DataSheet_1_Alphavirus Replicon Particle Vaccine Breaks B Cell Tolerance and Rapidly Induces IgG to Murine Hematolymphoid Tumor Associated Antigens.docx

De novo immune responses to myeloid and other blood-borne tumors are notably limited and ineffective, making our ability to promote immune responses with vaccines a major challenge. While focus has been largely on cytotoxic cell-mediated tumor eradication, B-cells and the antibodies they produce also have roles in anti-tumor responses. Indeed, therapeutic antibody-mediated tumor cell killing is routinely employed in patients with hematolymphoid cancers, but whether endogenous antibody responses can be incited to blood-born tumors remains poorly studied. A major limitation of immunoglobulin therapies is that cell surface expression of tumor-associated antigen (TAA) targets is dynamic and varied, making promotion of polyclonal, endogenous B cell responses appealing. Since many TAAs are self-antigens, developing tumor vaccines that enable production of antibodies to non-polymorphic antigen targets remains a challenge. As B cell responses to RNA vaccines are known to occur, we employed the Viral Replicon Particles (VRP) which was constructed to encode mouse FLT3. The VRP-FLT3 vaccine provoked a rapid IgG B-cell response to this self-antigen in leukemia and lymphoma mouse models. In addition, IgGs to other TAAs were also produced. Our data suggest that vaccination with RNA viral particle vectors incites a loss of B-cell tolerance that enables production of anti-tumor antibodies. This proof of principle work provides impetus to employ such strategies that lead to a break in B-cell tolerance and enable production of broadly reactive anti-TAA antibodies as potential future therapeutic agents for patients with hematolymphoid cancers.

针对骨髓和其他血源性肿瘤的天然免疫反应显著受限且效果不佳，这使得通过疫苗促进免疫反应成为一项重大挑战。尽管研究主要集中在细胞毒性细胞介导的肿瘤消除上，但B细胞及其产生的抗体在抗肿瘤反应中也扮演着重要角色。实际上，治疗性抗体介导的肿瘤细胞杀伤在血液淋巴瘤患者中已被常规应用，然而，诱导针对血源性肿瘤的内源性抗体反应的研究尚不充分。免疫球蛋白疗法的重大局限性在于肿瘤相关抗原（TAA）靶点的细胞表面表达动态多变，因此促进多克隆、内源性B细胞反应颇具吸引力。由于许多TAA是自身抗原，开发能够产生针对非多态性抗原靶点抗体的肿瘤疫苗仍然是一个挑战。已知RNA疫苗可以引发B细胞反应，因此我们采用了构建编码小鼠FLT3的病毒复制子颗粒（VRP）。VRP-FLT3疫苗在白血病和淋巴瘤小鼠模型中迅速诱导了对这一自身抗原的IgG B细胞反应。此外，还产生了针对其他TAA的IgG。我们的数据表明，使用RNA病毒颗粒载体进行疫苗接种可以引发B细胞耐受性的丧失，从而产生抗肿瘤抗体。这一原理性研究为采用能够打破B细胞耐受性并产生广谱反应性抗TAA抗体的策略提供了动力，这些策略可能成为未来血液淋巴瘤患者的潜在治疗药物。