Genome-wide association study of resistance to Mycobacterium tuberculosis infection identifies a locus at 10q26.2 in three distinct populations.

The natural history of tuberculosis (TB) is characterized by a large inter-individual outcome variability after exposure to Mycobacterium tuberculosis. Specifically, some highly exposed individuals remain resistant to M. tuberculosis infection, as inferred by tuberculin skin test (TST) or interferon-gamma release assays (IGRAs). We performed a genome-wide association study of resistance to M. tuberculosis infection in an endemic region of Southern Vietnam. We enrolled household contacts (HHC) of pulmonary TB cases and compared subjects who were negative for both TST and IGRA (n = 185) with infected individuals (n = 353) who were either positive for both TST and IGRA or had a diagnosis of TB. We found a genome-wide significant locus on chromosome 10q26.2 with a cluster of variants associated with strong protection against M. tuberculosis infection (OR = 0.42, 95%CI 0.35-0.49, P = 3.71×10-8, for the genotyped variant rs17155120). The locus was replicated in a French multi-ethnic HHC cohort and a familial admixed cohort from a hyper-endemic area of South Africa, with an overall OR for rs17155120 estimated at 0.50 (95%CI 0.45-0.55, P = 1.26×10-9). The variants are located in intronic regions and upstream of C10orf90, a tumor suppressor gene which encodes an ubiquitin ligase activating the transcription factor p53. In silico analysis showed that the protective alleles were associated with a decreased expression in monocytes of the nearby gene ADAM12 which could lead to an enhanced response of Th17 lymphocytes. Our results reveal a novel locus controlling resistance to M. tuberculosis infection across different populations.

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.

PARK2 mediates interleukin 6 and monocyte chemoattractant protein 1 production by human macrophages.

Leprosy is a persistent infectious disease caused by Mycobacterium leprae that still affects over 200,000 new patients annually. The host genetic background is an important risk factor for leprosy susceptibility and the PARK2 gene is a replicated leprosy susceptibility candidate gene. The protein product of PARK2, Parkin, is an E3 ubiquitin ligase that is involved in the development of various forms of Parkinsonism. The human macrophage is both a natural host cell of M. leprae as well as a primary mediator of natural immune defenses, in part by secreting important pro-inflammatory cytokines and chemokines. Here, we report that down-regulation of Parkin in THP-1 macrophages, human monocyte-derived macrophages and human Schwann cells resulted in a consistent and specific decrease in interleukin-6 (IL-6) and monocyte chemoattractant protein 1 (MCP-1/CCL2) production in response to mycobacteria or LPS. Interestingly, production of IL-6 at 6 hours by THP-1 cells stimulated with live M. leprae and M. bovis BCG was dependent on pretreatment with 1,25-dihydroxyvitamin D(3) (VD). Parkin knockdown in VD-treated cells blocked IL-6 induction by mycobacteria. However, IκB-α phosphorylation and levels of IκB-ξ, a nuclear protein required for IL-6 expression, were not affected by Parkin silencing. Phosphorylation of MAPK ERK1/2 and p38 was unaffected by Parkin silencing while JNK activation was promoted but did not explain the altered cytokine production. In a final set of experiments we found that genetic risk factors of leprosy located in the PARK2 promoter region were significantly correlated with M. leprae sonicate triggered CCL2 and IL6 transcript levels in whole blood assays. These results associated genetically controlled changes in the production of MCP-1/CCL2 and IL-6 with known leprosy susceptibility factors.

Crohn's disease susceptibility genes are associated with leprosy in the Vietnamese population.

A genomewide association study in Chinese patients with leprosy detected association signals in 16 single-nucleotide polymorphisms (SNPs) belonging to 6 loci, of which 4 are related to the NOD2 signaling pathway and are Crohn's disease susceptibility loci. Here, we studied these 16 SNPs as potential leprosy susceptibility factors in 474 Vietnamese leprosy simplex families. We replicated SNPs at HLA-DR-DQ, RIPK2, CCDC122-LACC1, and NOD2 as leprosy susceptibility factors in Vietnam. These results validated the striking overlap in the genetic control of Crohn's disease and leprosy.

Genomewide linkage analysis of the granulomatous mitsuda reaction implicates chromosomal regions 2q35 and 17q21.

The Mitsuda reaction, a delayed granulomatous skin reaction elicited by the intradermal injection of heat-killed Mycobacterium leprae, is an in vivo test reflecting the ability to generate an immune granuloma after sensitization by diverse mycobacterial infections. Accumulating evidence for the genetic control of the Mitsuda reaction has been reported. We performed a genomewide linkage scan for the quantitative Mitsuda reaction in 19 large families from Vietnam with a history of leprosy (114 offspring). Suggestive linkage was found at chromosomal regions 2q35 (P = 9 x 10(-4) at the SLC11A1 locus) and 17q21-25 (P = 8 x 10(-4)). Interestingly, these 2 regions have been previously linked to mycobacterial infection and other granulomatous diseases.

A recessive major gene controls the mitsuda reaction in a region endemic for leprosy.

BACKGROUND: Leprosy is a chronic infectious disease caused by Mycobacterium leprae. The Mitsuda reaction is a delayed granulomatous skin reaction elicited by intradermal injection of heat-killed M. leprae. Interestingly, results of the Mitsuda test are positive in the majority of individuals, even in areas not endemic for M. leprae. Like leprosy, the Mitsuda reaction is thought to be genetically controlled, but its mode of inheritance is unknown, although the role of the NRAMP1 gene has previously been reported. METHODS: We conducted a segregation analysis of quantitative Mitsuda reactivity in 168 Vietnamese nuclear families ascertained through patients with leprosy. RESULTS: We found strong evidence (P<10-9) for a major gene controlling the Mitsuda reaction independently of leprosy clinical status. Subsequent linkage analysis showed that this major gene was distinct from NRAMP1. Under the major-gene model, approximately 12% of individuals are homozygous for the recessive predisposing allele and are predicted to display high levels of Mitsuda reactivity (mean, approximately 10 mm, versus 5 mm in other individuals). CONCLUSION: We provide evidence that the Mitsuda reaction is controlled by a major gene. Our study paves the way for the identification of this gene and should provide novel insight into the mechanisms involved in granuloma formation, especially in M. leprae infection.