Hepatitis B Virus
Dr Snehalata Pattnaik
Dr Manorama swain
Under the electron
microscope Hepatitis B virus is a double walled spherical
structure of 42 nm (nanometer) in diameter. Of these double
walls, the outer wall represents the core particle or 'c'
antigen and the inner wall represents the 'e' antigen. It
has an outer surface coat of particles measuring 22 nm,
which is known as the surface antigen or 'Australia Antigen'.
Hepatitis B virus is a DNA virus containing double stranded
DNA and an enzyme called DNA dependent DNA polymerase. The
Hepatitis B virus particle is also known as 'Dane particle'.
The virus only replicates in the liver and there is evidence
to suggest that
it becomes integrated with the host nuclear protein. This
integration may be an important link in the development
of hepatoma or 'liver cancer'. HbsAg or, Hepatitis B surface
Antigen or Australia Antigen was discovered by the Nobel
Blumberg in 1963. It has different antigenic subdeterminants.
They are a, d,
y, w and r. Combinations of these subdeterminants are useful
in epidemiology for studying geographical differences. Screening
of Hepatitis B surface Antigen or HBsAg in the blood
serves as a definite tool for the detection of the presence
of Hepatitis B virus in the
body. Besides, diagnosis of the antigenic subdeterminant is also
important because the different subtypes respond to treatment
in a different ways and hence this is important from prognostic
view point also.The
virus infects the host through parenteral route and produces
the diseases like acute hepatitis, chronic hepatitis, fulminant
hepatitis, cirrhosis and hepatocellular carcinoma.
Hepatitis B can be easily prevented
Hepatitis B vaccine :
In 1969 Blumberg and Irvin Millman invented the first hepatitis
B vaccine. The vaccine is administered as follows in three
dosages. First dose to start any day. Second dose after
one month of first dose and the third dose after six months
of first dose. One ml. vaccine is given
to adult where as 0.5 ml. is given to children. The best
way to administer the vaccine is at birth.