Simian Virus 40 Causes Persistent Infection of Muntjac Cells in the Absence of Virus Transformation

Abstract

SUMMARYSV40 infection of Muntiacus muntjak cells (ATCC, CCL: 157) resulted in abortive transformation with formation of T antigen and induction of cellular DNA replication in the absence of virus production. These cells were resistant to stable transformation by SV40 regardless of the route of infection, including microinjection of virus into cell nuclei. The present studies show that T antigen-containing cells persist and that the number of T antigen-positive cells remains constant in infected cultures, which is reflected in the nearly constant fraction of T antigen-positive cells in stationary cultures" and a decrease of the fraction of T antigen-positive cells in proliferating cultures. These data suggest that following cell division only one daughter cell on the average can maintain a detectable level of T antigen. The cell cycle kinetics of proliferating muntjac cultures were not altered by the abortively transforming infection, and infectious progeny was made following cell fusion with permissive CV-1 cells. It is suggested that the few copies of viral DNA that do persist are present in a 'plasmid-like' state as non-integrated DNA. In this way SV40 can appear to be lost from the majority of the cells in a culture but actually be conserved in a small population of cells for a long time. In such a state a papovavirus might go undetected in vitro as well as in vivo by even the most sensitive immunological and molecular techniques.

Effect of simian virus 40 on the temporal and spatial organization of DNA replication in Muntjac cells

“…Very little information is available concerning the effect of SV40 infection on the temporal organization of DNA replication. SV40 infection does not change the overall length of the S phase in Muntjac cells which are nonpermissive for SV40 and can be abortively transformed (17,18), but in permissive cell lines of African green monkey origin, such as AGMK and CV1, cells appear to be arrested after one round of cellular DNA synthesis (16). Similar observations have been made by Lehmann et al (34) and Hiscott and Defendi (25).…”

“…Cells fixed on cover slips in absolute ethanol at -70°C at 60 h after infection were stained for 60 min at 37°C with hamster anti-T serum (National Cancer Institute 79x-137) diluted 1:20 in PBS. The percentage of fluorescent nuclei remains essentially constant for the period from 24 to 72 h after infection (18). The anti-T serum had previously been adsorbed on subconfluent monolayers of Muntjac cells and clarified by centrifugation at 9,000 x g. Cells were then washed with PBS and incubated for 60 min at 37°C with fluorescein isothiocyanate-conjugated goat anti-hamster immunoglobulin G (IgG) (Antibodies Inc., Davis, Calif.) diluted 1:10 in PBS.…”

Papovaviral persistent infections.

“…The percentage of cells persistently infected with an episomal viral genome must continually PAPOVAVIRAL PERSISTENT INFECTIONS diminish if the cell population were dividing and viral DNA synthesis did not occur or did not keep pace with cellular replication. This was demonstrated in a system of nonpermissive muntjak cells infected with SV40 in which each cell division reduced the fraction of T antigenproducing cells by half (76). In contrast, T antigen continued to be synthesized by most cells of a nondividing culture.…”

“…In contrast, T antigen continued to be synthesized by most cells of a nondividing culture. These findings may be very important with respect to the negative results obtained in the screening of human tumor cell lines for BKV (see below), because the viral genome might persist in the tumors as an episome in a continually decreasing fraction of cells at a level below that detectable by current techniques (76). These results also indicate that episomal viral genomes might persist and remain biologically active in nonproductive nondividing cells, such as in the central nervous system (CNS).…”

Slowly Replicating Lytic Viruses: Pseudolysogenic Persistence and Within-Host Competition

“…However, if b v > b cell , viruses spread to all host cells. After the initial spread of viruses over all cells, new uninfected cells only emerge from divisions of infected cells where all viruses happen to end up staying in one daughter cell and the other daughter cell contains no virus-a common occurrence in infected cell populations [18,19]. Since there are more released viruses than uninfected cells, the extra free viruses accumulate, and are eventually eliminated being unable to find a new host.…”