V2: Herpes Viruses Flashcards
How many families of Herpetoviridae are there?
How many are known to infect man with any regularity?
- 25
- 6
HHV1;
Common name?
Subfamily?
Common disease it causes?
- Herpes Simplex Type 1
- α
- Cold sores
HHV2;
Common name?
Subfamily?
Common disease it causes?
- Herpes Simplex Type 2
- α
- Genital Herpes
HHV3;
Common name?
Subfamily?
Common disease it causes? (2)
- Varicella-Zoster
- α
- Chickenpox
- Shingles
HH4;
Common name?
Subfamily?
Common disease it causes? (3)
- Epstein-Barr Virus
- Gamma
- Glandular fever
- Burkitt’s Lymphoma
What are the 4 main components of structure for the herpes virus?
- Envelope
- Tegument
- Capsid
- Genome
What is the tegument? (2)
- The space between the envelope and the capsid
- Contains virally encoded proteins and enzymes involved in the initiation of replication
What is the Capsid?
These viruses have a doughnut shaped capsomere of about 100-200 nm in diameter with an icosahedral nucleocapsid.
What is the life cycle of herpes virus (6)
- Virus Binds to the cell surface
- The envelope fuses with the cell membrane
- Capsid moves to nucleus
- mRna moves to cytoplasm
- Protein is synthesised
- Virus exostoses from plasma membrane
What does latency mean in regards to the herpes virus
Once a patient has become infected by herpes virus, the infection remains for life
How many proteins do HSV genomes encode?
At least 80 proteins
What enzymes are encoded by genome of HSV? (4)
What do they each do?
- DNA-dependent DNA polymerase
- Thymidine kinase (phosphorylates thymidine and other nucleosides)
- Ribonucleotide reductase (converts ribonucleotides to deoxyribonucleotide)
- Serine-protease (convert a scaffolding protein to its final form)
How many surface glycoproteins are encoded by HSV?
What are they involved in? (3)
- 11
- Attachment
- Fusion of the viral membrane with that of the host cell (gB)
- Immune escape and other functions
How is HSV-1 normally spread?
Mouth to mouth
How is HSV-2 normally spread?
Frequently spread sexually
How does HSV cause Oral herpes?
- Infects epithelial mucous cells or lymphocytes with lesions at the dermatome
- Fluid in this blister is full of the virus
How does latency in oral herpes occur?
Travels up peripheral nerves to nucleated neurone may it may sit for years
How does reactivation occur in oral herpes
Virus travels down the nerve axon and reactivates
What causes reactivation of oral herpes? (2)
- Most triggers are stress related (UV, fever)
- Some degree of immune suppression
What is Herpes whitlow?
This disease of persons who come in manual contact with herpes-infected body secretions via small wounds on the hands or wrists
What is Eczema herpeticum?
- This is found in children with active eczema, preexisting atopic dermatitis, and can spread over the skin at the site of eczema lesions
- The virus can spread to other organs such as the liver and adrenals
What is HSV infection of neonates?
What steps may be taken to avoid this?
- Infection is especially possible if the mother is shedding virus at the time of delivery
- If a woman has active genital herpes at delivery, a cesarean- section delivery is usually performed
What is the most common HSV that causes genital herpes
HSV-2
What is the clinical presentation of a primary genital herpes infection?
Primary infection is often asymptomatic but many painful lesions can develop on the glans or shaft of the penis in men and on the vulva, vagina, cervix and perianal region of women
HSV Meningitis caused by which HSV?
HSV-2
Zoster means girdle. What is this characteristic?
Zoster means girdle from the characteristic rash that forms a belt around the thorax in many patients
VZV causes which 2 diseases?
- Chicken-pox (Varicella)
- Shingles (Zoster)
How is chicken pox spread?
- It is spread by respiratory aerosols or direct contact with skin lesions.
- Infection is via mucosa, this time in the respiratory tract
What is shingles?
- The recurrence of varicella replication
- Usually occurs later in life.
What is a potential complications in adults of VZV?
Fatal pneumonia can be associated with a varicella infection
What are some common symptoms of EBV? (7)
- Fatigue
- Fever
- Inflamed throat
- Swollen lymph nodes in neck
- Enlarged spleen
- Swollen liver
- Rash
What are some potential EBV Complications? (4)
- Further infections of other areas of the body including the brain, liver and lungs
- Severe anaemia
- Breathing difficulties as a result of the tonsils becoming significantly swollen
- Ruptured spleen
Comment on the viral structure of CMV (2)
- Largest genome of all herpes viruses
- Only one serotype
Primary infection of HSV1 normally affects which regions?
- The oropharynx
- Facial skin
Primary infection of HSV2 normally affects which regions?
Genitalia
What drug is normally the ideal drug choice for all herpes simplex infections?
ACV (nucleoside analogue)
