Maximizing Memory T Cell Responses by Matured Post Chemotherapy Dendritic Cells

描述(由申请人提供)：最近的临床前研究表明，过继T细胞转移到导致淋巴耗竭的宿主，然后接种疫苗和IL-2治疗有利于记忆细胞的分化，能够治愈相对晚期的实体瘤。虽然已经提出了几种机制，但最近的研究表明，这些机制可能不是淋巴清除增强过继T细胞治疗的主要手段。因此，更好地了解淋巴滤除的作用机制将为提高过继T细胞治疗的抗肿瘤记忆反应开辟新的途径。我们最近发现，在第9天到第16天的淋巴恢复阶段，CTX处理可以诱导未成熟DC的扩张，在第12天达到高峰。这些DC在体外表现出正常的吞噬能力，在体内表现出正常的抗原摄取。在DC扩增高峰期给予TLR3激动剂Poly(I：C)可引起迅速的炎症环境，这与淋巴结中活化的DC数量显著增加有关。利用CD8+T细胞识别gp100黑色素瘤多肽的PMEL-1TCR转基因小鼠模型，我们已经证明，在淋巴减少阶段用gp100多肽加聚(I：C)预注CTX处理的小鼠，然后在恢复期(DC扩张的高峰期)增强，可显著增加淋巴结中激活的DC的数量，并伴随PMEL-1细胞的扩张，从而对免疫原性较差的B16黑色素瘤的巨大(晚期)肿瘤具有强大的抗肿瘤治疗作用。因此，我们假设，提供由TLRs激动剂诱导的炎症环境，结合CTX后DC独特的扩大存在的最佳时机，可以产生强大的、持久的抗肿瘤免疫。为了解决这一假设，我们将比较由hgp100多肽和Poly(I：C)疫苗组成的治疗模式与由体外hgp100冲击的DC和IL-2组成的已建立的治疗模式的抗肿瘤效果。然后，我们将确定我们的模式的佐剂成分与已建立的模式的佐剂成分重叠(通过添加或替代)是否可以导致更高的抗肿瘤反应。最后，我们将确定这些抗肿瘤作用的内在和外在机制。我们相信，在CTX诱导的淋巴枯竭后的恢复期，DC频率的增加代表了一个新的机会，可以结合肿瘤免疫治疗策略来改进化疗的基本设计和临床应用。 公共卫生相关性：将T细胞过继转移到通过放射或抗癌化疗药物治疗而淋巴细胞减少的荷瘤宿主中，显著增强抗肿瘤T细胞反应，然而，淋巴去除方案这些有益效果背后的机制尚不清楚。我们发现，抗癌药物环磷酰胺治疗可诱导树突状细胞显著扩张，树突状细胞在形成抗癌免疫反应中起核心作用，这代表了该药物对过继免疫治疗有益的新机制。对我们观察结果的进一步分析将为抗癌过继免疫疗法的合理应用开辟新的途径。

DESCRIPTION (provided by applicant): Recent preclinical studies have demonstrated that adoptive T cell transfer into a host rendered lymphodepleted followed by vaccination and IL-2 therapy favors differentiation of memory cells capable of curing relatively advanced solid tumors. Although several mechanisms have been suggested, recent studies have demonstrated that these mechanisms might not be the principal means by which lymphodepletion augments adoptive T cell therapy. Therefore, a better understanding of the mode of action of lymphodepletion would open new avenues for improving anti-tumor memory responses of adoptive T cell therapy. We recently have found that CTX treatment induces the expansion of immature DCs during the lymphoid recovery phase from day 9 to day 16, peaking on day 12. These DCs demonstrated normal phagocytic ability in vitro and antigen uptake in vivo. Administration of the TLR3 agonist poly(I:C) at the peak of DC expansion induced a rapid inflammatory milieu that was associated with significant increases in the numbers of activated DCs in lymph nodes. Using the pmel- 1 TCR transgenic mouse model, in which CD8+ T cells recognize gp100 melanoma peptide, we have demonstrated that priming of the CTX-treated mice with gp100 peptide plus poly(I:C) at the lymphopenic phase followed by boosting at the recovery phase (the peak of DC expansion) resulted in significant increases in the number of activated DCs in lymph nodes with a temporal increase in the expansion of pmel-1 cells, resulting in a robust therapeutic anti-tumor effects toward a bulky (advanced) tumor of the poorly immunogenic B16 melanoma. Therefore, we hypothesize that providing the inflammatory milieu induced by TLRs agonists optimally timed to be in combination with a unique expanded presence of post CTX DCs can lead to robust long-lasting anti-tumor immunity. To address this hypothesis, we will compare the anti-tumor effects of our treatment modality consisting of vaccination with hgp100 peptide and poly(I:C) to those of the established modality consisting of vaccination with ex vivo hgp100-pulsed DCs and IL-2. We will then determine if overlapping (by addition or substitution) of the adjuvant components of our modality to those of the established modality can results in a much higher anti-tumor responses. Finally, we will define the intrinsic and extrinsic mechanisms mediating these anti-tumor effects. We do believe that the increased frequencies of DCs during the recovery phase post CTX-induced lymphodepletion represents a novel opportunity to improve the rationale design and clinical application of chemotherapy in combination with tumor immunotherapeutic strategies. PUBLIC HEALTH RELEVANCE: Adoptive T cell transfer into tumor-bearing hosts rendered lymphopenic by irradiation or treatment with anti- cancer chemotherapeutic drugs markedly enhances the anti-tumor T cell responses, however, the mechanisms underlying these beneficial effects of lymphodepleting regimens are poorly understood. We have made the novel observation that treatment with the anti-cancer drug cyclophosphamide induces a marked expansion of dendritic cells, which play central roles in shaping the immune responses against cancer, representing a novel mechanism underlying the beneficial effects of this drug to adoptive immunotherapy. Further analysis of our observation would open new avenues for the rationale applications of anti-cancer adoptive immunotherapies.