FCGR3A基因变异对克罗恩病发病风险及英夫利昔单抗临床应答的影响

目的：探讨FCGR3A（rs396991、rs4656317）基因变异对克罗恩病（CD）发病风险及英夫利昔单抗（IFX）临床应答的影响。方法：收集2012 年1月至2021年1月温州医科大学附属第二医院育英儿童医院确诊的225 例CD患者和476 名性别、年龄相匹配的正常对照者，应用基质辅助激光解吸-电离飞行时间质谱技术检测FCGR3A（rs396991、rs4656317）的基因型，并进行连锁不平衡（LD）和单倍型分析。225例CD患者中，98 例初发型活动期CD患者克罗恩病活动指数（CDAI）≥150分]于第0、2、6 周给予IFX（5 mg/kg）静脉注射诱导缓解，随后每隔8 周注射相同剂量的IFX。第14 周时，依据CDAI和CD简化内镜评分（SES-CD）分为应答组和无应答组，回顾性分析FCGR3A 基因变异对IFX临床应答的影响。结果：CD组中rs396991的变异等位基因C频率高于正常对照组（39.33% vs. 31.83%，P=0.006）。CD组中rs4656317 的变异等位基因C和变异基因型GC+CC频率均高于正常对照组（45.33% vs. 36.55%，P=0.002；71.11% vs. 61.76%，P=0.016）。分层分析发现结肠型+回结肠型CD患者中rs396991的变异基因型AC+CC频率及rs4656317的变异基因型GC+CC频率均低于回肠末段型CD患者（55.00% vs. 72.31%，P=0.016；66.25% vs. 83.08%，P =0.012）。LD分析结果显示FCGR3A 基因上rs396991和rs4656317 彼此紧密连锁（D ’=0.94，r 2=0.72）。LD分析结果显示CD组中单倍型AG的频率低于正常对照组（53.78% vs. 62.18%，P =0.003），而单倍型CC的频率高于正常对照组（38.67% vs.30.56%，P =0.003）。98例初发型活动期CD患者经IFX治疗14周后，应答组（82例）中rs396991的变异等位基因C频率低于无应答组（16例）（23.17% vs. 43.75%，P =0.016）。第14周时，依据IFX有效浓度和IFX抗抗体浓度对16例无应答患者分析发现，IFX抗抗体高浓度组（≥70 ng/mL）中携带rs396991变异等位基因C的比例高于IFX抗抗体低浓度组（＜70 ng/mL）（71.43% vs. 22.22%，P =0.011）。结论：FCGR3A 基因上rs396991变异和rs4656317变异都可能增加CD发病风险，尤其是可能增加CD患者回肠末端受累的风险。此外，rs396991基因变异可能有助于IFX抗抗体的生成，降低CD患者对IFX治疗的临床应答。

Influence of FCGR3A gene variations on the risk of Crohn’s disease and the clinical response to infliximab in Chinese patients

Objective: To investigate the influence of FCGR3A (rs396991, rs4656317) gene variations on the risk of Crohn’s disease (CD) and the clinical response to infliximab (IFX). Methods: After the collection of 225 CD patients and 476 age- and gender-matched controls from the Second Affiliated Hospital & Yuying Children’s Hospital of Wenzhou Medical University during January 2012 to January 2021, the genotypes of rs396991 and rs4656317 were determined by Matrix Assisted Laser Desorption Spectrometry for time-of-flight Mass Spectrometry technique. Linkage disequilibrium (LD) and haplotype were analyzed in all study subjects.Of 225 CD patients, who had initial active stage Crohn’s disease activity index (CDAI)≥150 points] were givenintravenous IFX (5 mg/kg) at week 0, 2, and 6 to induce remission, followed by the same dose of IFX every 8 weeks. These patients were divided into response group and non-response group based on CDAI and simplified endoscopic score for Crohn’s disease (SES-CD) at 14th week. A retrospective analysis was performed for the influence of FCGR3A gene variations on the clinical response of IFX in this cohort of CD patients. Results: The variant allele (C) of rs396991 was shown to be more prevalent in CD patients than in the controls (39.33% vs. 31.83%, P=0.006). Both the variant allele (C) and variant genotype (GC+CC) of rs4656317 were more frequent in CD patients than in the controls (45.33% vs. 36.55%, P=0.002; 71.11% vs. 61.76%, P=0.016). The stratified analysis indicated that the variant genotype (AC+CC) of rs396991 and variant genotype (GC+CC) of rs4656317 were decreased in the patients with type L2 CD or type L3 CD in contrast to those with type L1 CD (55.00% vs. 72.31%, P=0.016; 66.25% vs. 83.08%, P=0.012). The polymorphic loci of rs396991 and rs4656317 were in close linkage disequilibrium with each other in FCGR3A gene (D’=0.94, r2=0.72). The analysis for LD showed that the frequency of haplotype (AG) was lower in CD patients than in the controls (53.78% vs. 62.18%, P=0.003).In contrast, the frequency of haplotype (CC) was higher in CD patients than in the controls (38.67% vs. 30.56%,P=0.003). After the treatment of IFX for 14 weeks, 98 CD patients with initial active stage were divided into response group (82 cases) and non-response group (16 cases). The variant allele (C) of rs396991 was shown to be less prevalent in response group than in non-response group (23.17% vs. 43.75%, P=0.016). At the 14th week, 16 patients of non-response group were analyzed according to the effective concentration of IFX and the concentration of IFX anti-antibody. The result suggested that the proportion of rs396991 allele C in IFX anti-antibody highconcentration group (≥70 ng/mL) was higher than that in IFX anti-antibody low-concentration group (<70 ng/mL) (71.43% vs. 22.22%, P=0.011). Conclusion: Both the variations of rs396991 and rs4656317 in FCGR3A gene may increase the risk of CD, especially the risk of terminal ileal involvement. In addition, the variation of rs396991 might contribute to the production of IFX anti-antibody, thereby reducing the clinical response of CD patients to IFX treatment.