MicrobiologyBytes: Virology: Herpesviruses Updated: September 11, 2007 Search

Herpesviruses

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The name herpes comes from the Greek 'herpein' - 'to creep' - these viruses cause chronic/latent/recurrent infections. Epidemiology of the common Herpesvirus infections puzzled clinicians for many years. In 1950, Burnet and Buddingh showed that HSV could become latent after a primary infection, becoming reactivated after later provocation. Weller (1954) isolated VZV (HHV-3) from chicken pox and zoster, indicating the same causal agent. Approximately 100 Herpesviruses have been isolated, at least one for most animal species which has been looked at. To date, there are eight known human Herpesviruses. The Herpesvirus family is divided into three sub-families:

Herpesviridae:

 

Ictalurivirus

Ictalurid herpesvirus 1

Vertebrates

Alphaherpesvirinae

 

Mardivirus

Gallid herpesvirus 2

Vertebrates

Simplexvirus

Human herpesvirus 1 (HSV-1, -2)

Vertebrates

Varicellovirus

Human herpesvirus 3 (VZV)

Vertebrates

Iltovirus

Gallid herpesvirus 1

Vertebrates

Betaherpesvirinae

Cytomegalovirus

Human herpesvirus 5 (HCMV)

Vertebrates

Muromegalovirus

Murine herpesvirus 1

Vertebrates

Roseolovirus

Human herpesvirus 6 (HHV-6, -7)

Vertebrates

Gammaherpesvirinae

Lymphocryptovirus

Human herpesvirus 4

Vertebrates

Rhadinovirus

Simian herpesvirus 2 (HHV-8)

Vertebrates

Herpes simplex virus

Herpesviruses have large (genomes up to 235kbp DNA), and are complex viruses containing ~35 virion proteins. All encode a variety of enzymes involved in nucleic acid metabolism, DNA synthesis and protein processing (protein kinase). The Herpesviruses are widely separated in terms of genomic sequence and proteins, but all are similar in terms of virion structure and genome organization:

Size: 180-200nm
Envelope: Present; associated glycoproteins.
Tegument: Protein-filled region between capsid and envelope.
Capsid: Icosahedral, 95-105nm diameter; 162 hexagonal capsomers.
Core: Toroidal (DNA around protein), ~75nm diameter.
Genome: Linear, d/s DNA, 105-235kbp
Replication: Nuclear.
Assembly: Nuclear.
Common Antigens: None!

Structure:

The structure of the herpesvirus particle is very complex. The core consists of a toroidal shape with the large DNA genome would around a proteinaceous core. The complex capsid surrounds the core. Outside the capsid is the tegument, a protein-filled region which appears amorphous in electron micrographs. On the outside of the particle is the envelope, which contains numerous glycoproteins (see discussion of Herpes Simplex Virus, below). To view an electron micrograph of negatively-stained herpesvirus particles click here. N.B. All herpesviruses are almost indistinguishable in electron micrographs.

To view an image of the herpesvirus capsid click here.

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Genome:

Herpesvirus genomes

All herpesvirus genomes have a unique long (UL) and a unique short (US) region, bounded by inverted repeats. The repeats allow rearrangements of the unique regions and Herpesvirus genomes exist as a mixture of 4 isomers. Herpesvirus genomes also contain multiple repeated sequences and depending on the number of these, genome size of various isolates of a particular virus can vary by up to 10kbp.

More information:

Detailed notes can be found in Principles of Molecular Virology.

CoverStandard Version: The 4th edition contains new material on virus structure, virus evolution, zoonoses, bushmeat, SARS and bioterrorism, CD-ROM with FLASH animations, virtual interactive tutorials and experiments, self-assessment questions, useful online resources, along with the glossary, classification of subcellular infectious agents and history of virology. (Amazon.co.uk)

Cover Instructors Version: The 4th edition contains new material on virus structure, virus evolution, zoonoses, bushmeat, SARS and bioterrorism, CD-ROM with all the Standard Version content plus all the figures from the book in electronic form and a PowerPoint slide set with complete lecture notes to aid in course preparation. (Amazon.co.uk)

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