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77 Cards in this Set
- Front
- Back
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What are two clinically relevant families of double-stranded, nonenveloped DNA viurses?
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Papovaviridae
Adenoviridae |
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What is the only clinically relevant family of single-stranded nonenvelooped DNA virruses?
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Parvoviridae
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What does the acronym 'papova' stand for?
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PApilomma
POlyoma Simian VAcuolating viruses |
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What type of nucleic acid do Papovaviridae contain in their genome?
What is their capsid geometry? Do they contain an envelope? |
Supercoiled, ds, circular DNA
Icosahedral No, they are nonenveloped |
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What are the two subfamilies of Papovaviridae?
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Papillomaviridae
Polyomaviridae |
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What clinically relevant viruses are associated with Papillomaviridae and Polyomaviridae?
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Papillomavirus:
HPV Polyomavirus: BK virus JC virus |
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What type of lesions do all papillomaviruses cause?
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Papillomas
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What are warts?
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Hyperplastic epithelial lesions
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How is HPV transmitted?
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Direct contact, including sexual transmission
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What type of tissue does HPV show tropism for?
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Skin epithelium
Mucous membranes |
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Which layer of the skin is initially infected?
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Basal layer
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Is there a high viral load in the basal layer?
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NO
There are only a few virions in the nuclei of basal cells. |
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What does HPV do to cells in this layer?
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Induces cell multiplication (mitogenic effect)
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What is unique about the life cycle of HPV?
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The viral life cycle progresses with increasing differentiation of the epithelium.
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In which layers of the skin are HPV early genes expresed?
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Early genes are expressed in the undifferentiated stratum spinosum.
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In which layers of the skin are HPV late genes expressed>
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Lage genes are expressed in the differentiated stratum corneum (the outer layer)
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What is the characteristic histologic finding in papillomavirus infection?
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Koilocytes
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What is a Koilocyte?
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Cytoplasmic vacuoles found in infected squamous epithelial cells
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What are three clinical manifestations of genital warts?
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Condyloma accuminata (genital warts)
Benign papillomas Cancers of the anogenital region |
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What is condyloma acuminata?
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A commonly acquired sexually transmitted infection (STI) caused by HPV
Condyloma acuminata is caused by HPV and condyloma lata is caused by Treponema pallidum. |
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What HPV serotypes are associated with condyloma acuminata?
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HPV-6
HPV-11 |
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What are five benign papillomas caused by HPV?
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1) Common skin warts on the fingers and hands
2) Flat warts on the arms, face, and knees 3) Plantar warts on the soles of feet 4) Laryngeal papillomas 5) Epidermodysplasia verruciformis |
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What HPV subtypes are associated with skin and plantar warts?
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HPV-1 through HPV-4
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What are laryngeal papillomas?
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Most common benign epithelial tumor of the larynx.
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What is epidermodysplasia verruciformis?
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A condition characterized by multiple warts that spread to multiple sites and do not regress.
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What is thought to be the cause of epidermodysplasia verruciformis?
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Inherited deficiency in cell-mediated immunity.
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What is a complication of epidermodysplasia verruciformis?
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Squamous cell cancer
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HPV infection has been linked to what types of cancer?
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Cancer of the cervix, penis, and anus.
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Which HPV genes are implicated in carcinogenesis?
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E6 and E7, two of the eraly genes
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Which cellular proteins do E6 and E7 inactivate?
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E6 inactivates proteins encoded by p53
E7 inactivates proteins encoded by Rb p53 and Rb are both tumor-suppressor genes |
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Which HPV subtypes are implicated in cervical cancer?
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HPV-16 and HPV-18
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How is HPV infection diagnosed?
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1) Presence of Koilocytes
2) Hybridization of viral DNA to identify specific subtypes. 3) Papanicolaou (Pap) smear to screen for dysplastic changes induced by HPV infection. |
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What tests are not useful for diagnosis?
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Serologic tests because exposure to many of the different HPV serotypes in common.
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How are warts treated?
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Common warts usually regress on their own and removal is unnecessary.
Warts in uncomfortable places may be removed surgically or destroyed with liquid nitrogen, laser vaporization, or cytotoxic chemicals, including salicylic acid, podophyllin, and trichloacetic acid, all of which must penetrate the basal layer to eradicate the virus. |
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What are two additional treatments for genital warts?
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Injected interferon treats half of all genital warts
Topical cidofovir |
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How are laryngeal papillomas treated?
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Oral interferon is effective for regression.
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What are two polyomaviruses that infect humans?
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JC and BK
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How are JC adn BK viruses transmitted?
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Via respiratory droplets or urine of infected individuals.
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At what age does transmission of polyomaviruses usually occur?
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In childhood
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What cells does JC virus show tropism for?
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Oligodendrocytes
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What disease does JC virus cause?
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Progressive multifocal leukoencephalopathy (PML)
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What is PML?
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A rare demyelinating disease occurring only in immunocompromised patients.
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What are symptoms of PML?
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Impaired speedh and mental capacity rapidly followed by paralysis and death within 3-6 months.
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What disease does BK virus cause?
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Cystitis in immunocompromised patients, otherwise it rarely has clinical consequences.
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How is JC or BK viral infection diagnosed?
What tests are not useful for diagnosis? |
DNA hybridization of PML lesions (JC virus) or urine samples (BK virus)
Serologic tests |
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What type of nucleic acid do Adenoviridae contain in their genome?
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dsDNA; linear
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What is the capsid geometry of Adenoviridae?
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Icosahedral
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Do Adenoviridae contain an envelope?
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NO
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What is unique about the structure of adenoviruses?
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Contain hemagglutinin fibers protruding from each of 12 capsid vertices.
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What is purpose of the structure of Adenoviruses?
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Aid in viral attachement to host cells
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How do viral early genes allow cells to progress through the cell cycle?
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Inactivate cell regulatory proteins including p53 and pRB.
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What other enzyme do viral early genes encode?
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DNA polymerase
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How are newly replicated adenoviruses released?
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Cell lysis
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How are adenoviruses transmitted?
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1) Respiratory transmission
2) Fecal-oral ransmission 3) Direct inoculation of the eye, e.g., swimming in infected water. |
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What are four clinical manifestations of adenovirus infection?
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1) Upper and lower respiratory tract infections
2) Ocular disease 3) Infantile gastroenteritis 4) Hemorrhagic cystitis |
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What respiratory infections do adenoviruses cause?
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1) Acute febrile pharyngitis in young children presenting as cough, sore throat, fever, and nasal congestion.
2) Pharyngoconjunctival fever in school-aged children 3) Acute respiratory distress 4) Viral pneumonia |
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What ocular diseases do adenoviruses cause?
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"Pink eye"
1) Follicular conjunctivitis 2) Keratoconjunctivitis |
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How does infantile gastroenteritis present?
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Nonbloody diarrhea
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What percentage of viral diarrheal disease in children is caused by adenoviruses?
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By clinical presentation.
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How are adenovirus infection diagnosed in the laboratory?
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Cell culture, ELISA, neutralizatin or hemagglutionation inhibition with type-specific antisera.
Laboratory diagnosis is rarely performed |
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What vaccines are available for adenoviruses?
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Live-attenuated vaccines containing four serotypes are used only by military personnel.
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What is the treatment for adenovirus infections?
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Supportive treatment and quarantine because the virus is highly transmissible.
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What type of nucleic acid do Parvoviridae contain in their genome?
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ssDNA, linear
Parvoviruses are the only family of ssDNA. |
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What are two additional unique characteristics of the Parvoviridae genome?
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1) It is the smallest of the DNA viruses
2) Contains terminal hairpin loops |
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What is the purpose of the terminal hairpin loops?
What is their capsid geometry? Do they contain an envelope? |
To initiate host-mediated viral genome synthesis
Icosahedral NO |
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What is the most clinically important parvovirus?
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B19
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How is parvovirus transmitted?
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Respiratory transmission and transplacental infection.
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What percentage of adults have antibodies to parvovirus B19?
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Half of all adults
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Which cells are susceptible to damage from parvovirus B19?
Why? |
Mitotically active cells
The ssDNA must be converted to dsDNA before viral replication and transcription can occur. The enzymes that can convert ssDNA to dsDNA are only found in mitotically active cells. |
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What two types of cells do parvovirus B19 show tropism for?
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RBC precursors (erythroblasts)
Endothelial cells |
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What disease does parvovirus B19 infection cause in healthy children?
What are two other names for this disease? |
Erythema infectiosum
1) Fifth disease 2) Slapped-cheek syndrome |
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What are the clinical manifestations of fifth disease?
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1) Bright red rash prominent on teh cheeks
2) Low grade fever 3) Runny nose 4) Sore throat 5) Acute symmetrical arthritis that occurs 2 weeks after infection. |
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What is the cause for the rash in fifth's disease?
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Thought to be an immune-mediated response beause the rash develops when the virus is no longer detectable in the blood.
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What is the risk of parvovirus B19 infection in patients with sickle cell, thalassemia, spherocytosis, or an immuniocompromsed state?
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Aplastic anemia
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How can parvovirus B19 infection affect a fetus?
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1) First trimester: serious fetal infectoin may cause spontaneous abortion.
2) Second trimester: hydrops fetalis resulting in neonatal death. 3) Third trimester: no clinically significant disease. |
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How is parvovirus infection diagnosed?
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1) Serologically by immunoglobulin (Ig) M antibody detection.
2) Polymerase chain reaction of viral DNA from blood or amniotic fluid. 3) Isolation of virus from throat swabs (rare). |
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How is parvovirus B19 treated?
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Supportive treatment and limit contact with pregnant females.
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