A cytolytic virus is one that replicates within a host cell and ultimately causes cell lysis, releasing progeny virions and destroying the infected cell.
Explanation
Cytolytic viruses complete their life cycle by hijacking host cellular machinery to synthesize viral proteins and genomes, assemble new particles and disrupt cellular membranes. Unlike viruses that bud from the plasma membrane or establish persistent infections with minimal damage, cytolytic viruses produce a pronounced cytopathic effect, culminating in cell rupture. Picornaviruses such as poliovirus, coxsackievirus and rhinoviruses shut down host protein synthesis and restructure membranes for RNA replication, then induce lysis through viroporin activity. Adenoviruses assemble in the nucleus and produce proteins that alter nuclear transport and cause fragmentation of the cytoskeleton before cell disintegration. Orthomyxoviruses and reoviruses also culminate in host cell death, though budding may accompany lysis. The extent of lysis depends on cell type, viral load and innate immunity. Lytic replication triggers inflammation and tissue destruction that contribute to disease symptoms such as diarrhoea, respiratory epithelial loss or neuronal damage. In bacteriophages, the lytic cycle is contrasted with lysogeny, with temperate phages switching between the two states.
Illustrative examples
Poliovirus infection of motor neurons leads to rapid cell lysis and paralysis in severe cases. Rotavirus replicates in intestinal epithelial cells and causes diarrhoea through enterocyte destruction. Adenovirus type 5 causes lytic infection of respiratory or ocular epithelium, resulting in conjunctivitis or pharyngitis. Lytic bacteriophages, such as T4 phage infecting Escherichia coli, rapidly lyse bacterial cells. Oncolytic viruses such as a modified herpes simplex virus (talimogene laherparepvec) and adenovirus derivatives are engineered to preferentially infect and lyse tumour cells while sparing normal tissue.
Cytolytic viruses highlight the destructive potential of viral replication. Understanding the mechanisms of virus‑induced lysis informs antiviral strategies and the development of oncolytic therapies.
Related Terms: Lytic cycle, Cytopathic effect, Persistent infection, Oncolytic virus, Viroporin