Hepatitis B

  1. Hep B virion is a different family of viruses. It has a lot of really weird features about it. It also looks like a bunch of different viruses. 

    Explain its virion.
    • At its core, it is a DNA virus
    • Regular icosahedral capsid underneath a lipid envelope

    Has a lot of non-infectious particles that are spherical and filamentous and lack a nucleocapsid
  2. Genome of Hep B
    • one of the smallest DNA viruses known to infect anything
    • --> circular and partly double-stranded with a single-stranded region of variable length; there are gaps that are single-stranded
  3. Explain the special features of Hep B.
    When it replicates, it doesn't usually finish replicating the genome

    • Neither DNA strand forms a covalently closed circle
    • - The full length minus DNA strand is joined at its 5' end to a tyrosine residue in the P protein, a virus-coded DNA polymerase with reverse transcriptase activity
  4. Hep B plus strand versus minus strand
    the plus strand is shorter than the minus strand because its synthesis is interrupted before completion, giving rise to the single-stranded region

    The ends of DNA hare held together as a circle by Hydrogen bonding between short, repeated sequences called DR, near the 5' ends of both strands
  5. Hep B coding regions in the genome are organized in a highly efficient fashion. Explain.
    Four partly overlapping open reading frames, designated C (capsid), P (polymerase), S (surface protein), and X (for a regulatory protein) are translated to yield seven different viral proteins.
  6. HEP B

    Every base pair in the genome is involved in __. The genome also contains __ that __; a __; a __; and, __ that are involved in __. 
    coding for at least one viral protein

    • two enhancer elements
    • regulate levels of transcription

    polyadenylation signal

    packaging signal

    • direct repeats 
    • reverse transcription
  7. Hep B has a __ with __
    circular DNA genome

    overlapping reading frames
  8. Nucleocapsids enter the cytoplasm via __ and are _. 

    DNA Polymerase can __.
    • fusion
    • transported to the nucleus

    extend the plus strand, sealing the gap
  9. Explain Hep B RNA
    • pre-genome RNA is made, along with several mRNAs
    • depends on reverse transcriptase
    • transcription by cellular RNA pol II is influenced by two enhancer elements (Enh I and II)
  10. Hep B genes and proteins
    uses our own RNA polymerases to make virus particles

    has 5 different promoters and four reading frames

    • seven viral proteins and genes
    • - it is kind of impressive for a small virus
    • - these viruses are pretty unrelated
    • - protein X does a lot of weird stuff
  11. Virus history of hepadnaviruses in general
    • infect a lot of different animal hosts
    • they are highly specific and involved; live in the liver and liver cells. As a result of this, it is hard to grow them in culture

    Hep B itself is difficult to study; one system is duck hep virus
  12. Explain the types of particles that Hep B has?
    non-infectious particles that contain lipids and HBV surface proteins and infectious particles (Dane particles)
  13. Dane particles
    contain everything you could think of in the virus--surface proteins, polymerase, genome, Hep B core proteins, all working together

    If you have this in your body, your liver will be affected

    contains HBV surface antigen and lipids surrounding a core nucleocapsid

    Dane has its own name because those particles are actually the majority of what's in your serum. When infected, our cells make some Dane particles but they make more decoy non-infectious viruses
  14. Explain the non-infectious viruses in most details.
    they are like pseudoviruses made mostly of lipids and hep B surface proteins and contains no core proteins, reverse transcriptase, or viral genome DNA

    they induce an immune response; and, our immune system will focus on the pseudo-infectious virions, leaving the Dane particles in the blood
  15. How do immune systems divert the immune system?
    may divert the immune system by binding to antibodies and complement, allowing less abundant virions to transverse the bloodstream undetected
  16. There are __ major strains that exist and __ distinct serotypes.

    • 4

    8 major strains with different genome sequence variations (genotypes) cause a variation in the disease and severity and response to interferon

    4 distinct antigenic serotypes contain two pairs of mutually exclusive epitopes
  17. Explain what is inside the Dane particle?
    surface proteins, polymerase, genome, core protein, all working together

    • circular genome with two enhancers
    • different open reading frames
    • every single nucleotide encodes for at least one protein; and, a number encode for more than one protein. it is the same as the dane particle 

    the genome has positive and negative strands. All the genes are on one strand--the actual coding strand
  18. When the Hep B virus is made, it wants to replicate, but what? 

    It uses __ and __.
    it doesn't get done when it's out

    our own nucleases and ligases
  19. Explain inside of our cells.
    Inside of our cells--the nucleus--there is transcription of a number of different RNAs. There's pregenome RNA, which is a template for making new viral genome molecules
  20. There are two __.
    enhancer elements; this virus, because in our nucleus, uses the same language and machinery to get transcription of different RNAs
  21. There are a few different starting sites.
    five different promoter elements-- preC, pregenome, preS1, S, and X

    preC RNA: DR1 elements and DR2; the RNA for this is longer than the genome; it makes a turn and then some
  22. The roles of the Hep B virus proteins: X
    is not part of viral particle--nonstructural protein; does a lot of stuff
  23. Roles of X
    implicated in development of hepatocellular carcinoma

    upregulates: c-src kinase, Ras/raf/MAPkinase, SAPK, protein kinase C, and Jak/Stat pathway, NF-kB

    sequesters tumor suppressor protein p53

    inhibits apoptosis mediated by Fas, tumor necrosis factor, and other
  24. What happens if you add X by itself?
    to a genome of mice, they are at an increased risk of developing liver cancer

    turns on a lot of kinases and growth factors, stress response pathways, tumor suppressor proteins, things to turn off apoptosis
  25. Hep B is what kind of virus?
    a non-cytopathic virus; cells don't die and crank out a little bit of virus for a long time
  26. Surface protein
    • encoded by transcripts
    • formation of envelope and non-infectious particles 
    • small, middle, and large HB surface proteins 
    • --> related proteins that share domains because they have the small structure in it

    largest one has a site for myristate--hydrophobic chain of proteins, which help it fold properly
  27. Core proteins
    like the capsid--inner symmetrical surface of virus
  28. E proteins
    appears to help with packaging RNA into virus; taking it out of the virus helps an infection become persistent
  29. Polymerase protein
    RNA-DNA dependent DNA polymerase (reverse transcriptase)
  30. reverse transcriptase and ribonuclease H
    when you have reverse transcriptase, you don't really need to replicate genome until you're in the virus particle
  31. How is pre-genome RNA packaged?
    by interaction with polymerase and core proteins--replication occurs on pregenome RNA via reverse trasncription. 

    • Polymerase binds
    • Complementary sequences replace a piece of RNA with another strand, degrading it on the way down and making mroe nucleotides
    • From that, it actually uses the last couple of nucleotdies as a primer to make the secondary strand, running out of nucleotides before it gets around again. 
    • It waits until it gets into the nucleus of another cell
  32. Retrovirus vs Hep B
    Hep B is a DNA virus when it gets into the cell, goes into the nucleus, doesn't integrate but remains free in a circular form, makes a set of five mRNAs with cellular RNA polymerase II, one acts as pgRNA and gets turned into DNA when its on its way out. Essentially, its a DNA virus outside of the cell

    Retro: outside of cells, they are RNA that are reverse trascribed into DNA on the way in so it can integrate into our genome
  33. Retroviruses package an __ that is __ into DNA once it enters the host cell, whereas __ package a __ that is reverse transcribed from a __ in a cell during virus assembly.
    • RNA genome
    • reverse transcribed
    • hepadnaviruses
    • DNA genome
    • pgRNA
  34. What else is distinct about the virus' method of exit?
    uses our own ER and golgi and exocytosis pathways to its advantage

    genes are transcribed, LS, MS, and SS proteins go to the ER

    after transcription, they go to the cytoplasm and travels out after going through ER and Golgi
  35. Hep B incubation
    • up to half a year
    • in the initial stages of infection, half of the patients are asymptomatic, while the others suffer from flu-like symptoms, jaundice, serum sickness, elevated liver enzymes in the blood
    • 1% can get fulminant hepatitis
  36. Transmission of hep B
    direct contact, body fluids, sexual contact, blood transfusions, contaminated needles, unprotected sex
  37. Hep B:

    Acute can be __. It can also be _. 

    Serum sickness: __
    • mild to severe
    • persistent (you can get it for a long time, getting associated disease)

    your blood goes crazy trying to get things out
  38. Prevention of Hep B
    vaccines against it. 

    There are anti-hep B IG given from someone who had it to someone who had been exposed
  39. WHy is Hep B persistent?
    because of the X and E proteins

    Liver slowly degrades as IS tries to clear the system. You get a wonky liver infection and fulminant hep as the liver starts to shut down
  40. First vaccine
    • 1973: Dane particle ID'd
    • Afterwards, the search for the vaccine started. What scientists figured out was that there was abundant particles in the blood. They could clear out what isn't infectious and treat it with chemicals to inactivate it. Then, they injected it into people. However, with an HIV scare, they had to find another way.
  41. Next vaccine
    1986: recombivax replaced the other vaccine; it was teh world's first recombinant vaccine and a subunit vaccine

    They took the surface antigen gene out of the virus, put it into yeast, and then found taht yeast could successfully make the antigen. They purified it off and it became the basic purified subunit vaccine
  42. Recombivax is __
    the first vaccine babies get because of maternal transmission
  43. What are other treatments?
    • antiviral drug treatment has real success
    • 90% of people with Hep B will get it cleared

    10% of the people will go chronic

    80% of those 10% get hep cancer
  44. Drugs work--recombinant interferon
    cloned out recombinant interferon that has been treated so it lasts longer in the bodies. It is a way of ramping up the immune system

    interferon could really work
  45. There are also drugs that work against __. 

    These drugs can sometimes be __.
    • reverse transcriptase
    • nucleoside analogs
  46. Explain nucleoside analogs
    Resemble nucleotides but something is not quite right about them. Some have changes in the pyrimidine structures. SOme have changes down where the sugar should be and have trouble with chaining elongation
  47. Lamivudine
    a nucleoside analog that gets incorporated into Hep B reverse transcriptase; has a Sulfur and can no longer be added to the molecule

    they terminate chain elongation
  48. How is Hep B transmitted?
    by blood transfusions, contaminated needles, and unprotected sex

    passage of virus from mom to newborn
  49. A __ is available. __ can also be used to prevent infection via __.
    • recombinant vaccine
    • Anti-HBV immunoglobulins
    • immunoprophylaxis
Card Set
Hepatitis B
Test Two