Department of Physiology, Michigan State University, East Lansing, MI.
Division of Oncology, Children's Hospital of Philadelphia, Philadelphia, PA.
Blood Adv. 2019 Mar 12;3(5):813-824. doi: 10.1182/bloodadvances.2018028886.
Invariant natural killer T (iNKT) cells comprise a unique lineage of CD1d-restricted lipid-reactive T lymphocytes that potently kill tumor cells and exhibit robust immunostimulatory functions. Optimal tumor-directed iNKT cell responses often require expression of the antigen-presenting molecule CD1d on tumors; however, many tumor cells downregulate CD1d and thus evade iNKT cell recognition. We generated a soluble bispecific fusion protein designed to direct iNKT cells to the site of B-cell cancers in a tumor antigen-specific but CD1d-independent manner. This fusion protein is composed of a human CD1d molecule joined to a single chain antibody FV fragment specific for CD19, an antigen widely expressed on B-cell cancers. The CD1d-CD19 fusion protein binds specifically to CD19-expressing, but not CD19-negative cells. Once loaded with the iNKT cell lipid agonist α-galactosyl ceramide (αGC), the CD1d-CD19 fusion induces robust in vitro activation of and cytokine production by human iNKT cells. iNKT cells stimulated by the αGC-loaded CD1d-CD19 fusion also strongly transactivate T-, B-, and NK-cell responses and promote dendritic cell maturation. Importantly, the αGC-loaded fusion induces robust lysis of CD19CD1d Epstein-Barr virus immortalized human B-lymphoblastoid cell lines that are otherwise resistant to iNKT cell killing. Consistent with these findings; administration of the αGC-loaded fusion protein controlled the growth of CD19CD1d tumors in vivo, suggesting that it can "link" iNKT cells and CD19CD1d targets in a therapeutically beneficial manner. Taken together, these preclinical studies demonstrate that this B cell-directed fusion protein can be used to effectively induce iNKT cell antitumor responses in vitro and in vivo
不变自然杀伤 T(iNKT)细胞是一类独特的 CD1d 限制性脂质反应性 T 淋巴细胞，能够有效地杀伤肿瘤细胞，并具有强大的免疫刺激功能。最佳的肿瘤定向 iNKT 细胞反应通常需要肿瘤表达抗原呈递分子 CD1d；然而，许多肿瘤细胞下调 CD1d，从而逃避 iNKT 细胞的识别。我们生成了一种可溶性双特异性融合蛋白，旨在以肿瘤抗原特异性但不依赖 CD1d 的方式将 iNKT 细胞导向 B 细胞癌部位。这种融合蛋白由与人 CD1d 分子连接的单链抗体 FV 片段组成，该片段特异性针对广泛表达于 B 细胞癌上的抗原 CD19。CD1d-CD19 融合蛋白特异性结合表达 CD19 的细胞，但不结合 CD19 阴性细胞。一旦与 iNKT 细胞脂质激动剂 α-半乳糖基神经酰胺（αGC）结合，CD1d-CD19 融合物可在体外强烈激活和诱导人 iNKT 细胞产生细胞因子。用 αGC 负载的 CD1d-CD19 融合物刺激的 iNKT 细胞也强烈转激活 T、B 和 NK 细胞反应并促进树突状细胞成熟。重要的是，αGC 负载的融合物可强烈溶解 CD19CD1d Epstein-Barr 病毒永生化人 B 淋巴细胞系，而这些细胞系对 iNKT 细胞杀伤具有抗性。与这些发现一致；αGC 负载的融合蛋白的给药控制了体内 CD19CD1d 肿瘤的生长，表明它可以以治疗有益的方式“连接”iNKT 细胞和 CD19CD1d 靶标。综上所述，这些临床前研究表明，这种靶向 B 细胞的融合蛋白可用于有效地在体外和体内诱导 iNKT 细胞抗肿瘤反应。
