Читать книгу Principles of Virology - Jane Flint, S. Jane Flint - Страница 62

The production of new infectious particles can take place only within a cell (Fig. 2.1). Virologists divide viral infectious cycles into discrete steps to facilitate their study, although in virus-infected cells no such artificial boundaries occur. The infectious cycle comprises attachment and entry of the particle, production of viral mRNA and its translation by host ribosomes, genome replication, and assembly and release of progeny particles containing the genome. New virus particles produced during the infectious cycle may then infect other cells. The term virus reproduction is another name for the sum total of all events that occur during the infectious cycle.

Some events are common to virus replication in animals and in cells in culture, but there are also many important differences. While virus particles readily attach to cells in culture, in nature they must encounter a host, no mean feat for nanoparticles without any means of locomotion. After encountering a host, the virus particle must pass through physical host defenses, such as dead skin, mucous layers, and the extracellular matrix. Such barriers and other host defenses, such as antibodies and immune cells, which exist to combat virus infections, are not found in cell cultures. Virus infection of cells in culture has been a valuable tool for understanding viral infectious cycles, but the dissimilarities with infection of a living animal must always be considered.