肠道共生菌与HESN人群HIV-1高暴露不易感的相关性及机制研究

AIDS epidemic in China was severe, especially in Guangxi province. The study on the mechanism of why highly exposed seronegative (HESN) population were not susceptible to HIV-1 will help to clarify the key factors affecting HIV-1 infection. Previous studies have found that human intestinal commensal bacteria were closely related with the development of HIV-1 infection in body. We hypothesize that the intestinal commensal bacteria could block the progression of HIV-1 infection in the intestinal tract and cause HESN. Base on the preliminary findings, the differences between HESN, HIV-1 infected and healthy groups will be examined, in terms of the composition and proportion of the intestinal commersal bacteria. Meanwhile, different types of intestinal commersal bacteria are isolated from HESN people and co-cultured with HIV-1 infected human intestinal lamina propria mononuclear cells (LPMCs), and the impact of the intestinal commersal bacteria on inflammation and HIV-1 replication will be assessed. Finally the association between intestinal commensal bacteria and HESN, as well as the involved mechanism will be examined and investigated. This is the first study to explore the influencing factors involved in HIV-1 infection, by means of intestinal commersal bacteria analysis. The finding of this study will help to elucidate the mechanism of why HESN population were not susceptible to HIV-1 and give a foundation to develop new approaches for HIV prevention.

我国特别是广西的艾滋病疫情形势严峻。对HIV高暴露持续血清阴性者（HESN）HIV-1不易感机制的研究将有助于阐明影响HIV-1感染的关键因素。研究表明人体肠道共生菌与HIV-1的感染发展有密切关系，其有可能在肠道阻断HIV-1感染的进展从而造成人体不易感。本课题在前期发现的基础上，通过比较HESN人群和HIV-1感染人群及正常人群肠道菌群的差异；同时筛选HESN人群肠道菌种，与感染HIV-1的人肠道固有层单核细胞（LPMCs）共培养，观察各肠道共生菌对人肠道免疫细胞炎症反应及HIV-1感染复制的影响，探讨其与HESN的相关性及作用机制。课题首次从肠道共生菌角度研究HIV-1感染的影响因素，研究结果有助于阐明HESN人群HIV-1不易感的机制，并有望据此开发HIV预防新技术。

我国特别是广西的艾滋病疫情形势严峻。基于HESN人群和HIV感染及正常人群免疫状态存在差异的前期发现，我们进行了流行病学横断面研究，以治疗佳/治疗不佳的HIV-1感染者、重症/非重症HIV-1感染者为实验组，以HIV阴性的健康者作为对照组，分析他们肠道菌群和菌群代谢物的差异及其与HIV感染的相关性。我们对研究对象的血液样本进行检测分析发现，重症HIV-1感染者菌学感染指标（EndoCAb IgM，sCD14）与非重症HIV-1感染者及健康对照者存在显著差异。重症HIV-1感染者和非重症HIV-1感染者的免疫细胞（CD4+T细胞，CD8+T细胞）的激活水平显著高于健康对照组。对粪便样本进行16s rRNA测序及代谢组学检测分析发现，重症HIV-1感染者和治疗不佳HIV-1的感染者的肠道菌群Alpha多样性显著低于非重症HIV-1感染者和健康对照者，且重症HIV-1感染者和治疗不佳的HIV-1感染者肠道菌群组成较非重症HIV-1感染者和健康对照者存在显著差异。在菌种水平，HIV-1感染者与健康对照者之间存在多种差异菌种。不同免疫及治疗状态下的HIV-1感染者的肠道代谢物的组成和浓度较健康对照者也存在显著差异。联合分析发现，不同免疫及治疗状态的HIV感染者中的肠道差异菌群、肠道代谢物与菌群移位、免疫活化指标间存在显著的相关性。通过体外细胞实验，我们发现差异菌Bacteroides plebius与感染了HIV-1 Bal病毒的PBMCs共培养后CD4+T细胞的免疫激活水平显著高于HIV Bal组和空白对照组，且共培养上清的HIV-1 p24浓度显著降低。上述结果表明，HIV-1感染改变了人体的肠道菌群及代谢物，HIV感染者的免疫状态是影响肠道菌群稳态的重要因素，其中的差异细菌可能对HIV-1感染的发生发展具有促进或抑制作用，从而为后续研究奠定了重要基础。