Characteristics on the adenoviruses. III. Reproductive cycle of types 1 to 4

CORRELATION OF PRODUCTION OF INFECTIOUS VIRUS WITH SEQUENTIAL STAGES OF CYTOLOGIC ALTERATION IN HELA CELLS INFECTED WITH ADENOVIRUSES TYPES 5 AND 7

Studies correlating the production of infectious adenovirus (types 5 and 7) and the progression of the stages of virus-induced cytologic change in HeLa cells are presented. The results reveal a close relationship between the development of the characteristic nuclear changes and adenovirus synthesis. They suggest that cells manifesting the first stages of nuclear change, characterized by the appearance of eosinophilic, Feulgen-negative inclusions, contain little or no mature infectious virus, whereas cells in the later stages, with Feulgen-positive and basophilic inclusions, contain relatively large amounts.

Intracellular localization of type 4 adenovirus. I. Cellular fractionation studies

HeLa cells infected with types 1 or 4 adenovirus were separated into cytoplasmic and nuclear fractions by mechanical disruption and differential centrifugation and the quantity of infectious virus in each was determined. The results showed that the majority of infectious virus of both types could be isolated in the cytoplasmic fraction. It was not possible to explain the large amount of type 4 virus in the cytoplasmic fraction by the number of nuclei disrupted in the fractionation procedure, but the amount of type 1 virus in the cytoplasmic fraction could have been contributed by disrupted nuclei. This suggested that there might be a basic difference in the intracellular formation of the two types of virus. The intracellular distribution of complement-fixing antigen was similar to that of infectious virus in type 4-infected cells. Technical difficulties, inherent in cellular fractionation studies, were encountered but did not appear to explain the results obtained.

Deoxyribonucleic acid (DNA) and protein alterations in HeLa cells infected with type 4 adenovirus

During a single cycle of multiplication of type 4 adenovirus in HeLa cells an average 2-fold increase in total DNA occurred over that measured in uninfected cells. Of the total DNA from infected cells about 23 per cent was extractable into 0.15 M NaCl, a quantity approximately four and a half times greater than that of the DNA obtained from normal cells in 0.15 M NaCl. Ninety to 99 per cent of infectious virus was also extracted into the 0.15 M NaCl fraction. Concurrently with the accumulation of DNA in virus-infected cells there occurred a 2-fold increase in total protein. The proportionate increases in protein were approximately equal in 0.15 M NaCl and water extracts of infected cells. High speed centrifugation indicated that the bulk of the DNA and protein was not directly associated with infectious viral particles. Although in virus-infected cells a markedly increased synthesis occurred of a DNA which had solubility properties different from the major portion of normal host DNA, nucleotide analysis did not reveal any other qualitative differences. However, a marked change in nucleotide molar ratios was observed in the 0.15 M NaCl-soluble DNA from virus-infected cells. It seems apparent from the findings that the biochemical alterations found in HeLa cells infected with type 4 adenovirus are intimately related to the infectious process.

Characterization of a factor formed in the course of adenovirus infection of tissue cultures causing detachment of cells from glass

Infectious tissue culture fluids of the majority of serotypes of adenovirus at low dilutions detach HeLa or KB cells from glass surfaces within a few hours after inoculation. A reproducible method for testing cell detachment was devised. The factor present in infectious tissue culture fluids and responsible for cell detachment is trypsin-sensitive and non-dialyzable; it is smaller and more resistant to the effect of heat or ultraviolet light than the infectious virus particle. Cell detachment activity was found to be temperature-dependent, and the cell-detaching titer of infectious tissue culture fluids was not affected by repeated exposure to HeLa cells. Inhibition of cell detachment by human or rabbit sera was observed only when other antibodies to adenovirus antigens were also present, but the antibody inhibiting cell detachment could not be correlated quantitatively with complement-fixing or homologous neutralizing antibody.

The life and times of adenoviruses

With Wallace Rowe et al.'s and Hilleman and Werner's isolations of viruses, subsequently termed "adenoviruses," a new area of research opened for me and gradually for many others. I was quickly able to associate the viruses with diseases in humans, and then our attention turned to the structure of the virion and how it replicated. Many virologists entered these areas of adenovirus research, for they were the central themes for most virologists at that time. We obtained more and more knowledge of the structure of the virion, its genome, and how it replicated and killed cells in culture so that they could no longer divide, although the virus infection did not lyse the infected cells, but we did not have the slightest idea how Ad5 produced disease in vivo. Then Wallace Clyde's timely note appeared, and we entered an exciting and profitable new field: an investigation of the mechanism by which Ad5 produces pneumonia. It must again be emphasized that the pneumonia that WtAd5 produces in cotton rats is pathologically very similar to that induced in humans. One of our earliest sets of experiments in the cotton rats was designed to determine whether region E3 was really nonessential even though the genes contained therein were not required for viral replication. We soon demonstrated that deletion of the E3 region produced a mutant that induced a highly pathogenic viral pneumonia. The potential role in pathogenesis of each of the genes within the E3 region was then investigated. Of maximum importance was the finding that deletion of the 19-kDa gene near the 5' end of the region produced a severe inflammatory response. This result led to the discovery that the E3 19-kDa protein regulated expression of the MHC factor on the surface of infected cells, and deletion of this gene produced a marked increase in MHC on the surfaces of infected cells and, therefore, a marked increase in the response of cytotoxic T cells. In addition, deletion of the gene encoding the 14.7-kDa protein, which was situated at the 3' end of the E3 region, resulted in an increase in polymorphonuclear leukocytes in the inflammatory response. A number of these findings led to hypotheses that could not be tested in the cotton rat since the necessary reagents were not available. Fortunately, our findings that only early viral genes are required to produce full pathogenesis led us to test mice because we had shown in a culture of mouse cells that all of the early viral genes are expressed. The C57BL/6N mouse proved to be an excellent host in which Ad5 produced full pulmonary inflammation. Thus, it was possible to test our hypotheses and to demonstrate their validity, showing that the virus induces cytokine elaboration, as well as to demonstrate the role of cytotoxic T cells in permitting Ad5 to produce persistent infections in lymphoid cells of organs such as the adenoid, from which the first adenovirus was isolated, and which had immediately led to my interest in investigating it and helping to develop the story of adenoviruses.

Sequential cellular changes produced by types 5 and 7 adenoviruses in HeLa cells and in human amniotic cells; cytological studies aided by fluorescein-labelled antibody

The sequential cytological changes which develop in tissue culture cells infected with adenovirus types 5 and 7 are described and compared with those produced by adenovirus types 1, 2, 3, and 4. The evidence that is presented indicates that types 1, 2, and 5 belong to one major subdivision of the adenovirus group and types 3, 4, and 7 to another. That the host cell nucleus is the principal site of adenovirus synthesis has been confirmed by fluorescent antibody studies. They have demonstrated the occurrence of type-specific adenovirus antigen in the characteristic intranuclear inclusions and other virus-induced structures reported to contain virus-like particles or shown by electronmicroscopy.

Nucleuc acid synthesis in types 4 and 5 adenovirus-infected HeLa cells

Type 4 adenovirus infection of HeLa cells effected a marked increase in synthesis of the saline-soluble DNA fraction, but not the host-cell DNA (the water-soluble fraction). This was demonstrated by the marked increase in specific activity of saline-soluble DNA but not water-soluble DNA when P³²-inorganic phosphate or sodium formate-C¹⁴ was employed. When these isotopes were used to label cells before viral infection rather than during the process of viral propagation, the saline-soluble DNA from infected cells had a specific activity of 10 to 20 per cent less than that of uninfected cells, indicating that the saline-soluble DNA was synthesized both from prelabeled precursors of the cell pools and unlabeled materials from the medium. Saline-soluble DNA began to increase between 10 to 12 hours after viral infection and 3 to 4 hours before appearance of newly propagated infectious virus. The specific activity of the acid-soluble pool of infected cells also increased between 10 to 12 hours after viral inoculation when sodium formate-C¹⁴ was used as a radioisotope. When P³²-inorganic phosphate was utilized, the specific activity of infected-cell RNA was increased approximately the same relative amount as when total RNA was determined chemically; i.e., 30 to 40 per cent. With type 5 adenovirus, not only did a 3- to 5-fold increase in saline-soluble DNA occur, but also an increase was measured in specific activity of RNA when P³²-inorganic phosphate was used.

Synthesis of virus-specific polymers in adenovirus-infected cells; effect of 5-fluorodeoxyuridine

Biochemical synthesis in adenovirus-infected HeLa cells was studied utilizing 5-fluorodeoxyuridine (5-FUDR), a potent inhibitor of deoxyribonucleic acid production. Synthesis of saline-soluble DNA and infectious virus was completely suppressed by addition of the analogue to cells as late as 10 hours after infection. The inhibitory effect of this compound was totally reversed by addition of 10^–6M thymidine to the culture medium. Synthesis of DNA essential for virus production began 10 hours after infection and was completed by 16 hours after infection. These data support the hypothesis that the saline-soluble DNA is a precursor of infectious virus particles. Studies of antigen production indicated that formation of virus-specific proteins was directly dependent upon synthesis of DNA.

A correlative study by electron and light microscopy of the development of type 5 adenovirus. II. Light microscopy

The evolution of the intranuclear lesion produced by type 5 adenovirus in HEp-2 and HeLa cells is described as seen in the light microscope and the bodies formed in the course of the infection characterized histochemically. Some 12 hours after infection acidophilic protein bodies, without appreciable nucleic acid, first appear in the nucleus and coalesce into a network. Within or in association with this material, DNA-containing masses (viral aggregates) are formed which rapidly increase in amount and then coalesce. At the same time, a protein is produced, histochemically different from that of the acidophilic or basophilic structures mentioned, within the infected nucleus, which constitutes a matrix within which regular cytstals of a protein, (presumably non-viral) materialize. These structural and histochemical features are correlated with details which have been observed in parallel studies with the electron microscope.

Infectivity titers of adenovirus type 5 suspensions after exposure to cigarette smoke

Suspension of adenovirus type 5 in 2.0 ml of cell culture fluid at 37 degrees C were subjected to smoke from four cigarettes over a 4-h period. The cigarettes were smoked in a normal manner, and the inhaled smoke was exhaled through glass tubing into the virus-containing fluid. The virus suspensions were then titrated, using monolayer cultures of HEp-2 cells. Smoke from filter-tipped or regular cigarettes caused a 2- to 3-log drop in titer of tissue culture infectious doses of adenovirus type 5 per 0.1 ml of virus suspension. No reductions in titers were observed with parallel suspensions of the virus subjected to normal inhaled and exhaled air.

Beta-glucuronidase response of cells infected with Adenovirus types 5 and 12

Beta-glucuronidase activity was investigated during a 48-h period in which virus replication and changes in cell morphology occurred. Infection of an established line of chimpanzee liver cells with either nononcogenic adenovirus 5 or highly oncogenic adenovirus 12 under one-step growth conditions produced differing patterns of enzyme activity. There was an increase in total activity and also enhanced leakage of beta-glucuronidase from cells infected with adenovirus 12. In contrast, the enzymatic pattern of cells infected with adenovirus 5 was similar to that of uninfected cells. Hydrocortisone prevented the abnormal release of beta-glucuronidase from adenovirus 12-infected cells. The compound had no effect on total enzyme activity or on virus replication and the development of cytopathology.

Role of ribonucleic acid biosynthesis in multiplication of type 5 adenovirus

Flanagan, John F. (University of Pennsylvania, Philadelphia), and Harold S. Ginsberg. Role of ribonucleic acid biosynthesis in multiplication of type 5 adenovirus. J. Bacteriol. 87:977-987. 1964.-The requirement for ribonucleic acid (RNA) biosynthesis in the multiplication of type 5 adenovirus was investigated by using radioactive phosphorus to label nucleic acids and two pyrimidine analogues, 6-azauridine and 5-fluorouracil or 5-fluorouridine, to inhibit synthesis of functional RNA. The data indicate that biosynthesis of RNA after infection is essential for production of virus-specific deoxyribonucleic acid, virus antigens, and infectious particles. The onset of essential RNA synthesis occurs 8 to 9 hr after virus infection and prior to the biosynthesis of other known virus-induced macromolecules.