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Genome-Wide Association Study of Leprosy and Dapsone Hypersensitivity Syndrome (DHS) in Chinese population

Leprosy GWAS (1)

Leprosy is a chronic infectious disease caused by Mycobacterium leprae (M. leprae). Due to M. leprae's narrow host range and an inability to be cultured in vitro, the biological investigation of this disease has been difficult. Host genetic factors have been suggested to play an important role in disease development, but few have been identified.

In this study, we attempted to identify the host genetic factors by performing a two-stage genome-wide association study (GWAS) in Chinese population. The initial genome-wide scan was done by genotyping 706 patients and 1225 controls using the Illumina HumanHap610 BeadChip, and the follow-up study was performed by genotyping 93 SNPs in three independent samples consisting of 3254 cases and 5955 controls. We identified significant association (P < 10-10) within six genes CCDC122 (13q14), C13orf31 (13q14), NOD2(16q12), TNFSF15 (9q32), HLA-DR (6p21) and RIPK2 (8q21), and suggestive association (P = 5.68x10-6) within LRRK2 (12q12). We also revealed suggestive evidence for C13orf31, LRRK2, NOD2 and RIPK2 to show stronger association in the multibacillary form than the paucibacillary form of leprosy. Our findings highlight the importance of the innate immune response, particularly NOD2-mediated signaling, in leprosy and suggests a new therapeutic target for leprosy.

DHS GWAS

Dapsone (DDS), as both an antibiotic and an anti-inflammatory agent, has been widely used for preventing and treating pathogen-caused infectious diseases and chronic inflammatory diseases. Currently, about 0.5-3.6% of individuals treated with DDS develop severe dapsone hypersensitivity syndrome (DHS) and the mortality rate is up to about 11-13%. However, until now, no tests are available to predict the risk of DHS.

To identify the genetic risk factors of DHS, we performed a two-stage GWAS in Chinese population. In this study, the initial genome-wide scan was done by genotyping 39 DHS cases and 833 controls using Illumina Human 660W-Quad Beadchips and imputed human leukocyte antigen (HLA) molecules. Validation was performed by genotyping 24 SNPs using the Sequenom MassARRAY platform in additional 31 DHS cases and 1,089 controls through genotyping and 32 four-digit HLA-B alleles in an independent series of 37 DHS cases and 201 controls through Roche 454 sequencing. We identified significant association (OR =6.18, P = 3.84x10-13) with SNP rs2844573, which located between the HLA-B and MICA loci. HLA-B*13:01 was confirmed to be a strong risk factor for DHS (OR = 20.53, P = 6.84x10-25) and responsible for the association at rs2844573. The presence of HLA-B*13:01 had a sensitivity of 85.5% and specificity of 85.7% as a predictor for DHS, and its absence can reduce the risk by 7 fold (from 1.4% to 0.2%). HLA-B*13:01 is strongly associated with the development of DHS and can be used as a risk predictor of DHS in the individuals of Chinese and other Asian populations.

Leprosy GWAS (2)

This is a three-stage GWAS of leprosy in the Chinese population. The genome-wide discovery analysis involved two independent data sets: the new unpublished data set by genotyping 842 leprosy patients and 925 controls from northern and southern China using the Human660w-quad beadchips and a previously published GWAS data set of 706 leprosy cases, 1,225 healthy controls and 4,362 individuals with immune-related diseases as population controls from northern China of Chinese Han descent. Further validation studies were performed in two stages in a total of 6,765 cases and 9,505 controls from Chinese Han and minority descent in multiple areas of China, similar to the discovery stage. From this study, we discovered six new susceptibility loci with a combined P-value from discovery and validation stage surpassing genome-wide significance, including BATF3 at 1q32.3, CDH18 at 5p14.3, DEC1 at 9q32, EGR2 at 10q21.3, CCDC88B at 11q13.1 and CIITA at 16p13.13. Our current study has advanced the genetic understanding of leprosy by substantially increasing the number of confirmed genetic susceptibility loci.

Leprosy GWAS (3)

To discover additional leprosy susceptibility loci, we carried out a large-scale three-stage GWAS analysis of leprosy in Chinese population. The genome-wide discovery analysis (Stage 1) involved a new GWAS data set of 1,197 leprosy cases and 1,426 controls from northern and southern China conducted by using Illumina Omni Zhonghua chips with 900,015 single-nucleotide polymorphisms (SNPs), two published GWAS dataset (GWAS2 data set including 706 leprosy cases, 1,225 healthy controls genotyped by Illumina HumanHap610 beadchips, GWAS3 data set including 842 leprosy patients and 925 controls from northern and southern China genotyped by the Human660w-quad beadchips). Further validation studies were performed in two stages in a total of 5,413 cases and 9,771 controls from Chinese Han descent in multiple areas of China. In this study, we identified four novel associations at genome-wide significance (P < 5 x 10-8), all of which can indicate candidate genes within the susceptibility loci, SYN2 (3p25.2), BBS9 (7p14.3), CTSB (8p23.1) and MED30 (8q24.11), through a differential gene expression and eQTL analysis. Altogether, these findings have provided new insight and significantly expanded our understanding of the genetic basis of leprosy.

Leprosy GWAS (4)

In this study, we attempted to systematically investigate the contribution of protein-coding variants to leprosy susceptibility by performing a three-stage genome-wide association study (GWAS) of protein-coding variants in Chinese population. The initial genome-wide scan was done by genotyping 1,670 persons affected by leprosy and 2,321 controls using the Illumina Infinium Human Exome Beadchips (v1.0).The validation study was performed by genotyping 39 SNPs in an additional 3,169 leprosy patients and 9,814 healthy controls from the northern region of China, and the replication study was performed by genotyping eight SNPs in three independent samples from the southern regions of China consisting of 2,231 cases and 2,266 controls. We identified significant association (P < 1.23 x 10-6) within seven genes FLG (Gene ID: 2312), IL23R (Gene ID: 149233), CARD9 (Gene ID: 64170), NCKIPSD (Gene ID: 51517), TYK2 (Gene ID: 7297), SLC29A3 (Gene ID: 55315), IL27 (Gene ID: 246778). Our findings discover novel involvement of skin barrier and endocytosis/phagocytosis/autophagy, besides known innate and adaptive immunity, in the pathogenesis of leprosy, highlight the merits of protein coding variant studies for complex diseases.

Here, the summary statistics from the five genome-wide association analyses were published.