Development of a Vaccine for HIVAIDS: Cellular Immunity

我们的艾滋病毒疫苗方法是基于携带艾滋病毒基因(S)的复制型腺病毒(Ad)载体的初始免疫，然后用艾滋病毒包膜蛋白加强免疫。Ad-HIV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的、持久的细胞免疫。我们已经证明，用Ad-HIV疫苗进行初始免疫也能刺激抗HIV抗体的产生。总而言之，这种疗法可以诱导强烈而持久的保护性反应。我们已经证明，将Ad-HIV疫苗注射到上呼吸道和肠道(通过口服免疫)会引起具有“归巢受体”的记忆T细胞，使它们进入肠道，肠道是HIV感染的主要部位。因此，疫苗方法在对预防或控制艾滋病毒感染至关重要的位置引起细胞免疫。我们正在探索在接种疫苗后检测归巢受体作为细胞粘膜免疫的替代标志。当进行大规模的临床疫苗试验时，这种替代品将是无价的。从如此大量的志愿者身上获取组织活检是不可能的，可以在血液样本上测量的替代标记物将在评估粘膜免疫反应的发展方面至关重要。目前，我们正在研究恒河猴模型中的几种替代免疫途径，包括直肠内、阴道内和舌下免疫。这些研究将确定哪一种在血液以及胃肠道和生殖器/直肠部位产生最佳免疫反应，因此应转化为未来的临床试验。天然免疫的关键效应细胞NK细胞的研究也在进行中，以阐明它们对Ad-HIV疫苗免疫的反应，以及它们与疫苗诱导的抗体在介导抗体依赖的细胞毒性和抗体依赖的细胞介导的病毒抑制等细胞杀伤功能方面的合作。研究表明，这些跨越先天免疫和获得性免疫的活动与免疫猕猴在病毒攻击后减少病毒血症有关。通过细胞内细胞因子染色和多色流式细胞术分析对多功能记忆T细胞的扩展分析也旨在改进疫苗设计。最后，我们建立了评估大量细胞因子和趋化因子分泌的方法学，以响应Ad-重组主蛋白/包膜蛋白Boost方案。这一分析将进一步阐明宿主对疫苗方案的反应，为继续优化疫苗策略提供必要的基本信息。

Our HIV vaccine approach is based on initial immunization with a replicating adenovirus (Ad) vector carrying an HIV gene(s) followed by a booster immunization with an HIV envelope protein. The Ad-HIV 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 shown that initial immunizations with an Ad-HIV vaccine also stimulates production of anti-HIV antibodies. Together, the regimen induces strong and durable protective responses. We have demonstrated that administration of Ad-HIV vaccine to the upper respiratory tract as well as to the gut (by oral immunization) elicits memory T cells that possess "homing receptors" leading them to traffic to the intestine, a prime site of HIV infection. Thus the vaccine approach elicits cellular immunity at a location critical for preventing or controlling HIV infection. We are exploring the detection of homing receptors following vaccination as surrogate markers of cellular mucosal immunity. Such surrogates will be invaluable when large scale clinical vaccine trials are carried out. It will not be possible to obtain tissue biopsies from such large numbers of volunteers, and surrogate markers that can be measured on blood samples will be critical in evaluating the development of mucosal immune responses. Currently, we are investigating several alternative immunization routes in a rhesus macaque model including intrarectal, intravaginal, and sublingual. These studies will determine which one elicits optimal immune responses in blood as well as at gastrointestinal and genital/rectal sites, and thus should be translated to future clinical trials. The study of NK cells, key effector cells of innate immunity, is also on-going in order to elucidate their response to Ad-HIV vaccine immunization and their cooperation with vaccine-elicited antibodies in mediating cell killing functions such as antibody-dependent cellular cytotoxicity and antibody-dependent cell mediated viral inhibition. Studies have shown that these activities that span innate and adaptive immunity are correlated with reduced viremia following viral challenge of immunized rhesus macaques. Expanded analyses of polyfunctional memory T cells by intracellular cytokine staining and multi-color flow cytometry analysis are also aimed at improving vaccine design. Finally, we have established methodology to evaluate secretion of a large panel of cytokines and chemokines in response to the Ad-recombinant prime/envelope protein boost regimen. This analysis will further elucidate the host response to the vaccine regimen, providing basic information essential for continued optimization of the vaccine strategy.