Development of a Vaccine for HIVAIDS: Cellular Immunity

我们正在寻求基于可复制腺病毒（Ad）重组体的HIV疫苗方法。其理由是，减毒活疫苗在历史上一直是最具保护性的，基本上可以引发终身免疫。例如天花、小儿麻痹症、麻疹和黄热病的疫苗。我们在恒河猴中进行临床前疫苗研究，并用SIV进行挑战，SIV是一种适当模拟人类HIV感染的系统。我们使用初免-加强策略，首先用携带HIV/SIV基因的复制型腺病毒（Ad）载体免疫，然后用HIV/SIV包膜蛋白加强。腺病毒在粘膜诱导位点的上皮细胞中复制，并在粘膜效应位点和血液中激发强而持久的细胞免疫。一项评估复制载体生物分布的研究表明，无论免疫途径（舌下、鼻内/鼻内、阴道内或直肠内）如何，插入载体的基因在肺和直肠组织的巨噬细胞中表达，随后在肺的髓样树突细胞中表达。表达在直肠组织中持续至免疫后25周。这种对巨噬细胞和专职抗原呈递细胞的靶向以及持续表达提供了强免疫原性，包括全身性和粘膜性。与相似的生物分布一致，通过所有粘膜免疫途径引起了相当的SIV特异性免疫。我们还表明，复制的Ad载体激发一系列细胞因子/趋化因子反应，这有助于激发适应性免疫。此外，由于非中和抗体反应已被证明是保护功效的贡献者，我们已经进行了介导这些反应中的一些的效应细胞的研究。在本年度报告所涵盖的时期内，我们发现，在SIV感染的恒河猴的外周血单核细胞的GAG刺激后，在控制SIV感染的动物中诱导了NK细胞反应，但在未控制SIV感染的恒河猴中没有诱导NK细胞反应。发现NK细胞应答依赖于CD 4+中央记忆T细胞的抗原特异性IL-2产生。这些结果表明，SIV控制猕猴的疾病进展的控制与抗原特异性CD 4 + T细胞和NK细胞效应功能之间的合作有关，并强调了这种细胞间合作在适应性免疫中的重要性。目前的研究正在评估接受治疗的猕猴的这种合作互动。我们还评估了用靶向表达高水平PD-1的细胞的新型药物治疗的SIV感染猕猴中的免疫调节作用。SIV感染期间PD-1的高水平T细胞表达与受损的增殖和功能相关。我们发现，在抗逆转录病毒治疗期间和治疗后持续免疫调节PD-1hi细胞有助于维持较低的病毒血症和有利的T细胞/Treg库，同时调节抗原特异性应答。

We are pursuing an HIV vaccine approach based on replication-competent Adenovirus (Ad)-recombinants. The rationale is based on the fact that live attenuated vaccines historically have been the most protective, eliciting essentially life-long immunity. Examples include vaccines for small pox, polio, measles, and yellow fever. We conduct pre-clinical vaccine studies in rhesus macaques and challenge with SIV, a system that appropriately models HIV-infection of humans. We use a prime-boost strategy, first immunizing with a replicating adenovirus (Ad) vector carrying an HIV/SIV gene(s) followed by a boosting with HIV/SIV envelope protein. Ad replicates in epithelial cells that line mucosal inductive sites, and elicits strong, persistent cellular immunity at mucosal effector sites as well as in the blood. A study evaluating the biodistribution of the replicating vector showed that regardless of the immunization route (sublingual, intranasal/intratracheal, intravaginal, or intrarectal), genes inserted into the vector were expressed in macrophages in lung and rectal tissue, and subsequently in myeloid dendritic cells of the lung. Expression persisted in rectal tissue up to 25 weeks post-immunization. This targeting of macrophages and professional antigen presenting cells and the persistent expression provide potent immunogenicity, both systemically and mucosally. In line with the similar biodistribution, comparable SIV-specific immunity was elicited by all mucosal immunization routes. We have also shown that the replicating Ad vector elicits a spectrum of cytokine/chemokine responses, which contribute to elicitation of adaptive immunity. Additionally, because non-neutralizing antibody responses have been shown to be contributors to protective efficacy, we have undertaken studies of effector cells which mediate some of these responses. During the period covered by this annual report we showed that following Gag-stimulation of peripheral blood mononuclear cells of SIV-infected rhesus macaques, NK cell responses were induced in animals that controlled SIV infection but not in macaques that did not. The NK cell responses were found to be dependent on antigen-specific IL-2 production by CD4+ central memory T cells. These results suggest that control of disease progression in SIV controlling macaques is associated with co-operation between antigen-specific CD4+ T cells and NK cell effector function and highlight the importance of such cell-to-cell cooperation in adaptive immunity. Current studies are evaluating this co-operative interaction in macaques undergoing treatment. We have also evaluated the effects of immune modulation in SIV infected macaques treated with a novel drug that targets cells expressing high levels of PD-1. High-level T-cell expression of PD-1 during SIV infection is correlated with impaired proliferation and function. We found that continued immune modulation targeting PD-1hi cells during and post-anti-retroviral therapy helped maintain lower viremia and a favorable T-cell/Treg repertoire, while modulating antigen-specific responses.