human herpes virus

Question 1

What is the structure of herpesvirus?

Answer 1

120-200nm
Icosahedral capsid surrounding dsDNA
80 genes encoding for ~100 proteins

Question 2

What is the herpesvirus classification?

Answer 2

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

Question 3

What are diseases caused by human herpesvirus?

Answer 3

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

Question 4

How does herpesvirus infect?

Answer 4

Viral gD and gH+L bind to epithelial cell surface nectin-1 or heparin sulphate proteoglycans followed by gB

Question 5

What is herpes simplex?

Answer 5

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

Question 6

What is herpetic gingivostomatitis?

Answer 6

5 day incubation period
Halitosis, painful drinking/eating
Multiple oral vesicles- rupture- sloughing ulcers
Gingivitis w erythema
Malaise, pyrexia, lymphadenopathy
5-14 days

Question 7

How do you diagnose and treat herpetic gingivostomatitis?

Answer 7

Diagnose- typical appearance
Investigation
-rising antibody titre
-PCR
-presence of histological intraepithelial vesicles

Question 8

How does PCR work?

Answer 8

1. Denature DNA
2. Annealing of specific primers
3. Extension by polymerase
4. Amplification- repeat 30-35 times

Question 9

How is herpetic gingivostomatitis managed?

Answer 9

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

Question 10

What is the action of acyclovir?

Answer 10

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)

Question 11

What is herpes labialis?

Answer 11

Prodromal irritation
Vesicles at/near mucocutaneous junction of lips
Can be IO
Crusting
7-10 days
Reoccurs same sites

Question 12

How is herpes labialis managed?

Answer 12

Acyclovir cream 5%
OTC drying and antibacterial

Prophylactic- (oral 600-1000mg/day) only immunocompromised/susceptible to erythema multiforme

Question 13

What is the benefit of prophylactic acyclovir?

Answer 13

Reduce duration of pain
Reduce time to crusting
Reduce occurence of new lesions
Increase mean time to next reoccurrence

Question 14

What is herpetic whitlow?

Answer 14

Infection of fingers of someone handling oral tissues w someone w active herpes simplex

V painful/difficult to treat

Question 15

What is HSV encephalitis?

Answer 15

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

Question 16

What is HSV2?

Answer 16

Mainly genital
Multiple vesicles- rupture- sloughing ulcers

Question 17

What is VZV?

Answer 17

Primary- chicken pox (varicella) dormant in dorsal root/trigeminal ganglia

Secondary- herpes zoster (shingles) mostly adults, stress, illness, immunosuppression, mainly chest and back

Question 18

What is the oral disease associated w Herpes zoster?

Answer 18

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,

Question 19

If Herpes zoster affects the ophthalmic division, what are some complications?

Answer 19

Glaucoma
Cataract
Diplopia
Scarring of cornea

Question 20

How is Herpes zoster managed?

Answer 20

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)

Question 21

What is EBV (HHV4)?

Answer 21

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

Question 22

What is Burkitts lymphoma?

Answer 22

Malignant B cell lymphoma (many in tropical Africa)

Tx= cyclophosphamide (chemo)

Question 23

What is cytomegalovirus (HHV5)?

Answer 23

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