Molecular epidemiology of leprosy: An update

Ecological and evolutionary perspectives advance understanding of mycobacterial diseases

Predicting the outbreak of infectious diseases and designing appropriate preventive health actions require interdisciplinary research into the processes that drive exposure to and transmission of disease agents. In the case of mycobacterial diseases, the epidemiological understanding of the scientific community hitherto was based on the clinical studies of infections in vertebrates. To evaluate the information gained by comprehensively accounting for the ecological and evolutionary constraints, we conducted literature searches assessing the role of mycobacteria interactions with non-vertebrate species in the origin of their pathogenicity and variations in disease risk. The reviewed literature challenges the current theory of person-to-person transmission for several mycobacterial infections. Furthermore, the findings suggest that diverse non-vertebrate organisms influence virulence, mediate transmission, and contribute to pathogen abundance in relation to vertebrate exposure. We advocate that an ecological and evolutionary framework provides novel insights to support a more comprehensive understanding of the prevention and management of diseases in vertebrates.

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.

A challenging case of borderline lepromatous leprosy non-responsive to WHO-MDT: exploring approaches beyond WHO-MDT

Just as we prioritize personalized medicine for various other medical conditions, we should also include a neglected disease like leprosy, ensuring that patients receive the best care possible and improving their quality of life. Our case highlights the importance of instituting an alternate therapeutic regimen in a scenario where there is a lack of clinical response to multidrug therapy, even in the absence of documented drug resistance of the currently available molecular diagnostics. The search for the perfect regimen tailored for each individual leprosy patient should continue. Alternate anti-leprosy therapy is highly useful in cases with confirmed drug resistance or clinically non-responsive cases; however, their misuse should also be strictly avoided to prevent the development of resistance to them.

Identification of potential biomarkers of leprosy: A study based on GEO datasets

Leprosy has a high rate of cripplehood and lacks available early effective diagnosis methods for prevention and treatment, thus novel effective molecule markers are urgently required. In this study, we conducted bioinformatics analysis with leprosy and normal samples acquired from the GEO database(GSE84893, GSE74481, GSE17763, GSE16844 and GSE443). Through WGCNA analysis, 85 hub genes were screened(GS > 0.7 and MM > 0.8). Through DEG analysis, 82 up-regulated and 3 down-regulated genes were screened(|Log2FC| > 3 and FDR < 0.05). Then 49 intersection genes were considered as crucial and subjected to GO annotation, KEGG pathway and PPI analysis to determine the biological significance in the pathogenesis of leprosy. Finally, we identified a gene-pathway network, suggesting ITK, CD48, IL2RG, CCR5, FGR, JAK3, STAT1, LCK, PTPRC, CXCR4 can be used as biomarkers and these genes are active in 6 immune system pathways, including Chemokine signaling pathway, Th1 and Th2 cell differentiation, Th17 cell differentiation, T cell receptor signaling pathway, Natural killer cell mediated cytotoxicity and Leukocyte transendothelial migration. We identified 10 crucial gene markers and related important pathways that acted as essential components in the etiology of leprosy. Our study provides potential targets for diagnostic biomarkers and therapy of leprosy.

A Systemic Review and Meta-analysis on Natural Resistance-associated Macrophage Protein 1 (3'-Untranslated Region) and Nucleotide-binding Oligomerization Domain-2 (rs8057341) Polymorphisms and Leprosy Susceptibility in Asian and Caucasian Populations

The current meta-analysis aims to explore the potential correlation between natural resistance-associated macrophage protein 1 (NRAMP1) (3'-Untranslated region [3'-UTR]) and nucleotide-binding oligomerization domain-2 (NOD2 [rs8057341]) gene polymorphisms and their association with leprosy susceptibility in both Asian and Caucasian populations. Datas were retrieved from case control studies with NOD 2 and NRAMP 1 gene polymorphism associated with leprosy disease. Leprosy emerges as a particularly distinctive ailment among women on a global scale. The NRAMP1 (3'-UTR) and NOD2 (rs8057341) genetic variations play a crucial role in the progression of leprosy. A systematic review of relevant case-control studies was conducted across several databases, including ScienceDirect, PubMed, Google Scholar, and Embase. Utilizing MetaGenyo and Review Manager 5.4 Version, statistical analyses were carried out. Nine case-control studies totaling 3281 controls and 3062 leprosy patients are included in the research, with the objective of examining the potential association between NRAMP1 (3'-UTR) and NOD2 (rs8057341) gene polymorphisms and leprosy risk. The review methodology was registered in PROSPERO (ID520883). The findings reveal a robust association between NRAMP1 (3'-UTR) and NOD2 (rs8057341) gene polymorphisms and leprosy risk across various genetic models. Although the funnel plot analysis did not identify publication bias, bolstering these findings and elucidating potential gene-gene and gene-environment interactions require further comprehensive epidemiological research. This study identified a strong correlation between polymorphisms in the NOD2 (rs8057341) genes and susceptibility to leprosy across two genetic models. Further comprehensive epidemiological investigations are warranted to validate these findings and explore potential interactions between these genes and environmental factors.

Molecular epidemiological characteristics of Mycobacterium leprae in highly endemic areas of China during the COVID-19 epidemic

Objectives

The present study analyzed the impact of the COVID-19 pandemic on the prevalence and incidence of new leprosy cases, as well as the diversity, distribution, and temporal transmission of Mycobacterium leprae strains at the county level in leprae-endemic provinces in Southwest China.

Methods

A total of 219 new leprosy cases during two periods, 2018-2019 and 2020-2021, were compared. We genetically characterized 83 clinical isolates of M. leprae in Guizhou using variable number tandem repeats (VNTRs) and single nucleotide polymorphisms (SNPs). The obtained genetic profiles and cluster consequences of M. leprae were compared between the two periods.

Results

There was an 18.97% decrease in the number of counties and districts reporting cases. Considering the initial months (January-March) of virus emergence, the number of new cases in 2021 increased by 167% compared to 2020. The number of patients with a delay of >12 months before COVID-19 (63.56%) was significantly higher than that during COVID-19 (48.51%). Eighty-one clinical isolates (97.60%) were positive for all 17 VNTR types, whereas two (2.40%) clinical isolates were positive for 16 VNTR types. The (GTA)9, (TA)18, (TTC)21 and (TA)10 loci showed higher polymorphism than the other loci. The VNTR profile of these clinical isolates generated five clusters, among which the counties where the patients were located were adjacent or relatively close to each other. SNP typing revealed that all clinical isolates possessed the single SNP3K.

Conclusion

COVID-19 may have a negative/imbalanced impact on the prevention and control measures of leprosy, which could be a considerable fact for official health departments. Isolates formed clusters among counties in Guizhou, indicating that the transmission chain remained during the epidemic and was less influenced by COVID-19 preventative policies.

Multiplex PCR-based RFLP assay for early identification of prevalent Mycobacterium leprae genotypes

Mycobacterium leprae is classified into four SNP genotypes and 16 subtypes (from 1A to 4P) that exhibit phylogeographical association reported from around the world. Among them, genotypes 1D and 3I represent more than 60% of M. leprae strains. Here, we report a new method for M. leprae genotyping which identifies the genotypes 1D and 3I by combining multiplex PCR amplification and restriction fragment length polymorphism (RFLP) of a M. leprae DNA amplicons using AgeI restriction enzyme. Agarose gel electrophoresis showed a deletion of 11 bp only among 3I genotypes by electrophoresis. When this multiplex PCR reaction is subjected to AgeI digestion, successful restriction digestion shows three bands for all the genotypes except 1D where only two bands were observed due to loss of restriction site. This method gives us the advantage of 1-step identification of the two most prevalent strains of M. leprae without using specialized equipments such as the Sanger sequencing system or quantitative PCR.

Pathogenesis, Clinical Considerations, and Treatments: A Narrative Review on Leprosy

Hansen disease, known as Leprosy, is an infectious disease caused by Mycobacterium leprae. The disease was once thought to be highly contiguous, and patients with leprosy were treated poorly and had to face discrimination due to the gruesome disease's complications. Mycobacterium leprae, the bacterium causative of leprosy, can generally be found in the nine-banded armadillo. The bacterium is transmitted via aerosol droplets and broken skin-to-skin contact. Once M. leprae enters the body, it will target peripheral nerves and the lining mucosa of the skin and eyes, thus causing inflammation and tenderness of the affected area. Over time, this will lead to peripheral neuropathy and weakness of the affected body parts. Treatment of leprosy involves multi-drug combinations such as dapsone, rifampin, and clofazimine. Even though leprosy is curable, early detection and treatment are crucial to preventing irreversible damage and disabilities. Prevention measures include early detection, treatment regimen adherence, close contact prophylaxis, contact tracing, and community awareness. This review aims to provide the latest diagnostic and therapeutic recommendations for leprosy. It outlines the epidemiology, microbiology, clinical treatment, and immunological methods used to detect leprosy.

One Case of Tuberculosis-Like Leprosy with a Type I Leprosy Reaction

Leprosy is a chronic infectious disease primarily affecting the skin and peripheral nerves and is caused by Mycobacterium leprae. Although effective control measures have significantly reduced its global incidence in recent years, its insidious onset and diverse skin manifestations pose considerable challenges to early diagnosis, particularly among young medical practitioners. This study reports a case of tuberculoid leprosy accompanied by a type I reaction (T1R) to leprosy, aiming to contribute to the broader understanding and management of the disease. The patient came from a leprosy-endemic region and had a family history of leprosy. They first presented with neuritis, characterised by numbness in the left upper limb, which is an early-stage symptom often overlooked. This case accentuates the importance of comprehensive examination techniques, including bacteriological and histological investigations, ultrasound and magnetic resonance imaging, to identify early nerve damage, which is critical for prompt diagnosis and intervention. According to World Health Organization data, approximately 200,000 new cases of leprosy are reported worldwide each year, with a prevalence rate of 0.2 cases per 10,000 individuals. The disease exhibits two clinical forms based on the host's immune response: tuberculoid leprosy in a well-immunised population and lepromatous leprosy in a poorly immunised host. The patient in this study demonstrated signs of tuberculoid leprosy, marked by isolated skin papules and plaques, and a T1R, a tissue-destructive, immune-driven inflammatory process. This case underscores the need for ongoing education and updated diagnostic tools to facilitate the early detection of leprosy, particularly in endemic areas. Moreover, attention must be given to the comprehensive care of patients, encompassing both physical and psychological aspects, to improve their quality of life and mitigate social discrimination and prejudice.

Systematic Review of Hansen Disease Attributed to Mycobacterium lepromatosis

In 2008, bacilli from 2 Hansen disease (leprosy) cases were identified as a new species, Mycobacterium lepromatosis. We conducted a systematic review of studies investigating M. lepromatosis as a cause of HD. Twenty-one case reports described 27 patients with PCR-confirmed M. lepromatosis infection (6 dual M. leprae/M. lepromatosis): 10 case-patients in the United States (7 originally from Mexico), 6 in Mexico, 3 in the Dominican Republic, 2 each in Singapore and Myanmar, and 1 each in Indonesia, Paraguay, Cuba, and Canada. Twelve specimen surveys reported 1,098 PCR-positive findings from 1,428 specimens, including M. lepromatosis in 44.9% (133/296) from Mexico, 3.8% (5/133) in Colombia, 12.5% (10/80) in Brazil, and 0.9% (2/224) from the Asia-Pacific region. Biases toward investigating M. lepromatosis as an agent in cases of diffuse lepromatous leprosy or from Mesoamerica precluded conclusions about clinicopathologic manifestations and geographic distribution. Current multidrug treatments seem effective for this infection.

Antimicrobial resistance and genotyping of Mycobacterium leprae in Venezuela

Leprosy is a neglected tropical disease that leads to physical disability and social discrimination. The active surveillance of new cases and vigilance for drug resistance can decrease the incidence, and improve the clinical outcomes of people affected by it. We analyzed, with molecular biology techniques, a set of skin biopsy samples from 25 Venezuelan patients. The patients had been diagnosed with leprosy in 2014 and early 2015, and 15 were relapse cases. The samples were tested for molecular drug resistance to dapsone, rifampicin, and fluoroquinolones. In addition, we performed molecular epidemiology analysis through multiple-locus variable-number tandem repeat analysis (MLVA) and single nucleotide polymorphism (SNP) typing. We did not find evidence of drug resistance and 76% of the samples (n = 16) had isolates belonging to SNP type 3. Genotype profiles allowed us to rule out the possibility of re-infection in a patient with persistent symptoms after treatment, as well as that of household transmission in two more patients. Although our sampling is relatively small, very similar or even identical Mycobacterium leprae genotypes were observed in Miranda State. The presence of this cluster is highly suggestive of high rates of local transmission and, in turn, the need to better control this disease. Finally, the copy number distribution of minisatellite 18–8 in a considerable number of SNP type 3 strains strongly suggests the presence of a sublineage of this disease that is particular to Venezuela.

Leprosy in an Adopted Woman Diagnosed by Molecular Tools: A Case Report from a Non-Endemic Area

Coupled with its rarity in non-endemic areas, the clinical heterogeneity of leprosy makes diagnosis very challenging. We report a diagnosis of multibacillary leprosy in a 22-year-old Indian woman, adopted at the age of 10 and living in Italy. The patient presented with painful skin lesions on the face, trunk, and lower and upper extremities, associated with dysesthesia and a motor deficit in her left leg following corticosteroid therapy interruption. Histopathology results from the skin lesions suggested leprosy, but no acid-fast bacilli were identified. Molecular biology in a center specializing in tropical diseases confirmed the diagnosis, allowing prompt and adequate treatment. Genotype analysis allowed the identification of a genotype 1D of M. leprae, facilitating the epidemiological investigation of the plausible infection origin. No resistances to rifampicin, dapsone, or ofloxacin were detected. Leprosy will continue to exist in high-income nations, and the incidence may rise over time due to increasing migration and globalization. CARE guidelines were followed.

Genetic diversity of Mycobacterium leprae in the state of São Paulo, an area of low-leprosy incidence in Brazil

Background:

Brazil has the second largest number of leprosy cases worldwide, and the state of São Paulo has been considered non-endemic since 2006.

Methods:

We analyzed 16 variable number tandem repeats loci and three single nucleotide polymorphisms loci of Mycobacterium leprae (M. leprae) in 125 clinical isolates from patients in different municipalities in the state.

Results:

The clustering pattern of M. leprae indicated that the transmission of leprosy persisted in the state and included scenarios of intra-extra-familial transmission in areas with low endemicity.

Conclusions:

A significantly active circulation of M. leprae was observed. Therefore, surveillance and control measures must be implemented.

Leprosy Epidemiology According to Leprosy Type in 13 Teaching Hospitals in Indonesia between 2018 and 2020

BACKGROUND: Leprosy or Hansen’s disease is an infectious disease caused by Mycobacterium leprae (M. leprae) bacilli which results in chronic infections in humans that affect the peripheral nerves, skin, and other organs such as the eyes, mucous membranes, bones, and testicles. Leprosy has a variety of clinical presentations, depending on the cell-mediated immunity of the host. Leprosy is classified by the World Health Organization (WHO) as paucibacillary type (PB) and multibacillary type (MB) depending on the number of lesions. This multicenter study aims to provide representation of leprosy types and its epidemiology in Indonesia. AIM: The purpose of this study is to find out the epidemiology according to the leprosy type in 13 teaching hospitals in Indonesia between 2018 and 2020. METHODS: This is a descriptive study with cross-sectional design. All patients with the diagnosis of PB or MB type of leprosy who underwent Multidrug Therapy (MDT) treatment between 2018 and 2020 were included in this study. Data collection was carried out by tracing medical records data in 13 teaching hospitals in Indonesia. RESULTS: A total of 2129 leprosy patients were included in this study. There were 232 cases (10.8%) of PB leprosy and 1897 cases (89.1%) of MB leprosy. The average age of the patients is 38.7 years (SD ± 16.2 years). Males are more affected by leprosy (n = 1,441; 67.7%) compared to female (n = 688; 32.3%). CONCLUSION: Leprosy remains as a national health problem. The increasing cases of MB leprosy in Indonesia are caused by several factors including the lack of knowledge about leprosy, the delay in diagnosis of leprosy, and the stigma of leprosy within the community; therefore, it becomes a challenge to eliminate leprosy in Indonesia.

Utility of a Mycobacterium leprae molecular viability assay for clinical leprosy: An analysis of cases from the Philippines, Ethiopia, and Nepal

Mycobacterium leprae is a slow-growing species of mycobacteria that cannot be cultured in axenic media. This presents a number of challenges for monitoring treatment efficacy and advancing new drugs and regimens for treating leprosy. We previously developed a molecular viability assay (MVA) which measures expression of hsp18 and esxA transcripts to determine viability of M. leprae directly from infected tissue. The objective of the current study was to determine the utility of the MVA for practical use on clinical specimens. Leprosy cases from the Philippines (N = 199), Ethiopia (N = 40), and Nepal (N = 200) were diagnosed by clinical examination, slit-skin smears (SSS) from index sites, and/or histopathology. Biopsy specimens for MVA were collected from an active lesion and stored in 70% ethanol. DNA and RNA were extracted from the tissue, and M. leprae were enumerated on the DNA fraction via RLEP qPCR. Based on this count, DNased RNA was normalized to the equivalent of 3x103M. leprae per reverse transcription reaction, and hsp18 and esxA transcripts were amplified by PCR on the resulting cDNA. There was a strong correlation between RLEP enumeration on the specific biopsy specimen for MVA and the average SSS bacterial index (BI) in all three cohorts (p &lt; 0.001). The MVA could be performed on most biopsies with an average SSS BI ≥ 2 and showed a decrease in M. leprae viability with increasing duration of leprosy multidrug therapy (R2 = 0.81, p &lt; 0.001). The MVA also detected viable M. leprae in relapse patients where it showed significant correlation with the mouse footpad assay (p = 0.018). The MVA is a M. leprae-specific, sensitive, and relatively quick test. Clinically, the MVA would likely be most useful to monitor treatment, confirm suspected relapse cases, and determine efficacy of new leprosy drugs in clinical trials.

Epidemiological scenario of leprosy in marginalized communities of India: Focus on scheduled tribes

The Scheduled Tribes (STs) are designated among the most disadvantaged social groups in India. Until the year 2005 (pre-elimination era of leprosy in India), several leprosy-specific control field programmes were implemented, which have been discontinued subsequently. Since then, leprosy diagnosis and treatment have been integrated with General Health Services. Thereafter, specialized expertise for the early diagnosis of leprosy has been gradually diminishing, especially at the peripheral clinics in remote areas. Hence, leprosy cases usually remain undetected for a long time and persist as endemic reservoirs. The tribal population of India accounts for just 8.6 per cent of the overall population. However, 18.5 per cent of the new leprosy cases were detected within the tribal community in the year 2020, indicating a disproportionately high burden of leprosy among the tribal population. Recent data suggest that these health disparities can be mainly related to the increased marginalization of STs as compared to other communities. This shows the need to further explore the current situation of leprosy in STs so that suitable interventions can address the contributing factors, leading to health inequalities in disadvantaged socio-economic groups. Therefore, this review aims to present the current distribution of leprosy in marginalized communities with a special emphasis on STs. Further, this review discusses how resources might be mobilized for such communities to find and treat undetected leprosy patients in STs to enable effective control of leprosy through early detection and timely treatment.

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.

Role of TlyA in the Biology of Uncultivable Mycobacteria

TlyA proteins are related to distinct functions in a diverse spectrum of bacterial pathogens including mycobacterial spp. There are several annotated proteins function as hemolysin or pore forming molecules that play an important role in the virulence of pathogenic organisms. Many studies reported the dual activity of mycobacterial TlyA as 'hemolysin' and 'S-adenosylmethionine dependent rRNA methylase'. To act as a hemolysin, a sequence must have a signal sequence and transmembrane segment which helps the protein to enter the extracellular environment. Interestingly, the mycobacterial tlyA has neither a traditional signal sequences of general/sec/tat pathways nor any transmembrane segments are present. Still it can reach the extracellular milieu with the help of non-classical signal mechanisms. Also, retention of tlyA in cultivable mycobacterial pathogens (such as Mycobacterium tuberculosis and M. marinum) as well as uncultivated mycobacterial pathogens despite their extreme reductive evolution (such as M. leprae, M. lepromatosis and M. uberis) suggests its crucial role in evolutionary biology of pathogenic mycobacteria. Numerous virulence factors have been characterised from the uncultivable mycobacteria but the information of TlyA protein is still limited in terms of molecular and structural characterisation. The genomic insights offered by comparative analysis of TlyA sequences and its conserved domains reveal its pore forming activity which further confirms its role as a virulence protein, particularly in uncultivable mycobacteria. Therefore, this review presents a comparative analysis of mycobacterial TlyA family by sequence homology and alignment to improve our understanding of this unconventional hemolysin and RNA methyltransferase TlyA of uncultivable mycobacteria.

One Health Approaches to Trace Mycobacterium leprae's Zoonotic Potential Through Time

Hansen's disease (leprosy), mainly caused by infection with Mycobacterium leprae, has accompanied humanity for thousands of years. Although currently rare in Europe, there are over 200,000 new infections annually in South East Asia, Africa, and South America. Over the years many disciplines - palaeopathology, ancient DNA and other ancient biomolecules, and history - have contributed to a better understanding of leprosy's past, in particular its history in medieval Europe. We discuss their contributions and potential, especially in relation to the role of inter-species transmission, an unexplored phenomenon in the disease's history. Here, we explore the potential of interdisciplinary approaches that understand disease as a biosocial phenomenon, which is a product of both infection with M. leprae and social behaviours that facilitate transmission and spread. Genetic evidence of M. leprae isolated from archaeological remains combined with systematic zooarchaeological and historical analysis would not only identify when and in what direction transmission occurred, but also key social behaviours and motivations that brought species together. In our opinion, this combination is crucial to understand the disease's zoonotic past and current potential.

Mycobacterium leprae diversity and population dynamics in medieval Europe from novel ancient genomes

BACKGROUND

Hansen's disease (leprosy), widespread in medieval Europe, is today mainly prevalent in tropical and subtropical regions with around 200,000 new cases reported annually. Despite its long history and appearance in historical records, its origins and past dissemination patterns are still widely unknown. Applying ancient DNA approaches to its major causative agent, Mycobacterium leprae, can significantly improve our understanding of the disease's complex history. Previous studies have identified a high genetic continuity of the pathogen over the last 1500 years and the existence of at least four M. leprae lineages in some parts of Europe since the Early Medieval period.

RESULTS

Here, we reconstructed 19 ancient M. leprae genomes to further investigate M. leprae's genetic variation in Europe, with a dedicated focus on bacterial genomes from previously unstudied regions (Belarus, Iberia, Russia, Scotland), from multiple sites in a single region (Cambridgeshire, England), and from two Iberian leprosaria. Overall, our data confirm the existence of similar phylogeographic patterns across Europe, including high diversity in leprosaria. Further, we identified a new genotype in Belarus. By doubling the number of complete ancient M. leprae genomes, our results improve our knowledge of the past phylogeography of M. leprae and reveal a particularly high M. leprae diversity in European medieval leprosaria.

CONCLUSIONS

Our findings allow us to detect similar patterns of strain diversity across Europe with branch 3 as the most common branch and the leprosaria as centers for high diversity. The higher resolution of our phylogeny tree also refined our understanding of the interspecies transfer between red squirrels and humans pointing to a late antique/early medieval transmission. Furthermore, with our new estimates on the past population diversity of M. leprae, we gained first insights into the disease's global history in relation to major historic events such as the Roman expansion or the beginning of the regular transatlantic long distance trade. In summary, our findings highlight how studying ancient M. leprae genomes worldwide improves our understanding of leprosy's global history and can contribute to current models of M. leprae's worldwide dissemination, including interspecies transmissions.

Mycobacterium lepromatosis as a Second Agent of Hansen's Disease

Mycobacterium lepromatosis was identified as a new species and second causal agent of Hansen's disease (HD, or leprosy) in 2008, 150years after the disease was first attributed to Mycobacterium leprae. M. lepromatosis has been implicated in a small number of HD cases, and clinical aspects of HD caused by M. lepromatosis are poorly characterized. HD is a recognized zoonosis through transmission of M. leprae from armadillos, but the role of M. lepromatosis as a zoonotic agent of HD is unknown. M. lepromatosis was initially associated with diffuse lepromatous leprosy, but subsequent case reports and surveys have linked it to other forms of HD. HD caused by M. lepromatosis has been reported from three endemic countries: Brazil, Myanmar, and Philippines, and three non-endemic countries: Mexico, Malaysia, and United States. Contact with armadillos in Mexico was mentioned in 2/21 M. lepromatosis HD case reports since 2008. M. lepromatosis in animals has been investigated only in non-endemic countries, in squirrels and chipmunks in Europe, white-throated woodrats in Mexico, and armadillos in the United States. To date, there have only been a small number of positive findings in Eurasian red squirrels in Britain and Ireland. A single study of environmental samples found no M. lepromatosis in soil from a Scottish red squirrel habitat. Future studies must focus on endemic countries to determine the true proportion of HD cases caused by M. lepromatosis, and whether viable M. lepromatosis occurs in non-human sources.

Intramuscular Boosting with hIFN-Alpha 2b Enhances BCGphipps-Induced Protection in a Murine Model of Leprosy

Host immunity to Mycobacterium leprae encompasses a spectrum of mechanisms that range from cellular immunity-driven protection to damage associated with humoral immunity as in type-2 leprosy reactions. Although type I interferons (IFNs) participate in eliminating intracellular pathogens, their contribution to the production of antibodies and CD3+ FOXP3+ regulatory T cells (Tregs) in BCG vaccine-mediated protection in leprosy is unknown. BCGphipps (BCGph) priming followed by intramuscular hIFN-α 2b boost significantly reduced lesion size and Mycobacterium lepraemurium growth in the skin. T follicular regulatory cells (TFR), a subset of Tregs induced by immunization or infection, reside in the germinal centers (GCs) and modulate antibody production. We found impaired Treg induction and improved GCs in draining lymph nodes of BCGph primed and hIFN-α 2b boosted mice. Moreover, these mice elicited significant amounts of IL-4 and IL-10 in serum. Thus, our results support the adjuvant properties of hIFN-α 2b in the context of BCGph priming to enhance protective immunity against skin leprosy.