IL12RB1错义突变在播散性卡介病发病中的作用及其机制研究

Disseminated Bacillus Calmette-Guérin (BCG) disease is the systemic BCG infection after BCG vaccination. It usually occurs in children with primary immunodeficiency. However, the detailed immunodeficiency type of about 50-70% of the patients are still unclear. In our previous work, we used the whole exon sequencing to examine more than 20 pedigrees in children with disseminated BCG disease, and have identified a potential pathogenic site of the interleukin 12 receptor B1 gene with low frequency rare mutation ( IL12RB1 c.G271A). The mutated site and its upstream and downstream amino acid sequences are highly conserved among more than ten different animal species. Herein, we hypothesize that this newly identified IL12RB1 missense mutation is associated with pathogenesis of disseminated BCG disease. In order to verify this hypothesis, we intend to use flow cytometry, ELISA to detect cytokine expression profile of interleukin 12 / interferon gamma pathway in the patients’ peripheral blood and transgenic mouse model, and then use BCG challenge to further analyze the pathogenesis in the transgenic mice. These could verify the role of missense mutation IL12RB1 c.G271A in the pathogenesis of disseminated BCG disease and to thus explore its preliminary mechanism. The discovery of new pathogenic mutation site of dissemination BCG disease would facilitate early screening and intervention in patients, fetuses and neonates.

播散性卡介菌病是接种卡介苗(BCG)后导致的全身BCG播散感染，常发生于原发免疫缺陷儿童，但至今仍有50%-70%的患儿未明确具体的免疫缺陷类型。我们前期工作中对20余个播性卡介菌病患儿核心家系进行全外显子捕获测序分析，新发现了一个白介素12受体B1基因的低频罕见变异位点（IL12RB1 c.G271A），该突变位置及其上下游氨基酸序列在十几个不同动物物种之间高度保守。因此，我们推测这一新发现的IL12RB1错义突变与播散性卡接菌病致病相关。为了验证这一假设，我们拟利用流式细胞术、ELISA分析患者外周血中及转基因小鼠模型中白细胞介素12/干扰素γ通路效应细胞因子的表达情况，并用BCG攻毒试验进一步验证转基因小鼠中该突变介导的致病性，从而阐明该错义突变在播散性卡介病发病中的作用并初步探讨其机制，以期发现并验证新的播散性卡介菌病的致病基因突变，有助于对患者、胎儿及新生儿的早期筛查及干预。

播散性卡介菌病是接种卡介苗(BCG)后导致的全身BCG播散感染，常发生于原发免疫缺陷儿童，但至今仍有50%-70%的患儿未明确具体的免疫缺陷类型。我们前期工作中对20余个播性卡介菌病患儿核心家系进行全外显子捕获测序分析，新发现了一个白介素12受体B1基因的低频罕见变异位点（IL12RB1 c.G271A），该突变位置及其上下游氨基酸序列在十几个不同动物物种之间高度保守。因此，我们推测这一新发现的IL12RB1错义突变与播散性卡接菌病致病相关。为了验证这一假设，我们拟利用流式细胞术、ELISA分析患者外周血中及转基因小鼠模型中白细胞介素12/干扰素γ通路效应细胞因子的表达情况，并用BCG攻毒试验进一步验证转基因小鼠中该突变介导的致病性，从而阐明该错义突变在播散性卡介病发病中的作用并初步探讨其机制，以期发现并验证新的播散性卡介菌病的致病基因突变，有助于对患者、胎儿及新生儿的早期筛查及干预。.本研究利用IL12RB1-/-小鼠模型，发现感染BCG后IL12RB1-/-小鼠肺和脾脏内BCG荷菌量显著高于野生型小鼠，且肺组织中IFN-和TNF-的表达显著下降，在脾脏中IFN-的表达水平下降，肺组织中IL-17的表达水平增加。这一结果提示IL12RB1基因敲除后削弱了机体IL-12/IFN-通路对BCG的细胞免疫应答，并且可能存在与IL-17相关的代偿机制。