virionencoded

Virion-encoded refers to proteins, enzymes, and sometimes RNA that are encoded by the viral genome and packaged into the virion particle during assembly, and are delivered to a host cell at infection. These virion-encoded components can include structural elements such as capsid and envelope proteins, as well as non-structural enzymes and regulatory factors that participate in the earliest stages of replication.

Because virion-encoded products are already present in the incoming particle, they can function before the virus begins expressing its own genes. This allows them to influence initial events such as genome delivery, early transcription, replication, and modulation of host defenses. The term helps distinguish these components from those synthesized de novo after infection by the host cell.

Examples span multiple virus families. Some viruses package functional enzymes inside the virion, including RNA-dependent RNA polymerases in certain dsRNA viruses and influenza viruses, or reverse transcriptase in retroviruses. Tegument or matrix proteins in herpesviruses are classic virion-encoded regulatory factors delivered upon entry to modulate immediate-early gene expression and host cell pathways.

Significance and applications: virion-encoded components can determine infection efficiency, tissue tropism, and immune evasion. They are of interest in antiviral research and vaccine design because disrupting delivery or function of these factors can block the initiation of infection or alter disease progression.

Notes: the concept can extend to virion-associated host components, but virion-encoded typically refers to products encoded by the viral genome itself.