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Microbiology > Hepatitis Viruses > Flashcards

Hepatitis Viruses Flashcards

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0
Q

What are some common clinical features amongst the hepatitis viruses?

A

Anorexia.
Nausea + emesis.
Right upper quadrant pain.
Raised liver enzymes like AST/ALT.

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1
Q

What other viruses other than the hepatitis viruses cause acute hepatitis?

A 
Human Cytomegalovirus.
Epstein-Barr virus.
Herpes sSimplex Virus.
Yellow Fever Virus.
Rubella.
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2
Q

What kind of genome does hepatitis A have and is it an enveloped virus?

A

+ssRNA.

Non-enveloped.

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3
Q

What does convalescence mean?

A

Refers to the time spent recovering from an illness or medical procedure.
*recuperation

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4
Q

What is the incubation period of hepatitis A?

A

3-5 weeks ~ 28 days

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5
Q

Is hepatitis A an acute or chronic disease?

A

No chronic form of the disease.

Convalescence may be prolonged (fatigue + alcohol intolerance up to 18 months).

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6
Q

Relate the severity of a hepatitis A infection to the age at which one acquires the virus.

A

Severe - adults and pregnant women

Mild or asymptomatic - children

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7
Q

What is a complication of hepatitis A infection? Who are at risk ?

A

Fulminant hepatitis.

Pregnant women, elderly, pre-existing liver disease.

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8
Q

Outline the pathogenesis of hepatitis A.

A

Virus enters gut > replicates in alimentary tract > replicates in liver > virus excreted in stools for 2 weeks preceding the onset of symptoms.
*viraemia is transient!

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9
Q

How is hepatitis A transmitted?

A

Faecal-oral route. *virus shed in stools for 2weeks before symptoms.
Shell-fish grown in sewage-polluted water.

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10
Q

How does one diagnose hepatitis A?

A

Serology:

- HAV-specific IgM

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11
Q

Ways to prevent hepatitis A infection?

A

Active immunization:
- recommended form of post-exposure prophylaxis
Passive immunization:
- normal Ig given
*in cases where risk for severe disease both are given.

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12
Q

Which antibodies fall/rise towards the end of the disease?

A 
IgM falls (active immunity)
IgG rises (indicative of past exposure)
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13
Q

What kind of genome does HEV have and is it an enveloped virus?

A

+ssRNA.

Non-enveloped.

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14
Q

What is the incubation period of HEV and how bad is the illness it causes?

A

2-9 weeks ~ 45 days

Usually acute self-limiting hepatitis.

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15
Q

Relate HEV infection to the age at which one normally acquires the virus.

A

Mostly young adults.

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16
Q

What are the complications of HEV infection?

A 
Fulminant hepatitis (pregnant women greater risk).
Chronic hepatitis > cirrhosis (organ transplant/HIV infection).
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17
Q

Outline the pathogenesis of HEV infection.

A

Replicates in gut initially >replicates in liver > virus shed in stool prior to symptoms SIMILAR TO HAV

  • viraemia is transient
  • large innocuous required to establish infection
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18
Q

How is HEV spread?

A

Faecal-oral route. *contaminated water

Animals are reservoirs (pig, dog) *inadequately cooked meat

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19
Q

What pattern suggests that a large innocuous is required in order to establish a HEV infection?

A

Case-to-case transmission is low therefore suggests large innocuous required.

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20
Q

What specimens can be sent to the lab to test for HEV infection?

A

Stools and serum.

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21
Q

How does one test for HEV infection? Which tests are available here in SA?

A
  1. Virus particles in stools (electron microscopy)
  2. IgM in serum
  3. PCR for HEV genome in stool or serum
    * none available for routine test in SA
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22
Q

What kind of genomic material does HBV have and is the virion enveloped?

A 
Circular DNA (incompletely double-stranded) 
Enveloped.
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23
Q

What is the incubation period of HBV?

A

30-180 days.

Onset of symptoms is insidious.

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24
Q

Which tends to cause more severe disease between HAV and HBV?

A

HBV

25
Q

Relate the age of infection with HBV and the likeliness of subsequent chronic illness.

A

5% of adults develop chronic infection.

90% of infants vertically infected develop chronic infection.

26
Q

Why is it that infants develop chronic infection with HBV?

A

Very young develop immunotolerance > lesser immune response

*less inflammation of liver but higher rate of chronicity as a result

27
Q

How is HBV transmitted?

A

Parenternally.

28
Q

What does parenternal mean?

A

Administered or occurring elsewhere in the body than the mouth and alimentary canal.

29
Q

Outline the pathogenesis of HBV.

A

Virus replicates in liver > viraemia prolonged therefore blood highly infectious

30
Q

What is one way HBV visions avoid destruction by the immune system?

A

Excess viral surface antigen is produced (form sphere and cylinders) that bind to antibodies, mopping them up.

31
Q

What is responsible for hepatocellular damage in HBV infection?

A

Host immune response.

32
Q

Name 5 complications of HBV infection.

A 
Persistent infection.
Hepatocellular carcinoma(HCC).
Fulminant hepatitis. (Rare)
Extra hepatic manifestations. 
Co-infection with HIV (faster progression + severe liver damage)
33
Q

Name three extra-hepatic manifestations of HBV.

A

Serum sickness.
Glomerulonephritis.
Polyarteritis nodosa.
*caused by deposition of immune complexes

34
Q

What forms of persistent infection with HBV are there?

A

Chronic persistent hepatitis:
- virus persists/minimal liver damage
Chronic active hepatitis:
- aggressive destruction of liver tissue > rapid progression to cirrhosis + liver failure.

35
Q

What is polyarteritis nodosa?

A

Vascular is of medium/small-sized arteries > become swollen + damaged from attack by rogue immune cells.

36
Q

How is HBV transmitted?

A 
PARETERAL TRANSMISSION
Sexual intercourse.
Close personal contact (horizontal spread).
Vertical transmission.
Blood.
37
Q

What is a feature of the enzymes coded for by HBV?

A

HBV polymerase has DNA polymerase and reverse transcriptase activity.

38
Q

What can HBV vaccines contain?

A

Purified serum-derived sAg from HBV carriers.

Recombinat sAg via genetic engineering of yeasts.

39
Q

When do infants receive HBV vaccinations in SA?

A

6,10 and 14 weeks.
If mum is a chronic carrier then at:
- birth, 1m and 6m (additional dose at 2m if baby <2kg)

40
Q

What can one give to a person as a form of post-exposure prophylaxis for HBV?

A

Vaccine + HBV Ig

41
Q

What two classes of drugs are used to treat chronic HBV infection.

A

Interferons.

Nucleoside reverse transcriptase inhibitors.

42
Q

What does interferon-alpha do in the chronically HBV infected individual.

A

Enhances the host immune response to HBV and improves immune control of the virus.

43
Q

What two common nucleoside reverse transcriptase inhibitors are used to treat chronic HBV infection? What do they do?

A

Tenofovir and Lamividine.

They interfere with viral replication but CANNOT CLEAR HBV INFECTION!!!

44
Q

Which HBV viral surface antigens can be detected and what is each a a marker of?

A

sAg - viral replication in liver (secreted in excess)
eAg - indicative of high replication rates in liver
cAg - present in infected cells not in blood

45
Q

What surface antibodies can be detected against HBV and what is each indicative of?

A

sAb - indicates immunity (found in late convalescence)
eAb - indicates low infectivity (detectable as viral replication falls)
cIgM - indicates recent infection
cIgG - indicates exposure to HBV

46
Q

Which antibodies to HBV are found in chronic carriers and which aren’t?

A

sAb - not found in chronic carriers

cIgG - found in chronic carriers (also those who clear the infection)

47
Q

Genome of HCV and is it enveloped?

A

+ssRNA.

Enveloped.

48
Q

Incubation period of HCV?

A

15-150 days.

49
Q

How may a case of HCV present?

A

Mostly asymptomatic.

Some: fatigue + jaundice.

50
Q

What is a feature of HCV genome?

A

Genome has a high mutation rate.

51
Q

Can HCV cause chronic infection?

A

80% of newly infected individuals develop chronic infection.

52
Q

Complications of HCV infection?

A
  1. Chronic infection > cirrhosis
  2. HCC in 1-5% of HCV infected people
  3. Immune complex disorders
  4. Co-infection with HIV > aggressive liver disease
  5. Extra hepatic manifestations
53
Q

Transmission of HCV?

A

Parenteral transmission:

  • IVD
  • vertical transmission and sexual intercourse (minor roles)
54
Q

How to diagnose HCV?

A

Serology:
- IgG indicates exposure > useful for diagnosing chronic infections
PCR:
- HCV genome detectable in serum 4-6 weeks post-exposure
- indicative of infectivity

55
Q

How to treat a chronic HCV infection?

A

Interferon-alpha + ribavirin = clearance in ~40% of cases

*pegylated interferon-alpha

56
Q

Vaccine for HCV?

A

Not available.

57
Q

What is HDV?

A

A defective virus that requires HBV as a helper virus in order to replicate.

58
Q

Two forms of HDV infection?

A

Co-infection:
- HBV and HDV at same time
Superinfection:
- HDV after HBV infection

59
Q

How does HDV infection impact HBV infection?

A

Increases severity of liver disease.
Fulminant hepatitis 10X more common in co-infection that sole HBV infection.
70-80% chance of cirrhosis if co-infected.

60
Q

Genome of HDV and why does it need HBV to replicate?

A

Circular -ssRNA

sAg derived from HBV

61
Q

Treatment for HDV infection?

A

No specific treatment available.

*prevent HBV using vaccine!

Microbiology (18 decks)

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