Alpha Emitter Labeled Anti-T Cell Antibody: Targeting Latent HIV Infected Cells

 描述：在大多数患者中，通过联合抗逆转录病毒治疗(ART)可以控制HIV-1感染。即使在长期完全抑制ART的情况下，病毒载量在停药后的几周到几个月内也会增加。重新出现的HIV-1的来源主要是记忆性的CD4+T细胞，这些细胞含有复制能力强但转录沉默的亲病毒DNA。消除这种潜伏的艾滋病毒-1宿主是治愈艾滋病毒-1感染的主要障碍。通过刺激潜伏感染细胞中的HIV-1复制来根除潜伏库的策略，或者通过药物诱导的激活 病毒转录或细胞因子诱导的CD4+细胞周转加速，已取得有限的成功。另一种策略是直接瞄准并杀死潜伏感染的细胞。我们假设，记忆的CD4+细胞可以被单抗(MAb)靶向，并以阿尔法发射体的形式被辐射杀死，而不会对患者产生不必要的毒性。我们进一步假设，放射性标记的单抗耗尽记忆的CD4+细胞，然后采取措施在反弹增殖期间保护CD4+细胞，将大大缩短ART的持续时间，并实现灭菌治疗。在这里，我们建议开发放射性标记的单抗，并研究其在非人类灵长类动物中的疗效和毒性。我们提出了两种靶向策略，一种是消耗包括所有记忆CD4+亚群的CD4+细胞，另一种是广泛靶向CD3+细胞，这可能会导致更大的CD4+细胞消耗，我们已经在犬模型中证明了这种方法是安全的(无毒的)。在R21阶段，我们将生产针对猕猴和人类T细胞的放射性标记单抗，并表征与目标抗原的结合。在目标1中，我们将使用一种新的放射性标记方法将211At与抗CD4和抗CD3单抗偶联，并验证结合特异性。在目标2中，我们将利用人T细胞异种移植小鼠模型，在体内表征放射性标记的单抗，以确定其与靶抗原的结合和结合的稳定性。只有在放射性标记单抗(S)得到验证后，R33阶段才会继续进行。在这里，我们将在猕猴身上测试放射性标记的单抗，以确定用于耗尽记忆CD4+T细胞亚群的最佳剂量。在目标3中，我们将进行生物分布研究，以确定放射性标记单抗的剂量，这将导致目标抗原饱和50%。然后，在目标4中，我们将研究放射性标记单抗的毒性及其对外周血和淋巴组织中CD4+细胞亚群的影响。最后，我们将考虑毒性和疗效研究的结果，以得出每个放射性标记单抗的最佳剂量。我们建议的直接目标是开发一种高效的试剂来耗尽记忆中的CD4+细胞，并在HIV-1潜伏期的NHP模型中进一步测试。最终的目标是开发一种无毒的试剂，能够耗尽潜伏的感染 细胞达到的水平，当与完全抑制的ART和持续的水库腐烂相结合时，将允许艾滋病毒在几年内而不是几十年内传播。

 DESCRIPTION: Control of HIV-1 infection can be achieved in most patients with combination anti-retroviral therapy (ART). Even with a prolonged period of completely suppressive ART, the viral load increases within weeks to months after discontinuation. The source of re-emergent HIV-1 is found mainly in memory CD4+ T cells which harbor replication-competent but transcriptionally silent pro-viral DNA. Elimination of this latent HIV-1 reservoir is the major impediment to achieving a cure of HIV-1 infection. Strategies to eradicate the latent reservoir by stimulating HIV-1 replication in latently infected cells, either through drug-induced activation of viral transcription or cytokine-induced acceleration of CD4+ cell turnover, have met with limited success. An alternative strategy is to directly target and kill latently infected cells. We hypothesize that memory CD4+ cells can be targeted by monoclonal antibodies (MAb) and killed by radiation in the form of an alpha-emitter without undue toxicity to the patient. We furthr hypothesize that radiolabeled MAb depletion of memory CD4+ cells, followed by measures to protect CD4+ cells during rebound proliferation, would considerably shorten the duration of ART and accomplish a sterilizing cure. Here, we propose to develop the radiolabeled MAb and to study efficacy and toxicity in nonhuman primates. We propose two targeting strategies, one to deplete CD4+ cells that include all memory CD4+ subsets, and a second to broadly target CD3+ cells, which would likely result in a greater depletion of CD4+ cells and for which we have already shown in a canine model to be safe (nontoxic). In the R21 phase, we will produce the radiolabeled MAbs that target macaque and human T cells and characterize binding to target antigen. In Aim 1 we will conjugate 211At to both anti-CD4 and anti-CD3 MAb using a novel method for radiolabeling and validate binding specificity. In Aim 2 we will characterize the radiolabeled MAb in vivo, using a human T-cell xenograft mouse model to ascertain stability of the conjugation and binding to target antigens. The R33 phase will proceed only after the radiolabeled MAb(s) have been validated. Here, we will test the radiolabeled MAbs in rhesus macaques to determine the optimal dose for use in depletion of memory CD4+ T cell subsets. In Aim 3 we will conduct bio distribution studies to determine the dose of radiolabeled MAb that will result in >50% saturation of the target antigens. Then, in Aim 4 we will investigate the toxicity profile of the radiolabeled MAbs and their effects on CD4+ cell subsets in peripheral blood and lymphoid tissues. Finally, we will consider results of the toxicity and efficacy studies to arrive t the optimal dose of each radiolabeled MAb. The immediate goal of our proposal is to develop a highly effective agent to deplete memory CD4+ cells, to be tested further in NHP models of HIV-1 latency. The ultimate goal is to develop a non-toxic agent capable of depleting latently infected cells to a level that, when combined with fully suppressive ART and ongoing reservoir decay, would allow for HIV eradiation within years rather than decades.