Optimization of Tumor Vaccines for the Aged

描述(申请人提供)：考虑到超过50%的癌症发生在老年人，老年人的免疫系统与反应能力的急剧下降有关，我们小组和其他人的研究表明，对年轻人有效的免疫疗法不一定对老年人有效。为了有效地开发一种免疫治疗策略，并能够将这种方法转化为治疗老年人癌症的方法，有必要：1)使用与癌症患者的自我耐受和衰老同时存在的相关模型；以及2)识别和了解旧免疫系统的内在缺陷。我们将FVB-HER-2/neu小鼠与人类白细胞抗原A2(A2xneu)小鼠杂交，建立了一种肿瘤模型。这些动物对HER-2/neu抗原具有耐受性，22-27个月大时会出现自发性肿瘤。因此，A2xneu小鼠模型代表了一种独特的模型，其中衰老和耐受性同时存在，使我们能够评估在老年耐受性环境中的免疫和抗肿瘤反应。我们的初步结果表明，瘤内注射CpG-ODN+多肽疫苗和去除Tregs可在100%的A2xneu幼鼠中诱导排斥原发肿瘤的免疫反应，并且所有幼年动物都产生了保护性记忆反应。相比之下，老年A2xneu小鼠只能延缓肿瘤的生长。虽然我们能够克服年轻A2xneu小鼠的耐受性，但这些结果表明，老年A2xneu小鼠可能存在其他缺陷，阻碍了这些动物免疫反应的最佳激活。对年轻和老年树突状细胞(DC)功能的分析表明，与年轻DC相比，CpG-ODN刺激后老年DC被激活。而CpG-ODN联合抗CD40刺激可恢复老年DC的功能。此外，我们的结果表明，更多的古老的原始CD8+T细胞表达B7-H1。由于B7-H1负性调节T细胞反应，我们推测B7-H1在CD8+T细胞中的表达可以限制或削弱这些细胞的免疫功能。事实上，我们的结果表明，阻断旧的CD8+T细胞中的B7-H1可以恢复这些细胞的功能。基于这些结果，我们推测CpG-ODN、抗CD40、Tregs depletion和抗B7-H1联合应用将诱导更强的抗肿瘤免疫应答，能够控制老年耐受A2xneu小鼠的肿瘤生长。初步结果表明，情况的确如此。在我们的疫苗接种方案中加入抗CD40和抗B7-H1是很重要的，因为：1)在CpG-ODN接种方案中加入抗CD40将恢复DC的功能，从而产生更强的免疫反应；以及2)阻断B7-H1将恢复旧的CD8 T细胞的功能，从而允许这些细胞的最佳激活和扩增。目的1评价阻断B7-H1如何恢复陈旧CD8 T细胞的功能，以及CpG+抗CD40联合应用如何增强陈旧DC的功能。目的优化和评价CpG-ODN、抗CD40、Tregs depletion和抗B7-H1在老年耐受宿主(老年A2xneu小鼠)免疫后对免疫应答的生物学效应。目的3将在最佳免疫治疗条件下评估抗肿瘤反应。这些研究的信息将揭示控制和操纵免疫系统的新策略，以在老年耐受宿主中开发更有效的癌症免疫疗法。

DESCRIPTION (provided by applicant): Considering that more than 50% of cancer occurs in the elderly and the immune system of the old is associated with a dramatic reduction in responsiveness, studies from our group and others indicate that immunotherapies that are effective in the young are not necessarily effective in the old. To effectively develop an immunotherapeutic strategy and be able to translate this approach for the treatment of cancers in the old, it is necessary to: 1) use relevant models that closely reflect those of cancer patients where self-tolerance and aging are present simultaneously; and 2) identify and understand the intrinsic defects of the old immune system. We have developed a tumor model by crossing the FVB-Her-2/neu mice with HLA-A2 mice (A2xneu). These animals are tolerant to Her-2/neu antigens and spontaneous tumors appear when they are 22-27 months old. Therefore, the A2xneu mouse model represents a unique model where aging and tolerance are present simultaneously allowing us to evaluate the immune and antitumor responses in an old-tolerant environment. Our preliminary results indicate that treatment with intratumoral injections of CpG-ODN plus peptide vaccination and depletion of Tregs induce an immune response that reject the primary tumors in 100% of young A2xneu mice and all young animals developed a protective memory response. In contrast, old A2xneu mice only delay the tumor growth. Although we were able to overcome tolerance in young A2xneu mice, these results suggest that other deficiencies may exist in old A2xneu mice preventing the optimal activation of an immune response in these animals. Analysis of the function of young and old dendritic cells (DCs) indicates that old DCs were suboptimally activated after CpG-ODN stimulation when compared to young DCs. However, the function of old DCs could be restored if old DCs were stimulated with CpG-ODN plus anti-CD40. Additionally, our results indicate that a higher number of old naive CD8+ T cells express B7-H1. Since B7-H1 negatively regulates T cell responses, we hypothesized that the expression of B7-H1 in old CD8+ T cells could restrict or diminish the immune function of these cells. Indeed, our results indicate that blockade of B7- H1 in old CD8+ T cells restore the function of these cells. Based on these results, we hypothesized that the combination of CpG-ODN, anti-CD40, Tregs depletion and anti-B7-H1, will induce stronger antitumor immune responses capable of controlling the tumor growth in old tolerant A2xneu mice. Preliminary results indicate that this is the case. The incorporation of anti-CD40 and anti-B7-H1 in our vaccination protocol is important because: 1) the addition of anti-CD40 into the CpG-ODN vaccination protocol will restore the function of DC resulting in stronger immune responses; and 2) blockade of B7-H1 will restore the function of old CD8 T cells permitting the optimal activation and expansion of these cells. Aim 1 will evaluate how blockade of B7-H1 restore the function of old CD8 T cells and how the combination of CpG+anti-CD40 enhances the function of old DCs. Aim 2 will optimize and evaluate the biological effects on the immune responses following immunization with CpG-ODN, anti-CD40, Tregs depletion and anti-B7-H1 in old tolerant hosts (old A2xneu mice). Aim 3 will evaluate the antitumor responses using the optimal immunotherapy condition. The information of these studies will reveal new strategies for controlling and manipulating the immune system to develop more effective cancer-immunotherapies in old tolerant hosts.