptor (VDR), natural killer cells (NK), and T cells. These innate and adaptive immune response elements may be related to the Notch signaling pathway, which is involved in immune cell growth, differentiation, and proliferation. We hypothesize that failure in Notch signaling in leprosy patients may be associated to: 1) compromising NK cell maturation, lysing of infected cells, and CD4+ Th1 differentiation. 2) VDR alterations and TLR polymorphisms may affect expression of Notch Delta-like ligands (DLL) in antigen presenting cells (APCs). 3) altered DLL expression by APCs could compromise CD4+ T cell differentiation towards the Th1 and Th17 effector phenotypes; and finally 4) expression of Notch Jagged ligands would induce CD4+ T cell differentiation towards Th2 effector phenotype and alternative activation of macrophages. Altogether, these signaling failures could favor proliferation of M. leprae in the host. Therefore, evidence of the proposed immunologic failures in leprosy patients would be essential for the better understanding of immunopathogenesis of this disease, and would ultimately enable detection of susceptible individuals, providing a valuable tool for prevention of this debilitating disease., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

After entering tissues, monocytes differentiate into cells that share functional features with either macrophages or dendritic cells (DCs). How monocyte fate is directed toward monocyte-derived macrophages (mo-Macs) or monocyte-derived DCs (mo-DCs) and which transcription factors control these differentiation pathways remains unknown. Using an in vitro culture model yielding human mo-DCs and mo-Macs closely resembling those found in vivo in ascites, we show that IRF4 and MAFB were critical regulators of monocyte differentiation into mo-DCs and mo-Macs, respectively. Activation of the aryl hydrocarbon receptor (AHR) promoted mo-DC differentiation through the induction of BLIMP-1, while impairing differentiation into mo-Macs. AhR deficiency also impaired the in vivo differentiation of mouse mo-DCs. Finally, AHR activation correlated with mo-DC infiltration in leprosy lesions. These results establish that mo-DCs and mo-Macs are controlled by distinct transcription factors and show that AHR acts as a molecular switch for monocyte fate specification in response to micro-environmental factors., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Leprosy is a chronic granulomatous infection that manifests as different clinical forms related to the immunological response. The aim of the study was to evaluated the response of IL-22, STAT3, CD68 and iNOS in leprosy skin lesions. The mean number IL-22 positive cells was 12.12±1.90cells/field in the TT form and 31.31±2.91cells/field in the LL form. STAT3 positive cells was 5.29±1.96 cells/field in the TT form, while this number was 11.13±3.48cells/field in the LL form. The mean number of CD68 positive cells was 25.18±6.21cells/field in the TT form and 62.81±8.13cells/field in the LL form. Quantitative analysis of iNOS revealed a significant difference, with the mean number of cells expressing the enzyme being 30.24±2.88cells/field in the TT form compared to 35.44±4.69cells/field in the LL form. Linear correlations in lesions of TT patients showed a moderate positive correlations between CD68 and iNOS, STAT3 and Inos, IL-22 and STAT3, and IL-22 and iNOS. Our results demonstrate that these factors can act synergistically to induce a microbicidal activity in the population of macrophages in the leprosy lesions., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Background: The impact of leprosy reduces health-related quality of life of affected patients, interfering with different factors such as nutrition. This study investigated the lipid profile, nutritional status, and risk for cardiovascular disease (CVD) in patients who underwent leprosy treatment in Brazil., Methods: Eighty-four adult patients of both genders ranging in age from 20 to 60 years and diagnosed with paucibacillary (PB) or multibacillary (MB) leprosy were selected after undergoing multidrug treatment. The following data were collected: sociodemographic and clinical data; food intake; anthropometric measures (weight, height, and waist circumference); and lipid profile components (total cholesterol, high-density lipoprotein cholesterol [HDL-c], low-density lipoprotein cholesterol [LDL-c], and triglycerides)., Results: Among the study population, there was a predominance of males (65.48%) aged 50 to 60 years, patients with an income of 248-496 American dollars (63.10%), patients who completed elementary school (65.48%), inactive patients (76.19%), non-smokers (46.43%), and non-drinking patients (69.05%). The levels (mean ± standard deviation) of total cholesterol were 193.8 ± 29.4 mg/dL in the PB form and 203.5 ± 41.7 mg/dL in the MB form. The mean LDL-c was 116.9 ± 22.7 mg/dL in PB patients and 121 ± 31.3 mg/dL in MB patients. Mean triglyceride levels were 123.4 ± 45.2 mg/dL in the PB form and 147.4 ± 88.9 mg/dL in the MB form. The evaluation of nutritional status showed that 41.67% of the patients were eutrophic, while 55.96% had excess weight. Food intake was significantly associated with HDL-c in male patients (P = 0.0264) and with triglycerides in patients above the ideal weight (P = 0.0049)., Conclusions: The risk of acquiring CVDs was observed to be high due to patients' excess weight and increased waist circumference. This study will guide clinicians in the adequate treatment of patients with leprosy in order to avoid adverse cardiovascular events.

Leprosy is an ancient disease caused by gram positive, rod shaped bacilli called Mycobacterium leprae. Patients present with varied clinico-pathological disease depending on the host immune response to Mycobacterium leprae. Thus tuberculoid (TT) and lepromatous (LL) patients represent two ends of a spectrum where the former shows limited disease, high T cell mediate immune (CMI) response and low antibody (HI) levels in serum. In contrast the latter has low T cell and high humoral immune response i.e antibody levels. The mechanisms underlying these differences have been investigated intensely; however, there is no consensus on the primary immunological basis. Over three decades, Th1 and Th2 paradigm were thought to underling tuberculoid and lepromatous disease respectively. However many patients were shown to have mixed Th1/Th2 pattern of (IFN-γ/IL-4) cytokines. The present review was undertaken with a view to understand the T cells and cytokine dysregulation in leprosy. In recent years the sub classes of T cells that are Regulatory in nature (Treg) have been implicated in immune diseases where they were shown to suppress T cell functions. Additionally Th17 cells secreting IL-17A, IL17F, were implicated in immune inflammation. Taken together these regulatory cells may play a part in influencing immune responses in leprosy., (Copyright © 2017 European Federation of Immunological Societies. Published by Elsevier B.V. All rights reserved.)

Mycobacterium leprae must adopt a metabolic strategy and undergo various metabolic alterations upon infection to survive inside the human body for years in a dormant state. A change in lipid homeostasis upon infection is highly pronounced in Mycobacterium leprae. Lipids play an essential role in the survival and pathogenesis of mycobacteria. Lipids are present in several forms and serve multiple roles from being a source of nutrition, providing rigidity, evading the host immune response to serving as virulence factors, etc. The synthesis and degradation of lipids is a highly regulated process and is the key to future drug designing and diagnosis for mycobacteria. In the current review, an account of the distinct roles served by lipids, the mechanism of their synthesis and degradation has been elucidated.

Leprosy triggers a complex relationship between the pathogen and host immune response. Endothelium plays an important role in this immune response by directly influencing cell migration to infected tissues. The objective of this work is to investigate the possible role of endothelium in M. leprae infection, correlating the characteristics of endothelial markers with the expression pattern of cytokines. Thirty-six skin biopsy samples were cut into 5-μm thick sections and stained with hematoxylin-eosin and Ziehl-Neelsen for morphological analysis and then submitted to immunohistochemical analysis using monoclonal antibodies against ICAM-1, ICAM-2, VCAM-1, and VLA-4. Immunostaining for ICAM-1 showed a significantly larger number of stained endothelial cells in the tuberculoid leprosy (9.92 ± 1.11 cells/mm 2 ) when compared to lepromatous samples (5.87 ± 1.01 cells/mm 2 ) and ICAM-2 revealed no significant difference in the number of endothelial cells expressing this marker between the tuberculoid (13.21 ± 1.27 cells/mm 2 ) and lepromatous leprosy (14.3 ± 1.02 cells/mm 2 ). VCAM-1-immunostained showed 18.28 ± 1.46/mm 2 cells in tuberculoid leprosy and 10.67 ± 1.25 cells/mm 2 in the lepromatous leprosy. VLA-4 exhibited 22.46 ± 1.38 cells/mm 2 in the tuberculoid leprosy 16.04 ± 1.56 cells/mm 2 in the lepromatous leprosy. Samples with characteristics of the tuberculoid leprosy exhibited a larger number of cells stained with ICAM-1, VCAM-1 and VLA-4, demonstrating the importance of these molecules in the migration and selection of cells that reach the inflamed tissue., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

Background: Type 1 reaction (T1R) is an acute T-helper type 1 (Th1) inflammatory episode in patients with leprosy. While immunological responses associated with T1R have been investigated, the corresponding metabolic responses that could contribute to T1R pathology have received little attention., Methods: Metabolomics-based analyses of sera from 7 patients with and 9 without T1R were conducted via liquid chromatography-mass spectrometry. Serum metabolites present at levels that significantly differed (P < .05) with a log2 fold change of ≥ 1.0 between patient groups were interrogated against known metabolic pathways. The structural identification of targeted metabolites was confirmed and abundance changes validated by mass spectrometry and enzyme-linked immunoassay., Results: Forty metabolic pathways were perturbed in patients with T1R, with 71 dysregulated metabolites mapping to pathways for lipid mediators of inflammation. Of note was an increase in the abundance of the proinflammatory leukotriene B4 (LTB4) and a corresponding decrease in the level of proresolving resolvin D1 (RvD1). Also, levels of prostaglandin D2 (PGD2) and lipoxin A4 (LXA4) in patients with T1R were significantly increased, while the level of prostaglandin E2 (PGE2) was decreased., Conclusions: The dysregulation of metabolic pathways leading to abundance shifts between proinflammatory and proresolving lipid mediators provides a link between metabolic and cellular immune responses that result in the Th1-mediated pathology of T1R., (© The Author 2016. Published by Oxford University Press for the Infectious Diseases Society of America. All rights reserved. For permissions, e-mail: journals.permissions@oup.com.)

In spite of hyporesponsivity to Mycobacterium leprae, borderline lepromatous (BL) patients show clinical and immunological instability, and undergo frequent acute inflammatory episodes such as type 1 reaction (T1R), which may cause nerve damages. This work focused on the participation of T cell subsets from blood and skin at T1R onset. We observed a significantly increased ex vivo frequency of both effector and memory CD4+ and CD8+ T cells in T1R group. Besides, ex vivo frequency of T cell homing receptor, the Cutaneous Leukocyte-associated Antigen (CLA) was significantly increased in T cells from T1R patients. M. leprae induced a higher frequency of CD4+ TEM and CD8+ TEF cells, as well as of CD8+/TEMRA (terminally differentiated effector T cells) subset, which expressed high CD69+. The presence of IFN-γ‒producing-CD4+ TEF and naïve and effector CD8+ T lymphocytes was significant in T1R. TBX21 expression was significantly higher in T1R, while BL showed increased GATA3 and FOXP3 expression. In T1R, TBX21 expression was strongly correlated with CD8+/IFN-γ‒ T cells frequency. The number of double positive CD8+/CLA+ and CD45RA+/CLA+ cells was significantly higher in skin lesions from T1R, in comparison with non-reactional BL group. The observed increase of ex vivo T cells at T1R onset suggests intravascular activation at the beginning of reactional episodes. The antigen-specific response in T1R group confirmed the higher number of CD8+/CLA+ and CD45RA+/CLA+ cells in T1R lesions suggests possible migration of these cells activated by M. leprae components inside the vascular compartment to skin and participation in T1R physiopathology., Competing Interests: The authors have declared that no competing interests exist.

Leprosy is a chronic infectious disease that requires better understanding since it continues to be a significant health problem in many parts of the world. Leprosy reactions are acute inflammatory episodes regarded as the central etiology of nerve damage in the disease. The activation of endothelium is a relevant phenomenon to be investigated in leprosy reactions. The present study evaluated the expression of endothelial factors in skin lesions and serum samples of leprosy patients. Immunohistochemical analysis of skin samples and serum measurements of VCAM-1, VEGF, tissue factor and thrombomodulin were performed in 77 leprosy patients and 12 controls. We observed significant increase of VCAM-1 circulating levels in non-reactional leprosy (p = 0.0009). The immunostaining of VEGF and tissue factor was higher in endothelium of non-reactional leprosy (p = 0.02 for both) than healthy controls. Patients with type 1 reaction presented increased thrombomodulin serum levels, compared with non-reactional leprosy (p = 0.02). In type 2 reaction, no significant modifications were observed for the endothelial factors investigated. The anti-inflammatory and antimicrobial activities of the endotfhelial factors may play key-roles in the pathogenesis of leprosy and should be enrolled in studies focusing on alternative targets to improve the management of leprosy and its reactions.

Aim: Study anti-leprosy activity of.a 1.3-diazinon-4 compound derivative under the labora- tory code PYaTd1 on the model of intra-plantar infection of mice and evaluate the character of its antibacterial effect., Materials and Methods: Study of specific activity was carried out in vivo on the experimental model of leprosy, proposed by Shepard C.C., that assumes execution of intraplantar infection of mice with a suspension of mycobacteria, produced from lepromas or autopsy tissue of a non-treated leprosy infected, or from tissues of experimental mice, previously infected with Mycobacterium leprae from non-treated patients. The study was carried out on 120 CBA line-mice infected with M.leprae (VIII passage) from patient M; Dapsone and PYaTdl compound were administered to animals next day after the infection with forage at a dose of 25 mg/kg for 4.5, 6, 9 and 11 months. The mice were split into 3 groups: control (infected.without treatment), com- parison (infected, receiving.dapsone), experimental (infected, receiving PYaTdl). After.the control term the mice were euthanized under chloroform anesthesia. Suspensions for quantification of mycobacteria were prepared from paw pads. Smears were stained by Ziehl-Nilsson., Results: After 4.5 months the intensity of infect reproduction under, the effect of dapsone and PYaTd1 was reduced compared with control by 18 - 25 times. After a 6-mont course - by 50 - 75% and after 9 months - by 85 - 90%. After 11 months in mice that had received PYaTd1, an intensive suppression of microorganism reproduction as observed: the yield in paws was 70 times lower than in control. In the group that had received dapsone, a reduction of the number of mycobacteria by 20 - 25 times was detected, it was significantly less effective than under the conditions of PYaTd1 admnistration., Conclusion: A novel 1.3-diazinon- 4 derivative under the code PYaTd1 can actively supress reproduction of-M. leprae, that gives evidence regarding its specific anti-mycobacterial activity and determines perspectives of its further studies.

The innate immune system recognizes microbial pathogens via pattern recognition receptors. One such receptor, NOD2, via recognition of muramyl dipeptide (MDP), triggers a distinct network of innate immune responses, including the production of interleukin-32 (IL-32), which leads to the differentiation of monocytes into dendritic cells (DC). NOD2 has been implicated in the pathogenesis of human leprosy, yet it is not clear whether Mycobacterium leprae, which has a distinct MDP structure, can activate this pathway. We investigated the effect of MDP structure on the innate immune response, finding that infection of monocytes with M. leprae induces IL-32 and DC differentiation in a NOD2-dependent manner. The presence of the proximal l-Ala instead of Gly in the common configuration of the peptide side chain of M. leprae did not affect recognition by NOD2 or cytokine production. Furthermore, amidation of the d-Glu residue did not alter NOD2 activation. These data provide experimental evidence that NOD2 recognizes naturally occurring structural variants of MDP., (Copyright © 2016 Schenk et al.)

Genetic polymorphism within the 9q32 locus is linked with increased risk of several diseases, including Crohn's disease (CD), primary biliary cholangitis (PBC) and leprosy. The most likely disease-causing gene within 9q32 is TNFSF15, which encodes the pro-inflammatory cytokine TNF super-family member 15, but it was unknown whether these disparate diseases were associated with the same genetic variance in 9q32, and how variance within this locus might contribute to pathology. Using genetic data from published studies on CD, PBC and leprosy we revealed that bearing a T allele at rs6478108/rs6478109 (r(2) = 1) or rs4979462 was significantly associated with increased risk of CD and decreased risk of leprosy, while the T allele at rs4979462 was associated with significantly increased risk of PBC. In vitro analyses showed that the rs6478109 genotype significantly affected TNFSF15 expression in cells from whole blood of controls, while functional annotation using publicly-available data revealed the broad cell type/tissue-specific regulatory potential of variance at rs6478109 or rs4979462. In summary, we provide evidence that variance within TNFSF15 has the potential to affect cytokine expression across a range of tissues and thereby contribute to protection from infectious diseases such as leprosy, while increasing the risk of immune-mediated diseases including CD and PBC.