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MICR3320 > 19 - Blood Borne Viral Diseases > Flashcards

19 - Blood Borne Viral Diseases Flashcards

1
Q

Five viruses that cause hepatitis

A
  • HAV
  • HBV
  • HCV
  • HDV
  • HEV
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2
Q

HBV, HCV, and HDV transmission

A

Parenterally

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3
Q

HAV and HEV transmission

A

Enterally

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4
Q

HBV and HCV

A

Cause chronic infection, causing cirrhosis and hepatocellular carcinoma

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5
Q

HDV infection

A

Chronic infection in the presence of HBV

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6
Q

Other viruses that can cause liver inflammation

A
  • CMV
  • EBV
  • HSV
  • Yellow fever
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7
Q

HBV

A
  • Partially ds circular DNA 3.2kb
  • 4 overlapping open reading frames (S, C, P and X) that encode surface proteins, structural core protein, polymerase, and non structural precore proteins
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8
Q

HBV surface proteins

A

HBsAg

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9
Q

HBV structural core protein

A

HBcAg

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10
Q

Non structural precore proteins

A

HBeAg

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11
Q

HBV life cycle

A
  • Relaxed circular DNA (RC-DNA) –> cccDNA
  • DNA is transcribed by host RNA polymerase into pregenomic RNA (pgRNA) and subgenomic mRNAs
  • pgRNA is encapsidated, together with the P protein, and reverse transcribed inside the nucleocapsid
  • (+)DNA synthesis from the (-)DNA template generates new RC-DNA
  • Subviral particles (SVP) are present at much higher concentration than viral particles (VP) in serum
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12
Q

Two types of SVP

A
  • Sphere
  • Filament
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13
Q

SVP

A
  • Contain only envelope glycoproteins and host-derived
    lipids, and it is not a complete
    virion
  • Non-infectious.
  • Involved in antibody neutralisation (decoy)
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14
Q

HBV transmission

A
  • Parenteral (blood transfusion, needlestick injury tattooing)
  • Sexual
  • Vertical
  • Intra-familial
  • Aboriginal
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15
Q

How long can HBV survive outside the body and still be capable of causing infection/resistant to common household disinfectants

A

7 days

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16
Q

Hepatitis B disease

A
  • 45-180 day incubation period
  • Can cause acute and chronic disease
  • Most acute infections are symptomatic and cleared by IR
  • ~10% of infections are not cleared and virus continues to replicate
  • Risk of chronic infection varies according to age at infection (greatest in young children)
17
Q

Hepatitis symptoms

A
  • Flu like symptoms
  • Jaundice
  • Itching
18
Q

Prevention of perinatal HBV transmission

A

By providing hepatitis B immune globulin and hepatitis B vaccine to their infants within 12 hours of birth

19
Q

Chance of vertically infected infants will go on to chronicity

A

90%

20
Q

HBV infection recovery indications

A

Clearance of HBsAg from blood and appearance of anti-HBs

21
Q

HBV chronic infection indications

A

Persistence of HBsAg >6 months after infection andq lack of anti HBs

22
Q

HBeAg

A

Active viral replication

23
Q

Anti-HBs(Ab) and Anti-Hbe (Ab)

A

Recovery

24
Q

Anti-HBc (Ab)

A

If positive, indicates HBV exposure

25
Q

Management of chronic hepatitis B

A
  • Based on levels of serum HBV DNA, ALT and severity of liver disease
  • Nucleoside or nucleotide analogues (NUCs)
  • however Antiretroviral treatment can select
    for drug resistant virus
26
Q

Example of NUCs

A

Lamivudine inhibits HBV DNA synthesis ➔ suppression of viral replication and reduction of hepatic necrosis, and HBeAg seroconversion

27
Q

Hepatitis D virus

A
  • Circular,ssRNA(-) genome of 1,68 kb
  • Unique virus dependent on HBV - enveloped (HBsAg)
  • Considered a satellite virus of HBV but does not share sequence similarity (can replicate independently of HBV.)
  • Range of clinical outcomes from asymptomatic infection to fulminant hepatitis
28
Q

HDV Coinfection

A
  • Both HBV and HDV are acquired simultaneously
  • Severe acute disease/ low risk of chronic infection
29
Q

Superinfection

A
  • Chronic HBV carriers are infected with HDV
  • Usually develop chronic HDV infection/ high risk of severe chronic hepatitis
  • May present as an acute hepatitis
30
Q

T/F: Hepatitis D infections can be prevented by hepatitis B immunisation

A

TRUE

31
Q

Hepatitis C virus

A
  • High propensity for establishing chronic infection
  • Can lead to advanced liver fibrosis, cirrhosis and hepatocellular carcinoma
  • Most common indication for liver transplantation in developed countries.
  • Unlike HBV, is curable
32
Q

HCV structure

A
  • (+)ssRNA approximately 9,600
    nucleotide bases in length.
  • Flaviviridae family
  • Circulate as a hybrid lipoviral particle that consists of lipoproteins tightly associated with the HCV particle.
  • The formation of the lipoviral particle facilitates HCV entry into hepatocytes and it protects HCV from antibody neutralisation
  • 8 recognised genotypes
33
Q

HCV genome

A
  • Contains a single, long, open reading frame (3,006-3037 codons) flanked by 5’ and 3’ untranslated regions(UTRs)
  • Contains IRES
34
Q

HCV replication

A
  • Formation of replication complex which replicates the (+)RNA genome through (-) intermediates
  • RdRp NS5B is the key enzyme of RNA synthesis.
35
Q

HCV transmission

A
  • Contact with blood from an infected person and sexual transmission
  • 2-6 month incubation period
  • 80% asymptomatic
  • 70% result in chronic persistent infection

MICR3320 (25 decks)

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