PARK2 and proinflammatory/anti-inflammatory cytokine gene interactions contribute to the susceptibility to leprosy: a case-control study of North Indian population.

OBJECTIVES: Cytokines and related molecules in immune-response pathways seem important in deciding the outcome of the host-pathogen interactions towards different polar forms in leprosy. We studied the role of significant and functionally important single-nucleotide polymorphisms (SNPs) in these genes, published independently from our research group, through combined interaction with an additional analysis of the in silico network outcome, to understand how these impact the susceptibility towards the disease, leprosy. DESIGN: The study was designed to assess an overall combined contribution of significantly associated individual SNPs to reflect on epistatic interactions and their outcome in the form of the disease, leprosy. Furthermore, in silico approach was adopted to carry out protein-protein interaction study between PARK2 and proinflammatory/anti-inflammatory cytokines. SETTING: Population-based case-control study involved the data of North India. Protein-protein interaction networks were constructed using cytoscape. PARTICIPANTS: Study included the data available from 2305 Northern Indians samples (829 patients with leprosy; 1476 healthy controls), generated by our research group. PRIMARY AND SECONDARY OUTCOME MEASURES: For genotype interaction analysis, all possible genotype combinations between selected SNPs were used as an independent variable, using binary logistic regression with the forward likelihood ratio method, keeping the gender as a covariate. RESULTS: Interaction analysis between PARK2 and significant SNPs of anti-inflammatory/proinflammatory cytokine genes, including BAT1 to BTNL2-DR spanning the HLA (6p21.3) region in a case-control comparison, showed that the combined analysis of: (1) PARK2, tumour necrosis factor (TNF), BTNL2-DR, interleukin (IL)-10, IL-6 and TGFBR2 increased the risk towards leprosy (OR=2.54); (2) PARK2, BAT1, NFKBIL1, LTA, TNF-LTB, IL12B and IL10RB provided increased protection (OR=0.26) in comparison with their individual contribution. CONCLUSIONS: Epistatic SNP-SNP interactions involving PARK2 and cytokine genes provide an additive risk towards leprosy susceptibility. Furthermore, in silico protein-protein interaction of PARK2 and important proinflammatory/anti-inflammatory molecules indicate that PARK2 is central to immune regulation, regulating the production of different cytokines on infection.

Mapping of PARK2 and PACRG overlapping regulatory region reveals LD structure and functional variants in association with leprosy in unrelated indian population groups.

Leprosy is a chronic infectious disease caused by Mycobacterium Leprae, where the host genetic background plays an important role toward the disease pathogenesis. Various studies have identified a number of human genes in association with leprosy or its clinical forms. However, non-replication of results has hinted at the heterogeneity among associations between different population groups, which could be due to differently evolved LD structures and differential frequencies of SNPs within the studied regions of the genome. A need for systematic and saturated mapping of the associated regions with the disease is warranted to unravel the observed heterogeneity in different populations. Mapping of the PARK2 and PACRG gene regulatory region with 96 SNPs, with a resolution of 1 SNP per 1 Kb for PARK2 gene regulatory region in a North Indian population, showed an involvement of 11 SNPs in determining the susceptibility towards leprosy. The association was replicated in a geographically distinct and unrelated population from Orissa in eastern India. In vitro reporter assays revealed that the two significantly associated SNPs, located 63.8 kb upstream of PARK2 gene and represented in a single BIN of 8 SNPs, influenced the gene expression. A comparison of BINs between Indian and Vietnamese populations revealed differences in the BIN structures, explaining the heterogeneity and also the reason for non-replication of the associated genomic region in different populations.

IL12B SNPs and copy number variation in IL23R gene associated with susceptibility to leprosy.

BACKGROUND: Genome-wide studies have identified both human leucocyte antigen (HLA) and non-HLA regions in association with leprosy. Involvement of novel functional loci within these regions has been proposed by us earlier. METHODS: We investigated the role of 23 single nucleotide polymorphisms (SNPs) in IL12B and IL12RB2 in a total of 2345 individuals from India, using MassArray platform, along with the copy number variations in IL23R, IL12RB2 and IL10 genes in a representative set of 257 individuals, using real-time PCR. RESULTS: SNP rs2853694 in IL12B gene (AA vs AC+CC, p=2.6E-04, OR=1.42 (1.17-1.70)) showed an association with leprosy. Pairwise interaction analysis followed by combined analysis of multiple SNPs identified that IL12B, TNF and BTNL2-DRA inter-genic SNPs provided a major risk towards leprosy (p=2.6E-08, OR=3.94 (2.43-6.38)), showing a further increase (p=3.6E-14) for combined risk genotype interactions. On the other hand, IL12B, BAT1, NFKBIL1 and LTA SNPs together showed a disposition towards protection (p=0.000011, OR=0.32 (0.19-0.53)) with a further increase (p=6.38E-10) for combined protective genotype-interactions. Copy number variation analysis showed an increased copy number of the IL23R gene (PB=36.4%, controls=20.2%; p=0.026) associated with the pauci-bacillary form of leprosy, which correlated with a trend towards enhanced expression in memory T cells in a preliminary observation. CONCLUSIONS: The observations made here highlight the importance of interaction between specific genetic backgrounds of immune response related genes in the outcome of Mycobacterium leprae infection.

Association of variants in BAT1-LTA-TNF-BTNL2 genes within 6p21.3 region show graded risk to leprosy in unrelated cohorts of Indian population.

Host immune response against Mycobacterium leprae plays an important role in providing resistance to infection and disease progression. Genome-wide linkage and association studies suggest the possibility of multiple risk loci within HLA (6p21.3) region. Any systematic study of relevance within the histocompatibility complex of importance in host immune response would be pertinent because of non-replication of the known loci and unavailable information on some of the unexplored genes and regions. A systematic scan was performed of the selected region involving LTA-TNF-LTB genes within 6p21.3 with a resolution of 1SNP/127 bp; and the SNPs in flanking BAT1, NFKBIL and BTNL2-DRA genes on the basis of their tag status or their presence in promoter/exonic regions with MAF of >5%. Nine SNPs located in BAT1, LTA, TNF genes and BTNL2-DRA interval showed strong association with leprosy susceptibility in two independent sets of North Indian population which was replicated in a geographically distinct East Indian population. Conditional logistic regression showed at least one functional SNP remaining significant in each gene, suggesting an independent role of each of the disease associated SNPs. In vitro reporter assay revealed that two SNPs located at BAT1 promoter and 13 kb upstream to LTA gene affected the transcription factor binding site, hence the gene expression. We unravel the role of unexplored immunologically important genes, BAT1 and BTNL2, in addition to known LTA and TNF genes, and the haplotypes of the significantly associated SNPs therein, to understand susceptibility to the disease, leprosy and its differential severity.

Genetic variations and interactions in anti-inflammatory cytokine pathway genes in the outcome of leprosy: a study conducted on a MassARRAY platform.

BACKGROUND: Mycobacterium leprae is the etiologic pathogen that causes leprosy. The outcome of disease is dependent on the host genetic background. METHODS: We investigated the association of 51 single-nucelotide polymorphisms (SNPs) in anti-inflammatory cytokines (IL-10, TGFB1, IL-6, IL-4, and IL-13) and receptors (IL-10RA, IL-10RB, TGFBR1, TGFBR2, IL-6R, IL-4R, IL-5RA, IL-5RB, and IL-13RA1) with susceptibility to leprosy in a case-control study from New Delhi in northern India. This was followed by replication testing of associated SNPs in a geographically distinct and unrelated population from Orissa in eastern India. The functional potential of SNPs was established with in vitro reporter assays. RESULTS: Significant associations (P < .05) were observed for 8 polymorphisms (rs1800871, rs1800872, and rs1554286 of IL-10; rs3171425 and rs7281762 of IL-10RB; rs2228048 and rs744751 of TGFBR2; and rs1800797 of IL-6) with leprosy. This association was replicated for 4 SNPs (rs1554286 of IL-10, rs7281762 of IL-10RB, rs2228048 of TGFBR2, and rs1800797 of IL-6). The interaction study revealed a significantly greater association with leprosy risk than was obtained for any SNP individually. CONCLUSIONS: This study provides an interesting insight on the cumulative polygenic host component that regulates leprosy pathogenesis.

Leprosy and the adaptation of human toll-like receptor 1.

Leprosy is an infectious disease caused by the obligate intracellular pathogen Mycobacterium leprae and remains endemic in many parts of the world. Despite several major studies on susceptibility to leprosy, few genomic loci have been replicated independently. We have conducted an association analysis of more than 1,500 individuals from different case-control and family studies, and observed consistent associations between genetic variants in both TLR1 and the HLA-DRB1/DQA1 regions with susceptibility to leprosy (TLR1 I602S, case-control P = 5.7 x 10(-8), OR = 0.31, 95% CI = 0.20-0.48, and HLA-DQA1 rs1071630, case-control P = 4.9 x 10(-14), OR = 0.43, 95% CI = 0.35-0.54). The effect sizes of these associations suggest that TLR1 and HLA-DRB1/DQA1 are major susceptibility genes in susceptibility to leprosy. Further population differentiation analysis shows that the TLR1 locus is extremely differentiated. The protective dysfunctional 602S allele is rare in Africa but expands to become the dominant allele among individuals of European descent. This supports the hypothesis that this locus may be under selection from mycobacteria or other pathogens that are recognized by TLR1 and its co-receptors. These observations provide insight into the long standing host-pathogen relationship between human and mycobacteria and highlight the key role of the TLR pathway in infectious diseases.