Development of gene therapy model of retrovirus-induced disease

Fv-4是一种小鼠基因，其主要赋予对嗜亲性小鼠白血病病毒（MuLV）感染的抗性。Fv-4抗性（Fv-4^r）基因产物在携带Fv-4^r小鼠的造血细胞和部分腺体中表达。免疫电镜下，该抗原表达于细胞表面和部分内质网。流式细胞仪分析显示，Fv-4 ^r抗原在红系细胞、粒细胞、T细胞和B细胞中表达，表达强度几乎相同。免疫沉淀和Western blotting检测结果表明，Fv-4 ^r基因产物存在于Fv-4^r小鼠血清中。可溶性Fv-4^r抗原的分子量约为80 kDa。血清Fv-4^r抗原与亲嗜性MuLV受体结合，表现为与表达亲嗜性MuLV受体的转染貂细胞特异性结合，但不与亲本貂细胞特异性结合。将具有亲嗜性MuLV受体并已与可溶性Fv-4^r抗原预孵育的C3 H胸腺细胞或脾细胞与Friend白血病病毒（FLV）混合。用Fv-4^r抗原处理的C3 H细胞变得对FLV的结合不敏感。这些结果提供了证据，表明Fv-4^r抗原在体内从携带Fv-4^r的小鼠细胞中释放，并与表达亲嗜性MuLV表面受体的细胞结合，从而保护它们免受FLV感染。接下来，研究这些发现对逆转录病毒诱导疾病的基因治疗的意义。首次将Fv-4^r基因导入C_3H小鼠白血病细胞系，并成功表达Fv-4^r抗原。然后，用Fv-4^r基因转导C3 H小鼠的骨髓细胞，并将其移植到致死辐射的C3 H小鼠。所得嵌合体小鼠在造血细胞中表达Fv-4^r抗原。

Fv-4 is a mouse gene that dominantly confers resistance to infection by ecotropic murine leukemia virus (MuLV). Fv-4 resistant (Fv-4^r) gene product was expressed in hematopoietic cells and a part of glandular organs of Fv-4^r-bearing mice. Immunoelectron microscopically, this antigen was expressed on the cell surface and a part of endoplasmic reticulum. Flowcytometric analysis revealed that the Fv-4^r antigen was expressed in erythroid cells, granulocytic cells, T cells and B cells with almost the same intensity. Immunoprecipitaion followed by Western blotting revealed that Fv-4^r gene product existed in the serum of Fv-4^r-bearing mice. The soluble Fv-4^r antigen had a molecular weight of about 80 kDa. The serum Fv-4^r antigen binds to ecotropic MuLV receptors, shown by specific binding to transfectant mink cells expressing ecotropic MuLV receptor, but not to parental mink cells. C3H thymocytes or spleen cells that had ecotropic MuLV receptor and had been preincubated with soluble Fv-4^r antigen were mixed with Friend leukemia virus (FLV). C3H cells treated with Fv-4^r antigen became refractory to binding by FLV.These results provide evidence that the Fv-4^r antigen is released from cells of Fv-4^r-bearing mice in vivo and binds to cells expressing surface receptors for ecotropic MuLV,thereby protecting them from infection with FLV.Next, the implication of these findings for gene therapy of retrovirus-induced disease was examined. Fv-4^r gene was first transduced to leukemia cell line of C3H mouse origin and the cells successfully expressed Fv-4^r antigen. Then, the bone marrow cells of C3H mice were transduced with Fv-4^r gene and transplanted to lethally irradiated C3H mice. The resulting chimera mice expressed Fv-4^r antigen in hematopoietic cells.