■免疫疗法显示出巨大的希望,但并非对所有类型的肿瘤都有效,对不到3%的胰腺导管腺癌(PDAC)患者有效.为了对更多的癌症患者和患有PDAC的患者进行有效的免疫治疗,我们对沙门氏菌进行基因工程改造,将外源抗原直接传递到肿瘤细胞的细胞质中。我们假设外源免疫抗原的细胞内递送将激活抗原特异性CD8T细胞并减少免疫小鼠中的肿瘤。
■为了检验这一假设,我们给予细胞内递送(ID)沙门氏菌,将卵清蛋白作为模型抗原递送到荷瘤中,卵清蛋白接种的小鼠。ID沙门氏菌在诱导细胞侵袭后通过在细胞中自主裂解来递送抗原。
■我们表明所递送的卵清蛋白分散在培养物和肿瘤中的细胞的整个细胞质中。这种进入细胞质的递送对于抗原交叉呈递是必需的。我们表明,卵清蛋白受体癌细胞与卵清蛋白特异性CD8T细胞的共培养触发了细胞毒性T细胞反应。OT-ICD8T细胞过继转移后,卵清蛋白的细胞内递送减少了肿瘤生长并消除了肿瘤。这种作用取决于卵清蛋白特异性T细胞的存在。在小鼠中接种外源抗原后,抗原的细胞内递送清除了43%的已建立的KPC胰腺肿瘤,增加生存率,并防止肿瘤重新植入。
■免疫抑制KPC模型中的这种反应证明了治疗对检查点抑制剂无反应的肿瘤的潜力,并且对再攻击的反应表明针对内在肿瘤抗原建立了新的免疫力。在诊所里,ID沙门氏菌可用于从儿童免疫中递送蛋白质抗原,以重新集中针对肿瘤的预先存在的T细胞免疫。作为一种现成的免疫疗法,这种细菌系统有可能在广泛的癌症患者中有效。
Immunotherapies have shown great promise, but are not effective for all tumors types and are effective in less than 3% of patients with pancreatic ductal adenocarcinomas (PDAC). To make an immune treatment that is effective for more cancer patients and those with PDAC specifically, we genetically engineered Salmonella to deliver exogenous antigens directly into the cytoplasm of tumor cells. We hypothesized that intracellular delivery of an exogenous immunization antigen would activate antigen-specific CD8 T cells and reduce tumors in immunized mice.
To test this hypothesis, we administered intracellular delivering (ID) Salmonella that deliver ovalbumin as a model antigen into tumor-bearing, ovalbumin-vaccinated mice. ID Salmonella delivers antigens by autonomously lysing in cells after the induction of cell invasion.
We showed that the delivered ovalbumin disperses throughout the cytoplasm of cells in culture and in tumors. This delivery into the cytoplasm is essential for antigen cross-presentation. We showed that co-culture of ovalbumin-recipient cancer cells with ovalbumin-specific CD8 T cells triggered a cytotoxic T cell response. After the adoptive transfer of OT-I CD8 T cells, intracellular delivery of ovalbumin reduced tumor growth and eliminated tumors. This effect was dependent on the presence of the ovalbumin-specific T cells. Following vaccination with the exogenous antigen in mice, intracellular delivery of the antigen cleared 43% of established KPC pancreatic tumors, increased survival, and prevented tumor re-implantation.
This response in the immunosuppressive KPC model demonstrates the potential to treat tumors that do not respond to checkpoint inhibitors, and the response to re-challenge indicates that new immunity was established against intrinsic tumor antigens. In the clinic, ID Salmonella could be used to deliver a protein antigen from a childhood immunization to refocus pre-existing T cell immunity against tumors. As an off-the-shelf immunotherapy, this bacterial system has the potential to be effective in a broad range of cancer patients.