INCOMPLETE SIMIAN PAPOVAVIRUS SV40. FORMATION OF NON-INFECTIOUS VIRAL ANTIGEN IN THE PRESENCE OF FLUOROURACIL

Influence of SV40 Genome on the Replication of an Adenovirus-SV40 "Hybrid" Population

Feldman, L. A. (Baylor University College of Medicine, Houston, Tex.), J. L. Melnick, and F. Rapp. Influence of SV40 genome on the replication of an adenovirus-SV40 "hybrid" population. J. Bacteriol. 90:778-782. 1965.-Replication of a type 7 adenovirus-SV40 hybrid population in primary African green monkey kidney cells was accompanied by the formation of SV40 tumor antigen, adenovirus antigens, and cytopathic changes characteristic of adenovirus infection. Prior infection of the cultures with SV40 stimulated replication of nonintegrated adenovirus 7 but did not enhance the replication of the hybrid virus. These results suggest that the population of the adenovirus-SV40 hybrid studied contains many particles carrying SV40 information. Replication of SV40 virus was not enhanced by co-infection with nonintegrated adenovirus 7 or with the adenovirus-SV40 hybrid. Cytosine arabinoside strongly inhibited replication of the adenovirus-SV40 hybrid population in African green monkey kidney cells. Enhanced replication of nonintegrated adenovirus 7 by SV40 was blocked by cytosine arabinoside; this block could be reversed by 2-deoxycytidine or deoxycytidine triphosphate.

DETECTION OF SPECIFIC ANTIGEN IN SV40-TRANSFORMED CELLS BY IMMUNOFLUORESCENCE

With an immunofluorescent technique involving the use of serum of hamsters with SV40 tumors, nuclear fluorescence was detected in each of five cell lines, derived from four mammalian species, transformed by SV40 virus. Essentially all nuclei, including those of multinuclear cells, were fluorescent-stainable. Serum of hamsters bearing SV40 tumors was also found to give nuclear fluorescence in susceptible cells (AGMK or BSC-1) acutely infected with SV40 virus. These findings provide further evidence that cellular incorporation of the SV40 viral genome, with partial expression of the genome by synthesis of at least one virus-specific antigen, is an integral property of all SV40 transformed cells.

DIFFERENTIAL EFFECTS OF INHIBITORS ON THE STEPS LEADING TO THE FORMATION OF SV40 TUMOR AND VIRUS ANTIGENS

The effect of DNA antagonists and various antibiotics on steps in the synthesis of SV40 virus in green monkey kidney cells was investigated. Both the early forming tumor (T) antigen, as well as the later synthesized virus (V) antigen, were synthesized in the presence of fluorouracil and iododeoxyuridine. Cytosine arabinoside (and fluorodeoxyuridine in starved cells) prevented synthesis of V antigen but not T antigen. The synthesis of T antigen therefore does not require synthesis of virus DNA. Virus particles formed only in the presence of the iododeoxyuridine and they were non-infectious. Actinomycin D inhibited synthesis of both tumor and virus antigens, suggesting that the synthesis of these antigens involves DNA-dependent RNA. Puromycin allowed synthesis of the T antigen which remained localized at the nucleolar membrane. This finding with puromycin suggests that the T antigen is a protein of low molecular weight. Virus antigen forming in the presence of mitomycin C, p-fluorophenylalanine, iododeoxyuridine, or fluorouracil was distributed atypically. These inhibitors caused the V antigen to be diffusely spread throughout the nucleus, or to be concentrated at the nuclear membrane.

Inhibition of replication of rinderpest virus by 5-fluorouracil

5-Fluorouracil (5FU), an analogue of uracil, was found to inhibit the production of infectious particles of rinderpest virus (RPV) in Vero cells (African green monkey kidney cells) by 99%, at a concentration of 1 microgram/ml. The levels of individual mRNA specific for five of the virus genes were also reduced drastically, while the level of mRNA for a cellular housekeeping gene-glyceraldehyde-3-phosphate dehydrogenase (GAPDH)-was unaltered by fluorouracil treatment of infected cells. Both virus RNA and protein synthesis showed inhibition in a dose-dependent manner. The virions which budded out of 5-fluorouracil-treated cells also contained reduced amounts of virus proteins compared with virus particles from untreated cells.

The control of SV40 transcription during a lytic infection: late RNA synthesis in the presence of inhibitors of DNA replication

The transition from early to late transcription of SV40 DNA in productively infected BSC-1 cells was analyzed using both inhibitors of DNA replication, and early (Group A) temperature sensitive (ts) mutants of SV40. Late virus specific cytoplasmic RNA sedimenting at 16S in neutral sucrose gradients and complementary to the plus (L) DNA strand of SV40 was detected in cultures infected in the presence of three inhibitors of DNA replication (Ara-C, FdU, and chloroquine), even though the inhibition of viral DNA replication appeared to be essentially complete. After infection with the early SV40 mutant tsA58, no DNA replication was detected at the restrictive temperature (41 degrees C) and no significant late RNA complementary to the plus (L) strand was found, in either the cytoplasm or nuclei of infected cells. These data support the concept that expression of late viral functions requires the initiation of viral DNA synthesis or a functional gene A protein, or both.

Strand-specific transcription of polyoma virus DNA-early in productive infection and in transformed cells

The DNA strand origin of nuclear and cytoplasmic polyoma-specific RNA in productively infected mouse cells and in a line of polyoma-transformed hamster cells was determined by hybridization of unlabeled RNA with radioactively labeled separated strands of polyoma DNA. Early in the productive cycle (10 h postinfection) nuclear viral RNA is complementary to only about 40% of the E strand of viral CNA. No RNA complementary to the L strand was detected even when the RNA was first self-annealed to enrich for possible minor species. Early cytoplasmic RNA is complementary to the same 40% of the E strand. Thus, only that part of the poloma genome which codes for early virual messenger RNA appears to be transcribed. Late in infection, nuclear viral RNA is complementary to most or all of the L strand and to at least 60% of the E strand. Late cytoplasmic viral RNA hybridizes to 40 to 45% of the E strand and 50 to 55% of the L strand. The transformed cell nuclear viral RNA is complementary to 60% of the E strand, whereas cytoplasmic RNA is complementary to 40% of the E strand and comprises the same polyoma-specific sequences as are found in RNA early in productive infection. No L strand transcripts could be detected. Thus, in the transformed cells and late in productive infection, viral RNA sequences in the cytoplasm are a specific subset of those in the nucleus.

Early cytoplasmic vacuolization of African green monkey kidney cells by SV40

As early as 3--4 hours after infection with SV40 at a high input multiplicity, African green monkey (Cercopithecus aethiops) kidney (AGMK) cells developed cytoplasmic vacuolization. At 10--20 hours after infection, the vacuolization reached its maximal level, then disappeared and SV40 specific cytopathic change followed. This vacuolization developed before the synthesis of the specific T and V antigens. This early cytoplasmic vacuolization (ECV) was prevented by preincubating the virus with specific antiserum, or by heating the virus with MgCl2. The ECV could be induced by UV-irradiated SV40. Addition of metabolic inhibitors had no effect on the induction of the ECV. These results suggest that the capacity to induce the ECV resides in a structural component(s) of SV40 virion and the vacuolization is not associated with the replication of SV40.

Demonstration of oncogenic potential of mammalian cells transformed by DNA-containing viruses following photodynamic inactivation

The oncogenic properties of hamster embryo cells transformed by herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) and SV40 virus following photodynamic inactivation using neutral red were determined by subcutaneous inoculation into newborn Syrian hamsters. Cells transformed by all three viruses produced palpable tumors after different latent periods. Histopathological examination showed that HSV-2 tumors were fibrosarcomas and metastases were often seen in the lungs. HSV-2 primary tumors were reinoculated subcutaneously into weanling hamsters; they developed palpable tumors within 2 weeks. HSV-specific antigens were detected in the cytoplasm and/or on the surface of both the HSV-1 and HSV-2 tumor-cell cultures by the indirect immunofluorescence technique. The same method revealed SV40 tumor antigen in the nuclei of the SV40 tumor cells. Sera from HSV or SV40 tumor-bearing hamsters gave positive reactions when tested against HSV-infected hamster cells or SV40-infected monkey cells, respectively. These results demonstrate that herpes simplex virus and SV40, whose infectivity was lost following photodynamic inactivation, retained the virus genetic information necessary for transformation of normal cells to an oncogenic phenotype.

Variation in the oncogenic potential of human adenoviruses carrying a defective SV40 genome (PARA)

The acquisition of the defective SV40 genome by a variety of human adenovirus serotypes by the process of transcapsidation has resulted in the addition of oncogenic potential for newborn hamsters to the previously nononcogenic adenovirus types 1, 2, 5, and 6. These serotypes have previously been grouped together by the high GC content of their DNA. Transcapsidation of the SV40 genome to weakly oncogenic adenovirus types 3, 14, 16, and 21 has failed to increase their oncogenic potential although the parent adenovirus type 7 carrying PARA is highly oncogenic. These serotypes belong to the group possessing a DNA of intermediate GC content. All the PARA-adenovirus populations, even those that were nononcogenic, were able to induce SV40 transplantation immunity and therefore carry the SV40 transplantation marker as well as the marker for synthesis of SV40 tumor or T antigen.

Synthesis of virus deoxyribonucleic acid during abortive infection of simian cells by human adenoviruses

Rapp, Fred (Baylor University College of Medicine, Houston, Tex.), Lawrence A. Feldman, and Manley Mandel. Synthesis of virus deoxyribonucleic acid during abortive infection of simian cells by human adenoviruses. J. Bacteriol. 92:931-936. 1966.-Inoculation of green monkey kidney cells (GMK) with adenovirus types 2 or 12, under conditions where neither infectious virus was synthesized, resulted in an increase in the uptake of H(3)-thymidine into deoxyribonucleic acid (DNA). Extraction of the DNA from infected cells, followed by identification by isopycnic analysis in CsCl gradients, revealed the presence of virus DNA. Cells infected with adenovirus type 2 yielded DNA giving bands with peak densities of 1.699 g/ml [GMK DNA with 40 moles% guanine + cytosine (GC)] and 1.714 g/ml (adenovirus type 2 DNA with 55 moles% GC). Cells infected with adenovirus type 12 also yielded the GMK DNA and a band at 1.706 g/ml (adenovirus type 12 DNA with 47 moles% GC). The rate of synthesis of adenovirus type 2 DNA in KB cells (productive cycle) and in GMK cells infected only with adenovirus (nonproductive cycle) or with adenovirus and simian virus 40 (adeno-productive cycle) was not significantly different.

Effects of pancreatin on the growth of reovirus

Wallis, Craig (Baylor University College of Medicine, Houston, Tex.), Joseph L. Melnick, and Fred Rapp. Effects of pancreatin on the growth of reovirus. J. Bacteriol. 92:155-160. 1966.-The influence of pancreatin and other proteolytic enzymes on the growth, plaque formation, and antigenicity of reovirus was studied. Single-cycle yields of virus in the presence of enzyme were not increased, but multiple-cycle yields of virus were greatly enhanced. Immunofluorescence studies demonstrated that the transmission of reovirus from cell to cell is more rapid in the presence of the enzyme. These findings led to the development of a rapid plaque assay system for reovirus, a virus which has previously been difficult to assay by the plaque method. In the recommended procedure, pancreatin is incorporated into the agar overlay. Monkeys immunized with enzyme-treated reovirus yielded higher antibody titers than animals receiving the same amount of untreated virus.

Interaction of a simian papovavirus and adenoviruses. I. Induction of adenovirus tumor antigen during abortive infection of simian cells

Feldman, Lawrence A. (Baylor University College of Medicine, Houston, Tex.), Janet S. Butel, and Fred Rapp. Interaction of a simian papovavirus and adenoviruses. I. Induction of adenovirus tumor antigen during abortive infection of simian cells. J. Bacteriol. 91:813-818. 1966.-Adenovirus types 2, 7, and 12 undergo an abortive growth cycle in green monkey kidney cells; they induce the formation of adenovirus tumor antigen, but synthesis of adeno capsid antigen and infectious adenovirus was observed only when cultures were concomitantly infected with a simian papovavirus (SV40). Several other viruses, including herpes simplex and measles which replicate in monkey cells, and rabbit papilloma and human wart papovaviruses which do not, failed to stimulate adenovirus replication in the monkey cells. Adenovirus tumor antigen was detected 8 to 10 hr postinfection by immunofluorescent techniques. The antigen induced by adenovirus types 2 and 7 appeared as intranuclear masses; adenovirus type 12 tumor antigen also appeared as cytoplasmic and nuclear flecks. Sera from hamsters bearing tumors induced by adenovirus type 12 cross-reacted with tumor antigens induced by types 2 and 7 but not with antigens induced by SV40.

TUMOR AND VIRUS ANTIGENS OF SIMIAN VIRUS 40: DIFFERENTIAL INHIBITION OF SYNTHESIS BY CYTOSINE ARABINOSIDE

Cells infected with the papovavirus SV40 not only synthesize viral antigen but also synthesize the specific nonviral antigen found in SV40-induced tumors. In the presence of the DNA antagonist cytosine arabinoside, infected cells fail to make viral antigen but still synthesize the tumor antigen. Iododeoxyuridine does not inhibit the synthesis either of tumor or of virus antigen but does prevent the development of infectious virus.