从RLR/MAVS通路调节胸腺功能探讨HNA-1促进艾滋病免疫重建的作用机制

Improving the thymopoiesis and immune reconstitution is an important complementary therapy for HIV-1 infection. Although IL-7, IL-15 and some other potential agents are in development, none of them has been validated by clinical trial. HNA-1, a Chinese herb preparation owned patent by the research group, has exhibited clinical effect in past ten years. We also evaluated its effect on cyclosporine A induced immunodeficiency in mouse and simian immunodeficiency virus infection in reshus monkeys. With both models, it increased the naïve CD4 significantly. Thereafter, we proved that HNA-1 was capable of augmenting the homing of CD34+ progenitor cell to thymus, prompting the development of thymocytes and increasing the thymic output through uncertain mechanisms, which is probably mediated by retinoic acid-inducible gene I (RIG-I) like receptors and mitochondrial antiviral signaling protein (MAVS) contributed signal pathway. In this study, we aimed to investigate the effects of HNA-1 on immune reconstitution of chronical SIV infected monkeys under HAART treatment, on thymus atrophy caused by acute SIV infection, and on thymus atrophy induced by poly(I:C)in adult and aged mice. The role of “RLR—MAVS” signal pathway in HNA-1’s protective effect will also be explored simultaneously. This study will extend our knowledge on the regulation of thymocytes developmen, reveal the underlying mechanisms of HNA-1 clinical effect, and prompt the development of agents targeting thymopoiesis and CD4 reconstitution.

提高胸腺功能、促进免疫重建是艾滋病治疗的重要策略。虽然该领域已有IL-7、IL-15等多种有潜力的药物正在研制，但尚无成熟方案。HNA-1为课题组专利中药，临床应用十年来疗效满意；前期在小鼠免疫缺陷模型和猴艾滋病模型上均证实该药能显著提高初始型CD4+T细胞水平，且已初步证明其可促进CD34+细胞归巢到胸腺、促进胸腺细胞分化及提高胸腺输出，提示其机制与调节胸腺基质细胞的视黄酸诱导基因蛋白I样受体（RLR）/线粒体抗病毒信号蛋白（MAVS）通路有关。本项目拟从RLR/MAVS信号通路探讨HNA-1对HAART治疗慢性SIV感染免疫重建的促进作用、对急性SIV感染胸腺退化的调节作用和对poly(I:C)诱导的成年及老年小鼠胸腺退化的保护作用。研究结果将首次从RLR/MAVS信号通路介导胸腺细胞发育调节的角度阐明HNA-1的疗效机制，为艾滋病中药研发提供重要的实验依据。

前期研究发现，中药复方HNA-1有助于提高SIV感染猴外周血初始型CD4的数量，且影响到胸腺基质细胞的比例。而本项目试图阐释HNA-1是否通过RLR/MAVS通路调节胸腺细胞的发育、增加初始型CD4的数量。因此本研究分为4个部分：1) 比较地塞米松（DEX）、聚肌胞苷酸Poly(I:C)诱导的胸腺萎缩，探讨了RIG-I/MAVS/I型IFN的表达情况，并观察HNA-1疗效及机制。2) 通过对精英控制（EC）型SIV感染猴进行免疫学分析，探讨RIG-I/MAVS/I型IFN通路是否与SIV感染后的免疫学控制有关。3)开展HNA-1联用HAART治疗慢性SIV感染的中国恒河猴的实验研究；4) 观察HNA-1对急性SIV感染中国恒河猴的影响。给药7天后再感染，分析不同时间点各指标的变化。结果发现，HNA-1可明显抑制DEX诱导的小鼠胸腺萎缩以及胸腺RLR/Ⅰ型干扰素的活化。EC型SIV猴的NLRX1高表达、RIG-I/Ⅰ型干扰素低表达，NF-κB信号通路被抑制、IL-1β较低、CD4的增殖与活化较低，提示RIG-I、NF-κB通路活化较低，可能是保护机制。HNA-1联用HAART治疗SIV慢性感染猴，初始型CD4的小幅增加，脾、淋巴结套层的细胞更为致密，提示HNA-1对CD4的影响的部位也发生于胸腺以外。而在给予HNA-1后再感染SIV的研究中，HNA-1增强RIG-I、MAVS、IRF3/IRF7和抗病毒蛋白MxA的表达，提示HNA-1对于SIV急性感染，有增强RIG-I- MAVS- IRF3/IRF7- IFN的作用。另外，HNA-1降低了IκBα、p65、p-IκBα，有可能抑制NF-κB介导的生物过程。HNA-1还显著增加了血浆IL-1RA的水平、G-CSF也有增高的趋势，可能也是HNA-1的疗效机制。因此得出结论：本研究不仅发现HNA-1可有效对抗DEX引起的小鼠RIG-I/IFN-α/β活化及胸腺萎缩，还阐释了HNA-1对SIV感染恒河猴RIG-I/MAVS/I型IFN通路的影响，提示HNA-1可以在一定程度上提高I型IFN介导的抗病毒免疫能力。此外，HNA-1对NF-κB信号通路的抑制有可能通过抑制炎症发挥保护作用。至于HNA-1对I型IFN的影响在DEX和SIV感染的情况下完全不同，推测与线粒体ROS参与的TLR与RLＲ的互作有关，拟在下一步研究中探讨。