Target product profiles: leprosy diagnostics.

The World Health Organization (WHO) aims to reduce new leprosy cases by 70% by 2030, necessitating advancements in leprosy diagnostics. Here we discuss the development of two WHO's target product profiles for such diagnostics. These profiles define criteria for product use, design, performance, configuration and distribution, with a focus on accessibility and affordability. The first target product profile outlines requirements for tests to confirm diagnosis of leprosy in individuals with clinical signs and symptoms, to guide multidrug treatment initiation. The second target product profile outlines requirements for tests to detect Mycobacterium leprae or M. lepromatosis infection among asymptomatic contacts of leprosy patients, aiding prophylactic interventions and prevention. Statistical modelling was used to assess sensitivity and specificity requirements for these diagnostic tests. The paper highlights challenges in achieving high specificity, given the varying endemicity of M. leprae, and identifying target analytes with robust performance across leprosy phenotypes. We conclude that diagnostics with appropriate product design and performance characteristics are crucial for early detection and preventive intervention, advocating for the transition from leprosy management to prevention.

L'Organisation mondiale de la Santé (OMS) vise à réduire le nombre de nouveaux cas de lèpre de 70% d'ici 2030, ce qui nécessite un meilleur diagnostic de la maladie. Dans le présent document, nous évoquons le développement de deux profils de produit cible établis par l'OMS à cette fin. Ces profils définissent des critères en matière d'utilisation, de conception, de performances, de configuration et de distribution du produit, en accordant une attention particulière à l'accessibilité et à l'abordabilité. Le premier profil de produit cible décrit les exigences pour les tests servant à confirmer le diagnostic de la lèpre chez les individus qui présentent des signes cliniques et des symptômes, afin d'orienter l'instauration d'un traitement à base de plusieurs médicaments. Le second profil de produit cible décrit les exigences pour les tests servant à détecter une infection à Mycobacterium leprae ou M. lepromatosis parmi les contacts asymptomatiques de patients lépreux, ce qui contribue à l'adoption de mesures prophylactiques et à la prévention. Nous avons eu recours à une modélisation statistique pour évaluer les exigences de sensibilité et de spécificité de ces tests diagnostiques. Cet article met en évidence les obstacles à l'atteinte d'un niveau élevé de spécificité en raison de l'endémicité variable de M. leprae, et à l'identification d'analytes cibles offrant de bons résultats chez les phénotypes lépreux. Nous concluons qu'un diagnostic reposant sur des caractéristiques de performance et de conception appropriées est essentiel pour détecter rapidement la maladie et intervenir en amont, et nous plaidons pour une prévention plutôt qu'une gestion de la lèpre.

La Organización Mundial de la Salud (OMS) pretende reducir los nuevos casos de lepra en un 70% para 2030, lo que requiere avances en el diagnóstico de la lepra. Aquí se analiza el desarrollo de dos perfiles de productos objetivo de la OMS para este tipo de diagnósticos. Estos perfiles definen los criterios de uso, diseño, rendimiento, configuración y distribución de los productos, centrándose en su accesibilidad y asequibilidad. El primer perfil de producto objetivo describe los requisitos de las pruebas para confirmar el diagnóstico de la lepra en personas con signos y síntomas clínicos, con el fin de orientar el inicio del tratamiento con múltiples fármacos. El segundo perfil de producto objetivo describe los requisitos de las pruebas para detectar la infección por Mycobacterium leprae o M. lepromatosis entre los contactos asintomáticos de los pacientes con lepra, para facilitar las intervenciones profilácticas y la prevención. Se utilizaron modelos estadísticos para evaluar los requisitos de sensibilidad y especificidad de estas pruebas diagnósticas. El artículo destaca las dificultades para lograr una alta especificidad, dada la diferente endemicidad de M. leprae, y para identificar analitos diana con un rendimiento sólido en todos los fenotipos de lepra. Concluimos que los diagnósticos con un diseño de producto y unas características de rendimiento adecuados son fundamentales para la detección precoz y la intervención preventiva, lo que favorece la transición del manejo de la lepra a la prevención.

The Armadillo as a Model for Leprosy Nerve Function Impairment: Preventative and Therapeutic Interventions.

Mycobacterium leprae infection of peripheral nerves and the subsequent nerve function impairment (NFI), especially in response to reactional episodes, are hallmarks of leprosy. Improved treatments for M. leprae-induced nerve injury are needed, as most if not all of the disability and stigma associated with leprosy arises from the direct or indirect effects of NFI. Nine-banded armadillos (Dasypus novemcinctus), like humans, exhibit the full clinical spectrum of leprosy and extensive involvement of the peripheral nerves. In this study, state-of-the-art technology was used to compare nerve function between uninfected and M. leprae-infected armadillos. Motor nerve conduction velocity (MNCV) and compound muscle action potential (cMAP), which measure changes in the rate of impulse conduction velocity and amplitude, revealed a progression of impairment that was directly correlated with the duration of M. leprae infection and enabled development of an objective nerve impairment scoring system. Ultrasonography accompanied by color Doppler imaging detected enlargement of the M. leprae-infected nerves and increased vascularity, possibly due to inflammation. Assessment of epidermal nerve fiber density (ENFD), which shows a length-dependent innervation in armadillos that is similar to humans, identified small fiber degeneration early after M. leprae infection. Staining for neuromuscular junction (NMJ) integrity, which is an indicator of signal transduction efficiency into skeletal muscle, discerned a markedly lower number and structural integrity of NMJ in M. leprae-infected armadillo footpads. These tools for assessing nerve injury were used to monitor the effects of intervention therapy. Two potential neuro-protective drugs, ethoxyquin (EQ) and 4-aminopyridine (4-AP), were tested for their ability to ameliorate peripheral nerve injury in M. leprae-infected armadillos. 4-AP treatment improved MNCV, cMAP, and EFND compared to untreated animals, while EQ had less effect. These results support the armadillo as a model for M. leprae-induced peripheral nerve injury that can provide insights toward the understanding of NFI progression and contribute to the preclinical investigation of the safety and efficacy of neuro-preventive and neuro-therapeutic interventions for leprosy.

Mycobacterium lepromatosis as Cause of Leprosy, Colombia.

Leprosy is a granulomatous infection caused by infection with Mycobacterium leprae or M. lepromatosis. We evaluated skin biopsy and slit skin smear samples from 92 leprosy patients in Colombia by quantitative PCR. Five (5.4%) patients tested positive for M. lepromatosis, providing evidence of the presence of this pathogen in Colombia.

A Sensitive and Quantitative Assay to Enumerate and Measure Mycobacterium leprae Viability in Clinical and Experimental Specimens.

Mycobacterium leprae, the etiologic agent of leprosy, cannot be cultured on artificial media. This characteristic, coupled with its long generation time, presents a number of unique challenges to studying this pathogen. One of the difficulties facing both researchers and clinicians is the absence of a rapid test to measure the viability of M. leprae in clinical or experimental specimens. The lack of such a tool limits the understanding of M. leprae immunopathogenesis and makes determining the efficacy of drug treatments difficult. With this in mind, we developed a robust two-step molecular viability assay (MVA) that first enumerates the M. leprae in the tissue; then, this data is used to normalize bacterial RNA quantities for the second step, in which the expression of M. leprae esxA and hsp18 are measured. This assay is specific and sensitive enough to be used on most clinical samples. This protocol describes the steps required to extract DNA and RNA from M. leprae-infected tissue, enumerate M. leprae, and measure M. leprae viability based on the normalized expression of two M. leprae-specific genes (hsp18 and esxA). This protocol also outlines an optimal laboratory design and workflow for performing this assay. © 2022 The Leprosy Mission Nepal. Current Protocols published by Wiley Periodicals LLC. This article has been contributed to by US Government employees and their work is in the public domain in the USA. Basic Protocol 1: DNA and RNA P purification from M. leprae-infected tissue Basic Protocol 2: Enumeration of M. leprae by RLEP qPCR on the DNA fraction Basic Protocol 3: Calculation of M. leprae per tissue and normalization of RNA Basic Protocol 4: Reverse-transcription of normalized RNA to generate cDNA Basic Protocol 5: Determination of M. leprae viability using HSP18 and ESXA qPCR on the cDNA Support Protocol 1: M. leprae qPCR primer/probe stock preparation Support Protocol 2: Preparation of plasmid stocks and standard curves.

Sensitivity of Mycobacterium leprae to Telacebec.

The treatment of leprosy is long and complex, benefiting from the development of sterilizing, rapidly-acting drugs. Reductive evolution made Mycobacterium leprae exquisitely sensitive to Telacebec, a phase 2 drug candidate for tuberculosis. The unprecedented potency of Telacebec against M. leprae warrants further validation in clinical trials.

Mycobacterium leprae Infection in Ticks and Tick-Derived Cells.

Leprosy is a zoonosis in the southern United States involving humans and wild armadillos. The majority of patients presenting with zoonotic strains of Mycobacterium leprae note extensive outdoor activity but only rarely report any history of direct contact with wild armadillos. Whether M. leprae is transmitted to new vertebrate hosts through the environment independently or with the aid of other organisms, e.g., arthropod vectors, is a fundamental question in leprosy transmission. The objectives of this study were to assess the potential for ticks to transmit M. leprae and to test if viable M. leprae can be maintained in tick-derived cells. To evaluate tick transmission, nymphal Amblyomma maculatum ticks were injected with isolated M. leprae. Infection and transmission were assessed by qPCR. Ticks infected as nymphs harbored M. leprae through vertical transmission events (nymph to adult and adult to progeny); and, horizontal transmission of M. leprae to a vertebrate host was observed. Mycobacterium leprae DNA was detected in multiple tick life cycle stages. Likewise, freshly isolated M. leprae (Thai-53) was used to infect a tick-derived cell line, and enumeration and bacterial viability were assessed at individual time points for up to 49 days. Evaluations of the viability of long-term cultured M. leprae (Thai-53 and Br4923) were also assessed in a mouse model. Tick-derived cells were able to maintain viable M. leprae over the 49-day course of infection and M. leprae remained infectious within tick cells for at least 300 days. The results of this study suggest that ticks themselves might serve as a vector for the transmission of M. leprae and that tick cells are suitable for maintenance of viable M. leprae for an extended period of time.

Susceptibility and resistance in leprosy: Studies in the mouse model.

Leprosy is a chronic granulomatous infectious disease caused by the pathogen, Mycobacterium leprae, and the more recently discovered, M. lepromatosis. Described in 1873, M. leprae was among the first microorganisms to be proposed as a cause of a human infectious disease. As an obligate intracellular bacterium, it has still not thus far been reproducibly cultivated in axenic medium or cell cultures. Shepard's mouse footpad assay, therefore, was truly a breakthrough in leprosy research. The generation of immunosuppressed and genetically engineered mice, along with advances in molecular and cellular techniques, has since offered more tools for the study of the M. leprae-induced granuloma. While far from perfect, these new mouse models have provided insights into the immunoregulatory mechanisms responsible for the spectrum of this complex disease.

Mycobacterium leprae Transcriptome During In Vivo Growth and Ex Vivo Stationary Phases.

Mycobacterium leprae, the causative agent of leprosy, is an obligate intracellular pathogen primarily residing within host macrophages and Schwann cells. Whole genome sequencing predicts a highly degraded genome with approximately one third of the coding capacity resulting in the loss of many catabolic pathways. Therefore, it can be assumed that M. leprae obtains many of the necessary metabolites for intracellular survival and growth from the host cells. In this study, global transcriptomic analyses were done on freshly harvested M. leprae growing in athymic mouse footpads for five months (MFP5) and compared to those held in axenic medium for 48 (ML48) and 96 (ML96) hours. Results show that all of the genes and pseudogenes were transcribed under both in vivo and in vitro conditions. 24% and 33% of gene transcript levels were significantly altered in ML48 and ML96 respectively, compared to MFP5. Approximately 45% (39/86) of lipid metabolism genes were significantly downregulated in ML96 compared to MFP5, majority of which are in the ß-oxidation pathway. Cholesterol oxidase, acyl-CoA dehydrogenase, and coenzyme F420-dependent oxidoreductase, were significantly upregulated in both ML48 and ML96 compared to MFP5. 30% of cell wall and cell processes functional category genes had altered gene transcription at 96hr compared to MFP5. 40% of 57 genes associated with mycobacterial virulence showed significantly altered transcript levels with 52% significantly downregulated in ML96, including most of the Pro-Glu/Pro-Pro-Glu genes. All 111 hypothetical protein genes with unknown function were expressed. Adenosine triphosphate (ATP) synthesis in M. leprae appears to be significantly downregulated under ex vivo conditions. This is the first study comparing M. leprae global gene expression during in vivo growth and ex vivo stationery phase in axenic medium confirming that during the growth phase in the footpads of experimentally infected mice, M. leprae is metabolically active and its primary source of energy production is probably lipids.

Post-exposure prophylaxis (PEP) efficacy of rifampin, rifapentine, moxifloxacin, minocycline, and clarithromycin in a susceptible-subclinical model of leprosy.

BACKGROUND: Subclinical infection with Mycobacterium leprae is one potential source of leprosy transmission, and post-exposure prophylaxis (PEP) regimens have been proposed to control this source. Because PEP trials require considerable investment, we applied a sensitive variation of the kinetic mouse footpad (MFP) screening assay to aid in the choice of drugs and regimens for clinical trials. METHODOLOGY/PRINCIPAL FINDINGS: Athymic nude mice were inoculated in the footpad (FP) with 6 x 103 viable M. leprae and treated by gastric gavage with a single dose of Rifampin (SDR), Rifampin + Ofloxacin + Minocycline (SD-ROM), or Rifapentine + Minocycline + Moxifloxacin (SD-PMM) or with the proposed PEP++ regimen of three once-monthly doses of Rifampin + Moxifloxacin (RM), Rifampin + Clarithromycin (RC), Rifapentine + Moxifloxacin (PM), or Rifapentine + Clarithromycin (PC). At various times post-treatment, DNA was purified from the FP, and M. leprae were enumerated by RLEP quantitative PCR. A regression analysis was calculated to determine the expected RLEP value if 99.9% of the bacilli were killed after the administration of each regimen. SDR and SD-ROM induced little growth delay in this highly susceptible murine model of subclinical infection. In contrast, SD-PMM delayed measurable M. leprae growth above the inoculum by 8 months. The four multi-dose regimens delayed bacterial growth for >9months post-treatment cessation. CONCLUSIONS/SIGNIFICANCE: The delay in discernable M. leprae growth post-treatment was an excellent indicator of drug efficacy for both early (3-4 months) and late (8-9 months) drug efficacy. Our data indicates that multi-dose PEP may be required to control infection in highly susceptible individuals with subclinical leprosy to prevent disease and decrease transmission.

The Many Hosts of Mycobacteria 8 (MHM8): A conference report.

Mycobacteria are important causes of disease in human and animal hosts. Diseases caused by mycobacteria include leprosy, tuberculosis (TB), nontuberculous mycobacteria (NTM) infections and Buruli Ulcer. To better understand and treat mycobacterial disease, clinicians, veterinarians and scientists use a range of discipline-specific approaches to conduct basic and applied research, including conducting epidemiological surveys, patient studies, wildlife sampling, animal models, genetic studies and computational simulations. To foster the exchange of knowledge and collaboration across disciplines, the Many Hosts of Mycobacteria (MHM) conference series brings together clinical, veterinary and basic scientists who are dedicated to advancing mycobacterial disease research. Started in 2007, the MHM series recently held its 8th conference at the Albert Einstein College of Medicine (Bronx, NY). Here, we review the diseases discussed at MHM8 and summarize the presentations on research advances in leprosy, NTM and Buruli Ulcer, human and animal TB, mycobacterial disease comorbidities, mycobacterial genetics and 'omics, and animal models. A mouse models workshop, which was held immediately after MHM8, is also summarized. In addition to being a resource for those who were unable to attend MHM8, we anticipate this review will provide a benchmark to gauge the progress of future research concerning mycobacteria and their many hosts.

Development of LepReact, a defined skin test for paucibacillary leprosy and low-level M. leprae infection.

The persistence of new leprosy cases in endemic areas such as India, Brazil, Bangladesh, and the Philippines has encouraged studies of chemoprophylaxis among contacts of patients. Epidemiological screening tools to enable early detection of infected individuals in endemic populations would be critical to target individuals most in need of intervention. Despite decades of attempts, however, there still are no tests available for the early detection of low-level infection with Mycobacterium leprae. In this report, we describe the development of a leprosy skin test using M. leprae-specific antigens. We selected the chimeric LID-1 fusion protein, formulated to achieve maximum performance at a minimal dose, as a skin test candidate based on its ability to elicit delayed-type hypersensitivity (DTH) reactions in M. leprae immune guinea pigs in a sensitive and specific manner, i.e., with no cross-reactivity observed with other mycobacterial species. Importantly, evaluations in armadillos indicated that intradermal inoculation of formulated LID-1 could distinguish uninfected from M. leprae-infected animals manifesting with symptoms distinctly similar to the PB presentation of patients. Together, our data provide strong proof-of-concept for developing an antigen-specific skin test to detect low-level M. leprae infection. Such a test could, when applied with appropriate use of chemo- and/or immunoprophylaxis, be instrumental in altering the evolution of clinical disease and M. leprae transmission, thus furthering the objective of zero leprosy.

Isolation of Mycobacterium lepromatosis and Development of Molecular Diagnostic Assays to Distinguish Mycobacterium leprae and M. lepromatosis.

BACKGROUND: Mycobacterium leprae was thought to be the exclusive causative agent of leprosy until Mycobacterium lepromatosis was identified in a rare form of leprosy known as diffuse lepromatous leprosy (DLL). METHODS: We isolated M. lepromatosis from a patient with DLL and propagated it in athymic nude mouse footpads. Genomic analysis of this strain (NHDP-385) identified a unique repetitive element, RLPM, on which a specific real-time quantitative polymerase chain reaction assay was developed. The RLPM assay, and a previously developed RLEP quantitative polymerase chain reaction assay for M. leprae, were validated as clinical diagnostic assays according to Clinical Laboratory Improvement Amendments guidelines. We tested DNA from archived histological sections, patient specimens from the United States, Philippines, and Mexico, and US wild armadillos. RESULTS: The limit of detection for the RLEP and RLPM assays is 30 M. leprae per specimen (0.76 bacilli per reaction; coefficient of variation, 0.65%-2.44%) and 122 M. lepromatosis per specimen (3.05 bacilli per reaction; 0.84%-2.9%), respectively. In histological sections (n = 10), 1 lepromatous leprosy (LL), 1 DLL, and 3 Lucio reactions contained M. lepromatosis; 2 LL and 2 Lucio reactions contained M. leprae; and 1 LL reaction contained both species. M. lepromatosis was detected in 3 of 218 US biopsy specimens (1.38%). All Philippines specimens (n = 180) were M. lepromatosis negative and M. leprae positive. Conversely, 15 of 47 Mexican specimens (31.91%) were positive for M. lepromatosis, 19 of 47 (40.43%) were positive for M. leprae, and 2 of 47 (4.26%) contained both organisms. All armadillos were M. lepromatosis negative. CONCLUSIONS: The RLPM and RLEP assays will aid healthcare providers in the clinical diagnosis and surveillance of leprosy.

Differential growth of Mycobacterium leprae strains (SNP genotypes) in armadillos.

Leprosy (Hansen's Disease) has occurred throughout human history, and persists today at a low prevalence in most populations. Caused by Mycobacterium leprae, the infection primarily involves the skin, mucosa and peripheral nerves. The susceptible host range for Mycobacterium leprae is quite narrow. Besides humans, nine banded armadillos (Dasypus novemcinctus) and red squirrels (Sciurus vulgaris) are the only other natural hosts for M. leprae, but only armadillos recapitulate the disease as seen in humans. Armadillos across the Southern United States harbor a single predominant genotypic strain (SNP Type-3I) of M. leprae, which is also implicated in the zoonotic transmission of leprosy. We investigated, whether the zoonotic strain (3I) has any notable growth advantages in armadillos over another genetically distant strain-type (SNP Type-4P) of M. leprae, and if M. leprae strains manifest any notably different pathology among armadillos. We co-infected armadillos (n = 6) with 2 × 109 highly viable M. leprae of both strains and assessed the relative growth and dissemination of each strain in the animals. We also analyzed 12 additional armadillos, 6 each individually infected with the same quantity of either strain. The infections were allowed to fulminate and the clinical manifestations of the disease were noted. Animals were humanely sacrificed at the terminal stage of infection and the number of bacilli per gram of liver, spleen and lymph node tissue were enumerated by Q-PCR assay. The growth of M. leprae strain 4P was significantly higher (P < 0.05) than 3I when each strain was propagated individually in armadillos. Significantly (P < 0.0001) higher growth of the 4P strain also was confirmed among animals co-infected with both 3I and 4P strain types using whole genome sequencing. Interestingly, the zoonotic strain does not exhibit any growth advantage in these non-human hosts, but the varied proliferation of the two M. leprae strains within armadillos suggest there are notable pathological variations between M. leprae strain-types.

Vaccines for Leprosy and Tuberculosis: Opportunities for Shared Research, Development, and Application.

Tuberculosis (TB) and leprosy still represent significant public health challenges, especially in low- and lower middle-income countries. Both poverty-related mycobacterial diseases require better tools to improve disease control. For leprosy, there has been an increased emphasis on developing tools for improved detection of infection and early diagnosis of disease. For TB, there has been a similar emphasis on such diagnostic tests, while increased research efforts have also focused on the development of new vaccines. Bacille Calmette-Guérin (BCG), the only available TB vaccine, provides insufficient and inconsistent protection to pulmonary TB in adults. The impact of BCG on leprosy, however, is significant, and the introduction of new TB vaccines that might replace BCG could, therefore, have serious impact also on leprosy. Given the similarities in antigenic makeup between the pathogens Mycobacterium tuberculosis (Mtb) and M. leprae, it is well possible, however, that new TB vaccines could cross-protect against leprosy. New TB subunit vaccines currently evaluated in human phase I and II studies indeed often contain antigens with homologs in M. leprae. In this review, we discuss pre-clinical studies and clinical trials of subunit or whole mycobacterial vaccines for TB and leprosy and reflect on the development of vaccines that could provide protection against both diseases. Furthermore, we provide the first preclinical evidence of such cross-protection by Mtb antigen 85B (Ag85B)-early secretory antigenic target (ESAT6) fusion recombinant proteins in in vivo mouse models of Mtb and M. leprae infection. We propose that preclinical integration and harmonization of TB and leprosy research should be considered and included in global strategies with respect to cross-protective vaccine research and development.

Opening a Can of Worms: Leprosy Reactions and Complicit Soil-Transmitted Helminths.

BACKGROUND: >94% of new annual leprosy cases are diagnosed in populations co-endemic for soil-transmitted helminths (STH). STH can profoundly dysregulate host immune responses towards Th2 bias, which can be restored over time after deworming. We hypothesize that STH co-infection is associated with leprosy reaction (denoted as simply "reaction" herein) occurrence within a co-endemic population. METHODS: A cohort study was performed on a cohort of Nepalese leprosy patients across treatment and diagnostic classifications who were screened by routine fecal smear microscopy and multiplex quantitative PCR (qPCR) for Ascaris lumbricoides (Al), Strongyloides stercoralis (Ss), Ancyclostoma duodenale (Ad) and Necator americanus (Na). RESULTS: Among 145 patients, 55% were positive for ≥1 STH (STH+): 34% Al+, 18% Ss+, 17% Ad+and 5% Na+. Significant inverse STH and reaction relationships were evidenced by the bulk of cases: 63% reaction-negative were STH+ of total cases (p=0.030) while 65% reaction-positive were STH- in new cases (96; p=0.023). Strikingly, the majority of STH+ were reaction-negative, even when considering each species: 59% Al+, 60% Ss+, 62% Ad+and 67% Na+of new leprosy cases. CONCLUSIONS: Absence of STH co-infection is associated with leprosy reaction at diagnosis within a co-endemic population. This is likely due to immune reconstitution effects after deworming or interruption of chronic STH-mediated immune dysregulation.

IL-10 and NOS2 modulate antigen-specific reactivity and nerve infiltration by T cells in experimental leprosy.

BACKGROUND: Although immunopathology dictates clinical outcome in leprosy, the dynamics of early and chronic infection are poorly defined. In the tuberculoid region of the spectrum, Mycobacterium leprae growth is restricted yet a severe granulomatous lesion can occur. The evolution and maintenance of chronic inflammatory processes like those observed in the leprosy granuloma involve an ongoing network of communications via cytokines. IL-10 has immunosuppressive properties and IL-10 genetic variants have been associated with leprosy development and reactions. METHODOLOGY/PRINCIPAL FINDINGS: The role of IL-10 in resistance and inflammation in leprosy was investigated using Mycobacterium leprae infection of mice deficient in IL-10 (IL-10-/-), as well as mice deficient in both inducible nitric oxide synthase (NOS2-/-) and IL-10 (10NOS2-/-). Although a lack of IL-10 did not affect M. leprae multiplication in the footpads (FP), inflammation increased from C57Bl/6 (B6)

Semi-automated protocol for purification of Mycobacterium leprae from tissues using the gentleMACS™ Octo Dissociator.

Mycobacterium leprae, etiologic agent of leprosy, is propagated in athymic nude mouse footpads (FPs). The current purification protocol is tedious and physically demanding. A simpler, semi-automated protocol was developed using gentleMACS™ Octo Dissociator. The gentleMACS protocol provided a very effective means for purification of highly viable M. leprae from tissue.

Molecular assays for determining Mycobacterium leprae viability in tissues of experimentally infected mice.

BACKGROUND: The inability of Mycobacterium leprae to grow on axenic media has necessitated specialized techniques in order to determine viability of this organism. The purpose of this study was to develop a simple and sensitive molecular assay for determining M. leprae viability directly from infected tissues. METHODOLOGY/PRINCIPLE FINDINGS: Two M. leprae-specific quantitative reverse transcription PCR (qRT-PCR) assays based on the expression levels of esxA, encoding the ESAT-6 protein, and hsp18, encoding the heat shock 18 kDa protein, were developed and tested using infected footpad (FP) tissues of both immunocompetent and immunocompromised (athymic nu/nu) mice. In addition, the ability of these assays to detect the effects of anti-leprosy drug treatment on M. leprae viability was determined using rifampin and rifapentine, each at 10 mg/kg for 1, 5, or 20 daily doses, in the athymic nu/nu FP model. Molecular enumeration (RLEP PCR) and viability determinations (qRT-PCR) were performed via Taqman methodology on DNA and RNA, respectively, purified from ethanol-fixed FP tissue and compared with conventional enumeration (microscopic counting of acid fast bacilli) and viability assays (radiorespirometry, viability staining) which utilized bacilli freshly harvested from the contralateral FP. Both molecular and conventional assays demonstrated growth and high viability of M. leprae in nu/nu FPs over a 4 month infection period. In contrast, viability was markedly decreased by 8 weeks in immunocompetent mice. Rifapentine significantly reduced bacterial viability after 5 treatments, whereas rifampin required up to 20 treatments for the same efficacy. Neither drug was effective after a single treatment. In addition, host gene expression was monitored with the same RNA preparations. CONCLUSIONS: hsp18 and esxA qRT-PCR are sensitive molecular indicators, reliably detecting viability of M. leprae in tissues without the need for bacterial isolation or immediate processing, making these assays applicable for in vivo drug screening and promising for clinical and field applications.

The armadillo: a model for the neuropathy of leprosy and potentially other neurodegenerative diseases.

Leprosy (also known as Hansen's disease) is an infectious peripheral neurological disorder caused by Mycobacterium leprae that even today leaves millions of individuals worldwide with life-long disabilities. The specific mechanisms by which this bacterium induces nerve injury remain largely unknown, mainly owing to ethical and practical limitations in obtaining affected human nerve samples. In addition to humans, nine-banded armadillos (Dasypus novemcinctus) are the only other natural host of M. leprae, and they develop a systemically disseminated disease with extensive neurological involvement. M. leprae is an obligate intracellular parasite that cannot be cultivated in vitro. Because of the heavy burdens of bacilli they harbor, nine-banded armadillos have become the organism of choice for propagating large quantities of M. leprae, and they are now advancing as models of leprosy pathogenesis and nerve damage. Although armadillos are exotic laboratory animals, the recently completed whole genome sequence for this animal is enabling researchers to undertake more sophisticated molecular studies and to develop armadillo-specific reagents. These advances will facilitate the use of armadillos in piloting new therapies and diagnostic regimens, and will provide new insights into the oldest known infectious neurodegenerative disorder.