Medical Virology

Question 1

Outline the structure of HSV-1 and HSV-2.

Answer 1

They have a large double stranded DNA genome.
The virion consists of an icosahedral nucleocapsid which is surrounded by a lipid bilayer envelope.
Between the capsid and the envelope is an amorphous layer of proteins, termed the tegument.

Question 2

What is the epidemiology of HSV-1 and HSV-2?

Answer 2

Universal- 100% humans- HSV-1 Ab
Infection first few years of life
HSV-2 later acquired 20-40%
Shed via infected skin/mucous membrane, direct contact.

Question 3

What specific part of the ganglion do the genital area and oral-facial infection affect?

Answer 3

Sacral ganglia and trigeminal ganglion respectively.

Question 4

What is the epidemiology of the varicella virus (HHV3)?

Answer 4

Highly infectious
Droplet spread (Respiratory)
Chicken pox
80-90% world wide

Question 5

What are the complication of Varicella infections?

Answer 5

Pneumonia
Post-infectious encephalitis
stroke
hemorrhagic varicella

Question 6

How does varicella present clinically?

Answer 6

mild febrile illness
generalised vesicular rash,
Heals without scarring
long-lasting immunity

Question 7

What are the complications of Zoster re-infection?

Answer 7

Clinical:
vesicular eruption
dermatomal

complications:
post-herpetic neuralgia
encephalitis, myelitis
Multi-dermatomal rash
Strokes; retinitis,

Shingles

Question 8

Describe the epidemiology of EBV (HSV4).

Answer 8

90-100% adults have antibodies
Primary infection- Oro-pharyngeal
epithelium
Latency B Cell
reactivation- Asymptomatic shedding in saliva
Transmission:
Saliva, kissing
as for CMV

Question 9

What is the clinical presentation of EBV?

Answer 9

Benign lymphoproliferative disorder B lymphocytes

mononucleosis
Fever, malaise
rash
Generalized lymphadenopathy
sore throat
Hepato-splenomegaly
atypical lymphocytosis
self-limiting
Immune response clears (most) infected B
cells

Question 10

What are the key EBV oncogenes?

Answer 10

LMP-1 and LMP-2A
oncogenesis occurs if there is translocation of c-myc/Ig gene promoter

Question 11

What is the epidemiology of HHV5 CMV?

Answer 11

close contact, 90%d
Early life: mother to child BF
siblings
creches
Adulthood: close contact with person shedding virus, body viruses
Iatrogenic: blood transfusion
organ transplant

Question 12

What are the clinical syndromes of CMV?

Answer 12

1. Primary infection in adulthood
   Infectious mononucleosis-like illness
   Fever, rash, lymphadenopathy, hepatitis
2. Congenital infection-such as mental retardation, deafness, etc (10%)*, Tip of the iceberg: had hepato-splenomegaly,
   thrombocytopaenia and microcephaly

CMV disease in immuno-suppressed patients, low CMI:
1. Interstitial pneumonia (Transplant, HIV-infected infants)
2. Retinitis
3. GIT ulceration
4. Neurological disorders

Question 13

What is the treatment for CMV?

Answer 13

Ganciclovir/Valganciclovir

Question 14

Give examples of B lymphocytes LPDs that are associated with EBV.

Answer 14

1. Post transplant LPD
2. X-linked LPD
3. Non Hodgkin’s lymphoma:
   - endemic Burkitt’s
   - primary CNS lymphoma in HIV
   - Immuno-compromised
4. Hodgkins disease (certain forms)

Question 15

Give examples of Epithelial LPDs that are associated with EBV.

Answer 15

5. Naso-pharyngeal carcinoma
6. Gastric carcinoma

Question 16

What is the ideal therapy for EBV infection?

Answer 16

Reduction in immunosuppression
No benefit to using anti-virals
Rituximab:
Mono-clonal antibody to CD20
Removes EBV-transformed B cells

Question 17

What are the diseases associated with HH6?

Answer 17

1. Primary infection in babies
   Roseola Infantum
   febrile illness
   rash
   Febrile convulsions
2. Infectious mono-nucleosis
3. Immuno-compromised patients
   Reactivation is common, but role in
   Disease is unclear
4. Neurotropic: - encephalitis

Question 18

What is the epidemiology of HHV6?

Answer 18

Universal human infection
Exposure in early life
90% by the age of 5
persistence with periodic shedding
2 variants A and B

Question 19

Describe HSV1 and 2 infections.

Answer 19

Spread through close contact and direct contact with the skin lesion.
1- 100% of people are infected by this virus and infect oral-facial via the trigeminal ganglion.
2- 20-40% of people are infected by this virus and it infect the genitals via the sacral ganglion.
remains latent in the dorsal root ganglion.

Question 20

What are the stimuli for the reinfection of HSV-1 and HSV-2?

Answer 20

Sunlight
menstruation
febrile
stress
immunosuppression

Question 21

Clinically, how does HSV 1 and 2 reinfection appear?

Answer 21

keratitis
cold sores
genital herpes

Question 22

Explain the rare conditions caused by HSV1 and 2.

Answer 22

Neonatal Herpes, during birth, mother to child, the child is susceptible due to lack of Ab against the viruses, further, a lack of CMI causes a disseminated infection.
Encephalitis
Fulminant hepatitis, pneumonia (RDS) and multi-organ failure in adults, spontaneously in healthy people due to a primary or reactivated infections.

Question 23

What are the outcomes of a maternal infection of VZV during pregnancy?

Answer 23

<20 weeks, severe mother and congenital varicella syndrome (2%)
>20 weeks, severe mother and minimal disease, protected by maternal Ab

During birth and post natally, severe in baby no Ab, exposure without maternal Ab.

Question 23

What is the treatment for HSV and VZV, and what is its mechanism?

Answer 23

Acyclovir
Nucleoside analogs, and it interferes with DNA polymerase

Question 24

What does mean if the CMV virus is detected in your saliva and urine?

Answer 24

That is shedding and not necessarily disease.

Question 25

How do we confirm a CMV infection?

Answer 25

Ag in WBC (pp65 antigenaemia)
CMV viral load
Histology of infected organ