Multiplication of polyoma virus in mouse-hamster somatic hybrids: a hybrid cell line which produces viral particles containing predominantly host deoxyribonucleic acid.

The multiplication of polyoma virus in a mouse-hamster (3T3 x BHK) somatic hybrid line (10A), which, although permissive for viral multiplication, produces very low amounts of virus, has been studied. In this cell line, the efficiency of productive infection is high, but the yield of infectious virus is on the order of 0.5% of that of 3T3 cells. The amount of viral deoxyribonucleic acid (DNA) synthesized by these cells upon infection is about 5% of that of 3T3 cells. An examination of the virus produced in hybrid 10A revealed that it was only one-tenth as infectious as the virus grown in 3T3. Although the viral DNA synthesized in the infected 10A cells is normal, the DNA extracted from purified virus grown in 10A consists of approximately 10% of normal, supercoiled polyoma DNA molecules and of approximately 90% linear DNA molecules with a sedimentation coefficient of 14 to 16S. These DNA molecules appear to be of cellular origin but contain a limited amount of viral DNA sequences. The host DNA-containing particles are not infectious but appear to possess some biological activity; they give rise to a weak complementation effect, and part of them are able to induce T-antigen synthesis. In addition, the host DNA present in these particles is predominantly that which has been synthesized after infection. The correlation between the block in viral DNA synthesis in this cell line and the abnormal encapsidation of host DNA is discussed.