I am Arvind Sahu.
I am a Scientist at the National Center for Cell Science, Pune, India.
In this talk, I will try to provide you
an overview on the "Subversion of the Complement System by Viruses".
I have divided my talk in three parts.
First, I will talk on how complement recognizes viruses,
then I will talk on what role complement plays in antiviral immunity,
and then, I will talk about various complement subversion mechanisms of viruses.
So the first question,
that comes to anybody's mind,
is how complement marks viruses as non-self?
And the simple answer is,
it does so by labeling them with C3b.
That is, once C3b is covalently attached to viruses,
it is considered as non-self by the complement system.
So let us see how this occurs.
So, when a virus enters our body,
it can be labelled by C3b,
by three different mechanisms, that is,
by the classical pathway,
by the lectin pathway,
and by the alternative pathway.
Activation of these pathways result in the formation of an enzyme,
termed C3 convertase, which cleaves C3 into C3a and C3b.
The C3b moiety ,
then gets covalently attached to the surface forming an ester or sometimes amide bond.
The position of C3b then results in the activation of the
alternative pathway loop leading to
the position of more C3b molecules on the viral surface.
This also results in the formation of C5 convertase,
which can result in the activation of the terminal pathway leading to the formation of the
membrane attack complex on the lipid membranes of viruses resulting in virolysis.