Maximizing Memory T Cell Responses by Matured Post Chemotherapy Dendritic Cells

描述（由申请人提供）：最近的临床前研究已经证明，过继性T细胞转移到宿主中导致淋巴细胞耗竭，随后进行疫苗接种和IL-2治疗有利于能够治愈相对晚期实体瘤的记忆细胞的分化。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清除增强过继性T细胞治疗的主要手段。因此，更好地了解淋巴细胞清除的作用模式将为改善过继性T细胞治疗的抗肿瘤记忆应答开辟新的途径。我们最近发现，CTX治疗诱导扩增的未成熟的树突状细胞在淋巴恢复期从第9天到第16天，在第12天达到高峰。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扩增的峰值时给予TLR 3激动剂poly（I：C）诱导快速炎症环境，这与淋巴结中活化DC数量的显著增加相关。使用pmel- 1 TCR转基因小鼠模型，其中CD 8 + T细胞识别gp 100黑色素瘤肽，我们已经证明，在淋巴细胞减少期用gp 100肽加poly（I：C）引发CTX处理的小鼠，然后在恢复期（DC扩增的峰值）加强，导致淋巴结中活化DC的数量显著增加，同时pmel-1细胞的扩增暂时增加，导致对免疫原性差的B16黑色素瘤的大体积（晚期）肿瘤的稳健治疗性抗肿瘤作用。因此，我们假设，提供由TLR激动剂诱导的炎症环境最佳地定时以与独特的扩增的CTX后DC的存在组合，可以导致稳健的持久抗肿瘤免疫。为了解决这一假设，我们将比较我们的治疗方式的抗肿瘤效果，包括疫苗接种hgp 100肽和poly（I：C）的那些已建立的模式，包括疫苗接种与离体hgp 100脉冲的DC和IL-2。然后，我们将确定我们的模式的佐剂组分与已建立的模式的佐剂组分的重叠（通过添加或替代）是否可以导致更高的抗肿瘤应答。最后，我们将定义介导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期，DC频率的增加代表了一个新的机会，以改善化疗与肿瘤免疫策略相结合的基本设计和临床应用。 公共卫生相关性：通过辐射或用抗癌化疗药物治疗使携带肿瘤的宿主中的连续性T细胞转移呈现淋巴细胞减少显著增强抗肿瘤T细胞应答，然而，淋巴细胞清除方案的这些有益作用的机制知之甚少。我们已经做出了新的观察，即用抗癌药物环磷酰胺治疗诱导树突状细胞的显着扩增，树突状细胞在形成针对癌症的免疫反应中起着核心作用，代表了这种药物对过继免疫治疗的有益作用的新机制。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.