Medical Virology Flashcards
Outline the structure of HSV-1 and HSV-2.
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.
What is the epidemiology of HSV-1 and HSV-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.
What specific part of the ganglion do the genital area and oral-facial infection affect?
Sacral ganglia and trigeminal ganglion respectively.
What is the epidemiology of the varicella virus (HHV3)?
Highly infectious
Droplet spread (Respiratory)
Chicken pox
80-90% world wide
What are the complication of Varicella infections?
Pneumonia
Post-infectious encephalitis
stroke
hemorrhagic varicella
How does varicella present clinically?
mild febrile illness
generalised vesicular rash,
Heals without scarring
long-lasting immunity
What are the complications of Zoster re-infection?
Clinical:
vesicular eruption
dermatomal
complications:
post-herpetic neuralgia
encephalitis, myelitis
Multi-dermatomal rash
Strokes; retinitis,
Shingles
Describe the epidemiology of EBV (HSV4).
90-100% adults have antibodies
Primary infection- Oro-pharyngeal
epithelium
Latency B Cell
reactivation- Asymptomatic shedding in saliva
Transmission:
Saliva, kissing
as for CMV
What is the clinical presentation of EBV?
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
What are the key EBV oncogenes?
LMP-1 and LMP-2A
oncogenesis occurs if there is translocation of c-myc/Ig gene promoter
What is the epidemiology of HHV5 CMV?
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
What are the clinical syndromes of CMV?
- Primary infection in adulthood
Infectious mononucleosis-like illness
Fever, rash, lymphadenopathy, hepatitis - 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
What is the treatment for CMV?
Ganciclovir/Valganciclovir
Give examples of B lymphocytes LPDs that are associated with EBV.
- Post transplant LPD
- X-linked LPD
- Non Hodgkin’s lymphoma:
- endemic Burkitt’s
- primary CNS lymphoma in HIV
- Immuno-compromised - Hodgkins disease (certain forms)
Give examples of Epithelial LPDs that are associated with EBV.
- Naso-pharyngeal carcinoma
- Gastric carcinoma
What is the ideal therapy for EBV infection?
Reduction in immunosuppression
No benefit to using anti-virals
Rituximab:
Mono-clonal antibody to CD20
Removes EBV-transformed B cells
What are the diseases associated with HH6?
- Primary infection in babies
Roseola Infantum
febrile illness
rash
Febrile convulsions - Infectious mono-nucleosis
- Immuno-compromised patients
Reactivation is common, but role in
Disease is unclear - Neurotropic: - encephalitis
What is the epidemiology of HHV6?
Universal human infection
Exposure in early life
90% by the age of 5
persistence with periodic shedding
2 variants A and B
Describe HSV1 and 2 infections.
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.
What are the stimuli for the reinfection of HSV-1 and HSV-2?
Sunlight
menstruation
febrile
stress
immunosuppression
Clinically, how does HSV 1 and 2 reinfection appear?
keratitis
cold sores
genital herpes
Explain the rare conditions caused by HSV1 and 2.
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.
What are the outcomes of a maternal infection of VZV during pregnancy?
<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.
What is the treatment for HSV and VZV, and what is its mechanism?
Acyclovir
Nucleoside analogs, and it interferes with DNA polymerase
