Human Herpesvirus Flashcards
Structure human herpesvirus
dsDNA surrounded icosahedral capsid
Surface - glycoprotein for presentation
Classification of herpes viruses?
alpha - epidermal and neuronal virus (HHV 1,2,3)
beta - slow growing (T cell and leucocyte) (HHV 5,6,7)
gamma - b lymphocytes = (HHV 4,8)
How does HHV infect and replicate?
Glycoproteins on surface bind to host cell
Taken inside cell - uncoating DNA
Translocated to nucleus - transcribed mRNA
Viral protein made - replication viral DNA
Host cell membrane burst - cell damage and shed viral particles
Difference between HSV1/HSV2
HSVI = mainly oral, HSV2= mainly genital
Both have primary events of infection followed by reactivation events
What is HSV1
Herpetic gingivostomatitis
Virus enter trigeminal sensory neurone - migrate ganglia where it comes latent and integrate DNA
Reactivation of HSV1?
50% case remain dormant, 50% reactivated
Reactivate - virus migrate peripheral nerve ending - active viral particles are shed
Cause: UV, stress, immuno-suppression
Clinical features of herpetic gingivostomatis
3-10day initial incubation - duration 5-14 days
Multiple vesicles - rupture to form sloughing ulcer
Lesions: gingiva, lip, palate
Gingiva: erythema and sloughing
Malaise, pyrexia, lympahdenopathy
Diagnosis of HSV1
Typical clinical appearance
Investigation not usually done - PCR
Management HSV1
Acyclovir - 200mg 5 x day 5 days (only work in early infection)
Soft diet, paracetamol, antiseptic - chlorhexidine, cross infection
How does acyclovir work?
Converted triphosphate form - inhibit viral DNA polymerase = termination DNA chain
Human can’t phosphorylate ACV well - in HSV infected cells phosphorylated viral TK enzyme to ACV-P
ACV-P inhibit viral replication
Clinical features herpes labials?
Prodrome irritation
Vesicles at mucocutaenous junction
Crusting lesions - 7-10 days - infectious
Management HSV2
Acyclovir cream
Drying and antibacterial agent
Prophylaxis rarely justified - only immunocompromised
What is herpetic whitlow?
Herpetic infection of fingers from handling oral tissue w/ active lesion
What is HHV3?
Varicella-Zoster virus
Primary infection = chicken pox
Secondary infection = shingles
How does varicella infect?
Dormant dorsal root/ trigeminal gangia
1. Natural infection via nasophayrnx
2. Viral replication in regional lymph nodes
Primary Virdemia
3. Viral replication host tissue - viral Ag displayed
Secondary Virdemia
4. Skin/rash and fever
5. Cessation of fever and skin lesion +ve virus
6. Cessation of lesion - virus absent from skin
