Oliff A, Linemeyer D, Ruscetti S, Lowe R, Lowy D R, Scolnick E
J Virol. 1980 Sep;35(3):924-36. doi: 10.1128/JVI.35.3.924-936.1980.
Friend murine leukemia virus (G-MuLV) is a helper-independent, type C retrovirus isolated from stocks of Friend virus complex (spleen focus-forming virus plus MuLV). In cell culture, F-MuLV has an ecotropic and NB-tropic host range and causes XC cells to fuse. When injected into newborn NIH Swiss mice, F-MuLV produces hepatosplenomegaly, severe anemia, and numerous circulating hematopoietic precursors in the peripheral blood with normal thymus and lymph nodes after 3 to 6 weeks. Recently, we molecularly cloned an 8.5-kilobase pair (kbp) form of F-MuLV DNA from which we could recover the pathogenic F-MuLV virus by DNA transfection of NIH 3T3 cells. From this molecularly cloned F-MuLV DNA, we have now subcloned in pBR322 a 4.1-kbp HindIII fragment which contains in continuity 3.0 kbp from the 3' terminus (env and c region), 0.6 kbp of the terminal repeat sequences, and 0.5 kbp from the 5'terminus of the viral RNA (genome). NIH 3T3 fibroblasts were transfected with this DNA fragment an then infected with the wild mouse amphotropic retrovirus (cl 1504-A). In cell culture, 1504-A is a helper-independent type C virus which has an N-tropic host range and does not cause fusion of XC cells. When injected into newborn NIH Swiss mice, 1504-A does not produce splenomegaly or thymic enlargement in mice held for up to 8 months. The transfection with the F-MuLV fragment and the infection with 1504-A consistently yielded virus preparations that were XC positive. From such virus stocks we were able to isolate both helper-independent and replication-defective XC-positive viruses. The helper-independent virus was shown to be a recombinant virus since it contains a gp70 molecule derived at least in part from F-MuLV and a specific gag precursor derived from 1504-A as determined by radioactive immune precipitation assays. When injected into newborn Swiss mice, the recombinant helper-independent virus caused hepatosplenomegaly in approximately 50% of the mice in 6 to 8 weeks. The histology of the diseased splenic tissue was indistinguishable from that seen in the disease caused by the whole F-MuLV. The replication-defective virus could be pseudotyped with new 1504-A virus, and this viral complex also caused the F-MuLV disease picture when the complex was injected into newborn Swiss mice. We conclude that the genetic information responsible for the pathogenicity of F-MuLV is contained within the 4.1-kbp DNA fragment, which includes env gene sequences, the terminal repeat sequences, and the c region sequences of the F-MuLV genome.
弗氏小鼠白血病病毒（F-MuLV）是一种辅助病毒非依赖型C型逆转录病毒，从弗氏病毒复合物（脾灶形成病毒加MuLV）毒株中分离得到。在细胞培养中，F-MuLV具有亲嗜性和NB嗜性宿主范围，并可使XC细胞发生融合。将其注射到新生的NIH瑞士小鼠体内，3至6周后，F-MuLV会导致肝脾肿大、严重贫血，外周血中出现大量循环造血前体细胞，而胸腺和淋巴结正常。最近，我们通过分子克隆获得了一个8.5千碱基对（kbp）的F-MuLV DNA，通过将其转染到NIH 3T3细胞中，我们能够回收致病性F-MuLV病毒。从这个分子克隆的F-MuLV DNA中，我们现在已将一个4.1-kbp的HindIII片段亚克隆到pBR322中，该片段连续包含来自3'末端（env和c区）的3.0 kbp、0.6 kbp的末端重复序列以及来自病毒RNA（基因组）5'末端的0.5 kbp。用该DNA片段转染NIH 3T3成纤维细胞，然后用野生小鼠嗜异性逆转录病毒（cl 1504-A）进行感染。在细胞培养中，1504-A是一种辅助病毒非依赖型C型病毒，具有N嗜性宿主范围，不会导致XC细胞融合。将其注射到新生的NIH瑞士小鼠体内，在长达8个月的观察期内，小鼠不会出现脾肿大或胸腺增大。用F-MuLV片段转染并感染1504-A后，始终产生XC阳性的病毒制剂。从这些病毒株中，我们能够分离出辅助病毒非依赖型和复制缺陷型的XC阳性病毒。通过放射性免疫沉淀试验确定，该辅助病毒非依赖型病毒为重组病毒，因为它包含至少部分源自F-MuLV的gp70分子和源自1504-A的特定gag前体。将该重组辅助病毒非依赖型病毒注射到新生瑞士小鼠体内，约50%的小鼠在6至8周内会出现肝脾肿大。患病脾脏组织的组织学特征与整个F-MuLV所致疾病中的表现无法区分。复制缺陷型病毒可以用新的1504-A病毒进行假型化，当将这种病毒复合物注射到新生瑞士小鼠体内时，也会导致F-MuLV疾病表现。我们得出结论，负责F-MuLV致病性的遗传信息包含在4.1-kbp的DNA片段中，该片段包括F-MuLV基因组的env基因序列、末端重复序列和c区序列。
