Lecture 21

Question 1

What kind of virus is Hepatitis B?

Answer 1

A non-lytic, virus which does not have a latent phase or damage the liver cell

Question 2

Where do bacterial infections usually infect the gut?

Answer 2

The biliary system

Question 3

Where do viral infections typically infect the liver?

Answer 3

Affect the liver diffusely, where all hepatocytes are equally affected

Question 4

What are the features of Hepatitis A?

Answer 4

Source of infection is from water contaminated by faeces
Very low (1%) mortality from acute infection, with no risk of chronic infection and an available vaccine

Question 5

What are the features of Hepatitis B?

Answer 5

Transmitted through blood contact, with a 5-10% mortality from acute infection, variable risk of chronic infection and a vaccine available

Question 6

What are the features of hepatitis C?

Answer 6

Transmitted through blood contact, 0.1% mortality risk for acute infection with a 70% risk if chronic infection and no vaccine available

Question 7

What are the rates of Hepatitis B infection?

Answer 7

10% in Maori 4th form students
0.5% in European students
8% In Maori, Pacific and chinese people

Question 8

What explains the disproportionate numbers of increased infection of hepatitis B in Maori, Pacific and Chinese?

Answer 8

The virus is transmitted from mother to child or child to child in preschool years
This results in chronic infection, and the early ancestors of the people that settled these regions had a large amount of HBV present

Question 9

What is the best diagnostic test for Hepatitis B?

Answer 9

A variation of the ELISA test where wells have bound antibodies for the HBV, patient blood is then used and if HBV is present then it will remain in the well due to the antibodies
A marker antibody is then used to detect the HBV virus stuck in the wells

Question 10

What antigen is detected in the diagnostic test for HBV

Answer 10

HBV Surface antigen (HBsAg)

Question 11

What are the antigens present in the HBV virus?

Answer 11

HBV Surface antigen (HBVsAg)
HBV Core antigen (HBVcAg)
HBeAg (similar to core antigen not structurally part of the virus but released when high concentrations of the virus are present)

Question 12

Does HBsAg always contain HBV DNA?

Answer 12

No, large amounts are made and released without DNA

Question 13

What is the clinical relevance of HBeAG?

Answer 13

It is only produced in high concentrations of the virus and as virus concentration determines the risk of transmission HBeAg can be used as a marker

Question 14

What are the risks of transmission from an HBeAg-ve infected person?

Answer 14

10% At birth, 3% with a needle stick

Shows an HBV concentration of 1-10^6 HBV/mL

Question 15

What are the risks of transmission from HBeAG +ve individuals?

Answer 15

90% at Birth
30% with needlestick
Shows HBV concentration of 10^5-10^9 HBV/mL

Question 16

What does the outcome of an HBV infection depend on?

Answer 16

The generated immune response as cytotoxic lymphocytes are responsible for clearing the infection, causing liver cell damage and illness

Question 17

What are the stages/features of the time course of an adult infection of HBV?

Answer 17

Initial rise in infected cells, this then peaks when cytotoxic T cells begin an aggressive attack on infected liver cells causing illness but reducing HBV virus levels dramatically, the infection is then eradicated and antibodes to the HBV virus increase in number

Question 18

What are the stages/features of a time course of HBV infection in infants?

Answer 18

Initial rise in HBV infected cells, this will eventually be counteracted by a WEAK cytotoxic T cell attack which only mildly reduces the amount of infected cells resulting in an asymptomatic illness, but a persistent infection and continued liver damage which can lead to cirrhosis

Question 19

What is the risk of developing a chronic HBV infection from adult to adult transmission?

Answer 19

1-5%

Question 20

What are the outcomes (and their %s) of chronic HBV Vaccine?

Answer 20

No serious sequellae (70-90%)

Cirrhosis (20% approx.), of these 10% die, 4-20% HCC

Question 21

What is the cycle of HBV infection?

Answer 21

Infection of neo-nate by mother, 90% of infected children develop a persistent infection, mothers will pass this on to their daughters causing a cycle of infection

Question 22

What are the two methods of preventing an HBV infection?

Answer 22

Vaccinate high risk individuals with HBsAG

In emergencies serum containing HBsAB is given

Question 23

What is the difference between the old and new vaccines for HBV and why was a new one developed?

Answer 23

The original old cheap vaccine was derived from HBsAG taken from individuals with the HBV virus and purified from their blood
Due concerns about what other virus may not be removed during purification and therefore infect those that got the vaccine a new, more expensive vaccine is generated from a recombinant yeast

Question 24

How effective is the HBV vaccine?

Answer 24

3 doses give life long immunity in approx. 90%