Development of a Vaccine for HIVAIDS: Cellular Immunity

我们的艾滋病毒疫苗策略使用携带艾滋病毒/SIV基因(S)的复制型腺病毒(Ad)载体进行初始免疫，然后用艾滋病毒/SIV包膜蛋白加强免疫。载体疫苗在黏膜诱导部位的上皮细胞中复制，从而在粘膜效应部位和血液中激发强大、持久的细胞免疫。我们比较了黏膜免疫途径，以评估复制载体的生物分布，它在宿主中的持久性，以及它引发全身和粘膜免疫反应的能力。利用SIV猕猴模型，我们发现无论免疫途径(舌下、鼻腔/气管内、阴道内或直肠内)，具有复制能力的Ad-SIV重组体免疫后，插入基因首先在肺和直肠组织的巨噬细胞中表达，然后在肺的髓系树突状细胞中表达，并在直肠组织中持续表达至25周。这种针对巨噬细胞和专业抗原提呈细胞的靶向和持续表达提供了强大的免疫原性，无论是在系统还是在粘膜上。根据相似的生物分布，所有粘膜免疫途径均可诱导类似的SIV特异性免疫。我们还在一项基于TAT和包膜的疫苗评估研究中表明，复制的Ad载体诱导了一系列细胞因子/趋化因子反应，这些反应有助于激发适应性免疫反应。这些基因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性疗效的贡献者，我们对介导其中一些反应的效应细胞进行了研究。最近，我们报道了一项用感染SIV的恒河猴进行的研究，结果表明，SIV对照组猕猴PBMCs在GAG刺激下可诱导NK细胞反应，而非SIV对照组恒河猴则不能。这些NK细胞反应依赖于由CD4+中央记忆T细胞产生的抗原特异性IL-2。NK细胞活化可被抗IL-2中和抗体所阻断，也可被CD4+T细胞耗竭所阻断，从而阻断GAG特异性应答。在组织驻留细胞中，脾和循环中的NK细胞表现出相似的激活谱，而肝脏和粘膜中的NK细胞表现出降低的激活谱，在SIV控制组和非控制组猕猴中相似。通过药物介导的病毒血症控制，SIV非控制性猕猴缺乏T细胞依赖的NK细胞功能。这些结果表明，在控制SIV的猕猴中，疾病进展的控制与抗原特异性CD4+T细胞和NK细胞效应器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.