9 Lytic Infection by Adenoviruses

Abstract

THE PRODUCTIVE CYCLE
For the most part, the productive cycle of human adenoviruses has been studied in HeLa or KB cells growing in suspension culture and synchronously infected by high multiplicities (10–150 plaque-forming units [pfu]/cell) of serotypes belonging to group C. The time course of infection of KB cells with adenovirus type 2 is shown in Figure 9.1. Similar results have been obtained with serotypes belonging to the highly oncogenic group whose growth cycles, however, are somewhat longer (Mak and Green 1968). The duration of the infection depends, to some extent, on the type of host cell. For example, when primary cultures of human cells (rather than established cell lines) are infected by adenovirus 2, the productive cycle is prolonged by at least 12–15 hours (Ledinko 1970).

The productive cycle is divided by convention into two phases, early and late, delineated by the onset of viral DNA replication. During the early phase, only a fraction of the information encoded by the viral genome is expressed as mRNA (Fujinaga et al. 1968; Green et al. 1971), which directs the synthesis of a small number of viral proteins. At this time, viral mRNA constitutes a minor proportion of the total RNA of the cell; but once replication of adenoviral DNA begins, the amount of viral mRNA increases dramatically until, by 18 hours, it comprises virtually all the mRNA bound to the cell’s polyribosomes (Thomas and Green 1966; Lindberg et al. 1972). Late mRNA, present once viral DNA synthesis has been...