Hodge J W, McLaughlin J P, Abrams S I, Shupert W L, Schlom J, Kantor J A
Laboratory of Tumor Immunology and Biology, National Cancer Institute, NIH, Bethesda, Maryland 20892, USA.
Cancer Res. 1995 Aug 15;55(16):3598-603.
At least two signals are required for the activation of naive T cells by antigen-bearing target cells: an antigen-specific signal, delivered through the T-cell receptor, and a costimulatory signal delivered through the T-cell surface molecule CD28 by its natural ligand B7-1. The immunological benefit of coexpression of B7 with target antigen has been demonstrated with the use of several retroviral systems to transfect antigen-bearing cells. Although engineering recombinant constructs with genes for two or more antigens can mediate the dual expression of those antigens, disadvantages of this approach include the time for construction of each desirable combination and the inability to control differential expression levels of each gene product. An alternative approach would utilize separate constructs that could be admixed appropriately before administration. In this report we describe the functional consequences of the admixture of recombinant vaccinia murine B7-1 (rV-B7) to recombinant vaccinia expressing the human carcinoembryonic antigen gene (rV-CEA). Coinfection of cells resulted in high levels of cell surface expression of both the CEA and B7 molecules. Immunization of mice with various ratios (1:3, 1:1, 3:1) of rV-CEA and rV-B7 demonstrated that an admixture of rV-CEA and rV-B7 at a 3:1 ratio resulted in the generation of optimal CEA-specific T-cell responses. Next, we examined the efficacy of this admixture on antitumor activity. Typically, injection of murine carcinoma cells expressing CEA leads to the death of the host. One immunization of C57BL/6 mice with rV-CEA:rV-B7 (3:1) resulted in no tumor establishment. In contrast, administration of rV-CEA or rV-B7 alone had little or no antitumor effects. These studies demonstrate the advantages of the use of recombinant vaccinia viruses to deliver B7 molecules in combination with a tumor-associated antigen. The availability of the rV-B7 single construct and the ability to alter the B7 ratio could also have potential utility when coinfecting rV-B7 with recombinant vaccinia viruses containing genes for infectious agents or other tumor-associated antigen genes.
带有抗原的靶细胞激活初始T细胞至少需要两种信号：一种是通过T细胞受体传递的抗原特异性信号，另一种是通过T细胞表面分子CD28与其天然配体B7-1相互作用传递的共刺激信号。利用多种逆转录病毒系统转染携带抗原的细胞，已证明B7与靶抗原共表达的免疫学益处。虽然构建含有两种或更多种抗原基因的重组体可介导这些抗原的双重表达，但这种方法的缺点包括构建每种理想组合所需的时间以及无法控制每个基因产物的差异表达水平。另一种方法是利用可在给药前适当混合的单独构建体。在本报告中，我们描述了重组痘苗鼠B7-1（rV-B7）与表达人癌胚抗原基因的重组痘苗（rV-CEA）混合后的功能后果。细胞的共感染导致CEA和B7分子在细胞表面高水平表达。用不同比例（1:3、1:1、3:1）的rV-CEA和rV-B7免疫小鼠表明，rV-CEA与rV-B7以3:1的比例混合可产生最佳的CEA特异性T细胞反应。接下来，我们研究了这种混合物的抗肿瘤活性。通常，注射表达CEA的鼠癌细胞会导致宿主死亡。用rV-CEA:rV-B7（3:1）对C57BL/6小鼠进行一次免疫接种可导致肿瘤无法形成。相比之下，单独施用rV-CEA或rV-B7几乎没有抗肿瘤作用。这些研究证明了使用重组痘苗病毒联合递送B7分子与肿瘤相关抗原的优势。当rV-B7与含有感染因子基因或其他肿瘤相关抗原基因的重组痘苗病毒共感染时，rV-B7单一构建体的可用性以及改变B7比例也可能具有潜在用途。
