猪肺炎支原体和PRRSV共感染激活IL-1β的分子机制及其生物学意义

Porcine respiratory disease complex (PRDC) is one of the most economically important diseases of the global swine industry. Mycoplasma hyopneumoniae (Mhp) and porcine reproductive and respiratory syndrome virus (PRRSV) are two of the most common pathogens isolated from pigs exhibiting PRDC. The previously studies indicated that there were the interaction and synergism between these two pathogens. However, the molecular mechanism of pathogenesis was not yet clear. In the youth fund of National Nature Science Foundation of China, our study showed the changes of the host gene expression profile after co-infections of Mhp and PRRSV, and found the inflammatory factor IL-1β in the center of co-infection interaction network. It revealed that the IL-1β is a key factor of collaborative pathogenic in co-infections of Mhp and PRRSV. In this project, we will research the role and mechanism of IL-1β in the co-infection of Mhp and PRRSV, include (i) the signal pathway of activate IL-1β in the single infection and co-infection; (ii) identify the Mhp and PRRSV proteins responsible for IL-1β activation; (iii) explain the interaction mechanisms of Mhp and PRRSV at the molecular level; (iiii)determine the impact of activate IL-1β on PRRSV proliferation, Mhp adhesion and inflammatory factor expression. The study will reveal the biology significance of IL-1β in the co-infection of Mhp and PRRSV. The new knowledge gained will provide the scientific basis for effective prevention and control.

猪呼吸道疾病综合症是危害全球养猪业生产最重要的疾病之一，其病原非常复杂，其中猪肺炎支原体（Mhp）和猪繁殖与呼吸综合征病毒（PRRSV）被认为是该病最主要的病原。研究证明这两种病原之间存在相互作用和协同致病，但是其协同致病的分子机制尚不清楚。在青年基金资助下，我们揭示了混合感染后宿主基因表达谱的变化，发现了以炎症因子IL-1β为中心的共感染互作网络，明确了IL-1β是Mhp和PRRSV协同致病的关键因子。本项目拟进一步开展IL-1β在Mhp和PRRSV协同致病中的作用与机制研究，比较单独感染和共感染激活IL-1β信号通路的异同，挖掘参与IL-1β激活的Mhp和PRRSV编码蛋白，解析两者在分子水平上互作的机制，揭示IL-1β产生对PRRSV增殖、Mhp黏附及炎症因子表达的影响，阐明IL-1β在两者共感染中的生物学意义，为有效预防和控制Mhp和PRRSV混合感染的发生与流行提供科学依据。

IL-1β是一种主要由单核细胞、巨噬细胞和淋巴细胞产生的促炎性细胞因子，是机体调节免疫和炎症反应的中心介质，能介导多种炎症反应, 诱导致炎性细胞因子的基因表达及其分泌，在炎性疾病的致病中扮演着十分重要的角色。本项目的前期研究发现，促炎症因子IL-1β的表达在Mhp和PRRSV混合感染及协同致病中扮演着十分重要的角色，因此推测这可能是混合感染导致炎症加重、病程延长的机制之一。本项目利用Mhp和PRRSV混合感染PAM细胞的感染模型，发现Mhp和PRRSV感染激活IL-1β mRNA水平的表达和蛋白分泌，发现两者共用TLR4信号级联及其下游的信号通路NF-κB，ERK1/2和p38 MAPK参与激活IL-1β，诱导更高水平的IL-1β产生，从而产生较强的炎症反应，解释了临床上两者的协同致病的分子机理。此外，本研究还分析了混合感染诱导IL-1β产生的生物学意义。通过IL-1β纯化蛋白及其中和性抗体处理PAM细胞后发现，IL-1β对Mhp和PRRSV的增殖无明显影响，但其中和性抗体能够抑制Mhp和PRRSV激活其他的促炎性因子的表达，说明IL-1β在Mhp和PRRSV诱导炎症反应中处于主导地位。本项目的结果进一步明确了IL-1β在两者协同致病中扮演着重要的角色，有利于更深入地了解Mhp和PRRSV混合感染的致病机理和免疫机制，为有效控制Mhp和PRRSV混合感染的发生与流行提供了科学依据。