Hello, I am doctor Aizaz from medicovisual.com back with another visual lecture on the topic
of concept of epitopes and serological types of hepatitis B virus.
In previous lecture we have discussed the structure of hepatitis B virus and in structure
you know we have studied that there were surface antigens right there were surface antigens
in the envelope of hepatitis B virus now let's suppose this is a surface antigen and I am
gonna enlarge it, Now!
Because it is an antigen by definition antigen means antibody generator antigen antibody
generator.
so because it is s antigen it means it can lead to generation of antibodies against itself
so it is an antigen now when antibodies are produced against this s antigen these relatively
small antibodies cannot bind with this huge protein as a whole.
Right.
These antibodies will bind with a small part or you can say small pieces of antigen let's
suppose this antibody it may bind here right or it may bind here or it may bind here right
it cannot bind this whole antigen and the part or piece of antigen to which the antibody
binds is called Epitope.
So what is epitope?
epitope is the part or piece of antigen which antibody recognizes and binds to right this
is the definition of epitope now based on the on the epitope there are several different
epitopes in surface antigen or s antigen of hepatitis B virus right this one epitope I
have shown here this one a epitope right of course there is another epitope here and then
another epitope here as well "A" epitope is universal it is present in all varieties or
you can say all serological subtypes of hepatitis B virus but the this antigen "Nose" epitope
that's what I like to call it actually it is not "Nose" epitope so and this lips epitope.
it has two variations right so the here epitope can be either of this variety or of this variety
and here epitope can also be either of this type or of this type so two variations can
be there right so let's create our antigen by using these epitopes so for here this nose
part or nose epitope which nose should I use this one or this one this one okay this one
I am using this one and for lips okay let's use this one for lips so now if we have created
a complete antigen with three epitopes and what are those epitopes yes this "A" is already
there so A and this one is d, d epitope ad and this is what.
adr, are so now this antigen now this serological type of antigen is called adr antigen or adr
surface antigen right and hepatitis B virus which has this type of surface antigen we
we like to call that hepatitis B virus as Adr serological subtype of hepatitis B virus
right it's very easy to understand let's create another let's create another serological subtype
for practice now this time which which one should we use okay let's use this nose, this
is not nose remember this is just an Epitope so this Epitope and now let's use this one right should
we use this or this okay let's you know what is the sero- logical type should be named.
"A" is already there "A" is always there and this is inverted "Y" nose I have shown.
so it is a "Y" and here is "W".
"Adw" serological subtype right so in this way by using these different combinations
we can have four serological subtypes of hepatitis B virus what is this Ayr a vial this is
Ayw right this is Adr and this is Adw in this way we have four serological subtypes
now what is the significance of serological subtypes first of all my question is that
let's suppose god forbid a person gets infected with this type this serological subtype Ayr
subtype of hepatitis b virus and fortunately he recovers from this infection right he is
able to clear this infection but my question is now let's suppose in his blood let's suppose
this serological subtype enters into this blood will his he'll will his antibodies that
are produced in his body will they be able to offer cross resistance or not or cross
protection against the new strain or not yes they can offer cross protection the reason
is that this "A" is universally present so even if the the nose and lips may be different
of the new strain those nose and lips may be different but the antibody will still recognize
from this part and antibody will catch this and it will kill this virus and in this way
it can offer cross protection or cross resistance but then what is the significance of this
subtypes why do we do a classify it into serological subtypes well it is of epidemiological importance
what do I mean by epidemiological importance it means that let's suppose in America usually
this virus may be present of this serological subtype for example in India or Pakistan this
serological subtype may be more prevalent or this serological subtype may be more prevalent
in let's say Japan so it is of just of epidemiological importance clinical significance is not that
relevant right even the vaccines they can also provide cross protection and reason I
have mentioned right so this was about the concept of epitope and serological subtypes
of hepatitis B virus thank you so much for watching this video lecture please like this
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