Cytomegalovirus

Question 1

Classification

Answer 1

1 cause of hearing loss and mental retardation —> in children

Family: Herpesviridae

Genus: cytomegalovirus

Species:

Common name: Cytomegalovirus

Official name: HHV5

Question 2

Characteristics

Answer 2

• enveloped virus
• icosahedral nucleocapsid
• linear, dsDNA
• no virion polymerase
• one serotype
• replicates in the nucleus of the host cell —> produces intranuclear inclusion bodies = “Owl’s eye” nuclear inclusions

Question 3

Transmission

Answer 3

• virus is found in many human body fluids: blood, saliva, semen, mucus, breast milk, and urine
• vertical transmission = TORCH infection
• sexual contact
• organ transplantation

Question 4

Pathogenesis

Answer 4

Initial infection usually in the oropharynx

In fetal infections, the virus spread to many organs (e.g. CNS, kidneys)

In adults, lymphocytes are frequently involved
»> a latent state occurs in mononuclear cells (monocytes, lymphocytes, macrophages …)

Reactivated by immunosuppresion

Question 5

Disease

Answer 5

1 cause of viral congenital infection

- Non immunocompromised infected individuals:
Mononucleosis:
- sore throat
- lymphadenopathy
- fatigue 

• Blueberry muffin rash (thrombocytopenia)
• jaundice and hepatosplenomegaly
• sensorineural deafness (#1 cause)
• ventriculomegaly
• periventricular calcification
• mental retardation (#1 cause)
• seizures

> > > > Congenital CMV is 80 - 90% asymptomatic

15% of affected children develop hearing loss (mostly unilateral but sometimes bilateral)

Infected pregnant women:

2nd trimester - highest risk of congenital CMV

Hydrops fetalis (heart failure with severe oedema - often leads to spontaneous abortion)

Transplantation risk:
- pneumonia

AIDS patients:
<50 CD4 count

• CMV retinitis (often unilateral but it could be bilateral) often describe as pizza pie retinopathy
• linear ulcerations in oesophagus
• CMV colitis with ulcerated walls

Question 6

Microbiological diagnosis

Answer 6

• Detection: CPE in cell culture
• identified by fluorescent antibody test
• “Owl’s eye” nuclear inclusions are seen
• Monospot tests (for mononucleosis) —> negative (it is only positive for EBV-mononucleosis)
• a four-fold or greater rise in antibody titer in convalescent-phase serum is diagnostic

Question 7

Treatment and prevention

Answer 7

Treatment:

• Ganciclovir is used to treat pneumonia and retinitis
• Resistance occurs due to mutations (of UL97 gene)
  In this case Foscarnet is used

Prevention:

• no vaccine is available
• Ganciclovir suppresss retinitis