Antigen Specific T-Helper to Enhance Antitumor Immunity

越来越多的证据表明，CD 4+辅助性T细胞（Th）是诱导有效的抗肿瘤反应的关键。 然而，细胞内肿瘤抗原通常难以被加工并呈递给MHC II类，限制了关键的CD 4 + Th细胞的活化。 在我们最近的研究中，将模型细胞内肿瘤抗原法师-3遗传连接至前导序列和DC靶向结构域，用于受体介导的内化，用于DC活化和抗原呈递。 通过表达sMAGE 3-Fc融合蛋白（retrogen）的转导的DC诱导上级抗原特异性CTL应答和抗肿瘤活性。 在这项提案中，我们将扩展这一初步研究，长期目标是通过激活抗原特异性Th和CTL反应来开发更有效的肿瘤疫苗。 我们推测，活化的CD 4 + Th的免疫与Th抗原表位来自相同的抗原或retrogens将提供同源的帮助CTL，因此，可能是一种有效的手段，以提高目前的肿瘤疫苗的效力。具体来说，我们将比较retrogen与其他MHC II类靶向方法和测试，如果CD 4 + Th在增强小鼠的抗肿瘤免疫反应中发挥关键作用的retrogen。 我们将通过利用逆转录酶提呈II类抗原的能力和HLA II类转基因小鼠的可用性来鉴定法师-3和相关肿瘤抗原中的新的II类限制性表位。 此外，我们将建立HLA-A2和DR 3/4双转基因小鼠，以测试抗原特异性Th细胞的激活是否可以增强肿瘤疫苗的效力。 我们还将测试来自相同抗原的Th表位是否比非特异性Th刺激更有效，以及在人源化小鼠中，逆转录酶基因转导的DC是否可以比用Th和CTL表位两者脉冲的DC诱导更有效的抗肿瘤CTL和Th应答。 这项拟议的研究将确定是否激活抗原特异性Th通过免疫与Th肽或逆转录酶可以增强CTL和抗肿瘤反应，如果逆转录酶转导的DC比DC脉冲与Th和CTL表位或重组蛋白诱导抗肿瘤免疫反应更有效。

Increasing evidence suggests that CD4+ helper T-cells (Th) are critical for the induction of an effective antitumor response. However, intracellular tumor antigens are usually difficult to be processed and presented to MHC class-II, limiting the activation of critical CD4+ Th cells. In our recent study, a model intracellular tumor antigen, MAGE-3, was genetically linked to a leader sequence and to a DC targeting domain for receptor- mediated internalization for DC activation and antigen presentation. Superior antigen-specific CTL responses and antitumor activity were induced by transduced DCs expressing the sMAGE3-Fc fusion protein (retrogen). In this proposal, we will extend this preliminary study with a long-term goal of developing more potent tumor vaccines by activating both antigen-specific Th and CTL responses. We hypothesize that activation of CD4+ Th by immunization with Th epitopes derived from the same antigen or retrogens will provide cognate help to CTLs and, thus, may be an effective means to enhance the potency of current tumor vaccines. Specifically, we will compare retrogen with other MHC class II targeting approaches and test if CD4+ Th plays a critical role in the enhancement of anti-tumor immune responses by retrogen in mice. We will identify novel class-II-restricted epitopes in MAGE-3 and related tumor antigens by utilizing the ability of retrogens to class II antigen presentation and the availability of HLA class-II transgenic mice. Furthermore, we will generate HLA-A2 and DR3/4 double transgenic mice to test if activation of antigen-specific Th cells can enhance the potency of tumor vaccines. We will also test if Th epitopes from the same antigen are more potent than nonspecific Th stimuli and if retrogen- transduced DC can induce more potent antitumor CTL and Th responses than DC pulsed with both Th and CTL epitopes in humanized mice. This proposed study will determine if activation of antigen-specific Th via immunization with either Th peptides or retrogen can enhance CTL and antitumor responses and if retrogen-transduced DCs are more potent than DCs pulsed with both Th and CTL epitopes or recombinant proteins to induce antitumor immune responses.