Preventive and therapeutic T cell vaccines to mitigate HIV-1 replication; Preven

直接证据表明，Abs和CD8+T细胞均参与限制猴免疫缺陷病毒(SIV)的复制。然而，就CD4+T细胞而言，很难确定它们的作用，因为它们也是病毒感染的目标。SIVmac251感染猕猴是评估这些问题的一个很好的模型。由于预防性接种T细胞疫苗可以改善病毒攻击后的病毒学结果，我们探索了在已经接受抗逆转录病毒治疗(ART)的感染猕猴中增强病毒特异性免疫反应的策略。我们证明，CTLA-4阻断降低了SIVmac251感染猕猴组织中转化生长因子-β、IDO和病毒RNA的表达。调节性T细胞(Treg)是CD25+CD4+T细胞的一个亚群，它能表达高水平的细胞毒性T淋巴细胞抗原-4(CTLA-4)，并抑制T细胞的激活和效应功能。感染艾滋病毒-1的个体和感染猴免疫缺陷病毒(SIVmac251)的猕猴组织中的Treg细胞增加。在HIV-1感染中，Treg细胞可以发挥截然不同的作用：它们可能通过降低免疫激活来限制病毒复制，或者可能通过抑制病毒特异性免疫反应来增加病毒复制。因此，在HIV/SIV中阻断Treg功能的结果应该得到实证检验。我们证明，CD25+T细胞抑制了SIV感染猕猴血液和淋巴结中培养的T细胞中的病毒特异性T细胞反应。我们研究了使用抗CTLA-4人抗体MDX-010阻断CTLA-4对接受抗逆转录病毒治疗(ART)的SIV感染猕猴的影响。CTLA-4阻断可降低组织中色氨酸消耗酶IDO的表达和抑制细胞因子转化生长因子-β(TGF-β)的水平。阻断CTLA-4与淋巴结中病毒RNA水平降低以及SIV特异性CD4+和CD8+T细胞的效应器功能增强有关。因此，钝化SIV感染猕猴的Treg功能不会对病毒学产生不利影响，并可能为补充ART和治疗性疫苗治疗HIV-1感染提供一种有价值的途径。急性HIV/SIV感染导致淋巴间隔内严重的CD4+T细胞耗尽。在慢性感染阶段，即使病毒复制被ART抑制，血液中的CD4+T细胞数量也会反弹，但在肠道相关淋巴组织(GALT)中仍保持较低水平。因此，重新填充淋巴室的策略可能会改善HIV/SIV感染的临床结果。白细胞介素7(IL-7)是维持T细胞内稳态增殖的关键细胞因子。在HIV/SIV感染中，IL-7的表达增加，可能弥补T细胞的损失，这表明IL-7的超生理给药可能提供额外的好处。然而，T细胞对IL-7的反应能力取决于体内不同部位T细胞中IL-7受体(IL-7R)的表达水平。我们研究了健康猕猴和感染SIV的猕猴血液、脾、肠道和泌尿生殖道中IL-7R+T细胞的比例，这些猕猴有不同程度的CD4+T细胞耗竭。我们发现，在SIV感染的猕猴中，表达IL-7R的T细胞在CD4+和CD8+T细胞亚群中的百分比明显低于健康动物，并且这种下降与CD4+T细胞数量直接相关。重要的是，血液中表达IL-7R的CD4+和CD8+T细胞比例与组织中发现的比例相当。SIV特异性CD8+T细胞内的IL-7R+T细胞变化较大，在病毒期猕猴的大部分组织中最低，可能反映了效应细胞的持续抗原刺激。我们发现，在感染SIVmac251的猕猴中，IL-15可以消除疫苗诱导的病毒水平的下降。HIV感染中的CD4+T细胞丢失和CD8+T细胞功能受损提示，IL-7和IL-15这两种细胞因子的药物治疗可能是有益的，这两种细胞因子可以促进T细胞的稳态增殖，改善效应器功能。然而，这些细胞因子也可能对HIV-1感染者产生不利影响，因为这两种细胞因子都会在体外增加HIV的复制。我们评估了IL-7和IL-15治疗对感染SIVmac251的猕猴(猕猴)的病毒复制和活痘病毒疫苗免疫原性的影响。两种细胞因子都没有增加疫苗扩增的CD4+或CD8+记忆T细胞的频率，也没有增加SIV特异性CD8+T细胞池的克隆性募集，也没有增加CD8+T细胞的功能。在抗逆转录病毒治疗暂停后，单独接种疫苗会暂时降低病毒的设定点。IL-15诱导了CD4+效应T细胞的大量增殖，并使疫苗接种后降低定点病毒血症的能力丧失。相反，IL-7既不能增强也不能降低疫苗效果，而且与转化生长因子-β的表达降低有关。这些结果强调了在体内测试免疫调节方法以评估HIV-1感染者的潜在风险和好处的重要性。多年来，我们的临床前数据为人体试验的启动和继续提供了原则证据。基于ALVAC-HIV的候选疫苗目前正在泰国成人身上进行第三阶段试验，乌干达正在准备一项针对新生儿的第一阶段试验。DNA和NYVAC-HIV的组合将由EuroVac在健康志愿者身上进行测试。最后，ALVAC-HIV的I期和II期治疗试验正在几个地点进行，我计划在美国进行NYVAC-HIV的I期治疗试验

Direct evidence indicates that both Abs and CD8+ T cells contribute to restriction of simian immunodeficiency virus (SIV) replication. In the case of CD4+ T cells, however, it has been difficult to ascertain their contribution as they are also the target for viral infection. SIVmac251 infection of macaques is an excellent model whereby to assess these questions. As preventive vaccination with T cell vaccines ameliorates the virological outcome following viral challenge, we explored strategies to augment virus-specific immune responses in already infected macaques treated with antiretroviral therapy (ART). We demonstrated that CTLA-4 blockade decreases TGF-beta, IDO, and viral RNA expression in tissues of SIVmac251-infected macaques. Regulatory T (Treg) cells are a subset of CD25+CD4+ T cells that constitutively express high levels of cytotoxic T lymphocyte antigen-4 (CTLA-4) and suppress T-cell activation and effector functions. Treg cells are increased in tissues of individuals infected with HIV-1 and macaques infected with simian immunodeficiency virus (SIVmac251). In HIV-1 infection, Treg cells could exert contrasting effects: they may limit viral replication by decreasing immune activation, or they may increase viral replication by suppressing virusspecific immune response. Thus, the outcome of blocking Treg function in HIV/SIV should be empirically tested. We demonstrated that CD25+ T cells inhibit virus-specific T-cell responses in cultured T cells from blood and lymph nodes of SIV-infected macaques. We investigated the impact of CTLA-4 blockade using the anti-CTLA-4 human antibody MDX-010 in SIV-infected macaques treated with antiretroviral therapy (ART). CTLA-4 blockade decreased expression of the tryptophan-depleting enzyme IDO and the level of the suppressive cytokine transforming growth factor-beta (TGF-beta) in tissues. CTLA-4 blockade was associated with decreased viral RNA levels in lymph nodes and an increase in the effector function of both SIV-specific CD4+ and CD8+ T cells. Therefore, blunting Treg function in macaques infected with SIV did not have detrimental virologic effects and may provide a valuable approach to complement ART and therapeutic vaccination in the treatment of HIV-1 infection. Acute HIV/SIV infection results in severe CD4+ T cell depletion in lymphoid compartments. During the chronic phase of infection, CD4+ T cell numbers rebound in blood but remain low in the gut-associated lymphoid tissue (GALT), even when viral replication is suppressed by ART. Thus, strategies to repopulate lymphoid compartments may ameliorate the clinical outcome of HIV/SIV infection. Interleukin (IL)-7 is a key cytokine for the maintenance of homeostatic proliferation of T cells. In HIV/SIV infection, IL-7 expression is increased, likely to compensate for T cell loss, suggesting that supraphysiological administration of IL-7 could provide additional benefit. However, the ability of T cells to respond to IL-7 is dependent on the level of expression of the IL-7 receptor (IL-7R) in T cells in various body compartments. We investigated the proportion of IL-7R+ T cells in blood, spleen, gut, and genitourinary tract of healthy and SIV-infected macaques with various degrees of CD4+ T cell depletion. We found that the percentage of T cells expressing IL-7R was significantly lower in both CD4+ and CD8+ T cell subsets in SIV-infected macaques than in healthy animals and this decrease directly correlated with the CD4+ T cell number. Importantly, the proportion of CD4+ and CD8+ T cells expressing IL-7R in blood paralleled that found in tissues. IL-7R+ T cells within the SIV-specific CD8+ T cells varied and were lowest in most tissues of viremic macaques, likely reflecting continuous antigen stimulation of effector cells. We showed that IL-15 abrogates vaccine-induced decrease in virus level in SIVmac251-infected macaques. The loss of CD4+ T cells and the impairment of CD8+ T cell function in HIV infection suggest that pharmacological treatment with IL-7 and IL-15, cytokines that increase the homeostatic proliferation of T cells and improve effector function, may be beneficial. However, these cytokines could also have a detrimental effect in HIV-1-infected individuals, because both cytokines increase HIV replication in vitro. We assessed the impact of IL-7 and IL-15 treatment on viral replication and the immunogenicity of live poxvirus vaccines in SIVmac251-infected macaques (Macaca mulatta). Neither cytokine augmented the frequency of vaccine-expanded CD4+ or CD8+ memory T cells, clonal recruitment to the SIV-specific CD8+ T cell pool, or CD8+ T cell function. Vaccination alone transiently decreased the viral set point following antiretroviral therapy suspension. IL-15 induced massive proliferation of CD4+ effector T cells and abrogated the ability of vaccination to decrease set point viremia. In contrast, IL-7 neither augmented nor decreased the vaccine effect and was associated with a decrease in TGF-beta expression. These results underscore the importance of testing immunomodulatory approaches in vivo to assess potential risks and benefits for HIV-1-infected individuals. Over the years, our preclinical data provided proof of principle for the initiation and continuation of human trials. ALVAC-HIV-based vaccine candidates are now in a phase III trial in adults in Thailand and a phase I trial in neonates in Uganda is being prepared. The combination of DNA plus NYVAC-HIV will be tested by EuroVac in healthy volunteers. Lastly, therapeutic phase I and II trials with ALVAC-HIV are ongoing at several sites and I plan to perform a phase I therapeutic trial with NYVAC-HIV in the U.S