Fingerstick test quantifying humoral and cellular biomarkers indicative for M. leprae infection

Anti-phenolic glycolipid antibodies in Mycobacterium bovis infected cattle

Mycobacterium bovis, the causative agent of bovine tuberculosis (bTB), causes significant financial losses in the agricultural industry. Additionally, M. bovis transmission from animals to humans can result in zoonotic TB, especially in low- and middle-income countries (LMICs), highlighting the need to enhance One Health surveillance to mitigate this threat. Antibodies directed against a major mycobacterial cell wall component of M. leprae, phenolic glycolipid-I (PGL-I), have shown excellent performance in identifying M. leprae infection in humans and animals. In this study, we therefore investigated whether antibodies against M. bovis PGL similarly represent a useful biomarker for M. bovis infection in cattle. Comparing sera from naturally M. bovis-infected and the single intradermal comparative cervical tuberculin test (SICCT)-negative cattle, we assessed the potential of M. bovis PGL antibodies to identify this mycobacterial infection. Our results show that serum levels of anti-M. bovis PGL IgG and -IgM in M. bovis-infected cattle were significantly higher than in the SICCT-negative cattle. The sensitivity for anti-M. bovis PGL IgM in infected animals was, however, moderate (44.9 %) and the false-positive rate was 6.3 % in SICCT-negative cattle. Notably, vaccination with BCG- or heat-killed M. bovis did not affect serum levels of anti-M. bovis PGL IgM in cattle. Moreover, none of the 57 anti-M. bovis PGL-seropositive cattle tested positive in the anti-M. leprae PGL-I assay. This study shows for the first time that anti M. bovis PGL antibodies can be detected in infected cattle: anti-M. bovis PGL IgM is a highly specific, but moderately sensitive biomarker for M. bovis infection in cattle, showing potential for differentiate infected from vaccinated animals (DIVA). It could be a valuable component in a multi-biomarker approach for diagnosing bTB.

Comparison of Day-Specific Serum LH, Estradiol, and Progesterone with MiraTM Monitor Urinary LH, Estrone-3-glucuronide, and Pregnanediol-3-glucuronide Levels in Ovulatory Cycles

Background and Objectives: Fertility tracking apps and devices are now currently available, but urinary hormone levels lack accuracy and sensitivity in timing the start of the 6-day fertile window and the precise 24 h interval of transition from ovulation to the luteal phase. We hypothesized the serum hormones estradiol (E2) and progesterone (P) might be better biomarkers for these major ovulatory cycle events, using appropriate mathematical tools. Materials and Methods: Four women provided daily blood samples for serum E2, P, and LH (luteinizing hormone) levels throughout their entire ovulatory cycles, which were indexed to the first day of dominant follicle (DF) collapse (defined as Day 0) determined by transvaginal sonography; therefore, ovulation occurred in the 24 h interval of Day -1 (last day of maximum diameter DF) to Day 0. For comparison, a MiraTM fertility monitor was used to measure daily morning urinary LH (ULH), estrone-3-glucuronide (E3G), and pregnanediol-3-glucuronide (PDG) levels in three of these cycles. Results: There were more fluctuations in the MiraTM hormone levels compared to the serum levels. Previously described methods, the Fertility Indicator Equation (FIE) and Area Under the Curve (AUC) algorithm, were tested for identifying the start of the fertile window and the ovulation/luteal transition point using the day-specific hormone levels. The FIE with E2 levels predicted the start of the 6-day fertile window on Day -7 (two cycles) and Day -5 (two cycles), whereas no identifying signal was found with E3G. However, both pairs of (E2, P) and (E3G, PDG) levels with the AUC algorithm signaled the Day -1 to Day 0 ovulation/luteal transition interval in all cycles. Conclusions: serum E2 and (E2, P) were better biomarkers for signaling the start of the 6-day fertile window, but both MiraTM and serum hormone levels were successful in timing the [Day -1, Day 0] ovulatory/luteal transition interval. These results can presently be applied to urinary hormone monitors for fertility tracking and have implications for the direction of future fertility tracking technology.

Molecular and Serological Surveillance for Mycobacterium leprae and Mycobacterium lepromatosis in Wild Red Squirrels (Sciurus vulgaris) from Scotland and Northern England

Leprosy is a poverty-associated infectious disease in humans caused by Mycobacterium leprae or M. lepromatosis, often resulting in skin and peripheral nerve damage, which remains a significant public health concern in isolated areas of low- and middle-income countries. Previous studies reported leprosy in red squirrels in the British Isles, despite the fact that autochthonous human cases have been absent for centuries in this region. To investigate the extent of M. leprae and M. lepromatosis presence in wild red squirrels in the northern UK, we analyzed 220 blood/body cavity fluid samples from opportunistically sampled red squirrels (2004-2023) for specific antibodies against phenolic glycolipid-I, a cell wall component specific for these leprosy bacilli. Additionally, we assessed bacillus-derived DNA by real-time PCR (qPCR) in 250 pinnae from the same cohort. M. lepromatosis and M. leprae DNA were detected by qPCR in 20.4% and 0.8% of the squirrels, respectively. No cases of co-detection were observed. Detectable levels of anti-PGL-I antibodies by UCP-LFA were observed in 52.9% of animals with the presence of M. lepromatosis determined by qPCR, and overall in 15.5% of all animals. In total, 22.6% (n = 296) of this UK cohort had at least some exposure to leprosy bacilli. Our study shows that leprosy bacilli persist in red squirrels in the northern UK, emphasizing the necessity for ongoing molecular and serological monitoring to study leprosy ecology in red squirrels, gain insight into potential zoonotic transmission, and to determine whether the disease has a conservation impact on this endangered species.

Post-exposure prophylaxis in leprosy (PEOPLE): a cluster randomised trial

BACKGROUND

Post-exposure prophylaxis (PEP) using single-dose rifampicin reduces progression from infection with Mycobacterium leprae to leprosy disease. We compared effectiveness of different administration modalities, using a higher (20 mg/kg) dose of rifampicin-single double-dose rifampicin (SDDR)-PEP.

METHODS

We did a cluster randomised study in 16 villages in Madagascar and 48 villages in Comoros. Villages were randomly assigned to four study arms and inhabitants were screened once a year for leprosy, for 4 consecutive years. All permanent residents (no age restriction) were eligible to participate and all identified patients with leprosy were treated with multidrug therapy (SDDR-PEP was provided to asymptomatic contacts aged ≥2 years). Arm 1 was the comparator arm, in which no PEP was provided. In arm 2, SDDR-PEP was provided to household contacts of patients with leprosy, whereas arm 3 extended SDDR-PEP to anyone living within 100 m. In arm 4, SDDR-PEP was offered to household contacts and to anyone living within 100 m and testing positive to anti-phenolic glycolipid-I. The main outcome was the incidence rate ratio (IRR) of leprosy between the comparator arm and each of the intervention arms. We also assessed the individual protective effect of SDDR-PEP and explored spatial associations. This trial is registered with ClinicalTrials.gov, NCT03662022, and is completed.

FINDINGS

Between Jan 11, 2019, and Jan 16, 2023, we enrolled 109 436 individuals, of whom 95 762 had evaluable follow-up data. Our primary analysis showed a non-significant reduction in leprosy incidence in arm 2 (IRR 0·95), arm 3 (IRR 0·80), and arm 4 (IRR 0·58). After controlling for baseline prevalence, the reduction in arm 3 became stronger and significant (IRR 0·56, p=0·0030). At an individual level SDDR-PEP was also protective with an IRR of 0·55 (p=0·0050). Risk of leprosy was two to four times higher for those living within 75 m of an index patient at baseline.

INTERPRETATION

SDDR-PEP appears to protect against leprosy but less than anticipated. Strong spatial associations were observed within 75 m of index patients. Targeted door-to-door screening around index patients complemented by a blanket SDDR-PEP approach will probably have a substantial effect on transmission.

FUNDING

European and Developing Countries Clinical Trials Partnership.

TRANSLATION

For the French translation of the abstract see Supplementary Materials section.

The role of CXCL10 as a biomarker for immunological response among patients with leprosy: a systematic literature review

Introduction

Involvement of a chemokine known as C-X-C motif chemokine ligand 10 or CXCL10 in the immunopathology of leprosy has emerged as a possible immunological marker for leprosy diagnosis and needed to be investigate further. The purpose of this systematic review is to assess CXCL10's potential utility as a leprosy diagnostic tool and evaluation of therapy.

Methods

This systematic review is based on Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020. A thorough search was carried out to find relevant studies only in English and limited in humans published up until September 2023 using PubMed, Scopus, Science Direct, and Wiley Online Library database with keywords based on medical subject headings (MeSH) and no exclusion criteria. The Newcastle-Ottawa Scale (NOS) was utilized for quality assessment, while the Risk of Bias Assessment tool for Non-randomized Studies (RoBANS) was utilized for assessing the risk of bias. Additionally, a narrative synthesis was conducted to provide a comprehensive review of the results.

Results

We collected a total of 115 studies using defined keywords and 82 studies were eliminated after titles and abstracts were screened. We assessed the eligibility of the remaining 26 reports in full text and excluded four studies due to inappropriate study design and two studies with incomplete outcome data. There were twenty included studies in total with total of 2.525 samples. The included studies received NOS quality evaluation scores ranging from 6 to 8. The majority of items in the risk bias assessment, using RoBANS, across all included studies yielded low scores. However, certain items related to the selection of participants and confounding variables showed variations. Most of studies indicate that CXCL10 may be a helpful immunological marker for leprosy diagnosis, particularly in leprosy reactions as stated in seven studies. The results are better when paired with other immunological markers. Its effectiveness in field-friendly diagnostic tools makes it one of the potential biomarkers used in diagnosing leprosy patients. Additionally, CXCL10 may be utilized to assess the efficacy of multidrug therapy (MDT) in leprosy patients as stated in three studies.

Conclusion

The results presented in this systematic review supports the importance of CXCL10 in leprosy diagnosis, particularly in leprosy responses and in tracking the efficacy of MDT therapy. Using CXCL10 in clinical settings might help with leprosy early diagnosis. Yet the findings are heterogenous, thus more investigation is required to determine the roles of CXCL10 in leprosy while taking into account for additional confounding variables.

Field-friendly anti-PGL-I serosurvey in children to monitor Mycobacterium leprae transmission in Bihar, India

Background

It has been amply described that levels of IgM antibodies against Mycobacterium leprae (M. leprae) phenolic glycolipid I (PGL-I) correlate strongly with the bacterial load in an infected individual. These findings have generated the concept of using seropositivity for antibodies against M. leprae PGL-I as an indicator of the proportion of the population that has been infected. Although anti-PGL-I IgM levels provide information on whether an individual has ever been infected, their presence cannot discriminate between recent and past infections. Since infection in (young) children by definition indicates recent transmission, we piloted the feasibility of assessment of anti-PGL-I IgM seroprevalence among children in a leprosy endemic area in India as a proxy for recent M. leprae transmission.

Material and methods

A serosurvey for anti-PGL-I IgM antibodies among children in highly leprosy endemic villages in Bihar, India, was performed, applying the quantitative anti-PGL-I UCP-LFA cassette combined with low-invasive, small-volume fingerstick blood (FSB).

Results

Local staff obtained FSB of 1,857 children (age 3-11 years) living in 12 leprosy endemic villages in Bihar; of these, 215 children (11.58%) were seropositive for anti-PGL-I IgM.

Conclusion

The anti-PGL-I seroprevalence level of 11.58% among children corresponds with the seroprevalence levels described in studies in other leprosy endemic areas over the past decades where no prophylactic interventions have taken place. The anti-PGL-I UCP-LFA was found to be a low-complexity tool that could be practically combined with serosurveys and was well-accepted by both healthcare staff and the population. On route to leprosy elimination, quantitative anti-PGL-I serology in young children holds promise as a strategy to monitor recent M. leprae transmission in an area.

Low-Cost Microfluidic Systems for Detection of Neglected Tropical Diseases

Neglected tropical diseases (NTDs) affect tropical and subtropical countries and are caused by viruses, bacteria, protozoa, and helminths. These kinds of diseases spread quickly due to the tropical climate and limited access to clean water, sanitation, and health care, which make exposed people more vulnerable. NTDs are reported to be difficult and inefficient to diagnose. As mentioned, most NTDs occur in countries that are socially vulnerable, and the lack of resources and access to modern laboratories and equipment intensify the difficulty of diagnosis and treatment, leading to an increase in the mortality rate. Portable and low-cost microfluidic systems have been widely applied for clinical diagnosis, offering a promising alternative that can meet the needs for fast, affordable, and reliable diagnostic tests in developing countries. This review provides a critical overview of microfluidic devices that have been reported in the literature for the detection of the most common NTDs over the past 5 years.

Protocol, rationale and design of BE-PEOPLE (Bedaquiline enhanced exposure prophylaxis for LEprosy in the Comoros): a cluster randomized trial on effectiveness of rifampicin and bedaquiline as post-exposure prophylaxis of leprosy contacts

BACKGROUND

Leprosy is an ancient infectious disease with an annual global incidence of around 200,000 over the past decade. Since 2018, the World Health Organization (WHO) recommends single-dose rifampicin as post-exposure prophylaxis (SDR-PEP) for contacts of leprosy patients. The Post ExpOsure Prophylaxis for Leprosy (PEOPLE) trial evaluated PEP with a double dose of rifampicin in Comoros and Madagascar. Preliminary results of this trial show some reduction in leprosy incidence in intervention villages but a stronger regimen may be beneficial. The objective of the current Bedaquiline Enhanced ExpOsure Prophylaxis for LEprosy trial (BE-PEOPLE) is to explore effectiveness of a combination of bedaquiline and rifampicin as PEP.

METHODS

BE-PEOPLE is a cluster-randomized trial in which 44 clusters in Comoros will be randomized to two study arms. Door-to-door screening will be conducted annually during four years, leprosy patients identified will be offered standard of care treatment. Based on study arm, contacts aged five years and above and living within a 100-meter radius of an index case will either receive bedaquiline (400-800 mg) and rifampicin (150-600 mg) or only rifampicin (150-600 mg). Contacts aged two to four years will receive rifampicin only. Household contacts randomized to the bedaquiline plus rifampicin arm will receive a second dose four weeks later. Incidence rate ratios of leprosy comparing contacts who received either of the PEP regimens will be the primary outcome. We will monitor resistance to rifampicin and/or bedaquiline through molecular surveillance in all incident tuberculosis and leprosy patients nationwide. At the end of the study, we will assess anti-M. leprae PGL-I IgM seropositivity as a proxy for the population burden of M. leprae infection in 8 villages (17,000 individuals) that were surveyed earlier as part of the PEOPLE trial.

DISCUSSION

The COLEP trial on PEP in Bangladesh documented a reduction of 57% in incidence of leprosy among contacts treated with SDR-PEP after two years, which led to the WHO recommendation of SDR-PEP. Preliminary results of the PEOPLE trial show a lesser reduction in incidence. The BE-PEOPLE trial will explore whether reinforcing SDR-PEP with bedaquiline increases effectiveness and more rapidly reduces the incidence of leprosy, compared to SDR-PEP alone.

TRIAL REGISTRATION

NCT05597280. Protocol version 5.0 on 28 October 2022.

Host biomarker-based quantitative rapid tests for detection and treatment monitoring of tuberculosis and COVID-19

Diagnostic services for tuberculosis (TB) are not sufficiently accessible in low-resource settings, where most cases occur, which was aggravated by the COVID-19 pandemic. Early diagnosis of pulmonary TB can reduce transmission. Current TB-diagnostics rely on detection of Mycobacterium tuberculosis (Mtb) in sputum requiring costly, time-consuming methods, and trained staff. In this study, quantitative lateral flow (LF) assays were used to measure levels of seven host proteins in sera from pre-COVID-19 TB patients diagnosed in Europe and latently Mtb-infected individuals (LTBI), and from COVID-19 patients and healthy controls. Analysis of host proteins showed significantly lower levels in LTBI versus TB (AUC:0 · 94) and discriminated healthy individuals from COVID-19 patients (0 · 99) and severe COVID-19 from TB. Importantly, these host proteins allowed treatment monitoring of both respiratory diseases. This study demonstrates the potential of non-sputum LF assays as adjunct diagnostics and treatment monitoring for COVID-19 and TB based on quantitative detection of multiple host biomarkers.

Advances in the Diagnosis of Leprosy

Leprosy is a public health issue, and early detection is critical to avert disability. Despite the global attempt to eradicate this disease as a public health problem, it remains an important cause of global neurological disability. India, Brazil and Indonesia share more than 70% of the cases. The reduction of new cases is a priority in the WHO global strategy 2021-2030 which aims to reduce disease transmission in the community by diagnosing cases and identifying subclinical infection. The clinical manifestations of leprosy range from a few to several lesions. The identification remains difficult due to the limited sensitivity of traditional approaches based on bacillary counts of skin smears and histology. To aid in the diagnosis of this disease, molecular biology, and biotechnological technologies have been applied, each with its own set of benefits and downsides despite providing an essential tool to validate the clinical diagnosis of leprosy. Because of this, it is strongly recognized that specific, inexpensive point of care technologies should be developed, particularly to identify asymptomatic M. leprae infections or leprosy nearer to the suspected cases seeking medical attention. Thus, this review will provide an overview of the advancements in leprosy diagnosis over the world. The purpose of this review is to improve our understanding of the outcomes of current tests and technologies used in leprosy diagnosis and to emphasize critical aspects concerning the detection of leprosy bacilli.

Increased amphiregulin expression by CD4+ T cells from individuals with asymptomatic Leishmania donovani infection

Objectives

There is an urgent need to be able to identify individuals with asymptomatic Leishmania donovani infection, so their risk of progressing to VL and transmitting parasites can be managed. This study examined transcriptional markers expressed by CD4+ T cells that could distinguish asymptomatic individuals from endemic controls and visceral leishmaniasis (VL) patients.

Methods

CD4+ T cells were isolated from individuals with asymptomatic L. donovani infection, endemic controls and VL patients. RNA was extracted and RNAseq employed to identify differentially expressed genes. The expression of one gene and its protein product during asymptomatic infection were evaluated.

Results

Amphiregulin (AREG) was identified as a distinguishing gene product in CD4+ T cells from individuals with asymptomatic L. donovani infection, compared to VL patients and healthy endemic control individuals. AREG levels in plasma and antigen-stimulated whole-blood assay cell culture supernatants were significantly elevated in asymptomatic individuals, compared to endemic controls and VL patients. Regulatory T (Treg) cells were identified as an important source of AREG amongst CD4+ T-cell subsets in asymptomatic individuals.

Conclusion

Increased Treg cell AREG expression was identified in individuals with asymptomatic L. donovani infection, suggesting the presence of an ongoing inflammatory response in these individuals required for controlling infection and that AREG may play an important role in preventing inflammation-induced tissue damage and subsequent disease in asymptomatic individuals.

NDO-BSA, LID-1, and NDO-LID Antibody Responses for Infection and RLEP by Quantitative PCR as a Confirmatory Test for Early Leprosy Diagnosis

Diagnostic tests for leprosy are limited, especially to identify early leprosy cases. We performed active case findings of leprosy to validate three potential antigen candidates and one molecular target. Cases were diagnosed by characteristic skin lesions, nerve enlargement, or skin sensation loss. Serum samples obtained from all subjects were tested by ELISA to assess antibody titers to three Mycobacterium leprae specific antigens: NDO-BSA, LID-1, and NDO-LID. Most of the field cases on Mosqueiro Island, northern Brazil, also collected slit skin smear for qPCR. Active case finding diagnosed 105 new cases of leprosy out of 894 subjects (11.7%), revealing a high prevalence of M. leprae in the region. With the use of amplification of the M. leprae-specific RLEP by qPCR, 68/79 (86.07%) of these cases were positive, confirming leprosy in subjects diagnosed in the field. Patients diagnosed at the leprosy reference center showed much higher antibody titers to all three antigens, while titers of patients from the field were significantly lower. Our results support previous findings that active surveillance by experienced leprologists can diagnose additional cases based on clinical findings, that many would not be identified using ELISA assay with the available biomarkers, and that RLEP qPCR may be used to confirm the majority of the field cases.

Development and validation of a multiplex real-time qPCR assay using GMP-grade reagents for leprosy diagnosis

Leprosy is a chronic dermato-neurological disease caused by Mycobacterium leprae, an obligate intracellular bacterium. Timely detection is a challenge in leprosy diagnosis, relying on clinical examination and trained health professionals. Furthermore, adequate care and transmission control depend on early and reliable pathogen detection. Here, we describe a qPCR test for routine diagnosis of leprosy-suspected patients. The reaction simultaneously amplifies two specific Mycobacterium leprae targets (16S rRNA and RLEP), and the human 18S rRNA gene as internal control. The limit of detection was estimated to be 2.29 copies of the M. leprae genome. Analytical specificity was evaluated using a panel of 20 other skin pathogenic microorganisms and Mycobacteria, showing no cross-reactivity. Intra- and inter-operator C_p variation was evaluated using dilution curves of M. leprae DNA or a synthetic gene, and no significant difference was observed between three operators in two different laboratories. The multiplex assay was evaluated using 97 patient samples with clinical and histopathological leprosy confirmation, displaying high diagnostic sensitivity (91%) and specificity (100%). Validation tests in an independent panel of 50 samples confirmed sensitivity and specificity of 97% and 98%, respectively. Importantly, assay performance remained stable for at least five months. Our results show that the newly developed multiplex qPCR effectively and specifically detects M. leprae DNA in skin samples, contributing to an efficient diagnosis that expedites the appropriate treatment.

Leprosy is a chronic dermato-neurological disease caused by Mycobacterium leprae, an obligate intracellular bacterium. Diagnosis of leprosy often relies on skin examinations for clinical signs, bacilli staining from skin smears and invasive skin biopsies. However, the spectrum of clinical manifestations and, often, low bacilli numbers can hinder accurate diagnosis. Timely detection is a challenge in leprosy diagnosis, relying on clinical examination and requiring trained health professionals. Proper intervention for adequate care and transmission control depends on early and reliable pathogen detection. Quantitative PCR methods for detecting bacterial DNA are more sensitive and could aid in differentially diagnosing leprosy from other dermatological conditions. In this work, we present a new multiplex PCR that was assessed for quality control standards, and the data indicate that the assay is stable and reproducible. The results presented here are the basis of a novel and robust tool with potential to increase the accuracy of leprosy diagnosis in routine or reference laboratories.

Quantitative Rapid Test for Detection and Monitoring of Active Pulmonary Tuberculosis in Nonhuman Primates

Nonhuman primates (NHPs) are relevant models to study the pathogenesis of tuberculosis (TB) and evaluate the potential of TB therapies, but rapid tools allowing diagnosis of active pulmonary TB in NHPs are lacking. This study investigates whether low complexity lateral flow assays utilizing upconverting reporter particles (UCP-LFAs) developed for rapid detection of human serum proteins can be applied to detect and monitor active pulmonary TB in NHPs. UCP-LFAs were used to assess serum proteins levels and changes in relation to the MTB challenge dosage, lung pathology, treatment, and disease outcome in experimentally MTB-infected macaques. Serum levels of SAA1, IP-10, and IL-6 showed a significant increase after MTB infection in rhesus macaques and correlated with disease severity as determined by pathology scoring. Moreover, these biomarkers could sensitively detect the reduction of bacterial levels in the lungs of macaques due to BCG vaccination or drug treatment. Quantitative measurements by rapid UCP-LFAs specific for SAA1, IP-10, and IL-6 in serum can be utilized to detect active progressive pulmonary TB in macaques. The UCP-LFAs thus offer a low-cost, convenient, and minimally invasive diagnostic tool that can be applied in studies on TB vaccine and drug development involving macaques.

Detection and Monitoring of Mycobacterium leprae Infection in Nine Banded Armadillos (Dasypus novemcinctus) Using a Quantitative Rapid Test

Leprosy is an infectious disease caused by Mycobacterium leprae with tropism for skin and peripheral nerves. Incessant transmission in endemic areas is still impeding elimination of leprosy. Although detection of M. leprae infection remains a challenge in asymptomatic individuals, the presence of antibodies specific for phenolglycolipid-I (PGL-I) correlate with bacterial load. Therefore, serosurveillance utilizing field-friendly tests detecting anti-PGL-I antibodies, can be applied to identify those who may transmit bacteria and to study (reduction of) M. leprae transmission. However, serology based on antibody detection cannot discriminate between past and present M. leprae infection in humans, nor can it detect individuals carrying low bacillary loads. In humans, anti-PGL-I IgM levels are long-lasting and usually detected in more individuals than anti-PGL-I IgG levels. Inherent to the characteristically long incubation time of leprosy, IgM/IgG relations (antibody kinetics) in leprosy patients and infected individuals are not completely clear. To investigate the antibody response directly after infection, we have measured antibody levels by ELISA, in longitudinal samples of experimentally M. leprae infected, susceptible nine-banded armadillos (Dasypus novemcinctus). In addition, we assessed the user- and field-friendly, low-cost lateral flow assay (LFA) utilizing upconverting reporter particles (UCP), developed for quantitative detection of human anti-PGL-I IgM (UCP-LFA), to detect treatment- or vaccination-induced changes in viable bacterial load. Our results show that serum levels of anti-PGL-I IgM, and to a lesser extent IgG, significantly increase soon after experimental M. leprae infection in armadillos. In view of leprosy phenotypes in armadillos, this animal model can provide useful insight into antibody kinetics in early infection in the various spectral forms of human leprosy. The UCP-LFA for quantitative detection of anti-PGL-I IgM allows monitoring the efficacy of vaccination and rifampin-treatment in the armadillo leprosy model, thereby providing a convenient tool to evaluate the effects of drugs and vaccines and new diagnostics.

Minimally invasive sampling to identify leprosy patients with a high bacterial burden in the Union of the Comoros

The World Health Organization (WHO) endorsed diagnosis of leprosy (also known as Hansen’s disease) entirely based on clinical cardinal signs, without microbiological confirmation, which may lead to late or misdiagnosis. The use of slit skin smears is variable, but lacks sensitivity. In 2017–2018 during the ComLep study, on the island of Anjouan (Union of the Comoros; High priority country according to WHO, 310 patients were diagnosed with leprosy (paucibacillary = 159; multibacillary = 151), of whom 263 were sampled for a skin biopsy and fingerstick blood, and 260 for a minimally-invasive nasal swab. In 74.5% of all skin biopsies and in 15.4% of all nasal swabs, M. leprae DNA was detected. In 63.1% of fingerstick blood samples, M. leprae specific antibodies were detected with the quantitative αPGL-I test. Results show a strong correlation of αPGL-I IgM levels in fingerstick blood and RLEP-qPCR positivity of nasal swabs, with the M. leprae bacterial load measured by RLEP-qPCR of skin biopsies. Patients with a high bacterial load (≥50,000 bacilli in a skin biopsy) can be identified with combination of counting lesions and the αPGL-I test. To our knowledge, this is the first study that compared αPGL-I IgM levels in fingerstick blood with the bacterial load determined by RLEP-qPCR in skin biopsies of leprosy patients. The demonstrated potential of minimally invasive sampling such as fingerstick blood samples to identify high bacterial load persons likely to be accountable for the ongoing transmission, merits further evaluation in follow-up studies.

Leprosy is the oldest infectious disease known to humankind. We still do not succeed in curbing its transmission, with more than 200,000 new patients detected worldwide each year. Identifying persons with a high burden of bacteria is key to curb transmission. To identify these persons, bacteria are counted in invasive and painful samples like slit skin smears and skin biopsies. We evaluated whether we can use less invasive samples, like fingerstick blood or nasal swabs, to determine the bacterial load. We found that the level of antibodies against M. leprae (αPGL-I IgM) in fingerstick blood correlates well with the bacterial load determined in skin biopsies from the same leprosy patient. Therefore, a high level of antibodies against M. leprae in fingerstick blood might identify persons who pose a potential risk for transmission of leprosy and could be prioritized for contact screening, which is essential for control of the disease.

Developments in the Synthesis of Mycobacterial Phenolic Glycolipids

The highly lipophilic outer barrier of mycobacteria, such as M. tuberculosis and M. leprae, is key to their virulence and intrinsic antibiotic resistance. Various components of this mycomembrane interact with the host immune system but many of these interactions remain ill-understood. This review covers several chemical syntheses of one of these components, mycobacterial phenolic glycolipids (PGLs), and outlines the interaction of these PGLs with the human immune system, as established using these well-defined pure compounds.

Exploring clustering of leprosy in the Comoros and Madagascar: A geospatial analysis

OBJECTIVES

To identify patterns of spatial clustering of leprosy.

DESIGN

We performed a baseline survey for a trial on post-exposure prophylaxis for leprosy in Comoros and Madagascar. We screened 64 villages, door-to-door, and recorded results of screening, demographic data and geographic coordinates. To identify clusters, we fitted a purely spatial Poisson model using Kulldorff's spatial scan statistic. We used a regular Poisson model to assess the risk of contracting leprosy at the individual level as a function of distance to the nearest known leprosy patient.

RESULTS

We identified 455 leprosy patients; 200 (44.0%) belonged to 2735 households included in a cluster. Thirty-eight percent of leprosy patients versus 10% of the total population live ≤25 m from another leprosy patient. Risk ratios for being diagnosed with leprosy were 7.3, 2.4, 1.8, 1.4 and 1.7, for those at the same household, at 1-<25 m, 25-<50 m, 50-<75 m and 75-<100 m as/from a leprosy patient, respectively, compared to those living at ≥100 m.

CONCLUSIONS

We documented significant clustering of leprosy beyond household level, although 56% of cases were not part of a cluster. Control measures need to be extended beyond the household, and social networks should be further explored.

Synthetic Phenolic Glycolipids for Application in Diagnostic Tests for Leprosy

Point-of-care (POC) diagnostic tests for the rapid detection of individuals infected with Mycobacterium leprae, the causative pathogen of leprosy, represent efficient tools to guide therapeutic and prophylactic treatment strategies in leprosy control programs, thus positively contributing to clinical outcome and reducing transmission of this infectious disease. Levels of antibodies directed against the M. leprae-specific phenolic glycolipid I (PGL-I) closely correlate with an individual's bacterial load and a higher risk of developing leprosy. We describe herein the assembly of a set of PGL glycans carrying the characteristic phenol aglycon and featuring different methylation patterns. The PGL trisaccharides were applied to construct neoglycoproteins that were used to detect anti-PGL IgM antibodies in leprosy patients. ELISAs and quantitative lateral-flow assays based on up-converting nanoparticles (UCP-LFAs) showed that the generated PGL-I and PGL-II trisaccharide neoglycoconjugates can be applied for the detection of anti M. leprae IgM antibodies in POC tests.

Insights into Mycobacterium leprae Proteomics and Biomarkers-An Overview

Although leprosy is curable, the identification of biomarkers for the early diagnosis of leprosy would play a pivotal role in reducing transmission and the overall prevalence of the disease. Leprosy-specific biomarkers for diagnosis, particularly for the paucibacillary disease, are not well defined. Therefore, the identification of new biomarkers for leprosy is one of the prime themes of leprosy research. Studying Mycobacterium leprae, the causative agent of leprosy, at the proteomic level may facilitate the identification, quantification, and characterization of proteins that could be potential diagnostics or targets for drugs and can help in better understanding the pathogenesis. This review aims to shed light on the knowledge gained to understand leprosy or its pathogen employing proteomics and its role in diagnosis.

A comprehensive research agenda for zero leprosy

BACKGROUND

Leprosy control achieved dramatic success in the 1980s-1990s with the implementation of short course multidrug therapy, which reduced the global prevalence of leprosy to less than 1 in 10 000 population. However, a period of relative stagnation in leprosy control followed this achievement, and only limited further declines in the global number of new cases reported have been achieved over the past decade.

MAIN TEXT

In 2016, major stakeholders called for the development of an innovative and comprehensive leprosy strategy aimed at reducing the incidence of leprosy, lowering the burden of disability and discrimination, and interrupting transmission. This led to the establishment of the Global Partnership for Zero Leprosy (GPZL) in 2018, with partners aligned around a shared Action Framework committed to achieving the WHO targets by 2030 through national leprosy program capacity-building, resource mobilisation and an enabling research agenda. GPZL convened over 140 experts from more than 20 countries to develop a research agenda to achieve zero leprosy. The result is a detailed research agenda focusing on diagnostics, mapping, digital technology and innovation, disability, epidemiological modelling and investment case, implementation research, stigma, post exposure prophylaxis and transmission, and vaccines. This research agenda is aligned with the research priorities identified by other stakeholders.

CONCLUSIONS

Developing and achieving consensus on the research agenda for zero leprosy is a significant step forward for the leprosy community. In a next step, research programmes must be developed, with individual components of the research agenda requiring distinct expertise, varying in resource needs, and operating over different timescales. Moving toward zero leprosy now requires partner alignment and new investments at all stages of the research process, from discovery to implementation.

Novel Diagnostics for Kaposi Sarcoma and Other Skin Diseases in Resource-Limited Settings

In resource-limited settings, point-of-care diagnostic devices have the potential to reduce diagnostic delays and improve epidemiologic surveillance of dermatologic conditions. We outline novel-point-of care diagnostics that have recently been developed for dermatologic conditions that primarily affect patients living in resource-limited settings, namely, Kaposi sarcoma, cutaneous leishmaniasis, leprosy, Buruli ulcer, yaws, onchocerciasis, and lymphatic filariasis. All of the technologies described in this article are prototypes, and some have undergone field testing. These devices still require validation in real-world settings and effective pricing to have a major impact on dermatologic care in resource-limited settings.

The immunology of other mycobacteria: M. ulcerans, M. leprae

Mycobacterial pathogens can be categorized into three broad groups: Mycobacterium tuberculosis complex causing tuberculosis, M. leprae and M. lepromatosis causing leprosy, and atypical mycobacteria, or non-tuberculous mycobacteria (NTM), responsible for a wide range of diseases. Among the NTMs, M. ulcerans is responsible for the neglected tropical skin disease Buruli ulcer (BU). Most pathogenic mycobacteria, including M. leprae, evade effector mechanisms of the humoral immune system by hiding and replicating inside host cells and are furthermore excellent modulators of host immune responses. In contrast, M. ulcerans replicates predominantly extracellularly, sheltered from host immune responses through the cytotoxic and immunosuppressive effects of mycolactone, a macrolide produced by the bacteria. In the year 2018, 208,613 new cases of leprosy and 2713 new cases of BU were reported to WHO, figures which are notoriously skewed by vast underreporting of these diseases.

Recombinant polypeptide of Mycobacterium leprae as a potential tool for serological detection of leprosy

Current prevention methods for the transmission of Mycobacterium leprae, the causative agent of leprosy, are inadequate as suggested by the rate of new leprosy cases reported. Simple large-scale detection methods for M. leprae infection are crucial for early detection of leprosy and disease control. The present study investigates the production and seroreactivity of a recombinant polypeptide composed of various M. leprae protein epitopes. The structural and physicochemical parameters of this construction were assessed using in silico tools. Parameters like subcellular localization, presence of signal peptide, primary, secondary, and tertiary structures, and 3D model were ascertained using several bioinformatics tools. The resultant purified recombinant polypeptide, designated rMLP15, is composed of 15 peptides from six selected M. leprae proteins (ML1358, ML2055, ML0885, ML1811, ML1812, and ML1214) that induce T cell reactivity in leprosy patients from different hyperendemic regions. Using rMLP15 as the antigen, sera from 24 positive patients and 14 healthy controls were evaluated for reactivity via ELISA. ELISA-rMLP15 was able to diagnose 79.17% of leprosy patients with a specificity of 92.86%. rMLP15 was also able to detect the multibacillary and paucibacillary patients in the same proportions, a desirable addition in the leprosy diagnosis. These results summarily indicate the utility of the recombinant protein rMLP15 in the diagnosis of leprosy and the future development of a viable screening test.

Application of new host biomarker profiles in quantitative point-of-care tests facilitates leprosy diagnosis in the field

BACKGROUND

Transmission of Mycobacterium leprae, the pathogen causing leprosy, is still persistent. To facilitate timely (prophylactic) treatment and reduce transmission it is vital to both early diagnose leprosy, and identify infected individuals lacking clinical symptoms. However, leprosy-specific biomarkers are limited, particularly for paucibacillary disease. Therefore, our objective was to identify new biomarkers for leprosy and assess their applicability in point-of-care (POC) tests.

METHODS

Using multiplex-bead-arrays, 60 host-proteins were measured in a cross-sectional approach in 24-h whole blood assays (WBAs) collected in Bangladesh (79 patients; 54 contacts; 51 endemic controls (EC)). Next, 17 promising biomarkers were validated in WBAs of a separate cohort (55 patients; 27 EC). Finally, in a third cohort (36 patients; 20 EC), five candidate markers detectable in plasma were assessed for application in POC tests.

FINDINGS

This study identified three new biomarkers for leprosy (ApoA1, IL-1Ra, S100A12), and confirmed five previously described biomarkers (CCL4, CRP, IL-10, IP-10, αPGL-I IgM). Overnight stimulation in WBAs provided increased specificity for leprosy and was required for IL-10, IL-1Ra and CCL4. The remaining five biomarkers were directly detectable in plasma, hence suitable for rapid POC tests. Indeed, lateral flow assays (LFAs) utilizing this five-marker profile detected both multi- and paucibacillary leprosy patients with variable immune responses.

INTERPRETATION

Application of novel host-biomarker profiles to rapid, quantitative LFAs improves leprosy diagnosis and allows POC testing in low-resource settings. This platform can thus aid diagnosis and classification of leprosy and also provides a tool to detect M.leprae infection in large-scale contact screening in the field.