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MM- Viruses > Hepatitis B > Flashcards

Hepatitis B Flashcards

1
Q

Hepatitis B was discovered before?

A

Hepatitis C

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2
Q

Hepatitis B is more likely to cause chronic infection in?

A

Younger individuals

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3
Q

Family?

A

Hepadnaviridae

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4
Q

Genus?

A

Orthohepadnavirus

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5
Q

Genome?

A

dsDNA-RT
RC-DNA= Relaxed circular DNA
Partially dsDNA

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6
Q

RC-DNA stands for?

A

Relaxed circular DNA

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7
Q

Baltimore classification?

A

VII

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8
Q

100 times more infectious than?

A

HIV

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9
Q

Does integration into the host genome occur?

A

No

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10
Q

Replication occurs where?

A

Cytoplasm within the nucleocapsid

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11
Q

Stages of HBV infection?

A

Immune tolerant
Immune active
Inactive

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12
Q

What is associated with the immune tolerant stage?

A

Immune system not yet active
High levels of viral replication- active infection
High levels of HBeAg present in the blood

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13
Q

A person can remain in the immune tolerant stage for?

A

Decades

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14
Q

Immune active stage is usually entered in?

A

When children who were infected reach their thirties

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15
Q

Immune tolerant stage is associated with?

A

Inflammation, liver damage

Anti HBeAg antibody presence

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16
Q

Immune inactive stage is associated with?

A

Anti HBeAg

The infection can re-activate

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17
Q

Why is there less genome diversity in HBV?

A

Overlapping genomes
There are 4 ORFs which are overlapping
Each nucleotide is coding, sometimes for multiple proteins. Therefore mutations are rare as it is highly likely a mutation will lead to a dysfunctional protein

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18
Q

What antigens are associated with HBV?

A

HBsAg
HBcAg
HBeAg

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19
Q

The e in HBeAg stands for?

A

Early

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20
Q

High levels of HBeAg are indicative of?

A

Active infection

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21
Q

HBcAg?

A

This is not secreted
It is at the surface of the nucleocapsid
Remains associated with the viral particle at all times

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22
Q

HBsAg?

A

This is the surface antigen

Also known as the Australia antigen

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23
Q

Infectious HBV particle is called what and is what size?

A

Dane particle 42nm

24
Q

HBsAg can form non-infectious particles known as?

A

Subviral particles

25
Q

What types of subviral particles are there?

A

Filamentous and spheres

26
Q

What size are subviral particles?

27
Q

Describe the virion structure?

A

Envelope made up of HBsAg

Icosahedral capsid

28
Q

What is the purpose of subviral particles?

A

May be to sequester antibodies to allow the infectious Dane particles to go undetected

29
Q

Why are subviral particles non-infectious?

A

Made up of solely HBsAg

Contain no nucleocapsid/core, no genome and no P protein

30
Q

P protein functions?

A

RT- RNA dependent DNA polymerase
DNA dependent DNA polymerase function
Ribonuclease H- RNase H activity

31
Q

How large is the viral genome?

32
Q

HBV genome is very?

A

Small, one of the smallest viral genomes

33
Q

What DNA is found in the virion?

34
Q

RC-DNA structure?

A

Relaxed circular DNA
Incomplete +ssDNA
P protein attached to -ssDNA

35
Q

The RC-DNA enters the nucleus and is rapidly repaired to form?

36
Q

cccDNA?

A

Covalently closed DNA

37
Q

How is cccDNA formed?

A

Repair of RC-DNA
Covalent ligation
Required the removal of P protein, ssDNA flap and RNA

38
Q

Does cccDNA integrate?

39
Q

cccDNA is transcribed by?

A

RNA pol-II

40
Q

cccDNA is transcribed into?

A

Long and short RNAs

41
Q

Long RNAs include?

A

pre-core RNA

pre-genomic pgRNA

42
Q

pre-core RNA encodes?

43
Q

pgRNA is used for?

A

Replication

44
Q

pgRNA encodes?

A

P protein

HBcAg

45
Q

Subgenomic RNAs encode?

46
Q

How many proteins are encoded by HBV?

A

7 proteins

47
Q

Which 7 proteins are encoded by HBV?

A 
HBsAg= small, medium and large 
HBcAg
HBeAg
HBX
P protein
48
Q

cccDNA is present as what in the nucleus?

A

Minichromosome

49
Q

How does the minichromosome form?

A

Due to histone and non-histone proteins

50
Q

What allows the expression of the cccDNA genes?

51
Q

Without HBX?

A

cccDNA is rapidly silenced

52
Q

What triggers encapsidation?

A

Binding of P protein to the 5’ RNA structural element epsilon of pgRNA

53
Q

Reverse transcription is triggered by?

A

Encapsidation

54
Q

Priming for reverse transcription in HIV is mediated by?

A

Cell derived tRNA

55
Q

Priming for reverse transcription in HBV is mediated by?

A

Novel protein priming mechanism

56
Q

Why is the +ssDNA of RC-DNA incomplete?

A

Due to the limited dNTP pool present in the nucleocapsid

57
Q

How is exit mediated?

A

Budding of the nucleocapsid through the ER and golgi

MM- Viruses (13 decks)

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