CSIM 1.19 Herpes Virus 1 Flashcards
List the members of the Herpesviridae virus family
- Herpes simplex virus (HSV)
- Varicella zoster virus (VZV)
- Cytomegalovirus (CMV)
- Epstein Barr Virus (EBV)
- Human Herpes Virus 6, 7 and 8 (HHV6, HHV7, HHV8)
Describe the virology of herpesviridae
- Double-stranded DNA
* Enveloped
What is latency? Which virus family exhibits latency?
What can this lead to?
Herpesviridae
• Viral DNA persists in specific cell types lifelong without producing virus
Viral reactivation
Describe viral reactivation
Intermittent production of virus from the latent genes which may or may not be symptomatic
Describe the primary infection and latency pathogenesis of HSV
- Herpes infects the mucosal cells lining the insie of the mouth and lips
- This causes vesicles (PRIMARY ORAL HERPES)
- As the immune response clears up the infection, some viral particles enter sensory nerve endings
- The virus travels up the sensory nerve to the cell body, where the viral DNA is stored
- This allows the virus to reactivate intermittently causing vesicles
- The immune system will quickly respond, but not quick enough to avoid coldsores in some reactivations
What can cause HSV reactivation?
- Immunosuppression
- Stress
- Menstruation
What is the seroprevelance of HSV 1 and 2?
- HSV1 80%
* HSV2 20%
How is HSV transmitted?
Mucosal contact
• Oral
• Genital
Which HSV usually causes:
1) Primary oral herpes
2) Oral reactivation
3) Primary genital herpes
4) Genital reactivation
1) HSV 1 or 2
2) Usually HSV 1
3) HSV 1 or 2
4) Usually HSV 2
What are the possible complications of HSV?
- Secondary bacterial infection
- Corneal ulcers
- Viral meningitis HSV 2
- Herpes simplex encephalitis HSV1
Who are the HSV risk groups?
- Neonates as there is a high mortality if untreated (dies of primary infection as it spreads from mother’s genitalia during childbirth)
- Immunocompromised as reactivations are more frequent and severe
If pregnant mother has a primary HSV genital infection during childbirth what is recommended?
C-section
What us herpetic whitlow?
HSV lesions on fingers after viral entry through wound (e.g. bitten)
What is the difference between primary and initial HSV infection?
Primary infection:
• First infection with either HSV 1 or HSV 2
Initial infection:
• First HSV 2 infection in those who have already been infected with HSV 1, or visa versa
How is HSV diagnosed?
PCR to detect viral DNA
How is HSV managed?
Symptomatic relief
Antivirals
• Aciclovir
Aciclovir is a prodrug. What enzyme activated it and where is this enzyme found? How does this enzyme structurally change aciclovir?
Therefore, what is the activated drug?
What does the activated drug do?
Thymidine kinase
• Viral enzyme only active in infected cells (thus few side effects)
• Adds a phosphate group to aciclovir
• Cellular kinases can then add 2 more phosphate groups
Aciclovir triphosphate
Inhibits viral DNA polymerase
How is aciclovir administered?
5 times a day orally (due to poor oral bioavailability)
Can be given IV in severe disease such as encephalitis or in immunocompromised
Can HSV be spread through respiratory routes?
No
Describe the pathogenesis of chickenpox and shingles
- Varicella Zoster Virus infection via respiratory mucosa/conjunctiva
- Replication in regional lymph nodes
- Primary viraemia
- Replication in liver and spleen
- Secondary viraemia
- Dissemination to skin causing chickenpox lesions
- Latency in dorsal ganglion
- Reactivation in later life as shingles
What is the proper name for chickenpox and shingles?
Chickenpox = varicella Shingles = zoster
What is the prodrome of chickenpox?
Describe the distribution of rash
What type of regions are present in chickenpox?
Fever
Centripetal distribution (around trunk)
Order: macules->papules->vesicles->pustules
How can smallpox lesions be differentiated from chickenpox lesions?
Smallpox lesions are all at the same stage, whereas chickenpox lesions are all at different stages along macules->papules->vesicles->pustules
How is chickenpox spread?
Respiratory (but not with shingles)
Direct contact
What is the average incubation of chickenpox and how long are people infectious with it?
14 days
Infectious from 2 days before rash to full crusting of vesicles (usually 5 days after rash start)
What are the possible chickenpox complications?
- Bacterial sepsis
- Varicella pneumonia
- Varicella encephalitis
Who are the risk groups for chickenpox?
- Pregnancy
- Neonates
- Immunocompromised
What are the zoster (shingles) compleications?
What are the zoster risk groups?
- Post herpetic neuralgia
- Opthalmic zoster
- Zoster encephalitis/meningitis
Which nerve does opthalmic zoster effect?
Trigeminal nerve (V1)
How is VZV diagnosed?
PCR to detect viral DNA
How is VZV treated?
Children not treated
Adults: aciclovir
What form of vaccine is used for varicella?
How does the zoster virus differ?
Who is this given to?
Live attenuated vaccine (this still becomes latent)
Identical, but 10x the dose. Given to elderly as it boosts the immunity to prevent reactivation
Given to over 70s
Describe post-exposure prophylaxis for VZV
Who is this given to?
Intramuscular zoster immunoglobulin in event of
Those who have had
• Face to face contact with infected individual
• >15 mins in the same room
• AND not immune
• AND a high risk group (Pregnant, neonates, immunocompromised)
Why do people usually only get shingles once?
The reactivation boosts the immune system response to that pathogen
