The retroviridae, viruses.
are going to be quite familiar to you
because the principal one's the human
immunodeficiency virus, HIV.
These are mid-sized, enveloped
viruses, with a helical capsid.
And they have 2 copies of a
positive-sense RNA genome,
along with transfer RNA.
In addition, these carry a
They carry all the machinery necessary
to generate their own copy
multiple times over
You can see in the micrograph or the
electron micrograph to the right,
2 circled forms of retrovirus.
These are HIV,
and they have a very distinctive
shape with a very
organized capsular structure.
As mentioned, the medically relevant
species we'll talk about
in this session are
human immunodeficiency virus, HIV,
and something which is quite related,
the to human T lymphotropic virus.
As you're getting a sense, both viruses
will target lymphocytes in their action.
Looking a bit more closely
at the retroviruses,
and again, using HIV as the model,
they carry very complex gene
products to encode various elements
and various proteins.
There's a gag protein which encodes
and you can see that identified
in the middle.
You can see the Pol gene which encodes
enzymes which are important for the
regeneration of the RNA, DNA,
and that would be your
And then integrase, protease
all responsible for various life
cycles of the HIV as it
replicates itself and buds off.
And then the env gene which encodes
specific envelope glycoproteins,
which are very important for the virus
binding to its target site
on the lymphocytes.
The challenge with HIV and you, I'm sure, have
followed this in the medical news, as
well as even the common news,
is to try and create vaccines and even
a way to address, by medication,
the virus itself.
And it's a challenge because
the virus is very complicated and thus, it
creates multiple mutations.
It changes itself quite frequently
So it's hard to identify a
single specific target,
either to create vaccine or
to create a treatment.
So, the reverse transcriptase is a
1 example of multiple mutations,
but so, too, there are changes in the
envelope and even the gag proteins,
all of which change how the virus has
tropism and binding strategies.
And as we just mentioned, drug resistance
is a significant challenge,
even under selective pressure, with the
currently available antiretroviral therapy
known as HAART, highly active