Biological and physical properties of the adenoviruses

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.

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

The strains of types 1 to 4 adenoviruses studied attained maximum combination with host cells, strain HeLa, in 5 to 6 hours. During this adsorption period approximately 75 per cent of the total virus became associated with the host cells. Following adsorption of virus to HeLa cells, these agents underwent cyclic multiplication periods similar to bacterial and other animal viruses. The latent or eclipse period of the multiplication cycle for types 1 and 2 viruses was 17 hours, whereas the types 3 and 4 agents had a latent period 14 to 15 hours in length. The rate of viral propagation during the incremental period was very similar for types 1, 2, and 4 viruses, but was slower for the type 3 agent. During the incremental period of viral propagation newly synthesized virus was not released into the fluid phase of the culture and even after 6 days of viral multiplication when marked cytopathic alterations of the infected HeLa cells had occurred, the spontaneous release was only 2 to 6 per cent of the total virus detectable.