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27 Cards in this Set
- Front
- Back
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What type of genome do Herpes viruses have?
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Double Stranded DNA
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Are herpes viruses enveloped?
How are the transmitted? |
- Yes they are enveloped
- Transmitted via body fluids |
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What type of herpesvirus are Herpes Simplex Virus 1, 2, and VZV?
What characteristic defines this type? |
- Alpha herpesvirus
- Neurotropic, like to infect neurons |
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What type of infection do herpesviruses tend to cause?
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Chronic or Latent infections
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How does HSV enter cells?
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Glycoprotein spikes bind to cell receptors and mediate fusion
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How does HSV infect cells?
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1. Glycoproteins bind to cell receptors, mediate fusion
2. Tegument/capsid deposited within cytoplasm 3. HSV uses microtubules to move to nucleus, delivers viral DNA 4. 3 Waves of transcription - IE Genes, E genes, L genes |
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What are the 3 types of genes expressed during the 3 waves of transcription?
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1. Immediate Early Genes (IE) - expressed early after infection
2. Early Genes (E) 3. Late Genes (L) |
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What types of cells does HSV initially infect?
What cell do they then spread to? |
- Initally infect mucosal and epidermal cells through breaks in skin
- Then spread to sensory neurons via retrograde transport on axon |
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Does HSV genome integrate into host neuron?
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No
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What can cause reactivation of HSV?
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Drop in immune system caused by stress, fever, UV lights, nerve trauma
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What immune cells are critical for the immune response to HSV?
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T Cells, thus co-infection with HIV is very serious
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What are the 2 main ways that HSV evades the immune system?
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1. Viral protein (ICP47) blocks presentation of viral antigens to MHC class I complex needed for CD8 T Cells to kill infected cells
2. Two viral glycoproteins (gC and gE) block antibody and complement responses |
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What are the symptoms of HSV-1?
HSV-2? |
HSV-1: Causes oral and genital lesions. Can cause encephalitis, keratinitis.
HSV-2: Causes genital lesions. Increases HIV risk |
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What percentage of HSV-1 and HSV-2 infections are asymptomatic?
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75%
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Which HSV type more often causes oral recurrences?
genital recurrences? |
Oral: HSV -1
Genital: HSV-2 |
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What percentage of adults are infected with HSV-1?
HSV-2? |
HSV-1 = 58%
HSV-2 = 17% |
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How is HSV-1 transmitted?
HSV-2? |
HSV-1: Very contagious through oral secretions
HSV-2: Sexual transmission. Perinatal transmission. |
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How is HSV diagnosed?
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- Swab Lesion and PCR (can sometimes be too sensitive)
- Rapid Antigen Assay (80% sensitive) - Tzank smear (60% sensitive) |
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What is the treatment for HSV?
How does it function? |
Acyclovir or Valacyclovir
- Both diffuse into cells and are activated by HSV enzyme thymidine kinase - Inhibit viral DNA replication |
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What is the pathogenesis of Varicella zoster virus (VZV)?
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- Infects and replicates in ORAL CAVITY
- Carried by lymphocytes to epidermis (occasionally liver, lung, brain) - Spreads to neurons and establishes latency |
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What does VZV cause?
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- Initial infection causes widespread lesions (chickenpox)
- Reactivation causes localized infection (shingles) |
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How is VZV spread?
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Via oral secretions 1-2 days before onset of rash
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What are the symptoms of a Zoster (shingles) infection?
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- UNILATERAL vesicular rash
- dermatomal, commonly chest/back - Pain over affected area before/after rash |
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What are 3 varicella complications?
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1. Bacterial superinfection of skin leasions with staph/strep
2. Spread to brain (encephalitis), lung (pneumonia), and liver (hepatitis) 3. Crossing placenta during pregnancy |
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What are 2 zoster complications?
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1. Prolonged pain
2. Damage to eye and large blood vessels |
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How is VZV diagnosed?
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Same as HSV
- PCR - Rapid antigen Assay - Tzank smear |
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How is VZV treated?
Vaccine? |
Acyclovir or Valacyclovir
Same method of action as HSV Varicella has a live virus vaccine. 85% effective in preventing chickenpox. 97% effective in preventing severe disease. - Higher dose vaccine for elderly to protect from zoster |
