Development of a Vaccine for HIVAIDS: Cellular Immunity

我们的HIV疫苗策略使用携带HIV/SIV基因的复制腺病毒（Ad）载体进行初始免疫，然后使用HIV/SIV包膜蛋白进行加强免疫。载体疫苗在粘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引发强烈、持续的细胞免疫。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。利用SIV恒河猴模型，我们发现，无论免疫途径如何（舌下、鼻内/气管内、阴道内或直肠内），用具有复制能力的Ad-SIV重组体进行免疫，都会导致插入基因首先在肺和直肠组织的巨噬细胞中表达，随后在肺骨髓树突状细胞中表达，并在免疫后25周在直肠组织中持续表达。这种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，无论是在系统上还是在粘膜上。与相似的生物分布一致，所有粘膜免疫途径均可引起相似的siv特异性免疫。我们还在一项评估基于Tat和Envelope的疫苗的研究中表明，复制的Ad载体引发了一系列细胞因子/趋化因子反应，这些反应有助于引发适应性免疫反应。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，我们已经对介导这些反应的效应细胞进行了研究。最近，我们报道了一项用siv感染的恒河猴进行的研究，结果表明，当Gag刺激猕猴PBMCs时，在siv控制的动物中诱导了NK细胞反应，而在非siv控制的动物中则没有。这些NK细胞反应依赖于CD4+中枢记忆T细胞产生抗原特异性IL-2。抗il -2中和抗体和CD4+ T细胞耗竭可阻断NK细胞的活化，从而消除gag特异性反应。在组织驻留细胞中，脾脏和循环NK细胞表现出相似的激活谱，而肝脏和粘膜NK细胞表现出降低的激活谱，这在SIV控制和非控制的猕猴中相似。通过药物介导的病毒血症控制，SIV非控制猕猴中缺乏T细胞依赖的NK细胞功能得以恢复。这些结果表明，SIV控制猕猴的疾病进展控制与抗原特异性CD4+ 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.