human herpes virus Flashcards
What is the structure of herpesvirus?
120-200nm
Icosahedral capsid surrounding dsDNA
80 genes encoding for ~100 proteins
What is the herpesvirus classification?
ALPHA
-epidermal/neuronal w wide host range
-Type 1 and 2 Herpes simplex, Varicella-Zoster
BETA
-slow growth, in T-cells/leukocytes
-Cytomegalovirus, 6 and 7
GAMMA
-in B-lymphocytes
-EBV and 8
What are diseases caused by human herpesvirus?
Herpes simplex 1-oropharyngeal herpes and 2- genital herpes
VZV- chicken pox/shingles
EBV- glandular fever, burkitts lymphoma, nasopharyngeal carcinoma
Cytomegalovirus- disease in utero
HHV6- exanthem subitum, fatigue syndrome
HHV7- pityriasis rosea
HHV8- Kaposis sarcoma
How does herpesvirus infect?
Viral gD and gH+L bind to epithelial cell surface nectin-1 or heparin sulphate proteoglycans followed by gB
What is herpes simplex?
Primary- infection- herpetic gingivostomatitis (trigeminal ganglion where 50% remain dormant)
Secondary- reactivation- herpes labialis (peripheral nerve endings where active viral particles shed) due to UV, stress, illness, immunosuppression
Lesion resolves then virus lays dormant in ganglion until reactivated
What is herpetic gingivostomatitis?
5 day incubation period
Halitosis, painful drinking/eating
Multiple oral vesicles- rupture- sloughing ulcers
Gingivitis w erythema
Malaise, pyrexia, lymphadenopathy
5-14 days
How do you diagnose and treat herpetic gingivostomatitis?
Diagnose- typical appearance
Investigation
-rising antibody titre
-PCR
-presence of histological intraepithelial vesicles
How does PCR work?
1. Denature DNA
2. Annealing of specific primers
3. Extension by polymerase
4. Amplification- repeat 30-35 times
How is herpetic gingivostomatitis managed?
Acyclovir (500mg 5x daily 5 days) if found early or immunocompromised
Children- 100-200mg
Fluids/soft diet
Analgesics/antipyretics
Local antiseptics eg. Chlorhexidine
Topical analgesics eg. Difflam
Cross infection control
What is the action of acyclovir?
1. HSV thymidine kinase (TK) phosphorylates guanosine
2. ACV is a false nucleotide, human cells can’t phosphorylate it
3. TK phosphorylates ACV into ACV-P
4. ACV-P inhibits virus replication (chain terminator)
What is herpes labialis?
Prodromal irritation
Vesicles at/near mucocutaneous junction of lips
Can be IO
Crusting
7-10 days
Reoccurs same sites
How is herpes labialis managed?
Acyclovir cream 5%
OTC drying and antibacterial
Prophylactic- (oral 600-1000mg/day) only immunocompromised/susceptible to erythema multiforme
What is the benefit of prophylactic acyclovir?
Reduce duration of pain
Reduce time to crusting
Reduce occurence of new lesions
Increase mean time to next reoccurrence
What is herpetic whitlow?
Infection of fingers of someone handling oral tissues w someone w active herpes simplex
V painful/difficult to treat
What is HSV encephalitis?
Frontal lobes of brain
70-80% mortality
>50 years and neonates
Adults- headache, fever, behaviour change
Neonates- skin rash, lesions, CNS symptoms, in liver lung adrenal glands, resp distress, fits/convulsions, raised intracranial pressure
What is HSV2?
Mainly genital
Multiple vesicles- rupture- sloughing ulcers
What is VZV?
Primary- chicken pox (varicella) dormant in dorsal root/trigeminal ganglia
Secondary- herpes zoster (shingles) mostly adults, stress, illness, immunosuppression, mainly chest and back
What is the oral disease associated w Herpes zoster?
Pre herpetic neuralgia
-pain of infected division, may mix dental pain
Rash
-unilateral vesicles in distribution of branch, vesicles rupture into ulcers and crusting lesions, 2-3 weeks
Post hepatic neuralgia- burning pain in distribution of nerve, elderly,
If Herpes zoster affects the ophthalmic division, what are some complications?
Glaucoma
Cataract
Diplopia
Scarring of cornea
How is Herpes zoster managed?
Acyclovir (800mg 5x daily 7 days)
Analgesics
Ophthalmic referral if eye involved
Avoid contact w children
If post herpetic neuralgia- tricyclic anti depressants and Gabapentin (neuropathic pain drug)
What is EBV (HHV4)?
Associated w glandular fever, Burkitts lymphoma, nasopharyngeal carcinoma and oral hairy leukoplakia
Primary replicated in oropharyngeal epithelial cells
Latency in B-lymphocytes
Most asymptomatic, sore throat, swollen cervical lymph nodes and mild fever, petechiae on soft palate
What is Burkitts lymphoma?
Malignant B cell lymphoma (many in tropical Africa)
Tx= cyclophosphamide (chemo)
What is cytomegalovirus (HHV5)?
Viral inclusion bodies, dormant in lymphocytes (interfere w MHC I presentation)
Rarely causes disease
In immunocompromised- large ragged oral mucosal ulcers, salivary gland swelling, retinitis
Life threatening in new borns
