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，过继性T细胞转移到淋巴细胞枯竭的宿主，然后接种疫苗和IL-2治疗有利于记忆细胞的分化，能够治疗相对晚期的实体瘤。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细胞耗竭增强过继T细胞治疗的主要手段。因此，更好地了解淋巴细胞耗竭的作用模式将为改善过继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，CTX治疗在淋巴细胞恢复阶段（第9天至第16天）诱导未成熟dc的扩张，在第12天达到峰值。这些dc在体外表现出正常的吞噬能力和体内抗原摄取能力。在DC扩张的高峰期给予TLR3激动剂poly（I:C）诱导快速炎症环境，这与淋巴结中活化的DC数量显著增加有关。使用pmel-1 TCR转基因小鼠模型，CD8+ T细胞识别gp100黑色素瘤肽，我们已经证明，在淋巴减少期用gp100肽加poly（I:C）引发ctx处理的小鼠，然后在恢复期（DC扩增的高峰期）增强，导致淋巴结中活化的DC数量显著增加，pmel-1细胞扩增的时间增加。对免疫原性差的B16黑色素瘤的大块（晚期）肿瘤产生强大的治疗抗肿瘤作用。因此，我们假设，提供TLRs激动剂诱导的炎症环境，以最佳时机与CTX后dc的独特扩展相结合，可以导致强大的持久抗肿瘤免疫。为了解决这一假设，我们将比较由hgp100肽和聚（I:C）疫苗接种组成的治疗方式与由体外hgp100脉冲dc和IL-2疫苗接种组成的治疗方式的抗肿瘤效果。然后，我们将确定是否重叠（通过添加或替代）我们模式的辅助成分与那些已建立的模式可以导致更高的抗肿瘤反应。最后，我们将定义这些抗肿瘤作用的内在和外在机制。我们确实相信，在ctx诱导的淋巴细胞耗竭后的恢复阶段，DCs的频率增加代表了一个新的机会，可以改善化疗与肿瘤免疫治疗策略联合的基本原理设计和临床应用。

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.