Mechanism of Host Cell Restriction in African Green Monkey Kidney Cells Abortively Infected with Human Adenovirus Type 2

Host cell restriction by GMK cells in abortive infections of adenovirus type 2 can be partially relieved by co-infection with SV40.     

Transcription and Transport of Virus-Specific Ribonucleic Acids in African Green Monkey Kidney Cells Abortively Infected with Type 2 Adenovirus

The techniques of deoxyribonucleic acid-ribonucleic acid (DNA-RNA) hybridization and immunological precipitation were used to compare the synthesis of adenovirus-specific macromolecules in African green monkey kidney (AGMK) cells infected with adenovirus, an abortive infection, and coinfected with both adenovirus and simian virus 40 (SV40), which renders the cells permissive for adenovirus replication. When viral protein synthesis was proceeding at its maximum rate, the incorporation of (14)C-amino acids into adenovirus structural proteins was about 90 times greater in the doubly infected cells than in cells infected only with adenovirus. However, the rates of synthesis of virus-specific ribonucleic acid appeared to be comparable in the two infections at all times measured. A time-dependent increase in the rate of RNA synthesis observed late in the abortive infection was dependent upon the prior replication of viral DNA. Moreover, all virus-specific RNA species that are normally made late in a productive adenovirus infection (i.e., the true late and class II early RNA species) were also detected in the abortive infection. Adenovirus-specific RNA was detected by molecular hybridization in both the cytoplasm and nuclei of abortively infected cells. Comparable amounts of viral RNA were found in the cytoplasmic fractions of AGMK cells infected either with adenovirus or with both adenovirus and SV40. The results of hybridization-inhibition experiments clearly showed that there was a class of virus-specific RNA molecules, representing about 30% of the total, in the nucleus that was not transported to the cytoplasm. This class of RNA was also identified in similar amounts in productively infected human KB cells. The difference in the abilities of cytoplasmic and nuclear RNA to inhibit the hybridization of virus-specific RNA from whole cells was shown not to be due to a difference in the molecular size of the RNA species from the two cell fractions or to the specific loss of a cytoplasmic species during RNA extraction procedures.     

Enzyme Induction in Green Monkey Kidney Cultures Infected with Simian Adenovirus

Thymidine kinase was induced after infection of an established strain of green monkey kidney cells (CV-1) with simian adenovirus SV15. Increased levels of thymidine kinase were first observed 8 to 10 hr postinoculation (PI), and the levels increased four- to eightfold by 16 to 24 hr PI. A transient increase (1.5- to 3-fold) of deoxyribonucleic acid (DNA) polymerase activity was also observed about 18 hr PI, but the level of deoxycytidylic deaminase was not enhanced. The inductions of thymidine kinase and DNA polymerase were not obtained when protein synthesis was inhibited with 10⁻⁵ M cycloheximide. However, the enzyme increases did take place when infected cultures were treated with 1-β-D-arabinofuranosylcytosine (ara-C), an inhibitor of DNA synthesis and SV15 replication. The incorporation of tritium-labeled thymidine (H³-dT) into DNA was also stimulated 8 to 24 hr after infection with SV15.     

Defectiveness of Interferon Production and of Rubella Virus Interference in a Line of African Green Monkey Kidney Cells (Vero)

Vero cells, a line of African green monkey kidney cells, failed to produce interferon when infected with Newcastle disease, Sendai, Sindbis, and rubella viruses, although the cells were sensitive to interferon. Further, infection of Vero cells with rubella virus did not result in interference with the replication of echovirus 11, Newcastle disease virus, or vesicular stomatitis virus, even in cultures where virtually every cell was infected with rubella virus. Under the same conditions, BSC-1 cells and other cells of primate origin produced interferon and showed rubella virus interference. The results indicate that the presence of rubella virus in the cell does not in itself exclude multiplication of other viruses and that rubella virus interference appears to be linked to the capability of the cell to produce interferon.     

Transformation of African Green Monkey Kidney Cells by Irradiated Adenovirus 7-Simian Virus 40 Hybrid

The ability of adenovirus 7-simian virus 40 (SV40) hybrid (strain LL "E-46") to replicate decreased exponentially as a function of the amount of gamma-irradiation; the ability to induce SV40 and adenovirus 7 T antigen decreased at a much slower rate. Nevertheless, the virus was still able to transform African green monkey kidney cells at a radiation dosage that had completely destroyed its replication ability. All transformed colonies were positive for SV40 T antigen but were negative for adenovirus 7 T antigen. The adenovirus 7-SV40 hybrid transformed cells were superinfectible with SV40 virus. Two of the three transformed cell populations apparently did not sensitize hamsters against the appearance SV40 primary tumors, thus suggesting a deficiency in the SV40 transplantation antigen.     

Site of Host Restriction of Simian Virus 40 Mutants in an Established African Green Monkey Kidney Cell Line

A previously described large-plaque morphology mutant of SV40 (SV-L) in primary African green monkey kidney (AGMK) cells has been shown to be restricted in the established AGMK line CV-1. The site of restriction is an early step in infection, involving the virus particle. A block in penetration or uncoating has been tentatively proposed. Restriction is observed in a number of other established lines, including monkey, human, and mouse. Independent large-plaque mutants were isolated in AGMK and their properties were compared with SV-L (temperature restriction, host restriction, and virion antigen). They can be separated into two classes. Both are restricted on CV-1, though to a lesser degree than SV-L. Further-more, both are coat mutants as determined by immunological analysis of their virions, suggesting a relationship between coat mutants associated with large-plaque morphology in AGMK and host restriction in established cell lines. Temperature restriction is seen with one but not the other of the mutants.     

Biochemical Consequences of Type 2 Adenovirus and Simian Virus 40 Double Infections of African Green Monkey Kidney Cells

African green monkey kidney (AGMK) cells were nonpermissive hosts for type 2 adenovirus although the restriction was not complete; when only 3 plaque-forming units/cell was employed as the inoculum, the viral yield was about 0.1% of the maximum virus produced when simian virus 40 (SV40) enhanced adenovirus multiplication. The viral yield of cells infected only with type 2 adenovirus increased as the multiplicity of infection was increased. Type 2 adenovirus could infect almost all AGMK cells in culture; adenovirus-specific early proteins and DNA were synthesized in most cells, but small amounts of late proteins were made in relatively few cells. Even when cells were infected with both SV40 and adenovirus, only about 50% were permissive for synthesis of adenovirus capsid proteins. Approximately the same quantity of adenovirus deoxyribonucleic acid (DNA) was synthesized in the restricted as in the SV40-enhanced infection. However, in cells infected with SV40 and type 2 adenovirus, replication of SV40 DNA was blocked, multiplication of SV40 was accordingly inhibited, and synthesis of host DNA was not stimulated. To enhance propagation of type 2 adenovirus, synthesis of an early SV40 protein was essential; 50 mug of cycloheximide per ml prevented the SV40-induced enhancement of adenovirus multiplication, whereas 5 x 10(-6)m 5-fluoro-2-deoxyuridine did not abrogate the enhancing phenomenon.     

Morphogenesis of Respiratory Syncytial Virus in a Green Monkey Kidney Cell Line (Vero)

The structure and morphogenesis of respiratory syncytial (RS) virus particles in a green monkey kidney cell line (Vero) were examined. Infected cells contained dense intracytoplasmic inclusions composed of filamentous structures. In places where inclusion material was associated with membranes, structural modifications were induced. There was a thickening of the membrane and an addition of projections 12 to 15 nm in length. The same changes were most frequently observed after association of isolated filamentous structures with the cytoplasmic membrane. The budding-off process was clearly visualized. The diameter of mature virus particles varied between 90 and 130 nm and that of the internal component varied between 11 and 15 nm. The similarities between ultrastructural features of cells infected with RS virus and pneumonia virus of mice are pointed out. It is proposed that these two viruses should be classified together in a third subgroup of myxoviruses.     

The Genome Landscape of the African Green Monkey Kidney-Derived Vero Cell Line

Continuous cell lines that originate from mammalian tissues serve as not only invaluable tools for life sciences, but also important animal cell substrates for the production of various types of biological pharmaceuticals. Vero cells are susceptible to various types of microbes and toxins and have widely contributed to not only microbiology, but also the production of vaccines for human use. We here showed the genome landscape of a Vero cell line, in which 25,877 putative protein-coding genes were identified in the 2.97-Gb genome sequence. A homozygous ∼9-Mb deletion on chromosome 12 caused the loss of the type I interferon gene cluster and cyclin-dependent kinase inhibitor genes in Vero cells. In addition, an ∼59-Mb loss of heterozygosity around this deleted region suggested that the homozygosity of the deletion was established by a large-scale conversion. Moreover, a genomic analysis of Vero cells revealed a female Chlorocebus sabaeus origin and proviral variations of the endogenous simian type D retrovirus. These results revealed the genomic basis for the non-tumourigenic permanent Vero cell lineage susceptible to various pathogens and will be useful for generating new sub-lines and developing new tools in the quality control of Vero cells.     

Electron Microscopy of Monkey Kidney Cell Cultures Infected with Rubella Virus

Two rubella virus strains isolated in this laboratory were investigated in terms of their growth in LLC-MK(2) cell cultures and their effect on cell morphology. Rubella virus grew readily in LLC-MK(2) cells, but cytopathic effects of the virus were not observed in infected cultures. Such infected cultures can be subcultured indefinitely and continue to shed virus. Examination of rubella-infected cell cultures by electron microscopy showed the presence of annulate lamellae in the cytoplasm of 15% of the cells. No changes were evident in the nuclei. These membranous inclusions varied in complexity from parallel arrays of annulate lamellae to large lamellar structures of complex morphology. An occasional cell contained a crystal lattice structure in association with the lamellae. Larger inclusions, consisting of disorganized arrays of "unit" membranes, were also found. Uninfected cells were devoid of annulate lamellae, crystals, and complex membranous inclusions. No viruslike particles were observed in any part of the cells from infected cultures. The significance of the structures observed has not been determined.     

Replication of Canine Herpesvirus: II. Virus Development and Release in Infected Dog Kidney Cells

The studies reported in this paper demonstrate that, although canine herpesvirus differs from other herpesviruses in that it is characterized by a restricted host range, the pattern of virus development in the permissive host closely resembles that previously described for herpes simplex virus. These experiments also reveal the formation in the infected dog kidney cells of a system of tubules and channels in which virions accumulate. It is suggested that these membrane-bound structures serve to protect enveloped virus from being uncoated in the cytoplasm and function in virus release from the infected cells.     

Replication of Simian Foamy Virus in Monkey Kidney Cells

The structure of foamy virus, its mode of maturation, and the origin of vacuoles in monkey kidney cells are described.     

Experimental Infection of African Green Monkeys and Cynomolgus Monkeys With a SIVAGM Strain Isolated From a Healthy African Green Monkey

An infection occurred in all African green monkeys and cynomolgus monkeys experimentally inoculated with SIV_AGM [TYO-1], as demonstrated by the appearance of an antibody to SIV_AGM [TYO-1] and the isolation of the virus. No monkey exhibited overt clinical disorders throughout the experimental period of 42 weeks. Thus, SIV_AGM was not pathogenic to its original host or to macaques, This system is proposed as a model for HIV infection manifesting no overt disease.     

Pattern of Protein Synthesis in Monkey Cells Infected by Simian Virus 40

After infection of several permanent monkey cell lines by simian virus 40 (SV40), four additional protein bands can be detected by simple sodium dodecyl sulfate-polyacrylamide gel electrophoresis of whole-cell extracts. These bands appear only after the onset of viral deoxyribonucleic acid (DNA) synthesis, and inhibitors of DNA synthesis prevent their appearance. Three of them correspond to three previously identified capsid components, VP1, VP2, and VP3. The fourth protein band, which does not correspond to a previously identified virion component, is induced by SV40 infection of CV-1 and BSC-1 cultures but not by infection of MA-134 cultures.