SummarySA12, a newly recognized SV40-related primate papovavirus, transformed early passage hamster kidney cells. These cells, designated SAHK-1, were characterized by increased saturation density, altered morphology, loss of contact inhibition, increased growth rate, an indefinite life span, reduced serum requirements for growth, an ability to grow in soft agar, and the presence of SA12-specific T-antigen. Infectious virus was not rescued by Sendai virus-induced fusion of SAHK-1 cells with permissive cells. Inoculation of transformed hamster cells into syngeneic hosts produced adenocarcinomas, undifferentiated sarcomas, and mixed tumors containing both elements. SA12 T antibodies were demonstrated in all the tested sera from tumor bearing animals.
SA12 virus, originally isolated from an uninoculated South African vervet monkey kidney culture, was identified as a new member of the simian virus 40 (SV40)-polyoma subgroup of papovaviruses. The virus produced a cytopathic effect with nuclear enlargement in primary rhesus kidney cells. The virion had papovavirus morphology and a diameter of 44 to 45 nm. The DNA of the virus was a circular, double-stranded, superhelical molecule with a mean length 101% that of SV40 DNA and an estimated molecular weight of 3.3 X 10(6). The virus was found to be unrelated to other papovaviruses by neutralization, immune electron microscopy, and immunofluorescence tests with antiviral sera. SA12 virus-infected cells exhibited a capsid antigen, which has recently been found to be common to viruses of the SV40-polyoma subgroup. The virus readily transformed kideny cells from 10-day-old hamsters. Inoculation of transformed cells produced tumors in 3- to 4-week-old hamsters. The T antigens of SA12 and SV40 viruses were strongly and reciprocally cross-reactive. A high proportion of the sera of chacma baboons, Papio ursinus, and a comparatively lower proportion of the sera of vervet monkeys, Cercopithecus pygerythrus, had neutralizing antibodies to SA12 virus
Simian papovavirus SA12 agglutinated human, guinea pig, and chicken erythrocytes. SA12 hemagglutinin was most effectively released from debris of infected tissue culture cells at an alkaline pH.
Cell cultures derived from foreskins of 19 newborn infants were exposed to irradiated or unirradiated BK virus (BKV), an SV40-related papovavirus infection of man, and were observed for viral cytopathic effect (CPE) and for possible transformation. Four of the cultures were passed serially and maintained for a period of 9 weeks on medium containing BKV anti-serum. All infected cultures developed viral CPE. Irradiation of virus delayed but did not prevent viral CPE. In nearly one-half of the cultures, some regrowth occurred following extensive virus-induced destruction of the cell sheets but the regrown cells, as a rule, remained infected with BKV and could not be passed. In two instances, regrown cells (JV-1 and JV-2) could be passed, and these had some of the characteristics of transformed cells. They were essentially free of BKV viral antigen but contained, in over 90% of the cells, the intranuclear T antigen. They were resistant to superinfection with BKV. In contrast to the uninfected control cells which were uniformly fibro-blastic in appearance, cells in JV-1 and JV-2 cultures were pleomorphic with a predominance of stellate cells and multinucleated giant cells. However, JV-1 and JV-2 cultures were contact inhibited, did not reach high saturation densities, and could not be maintained beyond the 30th passage.
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