Types of Virus Cell Interactions

First, even when an infectious virion enters a susceptible cell, more often than not the encounter will be nonproductive — for reasons not fully understood. Second, some types of cells are nonperiiiisswe for particular types of virus. The viral replication cycle may be blocked at any point from attachment (owing to the absence of an appropriate receptor) through to the final stage of assembly and lelease (e.g., owing to the absence of an appropriate cellular protease to cleave an envelope glycoprotein and thus render the progeny virions infectious) If there is a defect in the viral genome, abortive replication will occur even within a fully permissive cell Two particular examples, discussed in Chapter 4, are the deletion mutants known as defective interfering (Dl) mutants and the point mutants known as conditional lethal mutants Olten a wild-type virus that replicates perfectly well in a particular type of host cell linds another cell type nonpermissive; in such cases it is a moot point whether

Table 5-1

Types of Virus-CHI Interactions

Table 5-1

Types of Virus-CHI Interactions

Type of infection

fcffects on cell

Production of infectious virions

Txamples

Cytocidal (lytic)

Morphological changes in cells

+

Alphaherpesvi ruses

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