THE CONTINUOUS MULTIPLICATION OF LIPOVIRUS-INFECTED HUMAN CELLS

On the nature of the "lipovirus"

Experiments designed to elucidate the nature of the "lipovirus" are described. The development of characteristic nuclear lesions in human cells in vitro depended on the presence of an ameboid cell in the inoculum. The spatial separation of the ameboid cells from the human cells by a membrane filter 150 micro in thickness was sufficient to prevent the development of nuclear lesions. Nuclear lesions appeared to be the primary change of the affected human cells. This development of nuclear lesions was partially suppressed by FUDR and the suppression was reversed by thymidine. Time-lapse microcinematography showed that a 30 min intermittent contact between an ameboid cell and a human cell resulted in the retraction of both progenies of the human cell after a lapse of about 36 hr. Other human cells not in contact with the ameboid cell remained polygonal and continued to divide. Radioautography of the ameboid cell revealed the presence in the cytoplasm of thymidine-containing DNAse-sensitive materials. The development of antigens related to the ameboid cell within the cytoplasm of the human cell is described in the accompanying report (4).

Characteristics of serially propagated monkey kidney cell cultures with persistent rubella infection

Maassab, H. F. (University of Michigan, Ann Arbor), and J. A. Veronelli. Characteristics of serially propagated monkey kidney cell cultures with persistent rubella infection. J. Bacteriol. 91:436-441. 1966.-A persistent infection of LLC-MK(2) cells with rubella virus has been established and maintained for over 3 years. This "carrier culture," designated as LLC-MK(2)-RAL, possesses distinct morphological and biological characteristics when compared with the original uninfected LLC-MK(2) line. The mechanism of viral persistance has not been entirely elucidated, but available data suggest a regulated infection with transmission of the virus directly from cell to cell or through cell division. Interferon was isolated from RAL (rubella-associated line) culture, which explains partly the wide spectrum of resistance to superinfecting viruses. Amantadine, although inhibiting cultures of LLC-MK(2) cells infected with rubella virus, failed to cure the "carrier culture."

Radiation Resistance in Lipovirus-Altered Human Cells

Human cells altered by infection with the "lipovirus," a transmissible cytopathic agent, are highly resistant to ionizing radiation. Whereas about 500 roentgens will inhibit cell multiplication in normal cells, more than 500,000 roentgens are required to produce a similar effect in the altered cells. This gross change in cellular radiosensitivity may provide a useful system for studying in vitro the mechanisms of inhibition of cell division by radiation.