Oral Viral Infections Flashcards
List characteristics of a viral cell. (4)
- Small size
- Simple chemical composition – proteins, phospholipids, glycoproteins and nucleic acids
- No intracellular organelles therefore these are obligate intracellular parasites
- Genetic information is stored as DNA or RNA
What makes a virus an obligate intracellular parasite?
No intracellular organelles
Name an example of a virus which contains genetic info as DNA.
Human herpes
Name an example of a virus which contains genetic info as RNA.
Mumps
In herpes simples (DNA virus) where does the primary infection occur?
Epithelial cells
In herpes simples (DNA virus) where does the secondary infection occur?
neurons of ganglia near the OG infection site
List the 8 stages of virus replication (herpes simplex)
- Binding
- Entry
- Release and nuclear transport
- Nuclear entry
- Gene expression
- DNA replication
- Packaging
- Egress
Describe what occurs in stage 1 of herpes simplex replication.
Viral cell binds (can bind to several) to receptor molecules on the hosts cell membrane
Describe what occurs in stage 2 of herpes simplex replication.
Once bound the viral cell’s envelope (capsule) fuses with the membrane and the cell contents (capsid) are released into the cytoplasm of host.
Describe what occurs in stage 3 of herpes simplex replication.
The released capsid then moves down a scaffold of microtubules and reaches the nuclear membrane
Describe what occurs in stage 4 of herpes simplex replication.
- Herpes chromosome enters the nucleus via a nuclear pore on the nuclear membrane
- DNA circularises
Describe what occurs in stage 5 of herpes simplex replication.
The DNA can either cause;
- A lytic expression via immediate early mRNA
Or
- A latent infection via LAT mRNA (where the DNA circle can persist within the cell for decades before switching to a lytic infection)
Commonly occurs in nerve cells
Describe what occurs in stage 6 of herpes simplex replication (5)
- The immediate early mRNA genes from a lytic infection leaves the nucleus and are transcribed into viral proteins by ribosomes. These translated proteins then renter the nucleus and cause the expression of another set of genes called early mRNA.
- The early genes then leave the nucleus and are translated into proteins.
- The early proteins re-enter the cell and because they contain viral DNA polymerase they replicate the circular viral DNA (rolling-circle method)
- The newly formed DNA then expresses late mRNA which leaves the nucleu for translation to create late-stage proteins.
- Late stage proteins re-enter the nucleus and form capsids which capture DNA genomes
What can trigger latent herpes simplex infection? (3)
- Stress (menstruation)
- Sunlight exposure
- Immunosuppression
What type of swab is required for a viral sample? Describe how this sample is taken.
flocked swab - Placed in molecular sample solution (extracts the viral DNA/RNA) for a period of time and then removed from the solution
What does 2x triangle symbol mean?
Provisional diagnosis
What does 1x triangle symbol mean?
Diagnosis
What details are required for a virology request? (5)
- Patient & clinician details (including phone no.)
- Clinical details & provisional diagnosis
- Date of onset
- Patient DOB or CHI number
- Specify which test you require (do not request “viral screen”)
List the common pathogens associated, the specimens and the tests required for a macula papular/erythematous lesion.
pathogen - enterovirus, HHV6, HHV7 Measles, rubella
specimen - mouth swab
test - DNA/RNA detection
List the common pathogens associated, the specimens and the tests required for a nucleic acid amplification of a vesicular lesion.
Pathogen - HSV1, HSV2, VZV, enterovirus
Specimen - Mouth swab
Test - DNA/RNA detection
List the common pathogens associated, the specimens and the tests required for serology testing of a maculo papular/erythematous lesion.
Pathogen - B19, CMV, EBV
Specimen - EDTA blood
Test - DNA/RNA detection or serology
What does the serological marker IgM detect? (3)
IgM = detects primary immune response
- Used to detect (herpes) cytomegalo virus or Epstein barr virus
What does the serological marker IgG detect? (3)
IgG = Secondary immunological response
- Used to detect (human herpes) herpes simplex virus or varicella zoster virus
List the 8 human herpes viral infections.
Herpes simplex type 1
Herpes simplex type 2
Varicella zoster
Epstein Barr
Cytomegalovirus
HHV-6
HHV-7
HHV-8 (Kaposi’s Sarcoma Associated virus)
What are features common to all hrepes viral infections? (3)
- Primary/acute Infection
- Latency
- Recurrent Infection
What are the clinical features of herpes simplex 1&2. (6)
- Gingivo stomatitis
- Herpes labialis
- Keratoconjuctivitis
- Herpetic whitlow
- Bell’s palsy
- Genital herpes