Anemia- and polycythemia-inducing isolates of Friend spleen focus-forming virus. Biological and molecular evidence for two distinct viral genomes.
Two distinct clones of Friend spleen focus-forming virus (SFFV), differing in their erythroleukemic potential, are described. These isolates have been cloned free of their associated helper viruses and shown to be replication-defective. Both SFFV isolates have been rescued from rat fibroblast nonproducer cell clones with cloned replication-competent viruses, F-MuLVA and F-MuLVP, obtained from the anemia- or polycythemia-inducing isolates of Friend virus complex, respectively. These rescued viruses induce a rapid proliferative disease associated with the appearance of macroscopic spleen foci and splenomegaly. In addition, each is subject to regulation by the W, Steel (Sl), and Fv-2 host gene loci. These two isolates of SFFV can, however, be distinguished by both biological and molecular criteria. Friend SFFVP induces a rapid polycythemia associated with the appearance of large numbers of erythropoietin (EPO)-independent erythroid colony-forming cells in the marrow and spleen. In contrast, SFFVA induces a rapid anemia associated with a progressive decrease in the number of EPO-dependent erythroid colony-forming cells in marrow, and a rapid increase in the number of EPO-dependent  erythroid colony-forming cells in spleen. Furthermore, the nature of the disease induced by the two isolates of SFFV is independent of the Friend helper virus: SFFVP, rescued from a nonproducer cell clone with either F-MuLVA or F0MuLVP, induced a polycythemic transformation, whereas SFFVA, rescued with either F-MuLVA or F-MuLVP, induced an anemic transformation. The two Friend SFFV isolates can also be discriminated on the basis of translational products encoded by their gag and env genes: SFFVP encodes the amino-terminal gag-gene protein p15, whereas SFFVA encodes the gag-gene proteins p15, p12, and p30. In addition, the SFFV isolates encode nonidentical 55,000-mol wt env gene-related proteins that can be distinguished by analysis of their methionine-containing tryptic peptides.
D000740:Anemia / Q000382:microbiology; D000818:Animals; D000956:Antigens, Viral / Q000235:genetics; D002472:Cell Transformation, Viral; D002999:Clone Cells / Q000382:microbiology; D005260:Female; D005622:Friend murine leukemia virus / Q000235:genetics* / Q000302:isolation & purification; D005814:Genes, Viral; D006023:Glycoproteins / Q000235:genetics; D004915:Leukemia, Erythroblastic, Acute / Q000382:microbiology; D007942:Leukemia, Experimental / Q000382:microbiology*; D051379:Mice; D011086:Polycythemia / Q000382:microbiology; D014764:Viral Proteins / Q000235:genetics
D000956:Antigens, Viral; D006023:Glycoproteins; D014764:Viral Proteins