Everything about Herpesviridae totally explained
The
Herpesviridae are a large
family of
DNA viruses that cause diseases in animals, including humans. The family name is derived from the Greek word
herpein ("to creep"), referring to the, re-occurring
infections typical of this group of viruses.
Herpesviridae can cause
latent or
lytic infections.
Viral structure
Herpes viruses all share a common structure—all herpesviruses are composed of relatively large double-stranded, linear
DNA genomes encoding 100-200
genes encased within an
icosahedral protein cage called the
capsid which is itself wrapped in a
lipid bilayer membrane called the
envelope. This particle is known as the
virion.
Herpes virus life-cycle
All Herpes viruses are
nuclear-replicating—the viral
DNA is
transcribed to
RNA within the infected cell's
nucleus.
Infection is initiated when a viral particle contacts a cell with specific types of
receptor molecules on the cell surface. Following binding of viral envelope
glycoproteins to cell membrane receptors, the virion is internalized and dismantled, allowing viral DNA to migrate to the cell nucleus. Within the nucleus,
replication of viral DNA and
transcription of viral genes occurs.
During symptomatic infection, infected cells transcribe
lytic viral genes. In some host cells, a small number of viral genes termed
latency associated transcript (LAT) accumulate instead. In this fashion the virus can persist in the cell (and thus the host) indefinitely. While primary infection is often accompanied by a self-limited period of clinical illness, long-term latency is symptom-free.
Reactivation of latent viruses has been implicated in a number of diseases (for example
Shingles). Following activation, transcription of viral genes transitions from latency-associated LAT to multiple
lytic genes; these lead to enhanced replication and virus production. Often, lytic activation leads to
cell death. Clinically, lytic activation is often accompanied by emergence of non-specific symptoms such as low grade fever, headache, sore throat,
malaise, and rash as well as clinical signs such as swollen or tender
lymph nodes and immunological findings such as reduced levels of
natural killer cells.
Human herpesviridae infections
There are eight distinct
viruses in this family known to cause
disease in humans.
Zoonotic infections
In addition to the Herpes viruses considered
endemic in humans, some viruses associated primarily with animals may infect humans. These are
zoonotic infections:
| Zoonotic Herpesviruses |
| Species |
Type |
Synonym |
Subfamily |
Human Pathophysiology |
| Macaque monkey |
CeHV-1 |
Cercopithecine herpesvirus-1, (Monkey B virus) |
α |
Very unusual, with only approximately 25 human cases reported. Symptom awareness and early treatment are important for laboratory workers facing exposure. |
| Mouse |
MHV-68 |
Murine gammaherpesvirus-68 |
γ |
Zoonotic infection found in 4.5% of general population and more common in laboratory workers handling infected mice. |
Animal herpesviridae
In
animal virology the most important herpesviruses belong to the
Alphaherpesvirinae. Research on
pseudorabies virus (PrV), the causative agent of
Aujeszky's disease in pigs, has pioneered animal disease control with genetically modified vaccines. PrV is now extensively studied as a model for basic processes during lytic herpesvirus infection, and for unravelling molecular mechanisms of herpesvirus neurotropism, whereas
bovine herpesvirus 1, the causative agent of
bovine infectious rhinotracheitis and
pustular vulvovaginitis, is analyzed to elucidate molecular mechanisms of latency. The
avian infectious laryngotracheitis virus is phylogenetically distant from these two viruses and serves to underline similarity and diversity within the Alphaherpesvirinae.
- Subfamily Alphaherpesvirinae
Taxonomy
The following genera are included here:
Subfamily Alphaherpesvirinae
Subfamily Betaherpesvirinae
Subfamily Gammaherpesvirinae
Unassigned
Further Information
Get more info on 'Herpesviridae'.
|
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