IFN-λ抑制IFN-γ抗类鼻疽伯克霍尔德菌感染机制研究

Acute melioidosis pneumonia caused by Burkholderia pseudomallei infection is the most common form of melioidosis infection in Hainan, and is associated with high misdiagnosis rate and mortality; however, its pathogenesis remains unclear. In our preliminary study, it was observed that IFN-λ could enhance B. pseudomallei infection, which is related to the inhibitory action of IFN-λ on IFN-γ-mediated anti-B. pseudomallei effect. In this study, based on our preliminary study results, in-vivo and in-vitro experiments will be performed in cells and mice with IFN-λ receptor deficiency, in an attempt to clarify the specific mechanism underlying the inhibitory action of IFN-λ on IFN-γ-mediated anti-B.pseudomallei effect. The premonitory value of IFN-λ and vitamin D metabolites for acute melioidosis pneumonia with different prognosis will be explored. The key effector molecules in the inhibitory action of IFN-λ on IFN-γ will be screened to establish the signaling regulatory network. This study is expected to further elucidate the mutual regulatory mechanism of type II and type III interferons, as well as the role of IFN-λ in B.pseudomallei infection, so as to provide evidence for further translational medical studies.

类鼻疽伯克霍尔德菌感染导致的急性类鼻疽肺炎是海南地区最常见的类鼻疽感染形式，误诊率和病死率较高，但发病机制不明。前期我们研究发现IFN-λ可增强类鼻疽伯克霍尔德菌感染，其作用与抑制IFN-γ介导的抗类鼻疽伯克霍尔德菌感染效应有关。本项目在前期工作基础上，拟利用IFN-λ受体缺陷型细胞及小鼠通过体内外实验，明确IFN-λ抑制IFN-γ介导抗类鼻疽伯克霍尔德菌感染效应的具体机制。探讨IFN-λ及维生素D代谢产物在不同预后急性类鼻疽肺炎的预警价值。筛选IFN-λ抑制IFN-γ关键效应分子，建立信号调控网络。本课题的实施有助于阐明Ⅱ、Ⅲ型干扰素间相互调控机制；明确IFN-λ在类鼻疽伯克霍尔德菌感染中的作用，为后续转化医学研究奠定基础。

在本研究中，我们对IFN-γ和IFN-λ调控经维生素D介导的抗菌肽cathelicidin(CAMP)、β-defensin2(DEFB4)表达在HCC827细胞抵抗类鼻疽伯克霍尔德菌（Burkholderia pseudomallei，B.p）感染中的效果进行了评估。经研究发现，B.p感染细胞后，可降低抗菌肽CAMP、DEFB4产生水平，从而有效感染HCC827细胞。而1,25(OH)2D3、IFN-γ可上调维生素D介导的抗菌肽产生途径中关键基因VDR，及CAMP、DEFB4表达效率，从而促进细胞对B.p感染的抵抗。IFN-λ的存在，有助于B.p对HCC827细胞的感染，该作用的发挥，主要通过降低维生素D代谢途径中关键基因VDR和CAMP、DEFB4表达水平完成。将IFN-λ特异性受体IFNLR1敲低后，HCC827细胞株的VDR、CAMP、DEFB4表达水平回调，B.p感染水平降低。在B.p感染的IFNLR1-/-HCC827细胞株中加入1,25(OH)2D3，细胞抵抗B.p感染能力较HCC827细胞野生株明显增强。另外,相比于正常人，B.p感染者体内IFN-λ水平明显增高。本项目的研究使我们认识到，IFN-γ和IFN-λ在B.p这一兼性胞内寄生菌感染中，从抵抗与促进感染不同方面发挥了作用，这丰富了我们对干扰素家族成员生物学功能的认知。同时对B.p感染中维生素D介导的抗菌肽所发挥作用也有了较为深入的了解。IFN-λ可能作为B.p感染鉴别诊断标志物，具有一定的应用前景。