Members of the family herpesviridae are found in a wide range of host systems.
To date, at least seven different species are known to infect man, including
herpes simplex virus (HSV); cytomegalovirus (CMV), varicella
zoster (VZV); and Epstein Barr virus (EBV).
Herpesviruses have an envelope
surrounding an icosahedral capsid, approximately 100nm in diameter,
which contains the dsDNA genome.
When the envelope breaks and collapses away from the capsid, negatively stained
virions have a typical "fried-egg" appearance.
The herpes virus CAPSID is an icosahedron of triangulation number
T = 16. There are 12 pentavalent capsomers (one at each apex) and 150 hexavalent
capsomers. Each capsomer has a deep central indentation.
The ENVELOPE that surrounds the nucleocapsid is derived from the inner
nuclear membrane of the host cell.
Virus-encoded glycoproteins are incorporated into the virion envelope and
are visible as "spikes" that project from its surface.
In the micrograph of HSV, the glycoprotein B (gB) is clearly visualised in
clusters of spikes appoximately 10 nm in length.
Between the capsid and the envelope is an ill-defined layer of proteins,
collectively known as the tegument.
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© Copyright Linda M Stannard, 1995.