A genome wide association study identifies a IncRna as risk factor for pathological inflammatory responses in leprosy

Leprosy Type-1 Reactions (T1Rs) are pathological inflammatory responses that afflict a sub-group of leprosy patients and result in peripheral nerve damage. Here, we employed a family-based GWAS in 221 families with 229 T1R-affect offspring with stepwise replication to identify risk factors for T1R. We discovered, replicated and validated T1R-specific associations with SNPs located in chromosome region 10p21.2. Combined analysis across the three independent samples resulted in strong evidence of association of rs1875147 with T1R (p = 4.5x10-8; OR = 1.54, 95% CI = 1.32-1.80). The T1R-risk locus was restricted to a lncRNA-encoding genomic interval with rs1875147 being an eQTL for the lncRNA. Since a genetic overlap between leprosy and inflammatory bowel disease (IBD) has been detected, we evaluated if the shared genetic control could be traced to the T1R endophenotype. Employing the results of a recent IBD GWAS meta-analysis we found that 10.6% of IBD SNPs available in our dataset shared a common risk-allele with T1R (p = 2.4x10-4). This finding points to a substantial overlap in the genetic control of clinically diverse inflammatory disorders.

Association of TNFSF8 regulatory variants with excessive inflammatory responses but not leprosy per se

BACKGROUND: Type 1 reactions (T1R) affect a considerable proportion of patients with leprosy. In those with T1R, the host immune response pathologically overcompensates for the actual infectious threat, resulting in nerve damage and permanent disability. Based on the results of a genome-wide association study of leprosy per se, we investigated the TNFSF15 chromosomal region for a possible contribution to susceptibility to T1R. METHODS: We performed a high-resolution association scan of the TNFSF15 locus to evaluate the association with T1R in 2 geographically and ethnically distinct populations: a family-based sample from Vietnam and a case-control sample from Brazil, comprising a total of 1768 subjects. RESULTS: In the Vietnamese sample, 47 single-nucleotide polymorphisms (SNPs) overlapping TNFSF15 and the adjacent TNFSF8 gene were associated with T1R but not with leprosy. Of the 47 SNPs, 39 were cis-expression quantitative trait loci (cis-eQTL) for TNFSF8 including SNPs located within the TNFSF15 gene. In the Brazilian sample, 18 of these cis-eQTL SNPs overlapping the TNFSF8 gene were validated for association with T1R. CONCLUSIONS: Taken together, these results indicate TNFSF8 and not TNFSF15 as an important T1R susceptibility gene. Our data support the need for infection genetics to go beyond genes for pathogen control to explore genes involved in a commensurate host response.

Genetics of leprosy reactions: an overview

Type-1 (T1R) and Type-2 (T2R) leprosy reactions (LR), which affect up to 50% of leprosy patients, are aggressive inflammatory episodes of sudden onset and highly variable incidence across populations. LR are often diagnosed concurrently with leprosy, but more frequently occur several months after treatment onset. It is not uncommon for leprosy patients to develop recurring reactional episodes; however, they rarely undergo both types of LR. Today, LR are the main cause of permanent disabilities associated with leprosy and represent a major challenge in the clinical management of leprosy patients. Although progress has been made in understanding the immunopathology of LR, the factors that cause a leprosy patient to suffer from LR are largely unknown. Given the impact that ethnic background has on the risk of developing LR, host genetic factors have long been suspected of contributing to LR. Indeed, polymorphisms in seven genes [Toll-like receptors (TLR)1, TLR2, nucleotide-binding oligomerisation domain containing 2, vitamin D receptor, natural resistance-associated macrophage protein 1, C4B and interleukin-6] have been found to be associated with one or more LR outcomes. The identification of host genetic markers with predictive value for LR would have a major impact on nerve damage control in leprosy. In this review, we present the recent advances achieved through genetic studies of LR.

Insights from animal models on the immunogenetics of leprosy: a review

A variety of host immunogenetic factors appear to influence both an individual's susceptibility to infection with Mycobacterium leprae and the pathologic course of the disease. Animal models can contribute to a better understanding of the role of immunogenetics in leprosy through comparative studies helping to confirm the significance of various identified traits and in deciphering the underlying mechanisms that may be involved in expression of different disease related phenotypes. Genetically engineered mice, with specific immune or biochemical pathway defects, are particularly useful for investigating granuloma formation and resistance to infection and are shedding new light on borderline areas of the leprosy spectrum which are clinically unstable and have a tendency toward immunological complications. Though armadillos are less developed in this regard, these animals are the only other natural hosts of M. leprae and they present a unique opportunity for comparative study of genetic markers and mechanisms associable with disease susceptibility or resistance, especially the neurological aspects of leprosy. In this paper, we review the recent contributions of genetically engineered mice and armadillos toward our understanding of the immunogenetics of leprosy.

Tuberculin skin test reactivity is dependent on host genetic background in Colombian tuberculosis household contacts.

The tuberculin skin test (TST) measures the intensity of antimycobacterial acquired immunity and is used to diagnose latent infection with Mycobacterium tuberculosis. We report evidence for a codominant gene explaining ∼65% of the TST variability. Disregarding the host genetic background may lead to misclassifications of TST-based diagnosis of latent M. tuberculosis infection.

Genetics of leprosy reactions: an overview.

Type-1 (T1R) and Type-2 (T2R) leprosy reactions (LR), which affect up to 50% of leprosy patients, are aggressive inflammatory episodes of sudden onset and highly variable incidence across populations. LR are often diagnosed concurrently with leprosy, but more frequently occur several months after treatment onset. It is not uncommon for leprosy patients to develop recurring reactional episodes; however, they rarely undergo both types of LR. Today, LR are the main cause of permanent disabilities associated with leprosy and represent a major challenge in the clinical management of leprosy patients. Although progress has been made in understanding the immunopathology of LR, the factors that cause a leprosy patient to suffer from LR are largely unknown. Given the impact that ethnic background has on the risk of developing LR, host genetic factors have long been suspected of contributing to LR. Indeed, polymorphisms in seven genes [Toll-like receptors (TLR)1, TLR2, nucleotide-binding oligomerisation domain containing 2, vitamin D receptor, natural resistance-associated macrophage protein 1, C4B and interleukin-6] have been found to be associated with one or more LR outcomes. The identification of host genetic markers with predictive value for LR would have a major impact on nerve damage control in leprosy. In this review, we present the recent advances achieved through genetic studies of LR.

Insights from animal models on the immunogenetics of leprosy: a review.

A variety of host immunogenetic factors appear to influence both an individual's susceptibility to infection with Mycobacterium leprae and the pathologic course of the disease. Animal models can contribute to a better understanding of the role of immunogenetics in leprosy through comparative studies helping to confirm the significance of various identified traits and in deciphering the underlying mechanisms that may be involved in expression of different disease related phenotypes. Genetically engineered mice, with specific immune or biochemical pathway defects, are particularly useful for investigating granuloma formation and resistance to infection and are shedding new light on borderline areas of the leprosy spectrum which are clinically unstable and have a tendency toward immunological complications. Though armadillos are less developed in this regard, these animals are the only other natural hosts of M. leprae and they present a unique opportunity for comparative study of genetic markers and mechanisms associable with disease susceptibility or resistance, especially the neurological aspects of leprosy. In this paper, we review the recent contributions of genetically engineered mice and armadillos toward our understanding of the immunogenetics of leprosy.

TNF -308G>A single nucleotide polymorphism is associated with leprosy among Brazilians: a genetic epidemiology assessment, meta-analysis, and functional study.

Leprosy is an infectious disease caused by Mycobacterium leprae. Tumor necrosis factor (TNF) plays a key role in the host response. Some association studies have implicated the single nucleotide polymorphism TNF -308G>A in leprosy susceptibility, but these results are still controversial. We first conducted 4 association studies (2639 individuals) that showed a protective effect of the -308A allele (odds ratio [OR] = 0.77; P = .005). Next, results of a meta-analysis reinforced this association after inclusion of our new data (OR = 0.74; P = .04). Furthermore, a subgroup analysis including only Brazilian studies suggested that the association is specific to this population (OR = 0.63; P = .005). Finally, functional analyses using whole blood cultures showed that patients carrying the -308A allele produced higher TNF levels after lipopolysaccharide (LPS) (6 hours) and M. leprae (3 hours) stimulation. These results reinforce the association between TNF and leprosy and suggest the -308A allele as a marker of disease resistance, especially among Brazilians.

TNF - 308G>A single nucleotide polymorphism is associated with leprosy among Brazilians: a genetic epidemiology assessment, meta-analysis, and functional study

Leprosy is an infectious disease caused by Mycobacterium leprae. Tumor necrosis factor (TNF) plays a key role in the host response. Some association studies have implicated the single nucleotide polymorphism TNF -308G>A in leprosy susceptibility, but these results are still controversial. We first conducted 4 association studies (2639 individuals) that showed a protective effect of the -308A allele (odds ratio [OR] = 0.77; P = .005). Next, results of a meta-analysis reinforced this association after inclusion of our new data (OR = 0.74; P = .04). Furthermore, a subgroup analysis including only Brazilian studies suggested that the association is specific to this population (OR = 0.63; P = .005). Finally, functional analyses using whole blood cultures showed that patients carrying the -308A allele produced higher TNF levels after lipopolysaccharide (LPS) (6 hours) and M. leprae (3 hours) stimulation. These results reinforce the association between TNF and leprosy and suggest the -308A allele as a marker of disease resistance, especially among Brazilians.

Stepwise replication identifies a low-producing lymphotoxin-alpha allele as a major risk factor for early-onset leprosy.

Host genetics has an important role in leprosy, and variants in the shared promoter region of PARK2 and PACRG were the first major susceptibility factors identified by positional cloning. Here we report the linkage disequilibrium mapping of the second linkage peak of our previous genome-wide scan, located close to the HLA complex. In both a Vietnamese familial sample and an Indian case-control sample, the low-producing lymphotoxin-alpha (LTA)+80 A allele was significantly associated with an increase in leprosy risk (P = 0.007 and P = 0.01, respectively). Analysis of an additional case-control sample from Brazil and an additional familial sample from Vietnam showed that the LTA+80 effect was much stronger in young individuals. In the combined sample of 298 Vietnamese familial trios, the odds ratio of leprosy for LTA+80 AA/AC versus CC subjects was 2.11 (P = 0.000024), which increased to 5.63 (P = 0.0000004) in the subsample of 121 trios of affected individuals diagnosed before 16 years of age. In addition to identifying LTA as a major gene associated with early-onset leprosy, our study highlights the critical role of case- and population-specific factors in the dissection of susceptibility variants in complex diseases.

Susceptibility to leprosy is associated with PARK2 and PACRG.

Leprosy is caused by Mycobacterium leprae and affects about 700,000 individuals each year. It has long been thought that leprosy has a strong genetic component, and recently we mapped a leprosy susceptibility locus to chromosome 6 region q25-q26 (ref. 3). Here we investigate this region further by using a systematic association scan of the chromosomal interval most likely to harbour this leprosy susceptibility locus. In 197 Vietnamese families we found a significant association between leprosy and 17 markers located in a block of approx. 80 kilobases overlapping the 5' regulatory region shared by the Parkinson's disease gene PARK2 and the co-regulated gene PACRG. Possession of as few as two of the 17 risk alleles was highly predictive of leprosy. This was confirmed in a sample of 975 unrelated leprosy cases and controls from Brazil in whom the same alleles were strongly associated with leprosy. Variants in the regulatory region shared by PARK2 and PACRG therefore act as common risk factors for leprosy.

Absence of association between mannose-binding lectin gene polymorphisms and HIV-1 infection in a Colombian population.

Mannose-binding lectin (MBL) is a calcium-dependent lectin shown to play an important role in innate immunity to infection by activating the classical complement pathway and phagocytosis. In vitro studies have shown that MBL is able to bind to the gp120 HIV-1 surface antigen, and variants of the gene are associated with increased risk of HIV infection among Scandinavians. We investigated the association of genetic MBL variants and HIV-1 infection in 278 Colombian HIV-infected and control individuals. MBL genotype frequencies were similar for both groups, and no association was detected between MBL alleles B, C, and D and susceptibility to HIV-1 infection ( P=1.0). Since there is a well-documented link between the tested MBL alleles and very low MBL serum concentration, these results do not support the hypothesis that MBL levels are a risk factor for HIV-1 infection in Colombia.

Chromosome 6q25 is linked to susceptibility to leprosy in a Vietnamese population

Leprosy, a chronic infectious disease caused by Mycobacterium leprae, affects an estimated 700,000 persons each year. Clinically, leprosy can be categorized as paucibacillary or multibacillary disease. These clinical forms develop in persons that are intrinsically susceptible to leprosy per se, that is, leprosy independent of its specific clinical manifestation. We report here on a genome-wide search for loci controlling susceptibility to leprosy per se in a panel of 86 families including 205 siblings affected with leprosy from Southern Vietnam. Using model-free linkage analysis, we found significant evidence for a susceptibility gene on chromosome region 6q25 (maximum likelihood binomial (MLB) lod score 4.31; P = 5 x 10(-6)). We confirmed this by family-based association analysis in an independent panel of 208 Vietnamese leprosy simplex families. Of seven microsatellite markers underlying the linkage peak, alleles of two markers (D6S1035 and D6S305) showed strong evidence for association with leprosy (P = 6.7 x 10(-4) and P = 5.9 x 10(-5), respectively).

No evidence for linkage between leprosy susceptibility and the human natural resistance-associated macrophage protein 1 (NRAMP1) gene in French Polynesia

In order to determine whether a human homolog (NRAMP1) to a murine candidate gene for resistance to mycobacteria influences susceptibility to human disease, we analyzed data from seven multicase leprosy families (84 individuals) from French Polynesia for linkage markers within the NRAMP1 gene and leprosy per se. Individual family members were typed at nine polymorphic loci within NRAMP1. In addition, three physically linked, polymorphic microsatellite markers-D2S104, D2S173 and D2S1471-were also typed. Linkage analyses were done using affected sibpair and LOD score methods employing different modes of inheritance with full and reduced penetrance. The results of this study strongly suggest that NRAMP1 is not linked to leprosy susceptibility in the French Polynesian families tested.