HSV 1 & 2 and VZV Flashcards
What type of virus is herpesvirus?
- dsDNA
- linear
- icosahedral
- enveloped
T/F: Herpesvirus can have lytic or latent infections and all have systemic/generalized infections
True!
What response in all herpes infections is critical to keeping virus in check?
CD8-CTL
What are the antivirals for herpesvirus?
acyclovir:
- stop viral DNA replication
- activated by viral thymidine kinase to cause viral DNA chain termination
(vacylclovir used bc it is a prodrug and metabolized in body to acyclovir and has a longer half life in to body so less pills need to be taken)
famciclovir:
- oral prodrug of topical ointment penciclovir used interchangeably with acyclovir and vacyclovir
ganciclovir:
- used for CMV infection
- prodrug: valganciclovir with more side effects than acyclovir
Where does resistance to acyclovir class usually occur?
- viral thymidine kinase
- if resistance happens, drugs that are NOT phosphorylated by viral kinase can be used
T/F: HSV-1 and 2 can infect a person at the same time
True!
- the 2 are similar but not identical with 50% genetic identity
What do HSV-1 and 2 both infect?
- mucosal epithelial cells, lesions
- become latent in nerve ganglia: trigeminal ganglia in oral infections and sacral ganglia in genital infections
What occurs in latency of HSV-1 and 2?
- miRNA prevents viral lytic gene expression
- does not produce any viral proteins so no presentation of viral proteins in MHC1 and no killing by CTL’s
How will HSV and VZV travel to lay dormant?
- go up nerve retrograde axial transport and lay dormant
- cell can eventually reactivate and produce virus
Which HSV (1 or 2) cause genital herpes and oral herpes?
They both can be caused by each.
HSV-2 causes 70% of all genital herpes (HSV-1 causes 30%)
What is herpes labialis?
- any reactivation/re current oral herpes after primary infection
- usually less severe, fewer lesion, same place as primary lesion
- triggered by: stress, UV light, menstruation, dental procedures
- oral asymptomatic shedding of HSV-1 common in people who have been infected
- HSV-1 way more common
T/F: Asymptomatic infections of genital herpes are common
True!
- it is most common to get HSV from an asymptomatic shedding of a sexual partner
What are characteristics of genital herpes?
- majority is HSV-2 (now more 50%)
- HSV-2 infections have more reoccurrence and asymptomatic shedding than genital HSV-1 (meningitis common with HSV-2)
- infections/lesions present in genital epithelium, upper thighs, and anal area
- -clovir drugs can be taken prophylactically or daily to prevent outbreaks and transmission but don’t entirely stop asymptomatic shedding
What is Herpetic Whitlow?
- herpetic lesions on fingers
- common in dentists and other health care workers due to patients secreting herpes in salvia without visible sores
- can also be caused by autoincilation (HSV-1 or 2)
- reoccurrence is common
- gloves/handwashing are preventive
- -clovir for tx
What is ocular herpes?
- cause by reactivated oral herpes going to eye or spread by touching the eye and contaminating it with HSV-1 (more common in contact wearers)
- usually resolves without a problem but can cause more severe infection that scar the cornea
- reoccurrence is common with higher chance of some permanent vision loss so use ophthalmologist and antiviral eyedrops for tx
Who does herpes simplex encephalitis infect?
- 1/3 children
- 50% in pt over 50
What are the characteristics of herpes simplex encephalitis?
- almost all cases are HSV-1
- travels up olfactory or trigeminal nerves to temporal or frontal lobes of brain (can happen during primary infection or during reactivation of virus)
- virus replicates, causing necrosis of brain tissue
- prompt tx is needed (in 1-2 days) with acyclovir
(without acyclovir, high mortality) - survivors can have neurological defects
How is neonatal herpes spread?
- vertically
- most cases are due to primary infection while pregnant but can also be due to reactivation of infection close to labor
- most causes due to HSV-2 (HSV-1 cases are rising)
What is the tx of neonatal herpes?
- acyclovir in an infant can drastically reduce mortality
- if genital lesions close to delivery, deliver by C-section and acyclovir recommended starting 36 weeks of pregnancy
How contagious is varicella zoster/chickenpox?
- very. 90% of susceptible people in household will contract chickenpox
How is Varicella/chicken pox spread?
- respiratory droplets and lesions are contagious
- most lesions on face and trunk and less on extremities
What are characteristics of Varicella/chicken pox?
- more severe in adults and pregnant woman and immunocompromised (pneumonia)
- defining feature: vesicular rash. lesions present in all stages
- latent in dorsal root and cranial nerve and trigeminal ganglia
- do not give aspirin to children with chickenpox or influenza because can cause Reye’s syndrome
What is there a high risk of with varicella in pregnancy?
- high risk for pneumonia with high mortality
- can be lowered with tx: CFR, VeriZig and acyclovir
What are the characteristics of varicella in pregnancy?
- severe congenital disabilities if infected in 1st trimester… 0.4 to 2% risk
- baby can have disseminated disease if before delivery and before maternal antibody response can occur
- very rare
How does Zoster/Shingles occur?
reactivation of varicella virus along dermatomes (usually 1 to 3 adjacent)
What are the characteristics of Zoster/Shingles?
- can be very painful and lesions can be infectious and cause chickenpox in others
- herpes zoster opthamalicus: shingles outbreak near eye which can lead to vision loss if left untreated
- post-herpetic neuralgia: 1/3 of people can develop this which is mild to severe pain after resolution of lesions and can last up to years (more common in people over 60)
- occurs in more people over 50 due to CTL response for VZV to be waning
What are the vaccines for Varicella?
Attenuated vaccine:
- for all children to
prevent chickenpox
- 2 shots for complete protection
- contraindicated in immunosuppressed and pregnant people because it is attenuated
Subunit Vaccine Shingrex (enveloped glycoprotein E) with adjuvant:
- approved for shingles for all people over 50 who had chickenpox
- very effective in preventing shingles and post herpetic neuralgia
- if exposed to chickenpox without having a vaccine before, it can still be taken if within 72 hours to help
- if contraindicated for live-attenuated: varicella IgI can be given to help prevent infection
