Viral tegument

Overview
Certain viruses contain a tegument, which is a cluster of non-essential and essential proteins that line the space between the envelope and nucleocapsid of many enveloped viruses. The tegument generally contains proteins that aid in viral replication and evasion of the immune response, typically with the signaling and activation of interferon. Hence the tegument is usually released shortly after infection into the cytoplasm. These proteins are usually formed within the late phase of the viral infectious cycle, after viral genes have been replicated. Much information regarding viral teguments have been gathered from studying Herpes Simplex Virus.

Tegumental Properties
Viral teguments can be symmetrically arranged via structural and scaffolding proteins or can also be asymmetrically arranged, depending on the virus. Teguments are rarely haphazardly placed and usually involve scaffolding proteins in its formation around the nucleocapsid. Non-essential proteins included in the tegument may aid in immune response suppression, suppression of host mRNA transcription or suppression of intrinsic or cellular defenses. Essential proteins will include factors that help in either recruiting host transcription or translation factors, or directly transcribing/translating viral genes. Tegumental contents are released into the cytoplasm upon entrance into the cell upon which many tegumental proteins become active. The tegument may also aid in insertion of the viral genome into host cell cytoplasm or nucleus.

Viruses that have Teguments
Teguments are generally a property of enveloped viruses which have nucleocapsids, as tegument proteins cannot be stored in an efficient fashion in capsid-only viruses. Many DNA viruses also have teguments due to the fact that DNA viruses often need to package their own proteases and polymerases to begin viral transcription. The best studied examples are the Herpesvirus family, in which the tegument is most prominent.