A series of viable recombinants between adenovirus 2 (Ad2) and simian virus 40 (SV40) (nondefective Ad2-SV40 hybrids) have been isolated. The members of this series (designated Ad2+ND, through Ad2+ND5

The nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid virus, Ad2+ND,, does not induce heat-labile SV40 T antigen but does induce a previously uncharacterized heat-stable SV40 antigen-the SV40 "U" antigen. This antigen is detectable by both immunofluorescence and complement fixation by using sera from hamsters with SV40 tumors. Sera from hamsters bearing SV40 tumors can be divided into two groups, those that react with both SV40 T and U antigens (T+U+ sera) and those that react with SV40 T antigen only (T+Usera). SV40 U-specific sera from monkeys immunized with Ad2+ND,-infected cells do not react with SV40

Abstract.-A new nondefective hybrid virus has been plaque-isolated from the Ad.2-SV40 hybrid population. This virus replicates efficiently with one-hit kinetics in both human embryonic kidney and African green monkey kidney cells, induces an SV40 specific antigen which is detectable by immunofluorescence and complement-fixation using sera from SV40 tumor-bearing hamsters, and produces SV40-specific RNA detectable by DNA-RNA hybridization. The SV40-specific antigen induced by this virus is heat-stable, sensitive to inhibitors of DNA synthesis, serologically different from SV40 T and viral antigens, and is an unrecognized SV40 antigen.Since the initial reports describing the hybridization of human adenoviruses (Ad.) and SV40, two types of hybrid populations have been described: those free of detectable SV40 virions represented by the Ad.3 and Ad.7 populations; and those which release detectable SV40 virions represented by the Ad.1, 2, 4, 5, and 12 populations.'-3 Characterization of the infectivity and the SV40 T antigen-inducing capacity of the progeny of plaques isolated from human embryonic kidney (HEK) and African green monkey kidney (AGMK) cells have established that these hybrid populations consist of a mixture of nonhybrid Ad. virions and hybrid particles containing SV40 genome in Ad. capsids.4-7Studies on adenovirus plaque formation by the two types of Ad.-SV40 hybrid populations have shown that the nonhybrid component induces adenovirus plaques by one-hit kinetics in human embryonic kidney cells, indicating that one virion initiates plaque formation. In green monkey kidney cells, however, the induction of adenovirus plaques by these populations proceeds by two-hit kinetics, indicating that both a nonhybrid adenovirion and a defective hybrid particle (i.e., a particle requiring nonhybrid adenovirus to replicate in either human embryonic or green monkey kidney cells) are required to initiate adenovirus plaque formation.2' [4][5][6][7] Biological and biophysical studies on the Ad.7-SV40 hybrid population, E46 +, have shown that the adenovirus and SV40 DNA in these hybrid particles is covalently linked; thus, these particles are true molecular hybrids.8-'0 All efforts to obtain a pure clone of E46+ hybrid particles free of nonhybrid adenovirions have failed.4Biological studies on the Ad.2-SV40 (Ad.2++) t population have demonstrated that, in addition to nonhybrid Ad.2 virions, there are adenovirus encapsidated particles which are capable of producing SV40 plaques on AGMK monolayers by one-hit kinetics.2 These particles contain the infectious SV40 genome.The purpose of this paper is to describe the isolation from the Ad.2++ popula-1128

The Polyomaviridae have small icosahedral virions that contain a genome of approximately 5,000 bp of circular double-stranded DNA. Polyomaviruses infect hosts ranging from humans to birds, and some members of this family induce tumors in test animals or in their natural hosts. We report the complete nucleotide sequence of simian agent 12 (SA12), whose natural host is thought to be Papio ursinus, the chacma baboon. The 5,230-bp genome has a genetic organization typical of polyomaviruses. Sequences encoding large T antigen, small t antigen, agnoprotein, and the viral capsid proteins VP1, VP2, and VP3 are present in the expected locations. We show that, like its close relative simian virus 40 (SV40), SA12 expresses microRNAs that are encoded by the late DNA strand overlapping the 3 end of large T antigen coding sequences. Based on sequence comparisons, SA12 is most closely related to BK virus (BKV), a human polyomavirus. We have developed a real-time PCR test that distinguishes SA12 from BKV and the other closely related polyomaviruses JC virus and SV40. The close relationship between SA12 and BKV raises the possibility that these viruses circulate between human and baboon hosts.The polyomaviruses are a family of viruses characterized by small circular double-stranded DNA genomes and by 45-nm icosahedral particles consisting only of protein and nucleic acid. Some members of the family, such as budgerigar fledgling disease virus (BFDV), goose hemorrhagic polyomavirus (GHFV), and pneumotropic polyomavirus, cause lethal diseases, while others, such as hamster polyomavirus and murine polyomavirus, induce tumors in their natural hosts (11,13,14,15,17,18,21,31,35). In other cases, exposure to polyomaviruses results in a lifelong persistent infection with no clear symptoms. This is the case for the two known human polyomaviruses, BK virus (BKV) and JC virus (JCV), and for the monkey virus simian virus 40 (SV40) (12). In fact, a majority of humans harbor asymptomatic BKV and JCV infections. However, JCV can cause progressive multifocal leukoencephalopathy in humans that are immunocompromised, and several reports have linked BKV with hemorrhagic and nonhemorrhagic cystitis and nephropathy that are linked to immunosuppressive transplant therapy (4, 9, 16).Although over 11 polyomaviruses have been identified thus far, SV40 and murine polyomavirus are the best characterized. This is because they were the first identified members of the family and because both viruses are easily propagated in culture, where they undergo a well-defined productive infectious cycle. Following attachment to a specific receptor and transport of virions to the nucleus, viral chromatin is released and the early viral promoter is activated by the cellular transcription apparatus. This results in the synthesis of the viral early proteins, the tumor antigens or T antigens. The multifunctional T antigens function to drive the infected host cells into S phase, activate transcription of the viral late promoter, initiate and maintain viral DNA replication, a...

Four new nondefective adenovirus 2 (Ad2)-simian virus 40 (SV40) hybrid viruses have been isolated. Although these viruses (designated Ad2+ND2, Ad2+ND3, Ad2+ND4, and Ad2+ND,) were clonal derivatives of the same Ad2-SV40 hybrid population, they differ significantly from each other and from the previously isolated nondefective hybrid, Ad2+ND,, in their biological properties or in the amount of SV40-specific RNA,induced during lytic infection. Like Ad2+ND,, Ad2+ND2, and Ad2+ND4 pass serially in both human embryonic kidney (HEK) and primary African green monkey kidney cells. In contrast, Ad2+ND, and Ad2+ND5 pass serially only in HEK cells. Ad2+ND2 is like Ad2+ND1 in that it induces the SV40 U antigen, but not SV40 T antigen; however, in contrast to the perinuclear SV40 antigen induced by Ad2+ND,, the SV40 antigen induced by Ad2+ND2 is located peripherally in the cytoplasm as well as in the perinuclear region of infected cells. Ad2+ND4 induces both the SV40 T and U antigens. Ad2+ND3 and Ad2+ND5 do not induce serologically detectable SV40 antigens and are distinguished from each other on the basis of the relative quantities of SV40-specific RNA which they induce. The induction of different SV40-specific functions suggests the incorporation of different segments of SV40 DNA within the genomes of the respective hybrid viruses.