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Human Herpesvirus Flashcards

1
Q

What is the structure of the herpesvirus?

A 
DNA
Caspid
Tegument
Envelope
Glycoprotein spikes
Icosahedral caspid surrounding dsDNA
Virus size 120-200nm
Have 80 genes coding for 100 proteins
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2
Q

How to classify human herpesvirus?

A

alpha herpesviruses: Epidermal/neuronal viruses with a wide host range

  • Type 1 Herpes Simplex - Virus HHV-1
  • Type 2 Herpes Simplex Virus HHV-2
  • Varicella-Zoster Virus (VZV) HHV-3
β-herpesviruses: Slow growth, primarily in T-cells and leukocytes
- Cytomegalovirus (HCMV) HHV-5
- Human Herpesvirus 6 HH
V-6
- Human Herpesvirus 7 HHV-7

γ-herpesviruses: primarily B-lymphocytes:
- Epstein-Barr virus (EBV) - Barr virus (EBV) HHV 4
Human Herpesvirus 8 HHV-8

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3
Q

What does does Herpes Simplex Virus 1&2 cause?

A

Oropharyngeal and genital herpes

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4
Q

What does Varicella-Zoster Virus (HHV-3) cause?

A

Chicken-pox (Varicella) / Shingles (Zoster)

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5
Q

What does Epstein

-Barr Virus (HHV-4) cause?

A

Infectious mononucleosis (glandular fever), Burkitt’s lymphoma, nasopharyngeal carcinoma

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6
Q

What does Cytomegalovirus (HHV-5) cause?

A

Cytomegalic inclusion disease in utero

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7
Q

What does HHV-6 cause?

A

Exanthem subitum, fatigue syndrome

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8
Q

HHV-7 causes what?

A

Pityriasis rosea?

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9
Q

HHV-8 causes what?

A

Kaposi’s sarcoma (in AIDS pts)

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10
Q

What does HSV1 mainly cause?

A

Oral infecs

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11
Q

What does HSV2 mainly cause?

A

Genital infecs

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12
Q

How does HSV 1 cause herpetic gingivostomatitis?

A

Virus enters trigeminal sensory neurones - migrates to trigeminal ganglion
HSV1 becomes latent in trigeminal ganglion but dormant in 50% of cases
Migrates to peripheral nerve endings where active viral particles are shed

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13
Q

What reactivates a herpes simplex infection?

A

UV light
Stress
Illness
Immunosuppression

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14
Q

HSV 2 can cause herpes labialis - features of this?

A

Lesion (on edge of lip) resolves

Virus lays dormant in trigeminal ganglion until reactivated

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15
Q

What causes a primary HSV infection?

A

Source of virus:

  • Skin lesions
  • Saliva
  • Usually HSV1

Passive immunity
From maternal
Antibody in infancy

Source of virus:

  • Genital lesions
  • Genital secretions
  • Usually HSV2
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16
Q

What percentage of the primary HSV infections are symptomatic and asymptomatic?

A 
Asymptomatic = 90-99%
Symptomatic = 1-10%
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17
Q

What occurs when there is establishment of the HSV latent infection?

A

Reactivation of latent virus and 2ndry/recurrent infection

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18
Q

Incidence of herpetic gingivostomatitis?

A

Very common
Mainly affects young children
Sometimes young adults - more severe

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19
Q

Clinical features of herpetic gingivostomatitis?

A 
Incubation period 3-10 days
Duration 5-14 days
Multiple vesicles - rupture to form extensive sloughing ulcers
Gingivitis with erythema and sloughing
Malaise, pyrexia, lymphadenopathy
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20
Q

How to diagnose herpetic gingivostomatitis?

A

Clinical appearance

Main diagnostic difficulty with erythema multiforme

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21
Q

How to investigate herpetic gingivostomatitis?

A

Not normally done
Rising antibody attire/presence of IgM antibodies
Viral culture or PCR

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22
Q

What is the basic method of PCR?

A

Denature DNA to single strands at 95 degrees
Annealing of specific primers to DNA at 55 degrees
Extension by polymerase at 72 degrees
Amplification - Repeat 30-35 times

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23
Q

What occurs by the end of each PCR cycle?

A

Amount of DNA has doubled

24
Q

What occurs by the end of 30 cycles of PCR?

A

1 billion molecules from the one you started with

25
How to manage herpetic gingivostomatitis?
``` Acyclovir (200mg 5x daily for 5 days) if found early or immunocompromised Fluids and soft diet Analgesics/antipyretics (paracetamol) Local antiseptics (chlorhexidine) Topical analgesics (difflam) X-infection control ```
26
How does acyclovir work?
HSV thymidine kinase (TK) phosphorylates guanosine (G) when HSV DNA replicates ACV is phosphorylated to ACVP Inhibits virus replication Is a chain terminator
27
Herpes labialis clinical features?
Prodromal irritation Vesicles at or near mucocutaneous junction of lips Crusting lesions lasting 7-10 days Usually re-occurs at same sites Rarely: may occur, intra-orally, in nose or elsewhere on skin
28
How to manage herpes labialis?
Acyclovir cream 5% if used very early | OTC drying and antibacterial agents
29
Prophylactic treatment of herpes simplex virus 2?
Rarely justified | Prophylactic acyclovir will prevent lesions in the immunocompromised or those susceptible to erythema multiforme
30
What does acyclovir do in herpes labialis?
Prophylactic - oral AVC (600-1000mg/day in 2 doses) is effective Reduces: - Duration of pain by 1.4 days - Time to lesion crusting by 2.1 days - Occurrence of new lesions by 50% - Mean number of recurrences over a 4 month observation period INCREASES mean time to next recurrence from 46 to 118 days
31
What is herpetic whitlow?
Herpetic infection of the fingers from handling the oral tissues of someone with active 1 or 2 herpes simplex lesions
32
Features of herpetic whitlow?
Very painful Difficult to treat Prevention better than cure - wear gloves
33
Features of HSV encephalitis?
Mainly affects frontal lobes of the brain 70-80% mortality if untreated Of survivors, only 3% return to normal Usually people >50yrs (HSV-1) and neonates (HSV-2) affected
34
Signs and symptoms of HSV encephalitis in adults (HSV-1)?
Adults Headache and behavioural changes over several days Fever 11% have history of recurrent HSV infecs
35
Signs and symptoms of HSV encephalitis in neonates (HSV-2)?
``` Adults Skin rash, lesions and CNS symptoms Virus present in liver, lung and adrenal glands Resp distress Fits and convulsions Raised intracranial pressure ```
36
Incidence of HSV encephalitis in neonates?
1 per 300,000
37
What do HHV-3 and HSV1 and 2 have in common?
Similarities in structure and infection
38
What happens if you get varicella-zoster virus (HHV3)?
``` Chicken pox/varicella (primary infec) = Dormant in the dorsal root/trigeminal ganglion = Remains dormant OR Reactivation: Age (70% >50yrs) Stress Illness Immunosuppression ``` = Herpes Zoster (2ndry infec) Seldom reoccurs
39
Where does herpes zoster 2ndry infection (shingles) most commonly affect? What does it look like?
Chest and back only on 1 side (opposite to the side infected) = Blisters, rash
40
Herpes zoster causing oral disease most commonly affects what nerve? What are the 3 phases?
``` Trigeminal nerve Phases: - Preherpetic neuralgia - Rash - Post herpetic neuralgia ```
41
Explain the pre-herpetic neuralgia?
Pain in the distribution of the affected division of the trigeminal nerve Prior to the development of the rash May mimic dental pain
42
Explain the rash phase of herpes zoster?
Unilateral vesicles in the distribution of a branch of the trigeminal nerve: - Opthalmic - Maxillary - Mandibular Vesicles break down to form: - Ulcers - Crusting lesions Lasts 2-3 weeks
43
What eye problems can herpes zoster cause?
Glaucoma Cataract Double vision Scarring of the cornea
44
How to manage herpes zoster?
Acylovir 800mg 5 x daily for 7 days if seen soon after lesions develop Analgesics Ophthalmic referral if eye involved Avoid contact with children Alternatives to acyclovir: - Valaciclovir 1g 3xdaily for 7 days - Famciclovir 250mg 3xdaily for 7 days
45
Explain post herpetic neuralgia of herpes zoster?
10% of pts = unpleasant intractable burning pain in the distribution of the affected nerve More common in elderly Effective early treatment of zoster may decrease risk of neuralgia Treat pain with tricyclic antidepressants and neuropathic pain drugs
46
What is HHV-4 (EBV) associated with?
Infectious mononucleosis (glandular fever) - acute 1 infec with EBV) Burkitt's lymphoma - a B cell malignancy Nasopharyngeal carcinoma - epi cell malignancy Oral hairy leukoplakia - seen in AIDS pts and some transplant recipients
47
Where does primary infection EBV replicate and establish latency?
Replicates in oropharyngeal epi cells | Establishes latency in B lymphocytes
48
What is EBV latent infection of B lymphocytes necessary for?
Virus persistency Subsequent replication in epi cells Release of infectious virus into saliva
49
What percentage of the world's population are infected with EBV?
95%
50
Symptoms of infectious mononucleosis EBV?
Most are asymptomatic Sore throat Swollen cervical lymph nodes Mild fever
51
EBV in the oral environment - infectious mononucleosis signs?
Petechiae on soft palate Creamy exudates on fauces Cervical lymphadenopathy
52
What is burkitt's lymphoma?
Malignant, B cell lymphoma of high prevalence in children in tropical Africa at elevations below 1500 metres where malaria is present Usually affects jaw bone - tumour mass
53
How to treat burkitt's lymphoma?
cyclophosphamide (chemo)
54
What can HHV-5 (Cytomegalovirus) rarely cause in healthy individuals?
Glandular fever like illness | Salivary gland swelling
55
What can HHV-5 (Cytomegalovirus) cause in immunocompromised/AIDS pts?
Large ragged oral mucosal ulcers Salivary gland swelling Retinitis
56
What can HSV-8 cause in AIDS pts?
Kaposi's sarcoma

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