Properties of Simian Virus 40 Rescued from Cell Lines Transformed by Ultraviolet-Irradiated Simian Virus 40

Saul Kit, T. Kurimura, D. R. Dubbs
1969 Journal of Virology  
Simian virus 40 (SV40) strains have been rescued from various clonal lines of mouse kidney cells that had been transformed by ultraviolet (UV)-irradiated SV40. To learn whether some of the rescued SV40 strains were mutants, monkey kidney (CV-1) cells were infected with the rescued virus strains at 37 C and at 41 C. The SV40 strains studied included strains rescued from transformed cell lines classified as "good," "average," ".poor," and "rare" yielders on the basis of total virus yield,
more » ... irus yield, frequency of induction, and incidence of successful rescue trials. Four small plaque mutants isolated from "poor" yielder lines and fuzzy and small plaque strains isolated from an "average" and a "good" yielder line, respectively, were among the SV40 strains tested. Virus strains rescued from all classes of transformed cells were capable of inducing the transplantation antigen, and they induced the intranuclear SV40-T-antigen, thymidine kinase, deoxyribonucleic acid (DNA) polymerase, and cellular DNA synthesis at 37 C and at 41 C. With the exception of four small plaque strains rescued from "poor" yielders, the rescued SV40 strains replicated their DNA and formed infectious virus with kinetics similar to parental SV40 at either 37 or 41 C. The four exceptional strains did replicate at 37 C, but replication was very poor at 41 C. Thus, only a few of the rescued virus strains exhibited defective SV40 functions in CV-1 cells. All of the virus strains rescued from the "rare" yielder lines were similar to parental SV40. Several hypotheses consistent with the properties of the rescued virus strains are discussed, which may account for the significant variations in virus yield and frequency of induction of the transformed cell lines. Of 83 cloned lines of mouse kidney cells (mKS-U) that were transformed at high input multiplicity by ultraviolet (UV)-irradiated SV40, 48 failed to yield simian virus 40 (SV40) by any rescue method so far employed. The remaining mKS-U lines have been classified as "rare," "poor," "average," and "good" yielders on the basis of (i) frequency of induction of SV40, (ii) size of SV40 yields, and (iii) the incidence of positive trials when the transformed cells were mixed with susceptible green monkey kidney (CV-1) cells in the presence of UV-irradiated Sendai virus (5). SV40 was recovered from "poor" yielders in less than 50% of the tests and from "rare" yielders on only one or two occasions in six or more trials, and in each case in very small amounts per culture. "Good" and "average" yielder lines yielded SV40 in all tests, and the frequencies of induction were > 10-4 and > l0-5, respectively. Transformed clonal mKS-U lines classified as nonyielders probably contain SV40 genomes defective in functions essential for release from integration or virus replication. However, the reason why the transformed clonal lines which did yield SV40 varied so significantly in the frequency of induction and virus yield is unclear. It seemed possible that some of the "rare" or "poor" yielder lines might contain leaky SV40 mutants and that virus rescued from these lines might be defective in some biochemical function. Although virus rescued from only 2 out of 19 lines classified as "good" or "average" yielders had mutant plaque morphology, SV40 rescued from 4 out of 11 "poor" yielder lines were plaque morphology mutants. On the other hand, SV40 rescued from all five "rare" yielder lines had normal plaque morphology. To learn whether some of the rescued SV40 strains were, in fact, defective in biochemical functions, the capacity of rescued virus strains to induce wild-type functions was studied after pro-585 on May 9, 2020 by guest
doi:10.1128/jvi.4.5.585-595.1969 fatcat:2quf7i3xkfeznlq5ekhtswek5a