Increased hematopoiesis in mice soon after infection by Friend murine leukemia virus.
Friend murine leukemia virus (F-MuLV), an erythroleukemogenic replication-competent retrovirus, induces leukemia in its host after a long latency. However, the early effects of infection may determine the pathway that eventually leads to malignant transformation. To determine how F-MuLV affects host cell proliferation soon after infection, BALB/c mice were inoculated with virus and then were assayed for susceptibility to appropriately pseudotyped spleen focus-forming virus (SFFV) as an indicator of erythropoietic activity. Twelve-week-old mice exposed to F-MuLV for 9 days were more susceptible (by a factor of 30) to superinfection by SFFV than were nonviremic mice. To test whether increased susceptibility was the result of increased hematopoietic activity, hematopoietic progenitors from the spleens of F-MuLV-infected mice were enumerated with a clonal culture assay. Nine days after inoculation with F-MuLV, the numbers of colony-forming progenitors increased by a factor of 4. Morphological analysis of the cultured colonies showed that erythroid, granulocytic, monocytic, and mixed granulocytic-monocytic progenitors all had increased. Thus, F-MuLV more rapidly induced a generalized increase in hematopoiesis than has previously been reported. The splenic hyperplasia induced by F-MuLV soon after infection may explain its ability to accelerate leukemogenesis in mice also infected by the polytropic Friend mink cell focus-forming virus.
McArdle Laboratory for Cancer Research, University of Wisconsin-Madison 53706.
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D000367:Age Factors; D000818:Animals; D002999:Clone Cells; D004912:Erythrocytes; D005260:Female; D005622:Friend murine leukemia virus; D006410:Hematopoiesis; D007942:Leukemia, Experimental / Q000503:physiopathology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008815:Mice, Inbred Strains; D013154:Spleen / Q000254:growth & development / Q000382:microbiology*; D013155:Spleen Focus-Forming Viruses / Q000472:pathogenicity; D015163:Superinfection; D014766:Viremia