Development of a Vaccine for HIVAIDS: Cellular Immunity

我们的HIV疫苗策略使用携带HIV/SIV基因的复制型腺病毒（Ad）载体进行初始免疫，随后使用HIV/SIV包膜蛋白进行加强免疫。载体疫苗在粘膜诱导位点的上皮细胞中复制，从而在粘膜效应位点以及血液中引发强烈、持久的细胞免疫。我们比较了粘膜免疫途径，以评估复制载体的生物分布、其在宿主中的持久性以及其引发全身和粘膜免疫反应的能力。使用SIV恒河猴模型，我们发现用复制能力的Ad-SIV重组体免疫，无论免疫途径（舌下、鼻内/直肠内、阴道内或直肠内）如何，导致插入基因首先在肺和直肠组织中的巨噬细胞中表达，随后在肺的髓样树突状细胞中表达，在免疫后25周在直肠组织中持续表达。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。我们还在评估基于达特和包膜的疫苗的研究中显示，复制型Ad载体激发一系列细胞因子/趋化因子应答，这有助于引发适应性免疫应答。它们不受插入基因的影响。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。最近，我们报道了一项使用SIV感染的恒河猴的研究，并显示在恒河猴PBMC的Gag刺激后，NK细胞应答在SIV对照动物中诱导，但在非对照动物中不诱导。这些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。NK细胞活化被抗IL-2中和抗体阻断，并通过消除GAG特异性应答的CD 4 + T细胞耗竭来阻断。在组织驻留细胞中，脾脏和循环NK细胞显示出相似的活化特征，而肝脏和粘膜NK细胞显示出降低的活化特征，在SIV控制和非控制猕猴中相似。通过药物介导的病毒血症控制，在SIV非控制猕猴中挽救了T细胞依赖性NK细胞功能的缺乏。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。

Our HIV vaccine strategy uses an initial immunization with a replicating adenovirus (Ad) vector carrying an HIV/SIV gene(s) followed by a booster immunization with an HIV/SIV envelope protein. The vectored vaccine replicates in epithelial cells that line mucosal inductive sites, thus eliciting strong, persistent cellular immunity at mucosal effector sites as well as in the blood. We have compared mucosal immunization routes to evaluate the biodistribution of the replicating vector, its persistence in the host, and its ability to elicit both systemic and mucosal immune responses. Using the SIV rhesus macaque model, we found that immunization with replication-competent Ad-SIV recombinants, regardless of the immunization route (either sublingual, intranasal/intratracheal, intravaginal, or intrarectal) led to expression of inserted genes first in macrophages in lung and rectal tissue, and subsequently in myeloid dendritic cells of the lung, with persistent expression 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 in a study evaluating vaccines based on Tat and Envelope, that the replicating Ad vector elicits a spectrum of cytokine/chemokine responses, which contribute to elicitation of the adaptive immune responses. These are unaffected by the inserted genes. 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. Recently we reported a study using SIV-infected rhesus macaques, and showed upon Gag stimulation of macaque PBMCs, NK cell responses were induced in SIV-controlling, but not non-controlling animals. These NK cell responses were dependent on antigen-specific IL-2 production by CD4+ central memory T cells. The NK cell activation was blocked by anti-IL-2 neutralizing antibody and by CD4+ T cell depletion which abrogated the Gag-specific responses. Among tissue-resident cells, splenic and circulatory NK cells displayed similar activation profiles, whereas liver and mucosal NK cells displayed a decreased activation profile, similar in SIV controlling and non-controlling macaques. Lack of T cell-dependent NK cell function was rescued in SIV non-controlling macaques through drug-mediated control of viremia. 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.