Cellular Deoxyribonucleic Acid Synthesis and Loss of Contact Inhibition in Irradiated and Contact-Inhibited Cell Cultures Infected with Fibroma Virus

Abstract

Cultural changes that follow infection of rabbit kidney cells with fibroma virus were studied. Characteristic alterations of cell morphology and development of multilayered piles and cords of cells were found to occur in infected cultures in which cell division was blocked by gamma radiation or by cell crowding and serum deprivation, thus indicating no dependence upon cell division. Fibroma virus infection did not remove blocks to cell division, but it did exert distinct effects upon nuclear deoxyribonucleic acid synthesis in cells blocked by radiation or cell crowding. Use of tritium-labeled thymidine and autoradiography demonstrated that after infection initial inhibition of nuclear incorporation was followed by sharply increased nuclear labeling at a time that coincided with beginning alterations of cell morphology and development of cell piling. MATERPALS AND METHODS Cells. Domestic rabbit kidney (DRK) cells, a strain of epithelial cells of New Zealand white rabbit origin (8), were used between the 20th and 35th subcultures.

Shope fibroma virus. II. Role of the virion-associated nucleases

“…By contrast, infection with the noncytocidal strain affects host DNA synthesis at a later time, to a lesser degree, and only temporarily. In addition, stimulation of host DNA synthesis is detected 3 days after infection with SFV-W, as has been reported by others (11,12,29). The differences in the host response to the two strains do not seem to be related to the uncoating or replication of viral DNA, since these processes take place at the same time with the two viruses (26); rather, they seem related to the content of nuclease activity in virions.…”

“…Inhibition of host DNA synthesis by vaccinia virus occurs very promptly after infection and is independent of virus replication (9,10,13,14). However, with Shope fibroma virus (SFV), a leporipoxvirus that causes benign tumors in rabbits, both stimulation and depression of host DNA synthesis have been reported (3,7,11,12,29). In an effort to resolve this contradiction, the effect of host DNA synthesis by infection with two strains of SFV, one that promotes cell growth and one that lyses cells (26), was studied.…”

Cytotoxic Antibody Response to Tumors Induced in Adult and Newborn Rabbits by Fibroma Virus

“…Cell cultures. Primary rabbit kidney (PRK) cells were prepared from 4-week-old New Zealand white rabbits by previously described methods (11). A cloned line of New Zealand white rabbit kidney cells (DRK3) 592 TOMPKINS A moved by scraping with a scalpel and small superficial crossing excisions were made in the dermis.…”

“…The Patuxent strain of fibroma virus and the WR strain of vaccinia virus were grown in monolayer of PRK cells in 0.473-liter prescription bottles as described previously (9). Fibroma virus was assayed by pock-forming units (PFU) on DRK3 monolayers under an overlay of 1% methylcellulose (11). Vaccinia virus was assayed in PRK cells by the plaque method using an overlay containing 1% agar (9).…”

“…Following infection of susceptible cells with fibroma virus, cellular deoxyribonucleic acid (DNA) synthesis and related functions are shut off while virus synthesis takes place (12 to 36 hr after infection). However, after this period of virus synthesis, cellular DNA synthesis resumes, and the cells may proliferate (11). Resumption of cellular DNA synthesis is accompanied by a concomitant decrease in infectious virus (11) and cytoplasmic virus antigen (3,6) suggesting that no further expression of virus genes occurs in these persistently infected cells.…”