What is the concept of Epitope (Antigenic determining) ?What are the Serological subtypes of hepatitis B virus ?
The surface antigen of Hepatitis B virus has several different serological sub-types.
Antigen means “Antibody Generator”. An immune response is generated against the surface antigen. But the tiny antibodies can not bind with the whole surface antigen. It rather binds the small parts of the antigen called “Epitope”. So Epitope means “Part of antigen that antibody recognizes and attaches itself to”.
Surface antigen (HbSAg) has several epitopes. But “A” epitope is universal or common in all serological strains of hepatitis B.
Lets suppose this complete face is the antigen. “A” on the head is “A”epitope that is present in all strains.
Now some of these virus particles may have “Y” style nose.! Not nose ( I mean) Epitope. While others may have “d” epitope (Nose :-D)
Then there is another epitope. Lips epitope. It could be “w” type or “r” type.
So, based on these epitopes, Hepatitis B virus can be of following serological types.
Adw, Adr, Ayw, Awr.
Because “A” epitope is present in all strains, an antibody against one strain can easily recognize the other strain due to the presence of this “A” epitope and can offer cross-protection.
These serological forms are of epidemiological importance only. One serological type may be present in a particular area for example.
This was about the structure of the Hepatitis B virus.