가와사끼병에서 면역글로불린 관련 유전자의 질병 연관성 연구

Abstract

Kawasaki disease (KD), the leading cause of pediatric acquired heart disease in the developed countries, is an acute, systemic vasculitis. The etiology of KD remains unknown. However, the current consensus is that KD can result from environmental or infectious trigger occurring in genetically susceptible children. Treatment for KD is a single dose of intravenous immunoglobulin (IVIG) and high-dose aspirin and it reduces the fever in most patients and the rate of coronary artery aneurysms (CAA). In spite of IVIG treatment, more than 10% of KD patients do not respond to the therapy and show persistent fever. So, the identification of the genetic variants associated with susceptibility and IVIG resistance in KD would help the KD patients for the understanding of pathogenesis and the additional treatments to prevent increased risk of developing coronary artery abnormalities. The susceptibility of KD and the mechanism of IVIG therapy are little known. We hypothesized that immunoglobulin-related genes, such as immunoglobulin Fc receptor genes and genes involved in glycosylation of immunoglobulin G, play a crucial role for the susceptibility and the mechanisms of IVIG therapy in KD. The objective of this thesis research is to identify the genetic risk factors associated with susceptibility of KD and IVIG-resistance in the immunoglobulin-related genes. This study consists of three chapters. In the first chapter, we initially sought to identify nonsynonymous SNPs (nsSNPs) in the coding region of a total of 15 immunoglobulin Fc receptor genes by capillary sequencing using pre-made ABI primer sets (Waltham, Massachusetts, USA) with DNA samples of 98 KD cases and 96 controls. Seven candidate nsSNPs were selected from capillary sequencing data for large scale case-control test. The genotyping for association study was performed using TaqManTM SNP genotyping system with 569 KD cases and 570 controls. The result of the association study for 7 candidate nsSNPs in Fc receptor genes did not show any significant association with KD. In the second chapter, we performed the association study for IVIG-resistance in KD. We initially selected seven candidate nsSNPs in the genes involved in glycosylation of immunoglobulin G from our unpublished whole exome sequencing (WES) data with 94 IVIG non-responders and 106 IVIG responders. An association study for validation was performed using DNA samples of a total 191 IVIG non-responders and 374 IVIG responders. However, there was no significant association of the candidate nsSNPs selected in the immunoglobulin G glycosylation genes with IVIG resistance. Lastly, in the third chapter, to identify coding variants associated with IVIG resistance in KD, we re-analyzed our previous genome-wide association study (GWAS) data made with DNA samples of 296 patients with KD, including 101 IVIG non-responders and 195 IVIG responders. Five nsSNPs in five immune-related genes, including a previously reported SAMD9L nsSNP (rs10488532; p.Val266Ile), were significantly associated with IVIG non-response (OR = 1.89–3.46, P = 0.0109–0.0035) (Table 13). In a replication study, only one in the interleukin 16 (IL16) gene (rs11556218, p.Asn1147Lys) was significantly associated with IVIG non-response (OR = 1.54, P = 0.0078). The same IL16 nsSNP was more significantly associated with IVIG non-response in combined analysis of all data (OR = 1.64, P = 1.25 × 10-4). These results implicate IL16 as involved in the mechanism of IVIG resistance in KD.