Herpes Viruses. Human Herpes Virus 1 & 2

Question 1

Classification

Answer 1

Family: Herpeviridae

Genus: simplex virus

Common name:
Herpes simplex virus 1
Herpes simplex virus 2

Official name:
HHV 1
HHV 2

Question 2

Characteristics

Answer 2

• enveloped virus
• linear, dsDNA
• no virion polymerase
• cross reaction (HSV 1 and HSV 2)
• intranuclear replication —> intranuclear = Cowdry bodies

Question 3

Transmission

Answer 3

• Saliva

- direct contact with virus from the vesicles

Question 4

Pathogenesis

Answer 4

Gingivoestomatitis (1s site of infection)

initial vescular lesions occur in the mouth or on the face

The virus then travels up the axon and becomes latent in sensory (trigeminal) ganglia
- recurrences occur in skin innervated by affected sensory nerve and induced by fever, sunlight, stress, etc.

Dissemination to internal organs occurs in patients with depressed cell- mediated immunity with life-threatening consequences

Question 5

Disease

Answer 5

Herpes labialis (cold sores)

Herpes rash —> “dew drops on rose petal” appearance

Herpetic Whitlow = herpes on fingers —> common in
dentists

Keratoconjunctivitis (serpiginous corneal ulcers seen on Fluorescein slit lamp exam)

Keratitis

Encephalitis —> HSV-1 encephalitis often affects the temporal lobe (causing haemorrhages and necrosis in it)

Erythema multiform (may appear 1 - 2 weeks after infection)

Question 6

Microbiological diagnosis

Answer 6

• Detection&raquo_space;> cytopathic effect (CPE) in cell culture
• Identification&raquo_space;> antibody neutralization or fluorescent antibody test
• Tzanck smear of cells reveals multinucleated giant cells with intranuclear inclusions (but not specific for HSV-1)
• A rise in antibody titer can be used to diagnose a primary infection but no recurrences
• HSV encephalitis can be diagnosed using a PCR assay to detect HSV-1 DNA in spinal fluid

Question 7

Treatment and prevention

Answer 7

Treatment:
Acyclovir for encephalitis and disseminated disease
- it has no effect on the latent state of the disease

Trifluorothymidine for keratitis

Prevention:

• no vaccine
• Acyclovir can reduce recurrences
• recurrences can be prevented by avoid specific inciting agent i.e. intense sunlight