A study of adenovirus-host cell system by the plaque technique

Application of human lymphoid cells for the evaluation of antivirals against human adenovirus type 19: Zalcitabine has superior activity compared to cidofovir

Human adenovirus type 19 (HAdV-19) is a major cause of the epidemic keratoconjunctivitis. Outbreaks of keratoconjunctivitis are problematic to human health, especially for infants, the elderly, and immunocompromised individuals. However, the development of anti-HAdV drugs has been hampered by inconvenient screening systems; therefore, development of a simple screening method is highly desirable. In this study, we identified that HAdV-19 can infect a human lymphoid cell line transformed with human T-cell leukemia virus (MT-2 cells). MT-2 cells supported HAdV-19 replication and showed apparent cytopathic effects within five days post-infection. Using a thiazolyl blue tetrazolium bromide (MTT)-based colorimetric assay on MT-2 cells, we were able to detect the anti-HAdV-19 activities of previously reported nucleoside/tide compounds, including (S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine (cidofovir), 2',3'-dideoxycytidine (zalcitabine) and 3'-deoxy-3'-fluorothymidine (trifluridine). Compared with previous methods, this system represents a more simple and rapid method to screen anti-HAdV-19 agents.

Adenovirus 41 growth in semi-permissive cells shows multiple-hit kinetics

Adenovirus type 41 infection of semi-permissive Chang conjunctival cells, monitored by fluorescent focus assay, followed multiple-hit kinetics. In non-permissive human cells, type 41 showed infectivity with two-hit kinetics in the presence of type 2. Type 41 infectivity was seen to be directly proportional to input concentration (one-hit) only in 293 cells, a continuous human line expressing Ad 5 E1 products.

Molecular biology of adenovirus type 2 semipermissive infections. I. Viral growth and expression of viral replicative functions during restricted adenovirus infection

As an initial step toward understanding the mechanisms underlying host cell restriction of adenovirus 2 (Ad2) replication, we have studied various cell lines derived from hamster (CHO-K1), rat (CREF, NRK-49F, C-3, C-9), and mouse (3T3-Swiss) tissues to determine their degree of permissivity to Ad2 replication. For each cell line tested, the time course of Ad2 growth was determined; the yield of infectious virus, as measured by titration on HeLa cell monolayers, was reduced 3 to 5 logs. This result is independent of the multiplicity of infection at multiplicities between 4 and 100 plaque-forming units (PFU) per cell. The Western immunoblotting technique was used to quantitate the amounts of early proteins (E1A 45-54K proteins, E1B 21 and 58K proteins, E2A 72K DNA binding protein) and late structural proteins (hexon, fiber) produced during restricted infections. All cell lines expressed 72K DNA binding protein and variable levels of other early proteins. C-3, C-9, and NRK-49F cells expressed hexon as well as low, but detectable levels of fiber protein. Mouse 3T3-Swiss cells failed to synthesize any detectable levels of late structural proteins. DNA synthesis analysis indicated all rodent cell lines were capable of replicating viral DNA. A decreased rate of viral DNA synthesis was observed in CREF cells. Evidence is presented which suggests newly synthesized viral DNA is unstable in 3T3-Swiss cells.

Assessment of specific virus infectivity and virus neutralization by a progeny virus immunotitration method as exemplified in an adenovirus system

An alternative method for the determination of specific virus infectivity and quantitative measurement of inhibitory activity of antibodies was developed using an adenovirus system. HeLa cells in 37 ml suspension cultures of 1.5 X 10(7) cells were infected with purified adenovirus 2 (Ad2) at different multiplicities of infection. After appropriate incubations, total progeny virus was isolated by a one-step CsCl gradient sedimentation procedure. Recovered virions were disrupted in the presence of 5 M urea and directly quantitated by rocket immunoelectrophoresis against an anti-hexon-antiserum. One infectious unit (IU) was defined as the lowest amount of virions capable of producing maximum yield of progeny virus in the standardized system, and corresponded to 32 physical particles, which also equalled one plaque-forming unit (pfu). The coefficient of the inter-experimental variation of the total virus yield determination was 13%. Reduction in progeny virus synthesis was taken as a measurement of the degree of the inhibitory effect of neutralizing antibodies. A linear relationship was obtained between dilution of a neutralizing antiserum and reduction in synthesis of progeny virus. Separate determinations of such neutralization revealed a coefficient of variation of 5.5%.

Microcalorimetric measurement of normal and adenovirus infected HeLa cells

The use of a simple microcalorimetric technique for the study of HeLa cells and adenovirus infected HeLa cells has been investigated. The calorimetric curves obtained with these two cellular systems showed characteristic differences. It is concluded that the method can serve as a useful analytical technique for the monitoring of the overall metabolic activity of tissue cells attached to a solid support.

Ocular herpes simplex infection. A clinical evaluation of virus isolation and studies on iodo-deoxyuridine resistance

Fifty-seven patients with ocular herpes simplex (HS) infection were studied for evaluation of existing methods for virus isolation and its application in diagnosis of HS infection. Virus was isolated in 90% of 34 cases with keratitis dendritica, when specimens were taken within eight days of onset of symptoms. The same isolation frequency was obtained in 10 cases of palpebral herpes with conjunctivitis. No isolation was possible in 11 cases of keratitis disciformis. Laboratory confirmation was obtained within four days in 70% of the positive cases. Ten strains of HS virus type 1 were examined for IDU resistance, 5 strains isolated prior to and 5 during IDU treatment. Nine of the strains had the same degree of sensitivity. One strain isolated during treatment was found to be highly resistant.

The kinetics of adenovirus infection and spread in cell cultures infected with low multiplicity

The cause for the long "incubation period" required till the appearance of the CPE in cell cultures inoculated with small amounts of adenovirus was investigated with adenovirus type 5 in HeLa cell cultures. The spread of virus in a culture from cell to cell is minimal, as shown in cultures with antiserum in the medium. The spread by spontaneously released virus via the medium is more important. It can be accelerated by repeated subcultivation after freezing and thawing the cells in 2 or 3 days' intervals. The quantity of virus produced by one infected HeLa cell was found to be 200 TCID50 within 48 hours, independent of the MOI. The growth cycle too is largely independent of the virus dose. The data suggest that the long duration of the "incubation period" is fully explained by a burst size of 200, a cycle length of 40 to 48 hours and the assumption of a slow and steadily working process of spontaneous release of virus into the medium. Some other possible causes, like impurities in the inoculum or slow and asynchronous early stages of infection, have been ruled out by appropriate experiments.

Statistical analysis of data bearing on the number of particles required to form a plaque

Methods of statistical analysis are presented for one or more dilution series experiments where the quantity of interest is the number of virus particles required to infect a cell. These methods are illustrated on several data sets drawn from the literature. Data from seven series, which have been used to support a two-particle model in the literature, are here shown to reject such a model decisively, whereas fifteen other experiments are found to be in excellent agreement with a one-particle model.

Separation and characterization of soluble adenovirus type 9 components

Four different soluble components of adenovirus type 9 (Rosen's group II) were identified. These were a complete hemagglutinin (HA), an incomplete HA, components carrying group-specific complement-fixing (CF) antigen, and components identified only by their hemagglutination-inhibition (HI) antibody consuming capacity and antigen activity in CF tests with an antiserum against complete HA. The complete HA sedimented relatively rapidly. It was composed of 12 pentons (vertex capsomers plus projections) aggregated into the form of a pentagonal dodecahedron. The length of the projections was about 12 to 13 mmu. Thus they appeared longer than the corresponding structures of types 3 and 11, but shorter than those of types 4 and 5. The rate of sedimentation of complete HA of type 9 was intermediate to those of the complete HA of types 3 and 11. The incomplete HA sedimented together with components carrying group-specific CF antigen, but could be separated from those by anion-exchange chromatography. Two different antigens were present in incomplete HA. One could absorb a group-specific hemagglutination-enhancing antibody, and was sensitive to treatment with trypsin. The other antigen could absorb the type-specific HI antibody and was not destroyed by trypsin. In addition to the incomplete HA, a separate population of more slowly sedimenting components showed a capacity to absorb HI antibody. These components could also be identified in CF tests when an antiserum against complete HA was applied. The incomplete HA, group-specific CF antigen, and slowly sedimenting HI antibody absorbing components are suggested to represent isolated penton, hexon, and fiber components, respectively.

Some physical and growth characteristics of a canine adenovirus isolated from dogs with laryngotracheitis

The canine adenovirus causing laryngotracheitis s was shown to exhibit a cytopathic effect, growth response, hemagglutinin synthesis, and complement-fixing antigen synthesis characteristic of adenoviruses in general. Infectious virus was not synthesized until at least 16 hours after infection. The release of the virus was prolonged for a considerable time after infection as was the hemagglutinin and complement-fixing antigen. The virus was elutetl from DEAE- and TEAE-cellulose columns with about 0.2–0.3 M NaCl at pH 7.3. Thermal inactivation of infectivity was similar to that of other adenoviruses, with almost complete inactivation in 40 minutes. Of the animal cells tested, only the canine primary cells and a continuous canine cell line were found to propagate the virus.

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.