Herpesviruses Flashcards
What are herpesviruses?
Large enveloped dsDNA viruses
How long do herpesvirus infections last?
Lifelong
What is the pattern of a herpesvirus infection?
Latency following the acute primary episodes and relapses occuring later in life when the individual becomes immunosuppressed
How many types of herpesvirus are there?
8
What are the classes of herpesviruses?
- α-herpesviruses
- ß-herpesviruses
- γ-herpesviruses
What are the features of class α-herpesviruses?
Fast growing cytolytic viruses that establish latent infection in sensory ganglia
What are the α-herpesviruses?
- HSV1
- HSV2
- VZV
What are the features of class ß-herpesviruses?
Slow growing viruses that lie latent in secretary glands and in the kidneys, and have long replication cyles
What are the ß-herpesviruses?
- CMV
- HHV6
- HHV7
What are the features of class γ-herpesviruses?
Latency occurs in lymphoid tissues
What are the γ-herpesviruses?
- EBV
- Karposi’s Sarcoma Virus
What type of envelope do herpes viruses possess?
Lipid
What surface do herpes viruses prefer?
Moist mucosal surfaces
Where are herpes viruses commonly secreted?
By oral and genital secretions
What is oral transmission of the herpes virus associated with?
Primary infection at an early age
When does genital tranmission of the herpes virus cause infection?
At a later period in life
Does oral or genital transmission of the herpes virus have a higher seroprevelance?
Oral
What are herpes viruses able to do with their genetic information?
Integrate it into host cells
What happens once herpes viruses’ have integrated their genetic information into host cells?
They remain as latent infections, and can occassionally reactivate their genetic material
What happens once herpes viruses’ have reactivated the genetic material they had previously integrated into host cells?
- Causes clinical illness
- Spreads to other susceptible individuals
What can some herpes viruses exhibit?
Oncogenic potential
How severe are primary infections of herpes?
Usually mild or subclinical
How severe are subsequent presentations of herpes?
Can have the potential to cause serious life-threatening illness
Who is especially at risk of subsequent life threatening presentations of herpes?
Immunosuppressed individuals
What is HHV 1 known as?
HSV1
What is HHV 2 known as?
HSV2
How are HSV1 and HSV2 spread?
By direct, person-to-person contact
Is HSV1 or HSV2 more common from oral transmission?
HSV1
Who is HSV1 common in?
Young children
What will HSV1 infection result in?
Asymptomatic response
What can HSV1 cause on reactivation?
- ‘Cold sores’
- Dendritic ulcers
- Herpetic whitlow in traumatised skin
- Fatal encephalitis
When does HSV1 reactivate as ‘cold sores’?
In times of stress
What are the symptoms of fatal encephalitis?
Personality changes and confusion
What can maternal transmission of HSV1 during childbirth result in?
Neonatal herpes
Is HSV1 or HSV2 more common from genital transmission?
Genital
What does HSV1 cause?
Genital ulceration
How does the recurrent infection of HSV2 differ from HSV1?
Milder and shorter lived
Why are the genital ulcers caused by HSV2 important?
Important in the transmission of the HIV infection
What class of herpesvirus are HSV1 and HSV2?
α
Where do HSV1 and HSV2 affect on initial epithelial cell infection?
The ganglion
Where do HSV1 and HSV2 viruses stay latent?
In the sensory neurone ganglion
What is HSV3 known as?
Varicella Zoster Virus (VSV)
How many serotypes does VSV have?
1
By what route is VZV spread?
Aerosol
How is VZV spread via the aerosol route?
The vesicles rupture to release the virus, and the VSV then spreads by aerosol spread
Where does VZV remain latent?
In the sensory ganglion
How does the primary infection of VZV appear?
Chicken pox
What is the infection rate of chickenpox?
90%
What happens in chickenpox?
Lesions and vesicular eruptions will form, which will subsequently rupture to release the VZV into the atmosphere and will heal spontaneously
What is the outcome of chickenpox?
Complete resolution is normal, unless lesions become infected as a result
What can VZV cause if its primary presentation is in adults?
VZV pneumonia
Who is especially at risk of VZV pneumonia?
Immunocompromised individuals
What is the prognosis of VZV pneumonia?
High mortality
What does the reactivation of VZV from the sensory root ganglion cause?
Shingles
What happens in shingles?
The virus travels down the axon of the sensory route ganglion to produce lesions in that dermatome
What is shingles commonly triggered by?
- Stress
- Immunocompromisation
What can shingles cause in the elderly?
- Ocular damage
- Post hepatic neuralgia
When does primary infection of VZV commonly occur?
Between 4-10 years
What does primary infection of VZV provide?
Lifelong immunity
What is HHV 4 known as?
The Epstein Barr virus (EBV)
What does EBV cause?
Infectious mononucleosis
What class of herpesvirus is EBV?
γ
How does EBV spread?
Via saliva
What % of the population is EBV found in?
90-95%
How does EBV gain entry?
Via the pharynx
What does EBV infect once it has gained entry?
B lymphocytes
What happens once EBV has infected the lymphocytes?
It remains latent
How can EBV evade immune responses?
By inhibiting class I MHC presentation, reducing the load of class I MHC molecules by viral peptides
What are the symptoms of EBV infection?
- Malaise
- Fever
- Sore throat
- Lymphadenopathy
What properties does EBV have?
Oncogenic
What cancers can be caused by EBV?
- Burkitt’s lymphoma
- Nasopharyngeal carcinoma
- Lymphoma
Where does EBV cause Burkitt’s lymphoma?
Sub-saharan Africa
What is EBV caused Burkitt’s lymphoma in association with?
Malaria
Where does EBV cause nasopharyngeal carcinoma?
China
In whom does EBV cause lymphoma?
Immunosuppressed individuals
How long do symptoms of EBV last?
Around 2 weeks
What is treatment of EBV infection based on?
Mainly symptoms based
What is HHV 5 known as?
Cytomegalovirus (CMV)
How is CMV transmitted?
- Vertical
- Saliva
- Blood
- Sexual transmission
What is the prevalance of CMV?
Around 50% of the population by 35 years
Where des CMV remain latent?
In monocytes and lymphocytes
What class of herpesvirus is CMV?
ß
What is the clinical presentation of CMV?
Often asymptomatic or subclinical in initial infection, yet can produce mononucleosis-like symptoms in some
When can CMV spread to neonates?
To the foetus before birth, or after birth
What can CMV cause in neonates?
- Serious infections
- Later developmental defects
What can reactivation of CMV in immunocompromised individuals cause?
- Severe pneumoitis
- Colitis
- Retinitis
What can retinitis develop to?
- Retinal detachment
- Blindness
What does CMV cause on histology?
A ‘giant owl’ inclusion body
By when is HHV 6 and HHV 7 found in most individuals?
The second year of life
What is often the effect of HHV 6 and HHV 7 infection?
It is often subclinical
How can HHV 6 and HHV 7 sometimes arise in some individuals?
As Rosala infantatum
What are the symptoms of Rosala infantatum?
Produces rash and fever
What class of herpesvirus are HHV 6 and HHV 7?
ß
What is HHV 8 also known as?
Kaposi’s sarcoma virus
How is HHV 8 transmitted?
Vertically, or via mucosal transmission
How does HHV 8 initially present?
With mononucleosis-like symptoms
In whom can HHV 8 reactivate?
Immunocompromised individuals
How does HHV 8 present on reactivation in immunocompromised individuals?
As a vascularised tumour
What causes the vascularised tumour in HHV 8 infection?
Excessive angiogenesis, inflammation, and proliferation
How can the tumour in HHV 8 infection be treated?
Radiotherapy
What is a HHV 8 tumour associated with?
HIV
How is diagnosis of the herpesvirus made?
Though NAAT using specimens ffrom rashes, blood, or urine, or through serological testing
What does treatment of herpesviruses involve?
Mainly supportive care, yet in severe cases anti-virals can be used
What antivirals are used in the treatment of herpesvirsuesa?
Mainly ganciclovir or aciclovir
