Quiz 1 Flashcards
What is obligatory viremia?
need for viruses to travel in blood; targeted more easily by vaccines via antibodies
what is plus-stranded RNA?
messenger RNA (positive stranded)
icosohedral symmetry has ___ faces
20
how do antibodies neutralize viruses?
binds to virion protein required for attachment to host. Therefore virus can’t get in.
incclusion bodies are:
visible areas on EM where viruses are being assembled and packaged into virions. area of cell helps classify virus
plaque
single virus dropped onto cell, spreads and causes cells to lyse and creates zone of death.
syncytia
single cell defined by plasma membrane that contains more than one nucleus.
Describe the series of steps in replication of polio virus:
1) +-stranded RNA enters cytoplasm
2) host machinery used for translation into polyprotein
3) cleavage into functional proteins & viral RNA polymerase
4) polymerase makes -RNA from +RNA.
5) -RNA = template for more +RNA
What are synonyms for asymptomatic infection?
Subclinical, inapparent or silent infection
the picornavirus group has what
a) symmetry
b) nucleic acid genome
c) 5 examples are:
a) icosahedral
b) single + RNA
c) Polio, coxsackie, echo, rhinoviruses, hepatitis A
reovirus group has what
a) symmetry
b) nucleic acid genome
c) example
a) icosahedral
b) multiple molecules of double-stranded RNA
c) rotaviruses
the two families of unenveloped RNA viruses are
picornavirus; reovirus
the 6 families of enveloped RNA viruses are:
orthomyxovirus; paramyxovirus; rhabdovirus; coronavirus; togavirus; retrovirus
rhabdovirus & paramyxovirus have what
a) symmetry
b) nucleic acid genome
a) helical
b) single negative RNA
What are four examples of the enveloped RNA virus family paramyxovirus
parainfluenza; respiratory syncytial; measles; mumps
Orthomyxovirus has what
a) symmetry
b) nucleic acid genome
c) example
a) helical
b) multiple molecules of negative RNA
c) influenza
most enveloped RNA viruses have what symmetry?
helical
What is the a) symmetry and b) nucleic acid genome of coronaviruses?
a) helical
b) single + RNA
ex: SARS
Togaviruses have what
a) symmetry
b) nucleic acid genome
c) example
a) icosahedral
b) single + RNA
c) equine encephalitis
retroviruses have what
a) symmetry
b) nucleic acid genome
c) example
a) uncertain
b) 2 identical + RNA
c) HIV-1; various tumor viruses
the three families of unenveloped DNA viruses are:
parvovirus; papovavirus; adenovirus
what is the nucleocapsid symmetry of the unenveloped DNA viruses parvovirus, papvavirus, and adenovirus?
icosahedral
what are two viruses with a single molecule of circular double stranded DNA?
papovavirus, adenovirus
what is the nucleic acid genome of parvovirus?
single molecule of single stranded DNA
ex: B-19
herpesvirus have what
a) symmetry
b) nucleic acid genome
c) example
a) icosahedral
b) single molecule double-stranded DNA
c) herpes simplex, varicella-zoster, cytomegalovirus, EB virus
poxvirus have what
a) symmetry
b) nucleic acid genome
c) example
a) none
b) single molecule double-stranded DNA
c) smallpox, molluscum contageosum
hepadnavirus have what
a) symmetry
b) nucleic acid genome
c) example
a) icosahedral
b) single molecule circular DNA
c) hepatitis B
Herpes, varicella, and hepatitis B have what in common?
icosahedral, enveloped DNA viruses
How is poliovirus transmitted?
fecaloral
What is the typical outcome of polio infenction?
sublinical: fever, stiff neck
paralytic polio is rare; two classes: spinal & bulbar
What is the IRES?
internal ribosome entry site: cutting in line! doesn’t need CAP
What is the consequence of a virus using RNA dependent RNA polymeraze (an enzyme foreign to host cells)?
no proofreading capacity, therefore increased mutations
do RNA or DNA viruses have a higher mutation rate?
RNA viruss
How many viral serotypes does polio have?
3
What are 8 examples of live/attenuated viruses given in the U.S.?
1) influenza (*intranasal)
2) MMR
3) MMRV
4) Rotavirus
5) Smallpox
6) Yellow fever
7) zoster
8) adenovrius (oral)
Hepatitis B vaccine is what type of vaccine?
subunit
Why don’t people vaccinated with live vaccine for polio excrete virulent virus if exposed? What is the significance of this relative to a large population?
anti-viral IgA in the gut neutralizes the virions; only live vaccine can produce immediate herd immunity
What are enteroviruses? what symptom is commonly associated with them?
subclass of picornoviruses. positive-sense single-stranded RNA viruses associated with several human and mammalian diseases. include polio, coxsackie, ECHO (enteric cytopathic human orphan), Hepatitis A Symptom: Aseptic meningitis
Neonatal myocarditis can be caused by
Some group B coxsackie viruses
What do rhinoviruses cause and how are they spread?
common cold; spread in air = very contagious
What is the symmetry and nucleic acid genome of reoviruses? is their RNA infectious?
icosahedral; double stranded RNA. no
How do reoviruses multiply?
they do not have mRNA activity, so the virion RNA must first function as a template for synthesis of mRNA via a polymerase included in virion.
What ist he structure of adenoviruses? how are they spread? what do they cause?
double-stranded DNA (mRNA and protein synthesis is regulated); fecal-oral or airborn (stable when dried); infection of respiratory tract, eyes, gastritis
What are the major viral causers of gastroenteritis?
rotaviruses multiple segments dbl-stranded RNA, enteric adenoviruses dbl-stranded DNA, norwalk virus +RNA (a calcivirus) *NOT commonly caused by enteroviruses.
What is the viral family of Hep C? the nucleic acid composition of Hepatitis C? what kind of test is done for blood donor hep C? How is it transmitted? Which has higher likelihood of transmission, Hep B or C?
Flavivirus; single +RNA; test w/ PCR; blood, STD; Hep C has a higher likelihood of chronic infection (75%);
What are the prodromal symptoms of Hep B or C infection? definitive symptom?
arthritis & rash; jaundice
Which hepatitis types cause chronic hepatitis? What are treatments?
HBV/HCV;
prolonged treatment w/ alpha-interferon (low success rate;
HBV chronic hepatitis w/ lamivudine (reverse transcriptase inhibitor)
HCV- interferon + ribavirin, telaprevir and boceprevir (inhibit protease)
What is the nucleic acid structure of Hepatitis D? Hepatitis D infections are only a risk for people with:
DEFECTIVE, circular (-) RNA;
Hepatitis B.
Hepatitis E belongs to what virus family?
Has what nucleic acid genome? How is it usually transmitted?
Hepevirus; non-enveloped +RNA; feco-oral
How does HAV pathogenesis differ from HBV and HCV?
HAV causes acute hep by killing liver cells, while B & C induce immune attack (chronic)
Which two Hepatitis viruses are typically transmitted via the fecooral route? What is their incubation period?
Hep A & E; 30 days
Which three Hepatitis viruses have + sense RNA genomes?
HAV, HCV, HEV
Which viruses cause herpangina?
USUALLY Cocksackie A, (but also, ECHO, Coxsackie B)
Where are adenoviruses assembled? is there mRNA and protein synthesis regulated? when does transcription of mRNA for structural proteins begin?
nucleus. yes. late in infection after viral DNA synthesis begins
adenoviruses cuase:
conjunctivitis, sarcomas in mice, gastritis w/diarrhea
Major causes of the common cold include:
rhinoviruses, cornoaviruses, respirtatory syncytial virus, parainfluenza viruses. also less common: coxsackie and ECHO
Why can’t rhinoviruses cause lower respiratory tract infections or GI infections?
they are killed at low pH and grow best at lower temperatures (upper R.tract).
All enteroviruses, including coxsackie, ECHO, and polio are transmitted via
fecal-oral pathway
Coxsackie virus A causes:
herpangina, hand foot & mouth, aseptic meningitis, paralytic disease
Coxsackie B causes:
pleurodynia, myocarditis, aseptic meningitis, paralytic diseases
What are five viruses that cause gastroenterities?
rotavirus, adenovirus, norovirus, astrovirus, other calciviruses
what is the difference between a capsomer and nucleocapsid?
capsomers are the proteins arranged in specific symmetry; nucleocapsid is the capsid + nucelocapsid
susceptibility is:
viruses ability to get into a cell
permissivity is:
virus ability to evade host defense
