DNA Viruses Flashcards
What type of virus is Papillomavirus?
- small circular dsDNA
- icosahedral
- naked
- does NOT contain DNA viral polymerase so must enter cell cycle to replicate
- localized only on the skin or mucosa, no viremic stage
What are the different types of human papilloma virus (HPV)?
- mucosal
- cutaneous
What are characteristics of cutaneous HPV?
- forms benign warts on skin that can persist and spread
- most warts will be cleated without tx
- tx usually need to be done more than once (removing with chemicals or burning)
- can occasionally spread to oral or genital mucosa through autoinoculation
What are the characteristics of mucosal HPV?
- anogenital warts are most common sexually transmitted disease in US
- most common types: 6 and 11 which are low risk and 90% of genital infections. 6 and 11 can also cause recurrent respiratory papillomatosis
- high risk types: 16 and 18 which are 70% of cervical/anogenital cancers
- warts can appear on larynx requiring surgical removal (reoccurrence is rapid)
How can oral HPV be acquired?
- children from their mother at birth
- adults from oral sex
What is the replication of HPV?
- break in skin/mucosa to infect basal cell layer
- basal cell layer will then replicate to repair wound
- virus will establish several copies of itself in episcopal form (circular piece of DNA that isn’t integrate into host cell membrane)
- virus will move through different epithelial laters and express different viral proteins
- in upper epithelial layers, virus will prod terminally differentiated cell to replicate so it can make 1,000s of copies of viral DNA and lots of capsid protein
(done via viral E7 protein binding and inactivating cellular Rb protein which causes the cell to go into cell cycle) - as top layer of cell sloughs off, cell breaks down, releasing virus
What is HPV cancer caused by?
- dysregulation of E6 and E7 genes by integrating viral RNA episome into basal cells cellular DNA
genome integration is NOT a normal part of HPV’s replication - integral of the episome leads to viral protein (E2) being turned off which controls the levels of E6 and E7… leading to high levels of E6 and E7 in basal cells
- big problem is that E2 is not made
In oncogenic forms of HPV, what does E7 do?
- bind and degrade Rb protein and causes to cell to go into cycle
(non cancerous forms bind Rb but doesn’t degrade it)
In oncogenic forms of HPV, what does E6 do?
- degrade p53 allowing the cell to continue to cycle and accumulate mutations
(non cancerous forms do not degrade p53)
In oncogenic forms of HPV, what does E6 do?
- degrade p53 allowing the cell to continue to cycle and accumulate mutations
T/F: In most cases, HPV infections spontaneously regress
True!
- problems occur if there is persistent infection with a high risk type and can result in cancer
What cancers are HPV known to contribute to?
- cervical, vulvar, vaginal, penile, and oropharyngeal cancers
What does HPV 16 cause almost all of (in regards to cancer type)?
oropharyngeal
- HPV 16 is a risk factor but smoking and drinking increases cancer risk
What is the vaccine for
HPV?
- subunit vaccine
When is HPV vaccine recommended to receive?
- between ages 9-14 with 2 doses before any sexual contact
- 3 dose catch up can be done after age 14
What type of virus if polyomavirus?
- small dsRNA circular
- naked
- icosahedral capsid
- no viral DNA polymerase; need cell to divide to replicate their viral DNA
What virus does polyomavirus cause?
JC- progressive multifocal leukoencephalopathy
T/F: JC causes severse symptoms in most people
False!
- they are usually mild or no symptoms
- only causes problems in immunocompromised of AIDS, transplant recipients, immunosuppressive drug takers, hematologic malignancies
When do problems arise with JC?
- only when virus mutates and become neurotropic and person is immunosuppressed
- mutant virus infects and kills oligodendrocytes causing CNS demyelination and progressive multifocal leukoencephalopathy
What is the tx for JC- progressive multifocal leukoencephalopathy?
- stop immunosuppressive agent
OR - start HIV therapy
the goal: to make immune system more active in fighting the infection
What type of virus is Parvovirus?
- small ssDNA linear
- naked
- icosahedral capsid
- no DNA polymerase, needs to infect actively dividing cells
What is Parvovirus B19?
- causes Erythema infectiosum-fifth disease
- generalized infection
- slapped check rash
How does Parvovirus B19 start and develop?
- starts with fever, runny nose, headache and is spread by respiratory secretions
- rash develops because immune response and the person is no longer contagious (arthralgia or arthritis can occur more common in women)
Why does the problem occur with parvovirus B19?
- virus needs to infect actively dividing cells and preferentially infects erythroid precursor cells and kills those cells causing transient anemia
- for most people, there is only slight drip in RBC and isn’t a problem
- for people with an increase turnover in RBC due to Hb disorders like sickle cell or chemo, B19 infection can cause transient aplastic crisis causing a severe drop in RBC
How does parvovirus B19 effect pregnancy?
- if infected during 1st trimester, chance of miscarriage (~10%)
- if anytime during pregnancy, can cause hydro fettles (~4%)
What type of virus is Poxvirus?
- complex DNA virus
- envelope
- dsDNA
- replicates solely in cytoplasm
- has own DNA dependent RNA polymerase so doesn’t have to enter nucleus and can make it’s own mRNA
What is Molluscum Contagiosum in regards to poxvirus?
- causes raised lesions on skin that appears smooth with a dimple in the middle
- lesions are secreting the virus
- local infection; no viremic stage
- spread: personal contact or auto inoculation
- infection can clear without tx by 2-12 months without scarring
- affects children more than adults
What are the orthopixviruses?
- variola, cowpox, mpox, and vaccinia
there is cross-protection meaning infection with one orthodox protects against infection with other orthopoxviruses
How is smallpox transmitted?
- respiratory route
- lesions are contagious (until all scabs fall of body- scab contains infectious virus)
T/F: Smallpox is eradicated
True!
- except there are stocks of virus in Russia and US
Is there a vaccine for small pox?
- there is a prophylactic vaccination within 3 days of exposure
- to prevent or substantially lessen disease
- if smallpox spread from germ warfare, CDC favors ring vaccination over mass vaccination/isolation
What is Vaccinia Virus?
- virus contained in the vaccine for smallpox
- attenuated virus in humans
- NOT a cowpox (although vaccine started with cowpox)
What are the risks with vaccinia vaccination?
- virus can replicate in human cells
there is a more inactivated form of vaccine that requires 2 shots 4 weeks apart
What is Mypox?
- looks similar to smallpox but with lymphadenopathy present
- endemic in some African countries with sporadic outbreaks
What is the animal reservoir for Mypox?
- unknown
- US outbreak was due to imported rodents from Africa
What is the vaccine for Mypox?
- live vaccinia virus is 85% effective
- non replicating attenuated vaccina virus is 69% effective
- an antiviral can also be used
How is the current outbreak of mycox seem to be spread?
- sex/close personal contact
- respiratory
Are smallpox, mypox, and vaccinia generalized or local infections?
Generalized/systemic: smallpox, mypox
Local: Vaccina (sometimes generalized and can show adverse effects with the vaccine)
