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26 Cards in this Set

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Papillomaviruses cause what?
Induce warts in skin and condylomas in mucous membranes. Some strains target skin squamous epithelial cells, others target mucosal squamous epithelial cells in genital tract, oral pharynx, or esophagus. Some strains cause cervical cancer and other epithelial tumors (head and neck cancer)
Describe papillomavirus characteristics.
Naked (no envelope), icosahedral particle with circular double stranded DNA genome.
It has 10 genes, 8 "early" and 2 "late"
What do the 2 "late" proteins code for?
Structural proteins of the virus - L1 and L2
What are the 2 most important HPV strains that cause genital malignancies?
HPV 16 and HPV 18 - these 2 strains cause cervical cancer. Recent evidence shows that these also cause oropharyngeal cancer
What are E6 and E7?
E6 and E7 are proteins of high-risk strains such as HPV 16/18 that lead to growth of immortalized cells.
What is the role of E6?
E6 targets p53 for proteolytic degradation
E6 complexes with p53 and causes degradation of p53. P53 normally blocks replication - it's a transcription factor that induces genes involved in apoptosis or genes that block cell cycle so cell can repair.
What is the role of E7?
E7 binds to the retinoblastoma protein in RB/E2F complexes, liberating the E2F transcription factor to induce S-phase genes
E7 mimics CDK and causes entrance into S phase and release of a transcriptional activator
Why is an immortalized cell dangerous?
Immortalized cells become resistant to terminal differentiation and hence virus production and cell destruction do not occur. If these cells take some other hits they can become cancerous.
How are E6 and E7 produces?
Viral episomal DNA randomly integrates into cellular DNA such that virions cannot be produced and HPV E6 and E7 proteins are synthesized, resulting in cell immortalization.
HPV Vaccines - what are they what do they protect against?
Composed of L1-like protein. Gardasil prevents HPV 16/18 (cervical cancer) and HPV 6/11 (90% of genital warts)
Describe characteristics of the Polyomaviridae class of viruses (JC Virus and BK Virus)
Naked, icosahedral particle, double-stranded circular DNA genome of 5,000 bp, 5 genes (2 "early" and 3 "late") virion proteins.
How do you get Polyomaviridae?
Ubiquitous, acquired in childhood, probably respiratory route, mostly asymptomatic, form persistent infections in kidney. Urinary excretion is common.
What do these viruses do - JC virus and BK virus - and who do they become symptomatic in?
In immunosuppressed patients, the viruses reactivate. JCV can cause progressive multifocal leukoencephalopathy (PML) in brain. BKV can cause hemorrhagic cystitis (kidney, bladder, ureter)
Describe characteristics of Adenovirus.
Non-enveloped - Linear double-stranded DNA genome containing 35 genes, about 20 "early" genes convert cell into factor for virus replication. Turn off genes involved in anti-viral cells. Most "late" genes encode viral structural proteins.
How many serotypes of human adenovirus are there?
57 serotypes - different serotypes cause different infections. Some cause upper resp tract infections in infants and young children and are very common. Some are asymptomatic. Some serotypes form long-term persistent infections. These can be reactivated in immune suppressed patients.
Name 2 Respiratory Diseases caused by adenoviruses.
1. Endemic Respiratory disease - Pediatric respiratory disease - fever, pharyngitis, tonsillitis, cough, etc. (~5% of common cold in children)
2. Sporatic infections - Pharyngoconjunctival Fever (PCF) - acquired from inadequately chlorinated swimming pools, by nasal or oral aspiration, or by direct conjunctival inoculation. Infection usually occurs in children. Fever, sore throat, conjunctivitis - disease is self-limiting and recovery is w/o sequelae
Describe Epidemic Keratonconjunctivitis (EKC) caused by Adenovirus
- associated with direct inoculation and ocular trauma. Corneal epithelial cells are infected
- Conjunctival and corneal inflammation which presents as ocular discomfort like that resulting from a foreign body
- can cause chronic and permanent visual impairment
- prolonged virus shedding occurs
Serious eye infection - can lead to partial blindness, occurs in crowded conditions
Acute Respiratory Disease (ARD), also from Adenovirus - describe what it is and who gets it
Upper and lower respiratory disease seen in military recruits - unusual bc it occurs mainly in bootcamps. Can be fatal or result in chronic lung damage. Not seen in comparable civilian adult populations.
Disseminated Adenovirus Infections in Immunosuppressed Patients - who gets these and why?
Especially pediatric allogeneic stem cell transplant patients. About 20% of these patients get these infections and half of these die. Caused by many serotypes, esp those that are common in children. Not known whether due to reactivation of latent virus or to new infections.
Human B19 Parvovirus - Describe it's virus characteristics
Single-stranded genome of 5 kpb; 2 "early" proteins, 2 "late" virion proteins. Host cell must be in S-phase for virus replication (doesn't have viral proteins to "push" cells into S-phase).
What cells does the Human B19 Parvovirus attach to?
Receptor for virion entry is limited to hematopoietic progenitor cells (erythroblasts).
Where does replication of B19 Parvovirus occur?
Mainly in bone marrow. B19 is an "autonomous" parvovirus - it does not require another virus as "helper"
Other Parvoviruses that are common?
Adeno-Associated Virus (AAV) is a very common human parvovirus that requires Adenovirus or some Herpesvirus as "helpers" - AAV does NOT cause disease
How is parvovirus released?
Released from lysed cell
Who does Parvovirus infect and how is it clinically presented?
Usually acquired in childhood (30-60% have antibody), Infection and spread mainly through respiratory droplets. Incubation period ~4-14 days. Intense viremia, asymptomatic in 25%, no rash in 50%, sometimes accompanied by flu-like symptoms.
At 10-14 days postinfection what is Parvovirus accompanied by?
"Fifth disease" ("slapped cheek disease"), or erythemia infectiosum, due to circulating immune complex formation. Child gets red cheeks, red lacy rash on the rest of the body, esp on arms and upper legs. Rash lasts a few days and may itch. No longer infectious once rash appears.