HSV I Flashcards
HSV
- Herpes Simplex virus genus of the Herpesviridae family
- Two Types - 1 and 2!
- linear, ds DNA enveloped
- numerous strains
HSV Structure
Herpes Simplex Viruses Genomic Organization
- 150 kb in length
- Can encode up to 70 polypeptide
- a - genes (immediate early genes): encode 5 regulatory proteins (a -0, 4, 22, 27, 47), latency associated transcript (LAT1)-antisense to a -0 gene
- b - genes (early genes): encode DNA binding proteins, DNA polymerase, and thymidine kinase
- g - genes (late genes): encode structural proteins (glycoproteins)
HSV Replication
- DNA released in the cytoplasm
- DNA migrates to the nucleus
- mRNA (transcription) synthesis takes place in the nucleus by using host RNA polymerase
- nuclear membrane
- mRNA transported to the cytoplasm
- virus replication involves regulatory proteins
- New viral proteins made and migrate to nucleus
- Genomic DNA (replication) synthesis takes place in the nucleus by using viral DNA polymerase
HSV 1 vs HSV 2 Infection Sites
- HSV 1 above umbilicus
- HSV 2 below umbilicus
HSV 1 Transmission
•primarily by direct contact
HSV 1 Incubation
•Incubation period: 7-10 days
HSV 1 is acute, latent or both?
- Acute and latent infection
- Primarily asymptomatic
HSV 1 site of primary infection?
- Gingivostomatitis – primary infection l most common in children 1-6 years, fever, oral blisters on buccal mucosa, tongue, gums vesicles which ulcerate 7-10 day duration
- Labialis (cold sores) - reactivation l vesicles at mucocutaneous junction of lips recurrent (latent) vesicles ulcerate, painful
Where does reactivated HSV 1 show up?
•Reactivated HSV is at near or same site of primary infection
HSV 1 Keratoconjunctivitis
•corneal ulceration, recurrent, blindness (one of the major causes of blindness in the U.S)
HSV 1 Encephalitis
•Temporal lobe, high mortality
HSV 1 Eczema herpaticum
- mild or fulminant
- Injured skin, burn patients, ulceration
HSV 1 Herpetic Whitlow
•tips of finger and nails, occupational
HSV 2 Transmission
•sexually transmitted
HSV 2 Incubation
- 2-12 days
- 80% of the patients develop recurrent infection within 12 months
HSV 2 Vulvovaginitis
- mucous membranes and skin of labia, lower vagina, cervix
- Lesions become ulcerated, painful, fever
HSV 2 Progenitalis
•ulcers on penis and/or on skin in groin or perianal area
HSV 2 Asceptic Meningitis
•self limiting
HSV 2 Neonatal Herpes
- 30-60% transmission rate with primary infection, lower rates in recurrent infection
- Contracted during delivery
- 6-10% babies develop neonatal herpes
- Widespread organ involvement
- High mortality - more than 60%
- Neurologic sequelae in survivors
HSV Latency
- All Herpes viruses establish latent infections
- Site of latency and features of reactivation disease are different for each virus
- During latent infection, certain viral proteins are produced, but no complete viral particles.
- The genome is present as a circular extrachromosomal element in the nucleus of the infected cell.
- Latent stage is not affected by treatment.
HSV Reactivation
- Reactivation - same site as primary infection
- DNA resides in ganglia (trigeminal root ganglion, sacral AREA, but dorsal root ganglion)
- Reactivation: trauma, fever, sunlight, excitement, emotional stress (EXAMS)
How does latent herpes reach peripheral sites?
HSV Diagnosis
- isolate virus in cell culture
- stain biopsy material (immunofluorescence)
- DNA detection by PCR (mainly in latency)
