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56 Cards in this Set
- Front
- Back
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What are the dimensions of the poxvirus?
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200 x 250 x 200nm
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What are the 2 forms in which poxviruses are found?
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IMV (intracellular mature virus particle - 1 lipid bilayer)
EEV (extracellular mature virus - 2 lipid bilayers) |
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What is the shape of the poxvirus?
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ovoid or brick-shaped
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Which 3 structures make up the virus?
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1. envelope (lipd, protein)
2. biconcave inner core (DNA, protein) 3. lateral bodies (protein |
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In which from is the poxvirus genome?
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-linear ssDNA with covalently closed hairpin ends
-150-300kb -150-200 genes! |
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Where does viral DNA replication occur in the cell?
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in the cytoplasm (but need viral enzymes and cellular NTPs)
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How is the internal envelope formed?
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de novo (NOT by budding!) -- mechanism unknown
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Name 2 historically important poxviruses:
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-Variolo - decimated human populations historically, discovery of vaccination, first virus ever erradicated (and only one)
-Vaccinia - first animal virus grown in culture! |
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What are the 2 subfamilies of poxviridae?
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-chodopoxviridae (chordate hosts)
-entemopoxviridae (insect hosts) |
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Name 2 genuses (geni?) of chordopoxviridae that can infect humans?
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-mulluscipoxvirises (only humans)
-orthopoxviridae (mammals) |
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What is the reservoir for vaccinia virus?
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It is unknown!!!
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Name the 2 strains of variola that cause disease:
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-Variola major = 30% of fatalities
-Variola minor = less than 1% of fatalities |
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How long is the incubation period of variola?
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12-14 days
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What kind of symptoms are experience from variola infection after the incubation period?
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2-3 days of flu-like symptoms
characteristic rash (centrifugally distributed) |
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What type of transmission of variola is most infectious?
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aerosol droplets from lesions inside mouth
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How long does it take for smallpox lesions to heal?
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8-14 days
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When is the most likely period of death during smallpox infection?
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at the peak of rash onset
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Name some rare complications of smallpox:
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limb deformities
blindness |
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Is there a treatment for variola besides vaccination (up to 4 days after infection)?
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No!
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How long ago is poxvirus thought to originate?
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about 5000 years ago (sedentary lifestyle, domesticated animals)
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Where are the earliest traces of smallpox seen?
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Egyptian mummies
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When did smallpox reach various parts of the world?
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India, Egypt - 1st C. A.D.
next China, Asia, Europe Americas in 16th C. |
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Where was variolation first practiced?
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China - scab powder blown up nose
India - spreads on skin |
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Who invented vaccination (using cowpox) virus?
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Edward Jenner
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When was smallpox eradicated?
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declared officially in 1980
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Where are 2 samples of smallpox virus kept?
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In Atlanta at the CDC and in Koltsovo.
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Which strain of poxvirus is phylogenetically closest to vaccinia?
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rabbitpox virus
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Which strain of poxvirus is phylogenically closest to Variola?
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camelpox
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How does the IMV enter the host cell? (2)
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-direct fusion (pH independent)
-endocytosis (pH dependent) |
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How does the EEV enter the cell?
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membrane shedding, then fusion
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Which stage of transcription is responsible for half the genes of the poxvirus?
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Early transcription
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Where does early transcription occur?
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partially dissassembled core of the virus
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How does the virus acquire its NTPs?
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It takes up NTPs from the cell cytoplasm and dehydrates them using a viral enzyme.
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When can viral infection be detected? When does it reach its max?
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20 min
1-2 hours |
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What types of post-transcriptional processing are permormed on poxvirus?
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5` cap and poly(A) tail
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Which categories of products are produced during early transcription? (3)
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1. proteins from host-defense
2. VITFs 3. enzymes from DNA replication |
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Name the viral enzymes used for DNA replication:
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-DNA pol. and processitivity factor
-topoisomerase I -ssDNA binding protein -DNA ligase -protein kinase -nucleoside triphosphatase -uracil DNA glycosylase -dUTPase -thymidine kinase -thimidylate kinase -nucleotide reductatse |
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How does the virus generate UTP?
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uracil DNA glycosylase
dUTPase |
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How is uncoating triggered?
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the beginning of DNA replication
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Where are the most important genes of poxvirus located on the genome?
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in the centre
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How many genes are conserved in the family of poxviruses?
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100
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How many genes are conserved in chordopox viruses?
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50 - different genes for host interactions
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What are located at the ends of the genome?
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ITRs (inverted terminal loops) that are AT-rich hairpins with several ORFs repeated at the end of the genome
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How are the genes of poxvirus organized?
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packed
not much ORF overlap early and late genes mixed up |
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What DNA replication model is used by poxviruses and what large agglomerates of DNA are formed?
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rolling-hairpin model
concatamers |
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Which genes are expressed during intermediate transcription?
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VLTFs
RNA helicase |
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Which genes are transcribed during late transcription?
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Major virion components:
-RNA pol. (8 subunits) -2 early TFs (VETF) -4 proteins from mRNA -5` capping, transcription termination, and 3` poly(A) enzymes -DNA topoisomerase -2 protein kinases -1 protein phosphatase |
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Describe the poxvirus cap:
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-5` poly(A) head
-slippage of pol. on TAAA upstream of ATG |
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Describe the poly(A) tail:
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heterogenenous so dsRNA does NOT form (less IFN secretion)
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Describe the steps of maturation of the poxvirus particle:
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-single-membrane bilayer crescents with surface proteins of IMV
-membranes coalesce -condensaction of core -of mation of lateral bodies and ovoid shape some virions become EEVs: -second bilayer from Golgi -actin tail |
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What happens to the second membrane of the EEV when it enters a cell?
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It is extruded by the PM to lose one lipid bilayer.
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What types of leukocyte products does the poxvirus want to evade? (3)
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-chemokines
-proteins -interferon (IFN) |
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Name 2 ways the poxvirus avoids IFN anti-viral action:
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-IFN gamma receptor homolog
-IFN alpha and beta binding proteins |
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Name a way the poxvirus evades chemokine action:
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-chemokine binding proteins I and II
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What does virokine do?
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Growth factor homolog
unknown mechanism for immune evasion |
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How does the poxvirus stop cellular protein synthesis?
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eIF2 alpha homolog inactivates translation (less IFN produced)
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