Defining and targeting high-risk populations in Buruli ulcer–Authors' reply

We thank Jordi Landier and colleagues for their comments about our recent Article in The Lancet Global Health. 1 In their work, Landier and coworkers generalise some of our observations on Buruli ulcer in Benin to those for Cameroon, the country that has the fifth highest prevalence of Buruli ulcer worldwide. Briefly, they make use of age and sex distribution from the Cameroon national census to show that patients aged 5–14 years were twice as likely to be affected by Buruli ulcer as older individuals; and that boys were over-represented in individuals younger than 15 years, women were over-represented in patients aged 15–50 years, and that men and women were equally represented in patients older than 50 years. They advocate the use of national census references to produce incidence rates and incidence rate ratios (IRRs), which they believe to be the proper way to draw valid conclusions

Clinical epidemiology of laboratory-confirmed Buruli ulcer in Benin: a cohort study

Background Buruli ulcer, caused by Mycobacterium ulcerans, was identifi ed as a neglected emerging infectious disease by WHO in 1998. Although Buruli ulcer is the third most common mycobacterial disease worldwide, understanding of the disease is incomplete. We analysed a large cohort of laboratory-confi rmed cases of Buruli ulcer from Pobè, Benin, to provide a comprehensive description of the clinical presentation of the disease, its variation with age and sex, and its eff ect on the occurrence of permanent functional sequelae. Methods Between Jan 1, 2005, and Dec 31, 2011, we prospectively collected clinical and laboratory data from all patients with Buruli ulcer diagnosed at the Centre de Dépistage et de Traitement de l’Ulcère de Buruli in Pobè, Benin. We followed up patients to assess the frequency of permanent functional sequelae. All analyses were done on cases that were laboratory confi rmed. Findings 1227 cases of laboratory-confi rmed Buruli ulcer were included in the analysis. Typically, patients with Buruli ulcer were children (median age at diagnosis 12 years) presenting with a unique (1172 [96%]) large (≥15 cm, 444 [36%]) ulcerative (805 [66%]) lesion of the lower limb (733 [60%]). Atypical clinical presentation of Buruli ulcer included Buruli ulcer osteomyelitis with no identifi able present or past Buruli ulcer skin lesions, which was recorded in at least 14 patients. The sex ratio of Buruli ulcer widely varied with age, with male patients accounting for 57% (n=427) of patients aged 15 years and younger, but only 33% (n=158) of those older than 15 years (odds ratio [OR] 2·59, 95% CI 2·04–3·30). Clinical presentation of Buruli ulcer was signifi cantly dependent on age and sex. 54 (9%) male patients had Buruli ulcer osteomyelitis, whereas only 28 (4%) of female patients did (OR 2·21, 95% CI 1·39–3·59). 1 year after treatment, 229 (22% of 1043 with follow-up information) patients presented with permanent functional sequelae. Presentation with oedema, osteomyelitis, or large (≥15 cm in diameter), or multifocal lesions was signifi cantly associated with occurrence of permanent functional sequelae (OR 7·64, 95% CI 5·29–11·31) and operationally defi nes severe Buruli ulcer. Interpretation Our fi ndings have important clinical implications for daily practice, including enhanced surveillance for early detection of osteomyelitis in boys; systematic search for M ulcerans in osteomyelitis cases of non-specifi c aspect in areas endemic for Buruli ulcer; and specifi c disability prevention for patients presenting with osteomyelitis, oedema, or multifocal or large lesions. Our fi ndings also suggest a crucial underestimation of the burden of Buruli ulcer in Africa and raise key questions about the contribution of environmental and physiopathological factors to the recorded heterogeneity of the clinical presentation of Buruli ulcer

Complementation of a pathogenic IFNGR2 misfolding mutation with modifiers of N-glycosylation

Germline mutations may cause human disease by various mechanisms. Missense and other in-frame mutations may be deleterious because the mutant proteins are not correctly targeted, do not function correctly, or both. We studied a child with mycobacterial disease caused by homozygosity for a novel in-frame microinsertion in IFNGR2. In cells transfected with the mutant allele, most of the interferon γ receptor 2 (IFN-γR2) protein was retained within the cell, and that expressed on the cell surface had an abnormally high molecular weight (MW). The misfolding mutation was not gain-of-glycosylation, as it created no new N-glycosylation site. The mutant IFNGR2 allele was null, as the patient's cells did not respond to IFN-γ. Based on the well-established relationship between protein N-glycosylation and protein quality control processes, we tested 29 compounds affecting maturation by N-glycosylation in the secretory pathway. Remarkably, up to 13 of these compounds reduced the MW of surface-expressed mutant IFN-γR2 molecules and restored cellular responsiveness to IFN-γ. Modifiers of N-glycosylation may therefore complement human cells carrying in-frame and misfolding, but not necessarily gain-of-glycosylation, mutations in genes encoding proteins subject to trafficking via the secretory pathway. Some of these compounds are available for clinical use, paving the way for clinical trials of chemical complementation for various human genetic traits

Family Relationship, Water Contact and Occurrence of Buruli Ulcer in Benin

Mycobacterium ulcerans disease (Buruli ulcer) is the most widespread mycobacterial disease in the world after leprosy and tuberculosis. How M. ulcerans is introduced into the skin of humans remains unclear, but it appears that individuals living in the same environment may have different susceptibilities. This case control study aims to determine whether frequent contacts with natural water sources, family relationship or the practice of consanguineous marriages are associated with the occurrence of Buruli ulcer (BU). The study involved 416 participants, of which 104 BU-confirmed cases and 312 age, gender and village of residence matched controls (persons who had no signs or symptoms of active or inactive BU). The results confirmed that contact with natural water sources is a risk factor. Furthermore, it suggests that a combination of genetic factors may constitute risk factors for the development of BU, possibly by influencing the type of immune response in the individual, and, consequently, the development of BU infection per se and its different clinical forms. These findings may be of major therapeutic interest

Evolutionary Dynamics of Human Toll-Like Receptors and Their Different Contributions to Host Defense

Infectious diseases have been paramount among the threats to health and survival throughout human evolutionary history. Natural selection is therefore expected to act strongly on host defense genes, particularly on innate immunity genes whose products mediate the direct interaction between the host and the microbial environment. In insects and mammals, the Toll-like receptors (TLRs) appear to play a major role in initiating innate immune responses against microbes. In humans, however, it has been speculated that the set of TLRs could be redundant for protective immunity. We investigated how natural selection has acted upon human TLRs, as an approach to assess their level of biological redundancy. We sequenced the ten human TLRs in a panel of 158 individuals from various populations worldwide and found that the intracellular TLRs—activated by nucleic acids and particularly specialized in viral recognition—have evolved under strong purifying selection, indicating their essential non-redundant role in host survival. Conversely, the selective constraints on the TLRs expressed on the cell surface—activated by compounds other than nucleic acids—have been much more relaxed, with higher rates of damaging nonsynonymous and stop mutations tolerated, suggesting their higher redundancy. Finally, we tested whether TLRs have experienced spatially-varying selection in human populations and found that the region encompassing TLR10-TLR1-TLR6 has been the target of recent positive selection among non-Africans. Our findings indicate that the different TLRs differ in their immunological redundancy, reflecting their distinct contributions to host defense. The insights gained in this study foster new hypotheses to be tested in clinical and epidemiological genetics of infectious disease.</p

A multiplex kindred with severe Buruli Ulcer dis playing Mendelian inheritance

Buruli Ulcer (BU), caused by Mycobacterium ulcerans, is the third most common mycobacteriosis worldwide after tuberculosis and leprosy, and has been flagged in 1998 by the World Health Organization as an emerging neglected infectious disease.  The physiopathology of Mycobacterium ulcerans infection primarily involves the lipidic toxin mycolactone, a unique feature among mycobacteria. The resulting extensive skin ulcers and/or osteomyelitis cause pathologic scarring responsible for severe life-lasting functional disabilities in the affected population, mainly composed of children of less than 15 year of age.  Buruli ulcer mainly strikes in Western Sub-Saharan Africa but cases have been reported in more than 30 countries worldwide. A common characteristic of the endemic countries consists in the extreme clustering of BU cases in families living in the vicinity of slow-flowing or stagnant waters in rural areas.  However, only a fraction of these heavily exposed individuals develop Buruli ulcer, which leads us to hypothesize a genetic etiology accounting for this variability.    To tackle this issue, we adopted an extreme-phenotype strategy, which consisted in recruiting the most severe of  the  &gt;1,500 BU cases diagnosed and treated during the last 7 years at the Centre de Détection et de Traitement de l\u27Ulcère de Buruli in Pobè, Benin. We report here the analysis of a single highly-informative consanguineous family in which two siblings were affected with exceptionally severe PCR-confirmed BU. The index case suffered from a multifocal edematous form of BU, which disseminated under treatment and involved the four limbs, eventually requiring amputation to heal. Her sister suffered from an edematous form which affected the right arm from shoulder to fingers.  Blood was obtained from the 2 parents, 2 affected and 3 unaffected children. DNA was processed for the genotyping of &gt;900,000 Single Nucleotide Polymorphisms by the Affymetrix Genome-Wide 6.0 array.  After quality control procedures, 120,156 independent SNPs were used for linkage analysis by homozygosity mapping. Three regions, on chromosome 5 and 8, cosegregated with the affected status following a Mendelian recessive inheritance mode, i.e. were shared homozygous by descent by the 2 affected individuals but not the 3 unaffected siblings (yielding the maximum possible LOD score given the pedigree. Sequencing of genes in these regions is currently ongoing and show promising results.  This first description of a genetic etiology for extremely severe BU will have far reaching biological and medical implications. 

Evidence for an association of HLA-DRB1*15 and DRB1*09 with leprosy and the impact of DRB1*09 on disease onset in a Chinese Han population

<p>Abstract</p> <p>Background</p> <p>Human leukocyte antigens (HLAs) have been proposed to modulate the immune response to <it>Mycobacterium leprae</it>. The association of HLA-DRB1 with leprosy has been reported in several populations, but not in a Chinese population.</p> <p>Methods</p> <p>The polymerase chain reaction-sequence-specific oligonucleotide probe with Luminex100 (PCR-SSOP-Luminex) method was used to genotype HLA-DRB1 alleles in 305 leprosy patients and 527 healthy control individuals.</p> <p>Results</p> <p>The HLA-DRB1*15 allele was significantly more prevalent among leprosy patients than healthy controls, whereas the frequency of the HLA-DRB1*09 allele was lower among leprosy patients, especially those with early-onset disease.</p> <p>Conclusion</p> <p>HLA-DRB1 alleles are associated with leprosy susceptibility in a Chinese population. The HLA-DRB1*09 allele was found to be protective exclusively in a subset of early-onset leprosy patients.</p

Chromosome 2p14 Is Linked to Susceptibility to Leprosy

BACKGROUND: A genetic component to the etiology of leprosy is well recognized but the mechanism of inheritance and the genes involved are yet to be fully established. METHODOLOGY: A genome-wide single nucleotide polymorphism (SNP) based linkage analysis was carried out using 23 pedigrees, each with 3 to 7 family members affected by leprosy. Multipoint parametric and non-parametric linkage analyses were performed using MERLIN 1.1.1. PRINCIPAL FINDINGS: Genome-wide significant evidence for linkage was identified on chromosome 2p14 with a heterogeneity logarithm of odds (HLOD) score of 3.51 (rs1106577) under a recessive model of inheritance, while suggestive evidence was identified on chr.4q22 (HLOD 2.92, rs1349350, dominant model), chr. 8q24 (HLOD 2.74, rs1618523, recessive model) and chr.16q24 (HLOD 1.93, rs276990 dominant model). Our study also provided moderate evidence for a linkage locus on chromosome 6q24-26 by non-parametric linkage analysis (rs6570858, LOD 1.54, p = 0.004), overlapping a previously reported linkage region on chromosome 6q25-26. CONCLUSION: A genome-wide linkage analysis has identified a new linkage locus on chromosome 2p14 for leprosy in Pedigrees from China