[music]
Today, mainly about the immunology of AIDS,then go on
to some of the treatment aspects of AIDSdismal as they may be.
I think it's worth discussingand maybe talking about
what's in store for the future.
What I'd like to do, first of all,is tell you a little bit
about the etiologic agent,which was isolated
by Bob Gallo in this countryand Luke Montagnier in France in 1983,
and almost simultaneously, by the way,and tell you what kind of agent this is.
First of all, it's an RNA virus.
It does not contain any DNA,and keep that in mind,
and we'll touch upon that pointa little later on in the lecture.
These retroviruses,it's called a retrovirus
because it has a very, very uniqueenzyme called reverse transcriptase,
which enables it to make DNA,which is necessary
for propagation and replicationof the virus.
Keep all those little points in mind,and we'll get to that again in the lecture.
This is the common categoryof the retroviruses that occur in nature.
These are exogenous retroviruses,
and I'm not going to getinto the endogenous retroviruses.
Many of which are proto-oncogenes.
That's material for another two lecturesmaybe in the summer.
Suffice to say these retrovirusesare very, very closely related.
They have very, very similar properties,and they behave in many respects,
very similarly.
The prototype that we learneda great deal from is HTLV-I,
because it was the first onethat was discovered.
It was discoveredat the University of Kyoto
in southern Japan in 1978.
It is the etiologic agentcausing adult T-cell leukemia.
This is an endemic diseasein the southwest islands of Japan.
It's interesting,the Japanese have learned
a great deal about HTLV-I,and so have the virologists
here in this country,especially Bob Gallo at NIH.
In fact, looking at HTLV-I,
we learned a great deal about the behaviorand the properties of HTLV-III,
which is the viruswe're going to be interested in today.
HTLV-II causes a very rare disease.
It was first isolated by Bob Galloin conjunction with Dave Goldie at UCLA,
good friend of Bill Hawkings.
They were able to find that there wasa different type of retrovirus
and HTLV virus
that caused leukemia in adults,
but a different type of leukemia.This was isolated
from a patient who had, of all thingsT-cell hairy cell leukemia.
Usually hairy cellleukemia is a B-cell disease.
I guess I should explain the lettering too.
This isthe Human T-cell Lymphotropic Virus.
That's what the HTLV stands for.
A type onejust is a different type of sub-typing
so that we understandwhat we're talking about.
We have the HTLV-I being discovered first.
Then in 1982,the HTLV-II virus being isolated.
Again, it's very rareand not very common at all,
and it can indeed cause leukemia.
In addition, and I wantto point this out very specifically,
that both these viruses can also causean immune deficiency state.
Now, most commonly,they cause a proliferative state,
which terminates in leukemia,but they can, in fact,
cause analogous statesas of the HTLV-III virus.
In 1983, when we first isolatedthe HTLV-III virus,
we noted that this virus hadmany different properties.
Its genome was much more complex.
Most of these viruses, by the way,have about three to five genes.
It's really not very many,but when you look
at the number of nucleotidesit comes out to quite a bit,
when you look at any genome, of course.
The HTLV-III virus isconsiderably more complex.
We now have beenable to show that there are
seven different genes in this virus.
It behaves somewhat differentlyin the major aspect of its behavior,
which differentiates itfrom these other very,
very closely related retroviruses.
Is that it's cytopathic, it's lympholytic.
It causes lysis of the cell,death of the cell.
The cells are not induced to proliferate,i.e., causing a leukemic state.
That's a major difference,
and it certainly was a major differencewhen the attempts were made
to isolate this virusand then grow it in a laboratory.
We had a great deal of trouble growingin a laboratory in certain cell lines
because it would lys all the cellsthat were infected by the virus.
It was in November of 1984when Mike Popovic finally found
a cell linethat he could immortalize the cells
and grow the virus and in that way,accumulate enough of viral protein
to make the necessary antigenic materialso that we can get a reliable test.
Feline leukemia virusis another interesting,
very closely related virus, but again,it induces proliferation of the cell,
and it causes a leukemic state.
Let me also addthat the people who
have been workingwith the feline leukemia virus
also note that not all cats get leukemiawhen they're infected with this virus.
They in fact,sometimes get an immune deficiency state,
just like we see in someof these other
very closely related retrovirusesthat I have here on the slide.
By looking at these prototypes,we were able to learn
a great deal about the HTLV-III virus.
In fact, it was through the studiesdone in Japan of the HTLV-I virus behavior
and its properties.
Looking at at the feline leukemia virusthat Bob Gallo and Max [?] up in Harvard,
really proposed that the AIDSwas due to a retro type of virus.
Of course, having an assay
for reverse transcriptasealso helped a great deal.
We can thank Howard Temin for that,who won a Nobel Prize
at the University of Wisconsinback in 1971 or '72.
I hope Joe Osley is not here.
He's going to correct me on that.I think it was '71.
Anyhow, you can seethat these viruses displayed
different behaviors and the CD-4is just another type of marker.
Just think of thatas being the lymphocyte and the key cell,
which is the target cell for these viruses.
These are lymphotrophic viruses,and you can see that HTLV-I causes
proliferation of the cellwhen it infects the cell.
HTLV-III is a cytopathic type of virus,which causes lysis of the cell.
Under certain circumstances
the HTLV-III virus may be alteredto cause proliferation of the cells.
We'll talk about that a little later on
when we get down into treatmentand talking about the genome.
First of all, before we really getinto how the virus does
all its damageand what this is all about,
I think we needa crash course on immunology.
I'm going to run through this very quickly.
I think it's appropriateto fill you in on the immunology
and where the T-cell comes fromand how important it is,
and how the virus impactson the decimation
of the host's immune system.
First of all,we know that
the immune system,and in fact,
all hematopoietic elements developearly embryonic life
from a common stem cell,and we call it
the multi potential stem cell,simply because it's so versatile
and under proper circumstancesduring embryogenesis,
this cell is stimulatedand can give rise to it differentiates
in very subtle ways to lymphocytes,as well as the myeloid cell lines.
When I talk about the myeloid stem cell,
that means also thatall the different types
of blood cellscan come off this myeloid stem cell;
the red cells, the granulocytes,the monocytes, and the megakaryocytes.
In addition, the monocyte,which is thought
to be the precursor for the macrophage,and this is important
because the macrophage plays a very,very important role in the immune response.
Now, in additionto giving rise to the myeloid elements
of the hematopoietic system,it also gives rise to the lymphocytes,
and of course,these are the very important cells
for the immune systemor the immune response.
Because lymphocytes and macrophagesreally make up the RE system,
reticuloendothelial system,which is the bulk of the immune system,
and is responsible primarilyfor the immune response.
Now, there are other cells, of course,
obviously involvedwith the immune response,
but these are the cellsthat are most important.
The multipotential stem cell gives rise
to two lineages of lymphocytes,one of which is the B-cell line.
Early in embryonic life,these embryonic B-cells will percolate
through the embryonic RE systemand will eventually be stamped
or coded or sensitizedin some way to become B-cells.
B-cells are destined to produce antibodies
when they're activatedby way of the plasma cells.
B-cell become plasma cells.
The important thingto remember about
B-cells and plasma cellsis that they produce antibodies.
For practical purposes,that's all they do do.
This needs modulation and regulation.
You can't just haveantibodies being produced helter-skelter.
The other line of lymphocyteswhich is very important,
and this is the linethat you should concentrate on,
is the T-cell lineage.
There are other lymphocytes,early in embryonic life
that are destined to become T-cells.
They percolate throughthe embryonic thymus gland,
which is a pretty good-sized glandduring embryogenesis.
They in some way are influencedby probably the epithelial cells
of the thymus gland, but they are destinedto become non-antibody-producing cells.
They are concernedprimarily with cell-mediated immunity
and this is really the importantor the fulcrum of the immune response.
Once the lymphocytes leavethe thymus gland after maturing
for an unknown period of time,they then are called T-cells.
The T-cells are importantbecause they regulate
and modulate the immune response.
As you'll see, they tell the B-cellshow big a clone they need to have.
They also can shut off the B-cell clone
or the antibody-producing cellswhenever it's appropriate.
They also interact with the macrophage.
There's a lot of cell-cell interaction
that I'll show youin the subsequent slides.
The one thing I want to point out hereis that once the T-cells mature,
and I should call them thymocytes,once these lymphocytes mature
in the thymus gland,they have different specific markers
at that time, and they're programmedfor different specific functions.
Some of these lymphocyteswill become helper inducer cells,
and this is the cellthat we want to concentrate on today.
Other cells will becomesuppressor cytotoxic cells.
These T4 and T8 just represent
the monoclonal antibodieswhich correspond to the antigens
on the cell membrane surface,which designates them
as either T4 helper cells orcytotoxic suppressor cells.
I had a crash course in the projector today,so I'm all set.
Now, let's zero in on this T4 helper cellbecause I think
you'll get a good perspectiveas to how important this T helper cell is.
This is the T4 helper effector cell.
Remember, this is the target cellfor the AIDS virus.
Not that the AIDS virus doesn't affectother cells, but this is the major problem.
This is the major way in whichthe AIDS virus will induce
this devastating immune deficiency state.
The T helper cell, as I said,
plays a very pivotal rolein the immune response.
It is the important cellthat controls or modulates,
or regulates, if you will,these other types of lymphocytes
in an effortto correspond to the antigen,
the inciting antigen of the hostto the host.
The host responds
to any kind of foreign proteinor any kind of foreign antigen.
It's the immune system which protects us
from these foreign incitingor threatening antigens,
whether they be bacteria,viruses or whatever.
Not inert substances.
Anyhow, the T4 helper cell,you can see how versatile this cell is.
It induces B-cells,and when B-cells are stimulated,
they become plasma cells,and then plasma cells produce
specific types of antibodies,which hopefully are directed
toward the inciting antigenthat threatens the host.
It also can induce the T cytotoxic cells.
It can induce the T suppressor cells.
The T suppressor cells can then suppresssome of the B-cells.
It has a very variable function.
This is the proliferation.
It can also by synthesizing and liberatingmany polypeptides such as the lymphokines.
It can influence cell growth.
It can also cause
proliferation of certain cellslike the T4 helper cell itself.
It can expand if necessary.
Again, it also influences the suppressor cell.
It causes maturation of someof the suppressor T-cells and the B-cells.
Again, it has a very wide modulatingand regulating effect
on these other subsets of lymphocytes,
which are so importantfor the immune response.
That's the key celland remember that that's
the target cell for the AIDS virus.
Now, when an inciting virusis picked up by the immune system
and it is interpreted as being a threat,
this is the usual sequenceof events that occurs.
The first line of defenseis the macrophage, that big cell,
which develops from the monocyte.
The macrophage first comesin contact with the antigenic material
and in this instance,we're saying it's a virus.
The macrophage will then takethat material and process it
in many various waysand extract certain antigenic information
from that inciting antigenor that material.
In this case, again, the virus,it could be a bacteria or whatever,
but it displays that antigenic informationto the other cells of the immune system,
primarily the lymphocytes.
These lymphocytes,
we're talking about T lymphocytes here again,and we're talking about B lymphocytes here.
These cells are ableto recognize one another
because of unique membrane antigensand these are class II antigens.
They're antigens that are encoded for,
by certain specific areason the C6 chromosome.
These are importantbecause only the cells of the RE system,
and the Langerhans cells in the skinare also included,
will have these class II antigens.
This isthe major histocompatibility complex,
and that's on chromosome six,and that's where the genes are that encode
for these specific class II antigenson the membranes of these cells,
which make up the RE systemor the immune system.
Through this specific class II antigenthese cells can recognize one another,
and they actually can talk to one anotherand pass on information
which is very important to elicitan appropriate and proper immune response.
Here's the macrophage.
The T-cell recognizes the class II antigen.
This is the antigenic material,
the antigenic informationthat this macrophage
after processing the antigenwill pass onto the T-cell.
The T-cell in turnwill then pass that antigenic information
onto the B-cellsor maybe to other T-cells.
In this instance,we're passing it onto B-cells.
It then has alsoanother influence on a B-cell
by elaborating certain growth factors.
It can cause the B-cellto differentiate and in fact,
cause the clone of B-cells to expand.
This B-cell in turn, remember,is destined to produce antibodies.
Here it is.
After it's been stimulatedand proliferation has occurred,
the mature B-cell then gets stimulatedand activated to a plasma cell.
The plasma cell then synthesizes antibodies.
The antibodies are very specificfor this antigenic information that
was extracted from the inciting antigenby the macrophage so that the antibodies
that are produced by the plasma cellthen neutralize the virus.
This is what we hope happens every timewe have an antigenic threat to the host.
Of course, the immune systemdoes a very good job of picking up
all the inciting or threatening antigensthat we come in contact with every day.
Once the immune system is bluntedor altered in some way, whatever way,
this whole concert of eventsis changed and you may end up
being in a very, very vulnerable position.
When we mix the AIDS virusin culture with human lymphocytes,
this is what happens,just to show you the devastating effect
that the AIDS virus will haveon lymphocytes.
These are uninfected lymphocytes.
You can seethat they really don't change very much.
These are the infected lymphocytes,
which the HTLV-III virus
or the virus which causes AIDS will do.
When these cells are infected,
you see a rather rapid devastating lossof these T4 helper cells.
This is a computerized diagramfrom a flow cytometer
where we can actually look atand characterize the different types
of subsets of lymphocytes.
This shows this very nicely.
I can't see it very well, that left panel,
but I think you can probably see itbetter than I can.
This is what we can showon the computerized diagram
when we look at these cellswhen they're specifically marked.
We're lookingat T4 helper
inducer cells and T8suppressor cells primarily.
This is a normal patient,and you can see these bumps back in here.
They're very high.
These spikes representthe T4 helper cells, inducer cells.
Here's another graft
of what we're seeing backin here from the computer.
You can seethat the T4 helper inducer cells,
as compared to the T8 suppressor cells,there's more than a 2:1 ratio.
The 2:1 ratio would be quite normal.
In an AIDS patient, you can seethat there's a dramatic decrease or loss
of these spikes in the T4 areaor the helper inducer cells.
You can see that very nicelyon the scheme here.
Now, these are percentages.
They do not represent an absolute increase
in the T8 suppressor cell'sreciprocal increase.
That does not always happen.
You can appreciate what happensto the T4 helper, inducer cell.
Again, that's that very important cell,
which really plays that versatile rolein the immune response.
We have a dramatic decrease in the cells.
This is exactlywhat happens in AIDS patients.
This is what happens in the ARC patients.
This is one of the first signs
and features of AIDSor HTLV-III infection.
This usually is presentin the patients who already have ARC.
It is certainly always
present in patients who have bonafide AIDSor have been registered as AIDS.
Now, as a result of the loss
of those all-importantT4 helper inducer cells,
as I mentioned earlier, we're leftwith a very blunted muted, immune system.
In fact, these patients,
the best way to describe themare immune cripples.
They can no longer respondto all the inciting antigens
that they come in contact with.
Remember, going back to the AIDS patients,these people have been bombarded
for many, many yearswith different types of antigens
and they've had, they've incurredmany, many different types of infections.
We're dealing here with an immune systemthat already has been stimulated many,
many times for long periods of timeand many people think that it's
because of this immune system fatigue,if you will,
that causes the AIDS virus to cause
this horrendous and rapiddeterioration of the immune system.
Many people think that in childrenwho have a normal immune system,
that when they become infected
by the AIDS virusthis sequence of events
does not happen in this wayand certainly not this fast
and, again, we're still not surewhat the incubation period of this virus
is and we're still not surewhether this virus can in fact
produce the immune deficiency statein all patients who become infected.
We do knowthat the high risk group of patients
that I showed you yesterdayhave an exhausted immune system.
They've been stimulated many,many times and this may be
a factor for how the AIDS virus worksand why it works so rapidly.
Again, reiterating some of the pointsI made on those illustrations,
we get a profound lymphopenia,and this is almost always
present with a decreasein the absolute number of T helper cells.
This is a T4 cell.
The H stands for the helperand that's the T4.
The T4 just simply represents the marker,
the monoclonal antibodywe use to mark the cell.
Excessive antibody production indeed.
The B-cells are left alone.
The B-cells no longer areunder the influence of
these regulatory and modulatory T-cells,the T helper cells, so that they're left
to go on and produce additional antibodiesand sometimes can lead
to autoimmune phenomenon,autoimmune problems.
It's not uncommon at allin AIDS patients to see
autoimmune induced thrombocytopenia.
Everyone wonderswhy the platelet count has decreased.
Well, the B-cells are producinga whole variety of autoantibodies,
rheumatoid factor,lupus type of antibodies,
just a whole array of antibodies.
Some of these of course can latch onto the platelets or the red cells
and cause immune problems.
There's also a decreasein the cytotoxic T cell activity
and this is important.
There's a decreasein the natural killer cells,
the number of natural killer cellsand many people think
that maybe the natural killer cells mightbe a target cell as well
for the AIDS virusbecause there are some people who think
that the natural killer cells do displaythe T4 marker,
and they have an IL-2 markerwhich is the interleukin-2 marker.
Of course,with the marked decrease and lysis
of the T4 helper cells,these are the cells that are
responsible for the T cell growth factoror interleukin-2.
This is a very, very important peptide
that's synthesizedand released by the T4 cells,
which enables the T-cellsto expand their size and activates T-cells
and enables the immune systemto respond appropriately if there's
need for additional lymphocytesand that in fact happens very frequently.
IL-2 as a growth factoris very important for the immune response.
It's really important in termsof expanding the number of lymphocytes
and causing proliferation of the cellsin an appropriate manner.
There's a decreased synthesisof many other kind of lymphokines
including interferon.
In fact, these cells makean abnormal interferon.
It's acid labile interferonand it really does not incur
any protection against any other viruseslike the normal interferons do.
There's a decreasein macrophage activation and here, again,
macrophages are very, very importantwith respect to the immune response,
especially the afferentLimothy immune response,
that is the processing of antigens
and passing on the antigenic information
onto the lymphocytesfor an appropriate efferent response.
Bone marrow suppression can occurand we're not quite sure why,
but many people thinkthat the virus is capable
of eliciting a soluble suppressor factor,
which some people thinkis a very specific peptide
and by way of elaboratingthis soluble suppressor factor,
it may in fact suppressthe whole bone marrow and pancytopenia,
of course, is not all that uncommonin looking at the AIDS patients.
Remember, we're dealing with patientsfor the most part
who have multiple opportunistic infections
and infection in itself can causea decrease in all the cell lines.
There's decreased thymic function as welland, again,
we're not quite sure why this occurs,but thymic hormones, there are
about five different thymic hormones,all of which
are decreased significantlyand, again, the thymus
is a very, very influential organwith respect to T cell function.
Now, to try to summarizewhat I said in those previous slides,
I thought this wasa good simplistic slide to bring out
some of the points I made without gettingtoo cluttered in all that immunology.
First of all, the dose and the routeof the antigen exposure to the virus
is very important and I thinkeverybody's in agreement with that
and I think that
small doses of the antigenmay not be enough
to cause infectivity or lead one onto an immune deficiency state
and I think that this is being shownwith so many, many people
who have had needle sticksfrom patients with AIDS.
Anyhow, the HTLV-III exposure is firstand then we have
to take into considerationthe immune system of each individual
and that is the state of receptivenessof the host's immune system.
Again, I mentioned to you about the children.
We're not quite sure if the same process,the same devastating process will continue
at the same rate in healthy childrenwho are infected by the virus.
I think that's why the studiesin Central Africa are so important
because there's a significant numberof children who are infected by the virus
that we're able to appreciate nowand I think we're going to get
a good handle on the incubation periodand how this virus goes
in terms of someonewho has an otherwise normal immune system.
In other words,these are children who have not
had the exhaustion of their immune system
as have the homosexualsand bisexual patients.
The HTLV-III infection, of course,then progresses on
to the usual types of problemsthat we see when the immune system
begins to be decimated by the virusand this is dependent
upon the ability of the hostto make a protective immune response.
Again, I showed youthat when the antigen is processed,
in this instance, the HTLV-III virus,it's hoped that the immune system
through the interaction ofthe various cellular components
and the mediator substancesand the ability to mount up
an appropriate response
such as neutralizing antibodiesor increase
the number of cytotoxic T-cellsthat we could destroy
or contain the inciting antigen,in this instance, the HTLV-III virus.
In patients who arein a high-risk category,
this apparently does not work.
The ability of the immune systemto live in symbiosis
with the virus or with the antigenis not there and this progresses
on to the immune deficiency syndrome.
We get lymphadenopathy,
which is part of the ARC syndromeand we get overt AIDS
with the opportunistic infectionsand a Kaposi's sarcoma.
It may very well be, however,that in individuals whose immune systems
have not been exhaustedor in individuals whose immune systems
are in better straits,we may get recovery
and we may have an asymptomatic carrier.
That is, we will havedetectable antibody titers
in the serum of these patients,but they will not progress on to
lymphadenopathy or ARCsyndrome and overt AIDS, hopefully.
Again, these are the thingswe have to learn
by watching these childrenin Central Africa and in South America
and seeing what happenswhen you have a normal immune system.
Now, the disappointing prototype of thatwould be the hemophiliac.
I forgot to mentionone important fact yesterday
when I was talking about the epidemiology.
About 82% of all the hemophiliacsin this country are HTLV-III positive.
I mentioned to you yesterdaythat there were about 284 cases of AIDS
in hemophiliacs so far,which make up almost exactly 1%
of the number of AIDS patientsthat have been registered at CDC.
Now, theoretically,
the hemophiliac should havea pretty normal immune system,
and many of these peopleare young, healthy appearing otherwise.
We are seeinga very small
percentage of these patientsthat are progressing to AIDS.
There may very well besomething to this business
of the host's immune systemand the ability
to make a protective response.
Then again, what about that groupthat does progress to ARC and AIDS?
Why aren't they protectedand why can't they mount up
an appropriate response?Why aren't they
just simply asymptomatic carriers?Well, the bulk of them are, obviously.
It's interestingthat the more we study this virus,
the more we beginto appreciate the versatility of the virus.
I told youit's a much more complex retrovirus
than the HTLV-I, and we don't know
a hell of a lot about the HTLV-II,but we're learning all the time.
I've been preaching todaythat the preferential cell
and the target cellis the OK T4 or the helper,
the T helper cellor the helper inducer cell.
Again, this OK T4 just simply meansthe monoclonal antibody that helps
type specifically this T helper cell.
That's why we call itthe T4 cell or the TH cell.
It is the helper inducer cell,just keep that in mind,
and it is the versatile cellwhich modulates the rest
of the immune response for the most part.
Interestingly enough, the virus also hasthe capability of infecting
monocytes and macrophages of the RE system.
It's probablydue to the specific antigenic markers
or receptorson the membranes of the macrophages,
which have some similarity
to the receptorsthat are on the OK T4 cells.
That is the T4 receptorand the IL-2 receptor,
the interleukin-2 receptor.
Now, these are not nearly as clearas on the T4 or the T helper cell,
but there are certainlya lot of similarities to these receptors.
There's enough similarityto cause the virus to be
able to contact this receptoron a membrane of these cells
and induce the cell to endocytose
or engulf the virusso that it can then begin
its process of replication and integrationinto the host cell DNA material.
Also, we have to appreciatethat there's a great number
of CNS problems that are being reportedin these AIDS patients.
In fact, there is some results nowwhich show that postmortem examination
that the virus can be foundin the glial cells.
These are the macrophage-like cellsof the central nervous system.
Again, it's not just the T helper celllike we originally thought,
the macrophage and the glial cellsof the central nervous system.
Of course, this whole syndrome,
this wholemultiple sclerosis-like syndrome
that we see in some of these AIDS patientswithout the other facets of AIDS
by the way,this answers the question
as to why these patients developthese multiple sclerosis-like syndromes,
a demyelinating processand a premature dementia.
It's because the virusdoes have the capability
of infecting directly the CNS.
Now there's some questionabout the virus being able
to infect platelets and B-cells,and these cells may act
as reservoirs for the virus,because the virus,
even though it can affect the cellsand, again, the macrophage,
it does not appear
to have the same capabilityof activating that cell,
integrating into the genome of these cells,and causing destruction of these cells.
The other possibility is thatthe virus may lay dormant
or may lay in an inactive statein these cells,
and these cells may then act as reservoirs.
We may find that asymptomatic carriersmay in fact have some of these other cells
infected with the virus as well.
Again, as I mentioned, we're learning
more and more about this virusas we study AIDS more.
This is the culprit.
This is the HTLV-III virus.
This is a picture I tookfrom Scientific American,
and I think this depicts things outvery, very nicely.
Again, this is an RNA virus.
Again, please keep in mindthat this does not contain any DNA.
The unique facets of this virusis that it contains a very unique enzyme
called reverse transcriptase,and it contains a strand of RNA.
This RNA consistsof only seven different genes.
Of course, you can't even call them genesbecause it's RNA.
You have to waittill you get a provirus in DNA.
Reverse transcriptase is a very,very special enzyme
which enables this virusto replicate without DNA.
That's a very unique phenomenon.
This was discovered by Howard Teminat the University of Wisconsin.
Now, looking at the structure of the virus,it has very specific envelope proteins,
and this is like a membrane,but we don't call it membranes on viruses.
We call it a viral envelope.
It has very specific glycoprotein markers,which enable us to type this virus
specifically from other virusesthat are very closely related,
such as the other retrovirusesthat I showed you on the very first slide.
These glycoproteinsand these protein markers,
which are in the envelope
enable us to selectively code this virus
by their specific amino acid arrangements.
This is the outer envelope,and this is the inner envelope.
There are very specific proteinswhich make up
the proteins of the inner envelope.
Then we have the corewhich houses the genetic information
in this instancethe RNA and the retrovirus.
Now it's through these special proteinsthat we find in the envelope
primarily that we're ableto identify the virus.
Of course,this is what all the different tests
that allow us to identify the virusare based upon.
The antibodies that are madeto the virus that we look at to identify
whether or not the patient has been infectedare specific antibodies directed
against some of these specific antigens,if you will.
They're proteins.
The antibodies that are madeby the host immune system
are directed at these different proteins,the glycoproteins of the envelope primarily,
but not uncommonlywe can pick up antibodies
to the inner envelope as well.
This is what the tests are based upon,which enable us to determine
whether or not a patient has been exposedto the virus or is infected by the virus.
Keep in mindthat the reverse transcriptase
will use the RNA as a templateand it'll produce DNA,
and it's the DNAthat is produced from the RNA.
Again, this is a real strange phenomenon,
but the reverse transcriptaseenables this phenomenon to happen.
The RNA is used as a template,and it produces DNA.
Once this virus produces DNA--
Now normally the virusdoes not produce DNA.
Only when it's in the host's celldoes it produce DNA
and the DNA that's produced from the RNA--
Remember that's not the usual waythings happen.
It's usually there's a strand of DNAthat produces RNA.
That's why they callthese reverse transcriptase
because of this unique abilityto produce DNA from RNA.
These are the only virusesthat we know of in nature
that are capable of doing this.
It's because of this unique enzyme,
reverse transcriptase,that this can happen.
This is a very important and necessarystep for the virus to replicate,
because once the virus produces the DNAfrom the RNA, that DNA material,
which I'm sorry I don't haveany slides to show you on this,
but I really couldn't find any good slidesto show you what happens.
The DNA that's produced from the RNA thenincorporates itself or integrates itself
into the cell genome.
The lymphocyte.
Get the picture.This is the virus.
The lymphocyte that it infectsis huge compared to the virus.
Once the virus makes the DNA,
that DNA material will then incorporateitself into the cell's DNA.
That's a key factor because when thatDNA from the virus
incorporates itself into the DNAor the genome of the lymphocyte,
it then can take over the genome functions
and cause the DNA from the lymphocyte
to produce the necessary proteinso that that virus can replicate itself.
The virus needs DNA to replicate itself.
In order to get DNA,
it uses the RNA strand as a template,because it has reverse transcriptase.
The DNA that's produced
will incorporate itselfinto the lymphocyte DNA.
Then once that DNA incorporates itself
into the lymphocyte DNA,it's called a provirus.
It has no other function.
It's not present outside the cell,but that provirus can then influence
the entire genome of the lymphocyteand cause the lymphocyte
or influence the lymphocyte to produceall these different viral
proteins that are necessaryfor the virus to replicate itself.
Without these steps, the virus is doomed.
That's why so manyof the therapeutic
approaches in AIDShave been aimed
at inhibiting reverse transcriptasebecause without that enzyme,
you can't then use RNAas a template to make DNA or the provirus.
I hope that's clear, and I apologizefor not having a couple of more slides
on that because that is a crucial point.
This is what the genomelooks like of the virus.
It's very, very simple.
Actually, there are three major genesthat we have to be concerned about.
This is much more complex.
The blue is the DNA, by the way,
and we'll call thatthe provirus, the blue-colored genes.
There's only seven different genesfor this HTLV-III virus.
The HTLV-I virus hasthree or four different genes.
It's very simple, but you got to rememberhow many nucleotides are in each gene,
and then it becomes much more complex.
Then if you alterone of those nucleotide sequences,
you get completely different behaviorand different properties of the viruses.
Anyhow, this is the DNAor the provirus that is produced
from reverse transcriptaseusing the viral RNA as a template.
Then this DNA which is incorporatedinto the genome of the cell,
then produces again, messenger RNAs,
which represent or encodefor the different viral proteins
that are necessaryfor the virus to replicate itself.
Basically, there are three,there's the gag, which is again
a relatively short nucleotide sequence,which is responsible for the core proteins.
We have the pool,which is responsible
for the inner protein areas, or the--
Actually this is the reverse transcriptase.
The pool is responsible forencoding for the all-important enzyme.
This is the core, the gene,which encodes for the core proteins
that I showed you which houses the RNA,and the reverse transcriptase.
Pool gene will encodefor the reverse transcriptase.
Then we havea variety of different envelope genes,
which will encodefor the envelope proteins.
Interestingly enough, again,as we study the virus more,
we're coming upwith additional short sequences
which may be very importantwith respect to the function of the virus.
This is the DNA, which, of course,gives rise to the messenger RNA,
which then encodeson the cell machinery of the lymphocyte
and causes the ribosomesto make the proteins
which are necessary or part of the virus.
You have to get the picture.
The virus initially has no DNA.
It makes DNA through its RNAby virtue of reverse transcriptase.
The viral DNA is then called a provirus.
The provirus integrates itselfinto the genome of the cell itself
that it has infected, and then it causesthe DNA of that lymphocyte to produce
the necessary RNA or messenger RNAsto make the proteins
that are so vital for viral replication.
This is all done in the cell.
This is encoded for on the ribosomes,
which areon the endoplasmic reticulum of the cells.
This is what protein synthesisis all about.
If you havethe appropriate messenger RNAs that come
from the appropriate DNA sequences,then by acting
as a template on the ribosomes,the ribosomes acting
as a template for these messenger RNAs,they then can produce
the different proteinsand cause the virus to replicate itself.
There are a few different genesthat we've been able to isolate now,
most of whichthree out of these four new genes
we're not quite sure what function theyplay or what role they have
in viral replication,but there's a short sequence called Tat.
This small gene seems to influencethe long terminal redundancies,
which are small sequencesat the end of the provirus.
They're interspersedthroughout the genome, actually.
It seems that the gene productof the Tat gene,
that is the proteinthat the Tat gene will encode for,
influences these longterminal redundant sequences
and causes them--These are, first of all,
they regulate production of the proteinsthat these genes encode for.
It's thought that this small gene
that we've just discoveredin the past two years
influences these regulatory genesin the genome and causes
the genes to produce more proteinsor accelerates production of the proteins,
allowing the virus to replicate very rapidlyand proliferation to occur very quickly.
This, in fact, is what happenswhen you have an infected cell,
and that cell becomes activated.
The virus is replicated rapidly,lysis occurs, the cell is destroyed,
and you're left withno T-cells and a devastated immune system.
How do we detect the infected patient?Well, we're learning more and more
about how we detect the infected patientand we're now in the third generation
of the ELISA testing kitsthat help us in a very sensitive way
pick up who's been exposedand who has antibodies for the virus,
but you can seethere are many, many different ways,
and I'm not going to go into all of these.
Jim [?] here. Jimmy.
These are all the different ways
that we can detect the patientwho's been exposed to the virus.
Of course, you all recognize this onebecause this is the mainstay
for all the blood banks,but you can see there are
more sophisticatedand even more sensitive tests,
but they all havesignificant disadvantages
and do not allow for the rapid testing,
which is so vitally importantwhen we're checking blood donors.
We even have more sophisticated testssuch as the Western blot,
which is somethingthat confirms the ELISA technique.
All that does is take the antibodiesin a patient's serum and overlays it
with some of the viral proteins,
which we're nowable to accumulate by being
able to grow the virus in culture,thanks to the H9 culture cell line,
and show usspecifically the viral proteins
in the whole sequenceof the viral proteins.
It's unmistakably
an HTLV-III infection rather thansome other type of retrovirus
or some other type of antigenthat may be mistaken.
Also, we even have,by using the Southern blot,
we can even pick upthe DNA sequence of the provirus.
Remember I mentioned the provirus isjust a term that's applied to the DNA
that is a result of reverse transcriptaseusing RNA of the virus as a template.
We're getting much better
in using the available studies in termsof picking up people who are infected.
I suspect these will get much more rapidand much more sensitive as time goes on,
but you got to keep in mindthat many of the countries that were
worried about the proliferation of AIDScan't afford such things
and not everybody, unfortunately,is using these.
Then the other problem is thatwhen we do detect positive carriers,
we're not able to report these peopleand put them through the proper channels
so that we can go on from there in termsof doing meaningful surveillance studies.
The period of timewhere everybody's waiting for,
and I summed upthe treatment of AIDS on this slide,
and I'm going to run through thisvery quickly, Dino.
The initial steps that we took
when we first startmaking a diagnosis of AIDS
and seeing the plethora of problemsthat they're confronted with
is to try and treat the Kaposi's sarcoma,which so many of the homosexuals
will terminate inand also the opportunistic
infections that we seein virtually all these patients.
This left much to be desired,to say the least.
We have pentamidine to treatPneumocystis carinii and intravenous
spectrum receptor and we've all used that,
but again sooner or later,they succumb to their disease.
The death is primarily due toraging opportunistic infections
or the Kaposi's sarcoma, but usually,it's an opportunistic infection superimposed.
Then we had the eraof the biological response modifiers.
This really hit the newsabout two years ago,
maybe two and a half years ago,because interferon came into vogue
and we were usingalpha recombinant interferon,
beta interferons, and gamma interferons,all of which, again, were a big bust.
Left an awful lot to be desired.
Despite what you read in the literatureat that time,
there were in some instances,in some small studies
where they saw a slight improvementin the immune response and attempts
to reconstitute the immune systemwere just totally unsuccessful.
Also, using interleukin-2.
Again, remember interleukin-2is the growth factor that was hoped
would elicit a proliferative responseby those devastated T-cells
to decrease T-cellsthat the virus has destroyed.
Interleukin-2 seemedto be the way to go in terms of causing
what T-cells we had left to proliferateand maybe expand
the population of T-cells, and again,to reconstitute the immune system.
It didn't work.
The antiviral agents
are still in vogue but many of themhave fallen by the wayside.
Ribavirin, Bruce Hathaway keepstelling me that this is not a bad drug,
and it may have some activity,
although there really aren'ta lot of studies to indicate that.
Suramin, which isa reverse transcriptase inhibitor,
and this was used to treat parasites.
Had too many side effectsin the trials of Suramin.
I will say this, there were a coupleof studies using Suramin
one of which is still going onin New England,
and that's probably the only studythat's going on.
It did showsome significant regression of the virus.
We were able to decreasethe viral antibody tighter.
Whether or not it hadany impact on disease progression,
we're not sure,but there are still a handful of patients
that are still getting Suramin up
in the Boston area,but this had a lot of side effects
and was discontinuedin all the other studies.
HPA-23, which isanother reverse transcriptase inhibitor,
and this is the agentthat the French we're using.
In fact, this is the agentthat Rock Hudson received.
We get down to Ansamycin,which is an antibiotic.
Again, it's reverse transcriptase inhibitor.
Hopefully, this substance was goingto inhibit the replication of the virus.
It's an old antibiotic.
It's been aroundfor a long period of time,
and it's been rejuvenatedbecause of the AIDS problem,
and it has not met with much success.
The same is truewith Azidothymidine and AZT.
This has really got a lot ofnews media hype right now.
It does appear to be the most effectiveantiviral agent we have seen thus far.
It has the most activity.
It's reverse transcriptase inhibitor.
It's made by Burroughs Wellcome.
Let me show youwhy everybody got
excited about AZTover the past year.
When we first found that AZT did havesome significant antiviral effects
and was a very efficientreverse transcriptase inhibitor,
there were 12 different centersthroughout the country
that garnered up about 270 patients,and they treated them
with Azidothymidine 250 milligramsQ4 hours, or QID.
This study went on from February 1986to September 1986.
It was pretty impressive
to show you a significant decreasein the incidence of major events.
These are the patientsthat received the placebo,
and these are the patientswho received the AZT.
When we talk about these arrows
indicate major eventsand these major events mean
opportunistic infection or lymphomaand Kaposi's sarcoma or death.
You can see that the peoplewho received the placebo
had a straight-line occurrenceof these things.
You can see after a couple of monthsof being on AZT,
there was a leveling offof the patients who received the AZT
and there werevery, very few major events that occurred.
This prompted everybody to thinkmaybe we should put everybody on AZT.
This group of patientsthat were included in his study,
were patientswho were very specifically chosen.
They were patientswho had pneumocystis carinii
within the recent pastwho were off all other medications
for a period of four weeksbefore there were started on the AZT.
The drug wasvery, very limited at the time,
and it was limited to specific people.
There was a limitationon the drug availability,
and there was also
a limitation on what type patientsit was going to be used in.
Anyhow, that's why the hype for the AZT.
I can tell you that, as of Septemberbecause of this type of response,
AZT has been released for general use,Burroughs Wellcome is making it.
A Burroughs Welcome stock has really goneup very nicely because of the AZT market,
but I think the last wordis out on this yet.
It does have significant side effects inthat it is significantly marrow toxic.
It suppresses the bone marrow.
In fact,in this study of the 12 institutions,
25% of these patientsrequired blood transfusions.
A significant number of the patients
also had a hypoplastic bone marrowwhen bone marrows were done on them,
because of the pancytopeniathat ensued with therapy.
This was a six-month trialfrom February to September
because of the resultsthat AZT is still in the running.
Let me go back to the other slide.
Bone marrow transplants have beenunsuccessful, unfortunately,
primarily because the graft becomes infected.
That young man that I showed you yesterdayhad two bone marrow transplants
from his identical twin brother,neither of which worked very well.
What about the HTLV-III vaccine?
This is a very disappointing story,no matter what you read in the magazines.
You can hardly pick up a magazinethese days
without reading something about AIDS.
The problem with HTLV-IIIand making a vaccine to it,
is it has such a diverse genome.
The genome has such a unique abilityof changing so rapidly.
Those protein markers, the glycoproteinson the envelope and the other proteins
which make up the proteins of the virus,have the unique ability in this virus
to change, so that we're not goingto need one vaccine,
we're going to needa whole host of vaccines,
which are different
for each change in the antigenic markerthat the vaccines are made from.
It's really very difficult right nowand everybody's very disappointed.
Interestingly enough along these lines,the feline leukemia virus, which is very,
very closely relatedto the HTLV-III and HTLV-I virus,
much through the work of Richard Olsonat the Ohio State University,
we now have a vaccine to use in cats,
to prevent feline leukemia.
Norton Laboratories made this vaccine,it became commercially available in 1985.
The work in many different centers
on trying to produce a vaccinefor the HTLV-III virus,
looking at the different viral proteins,has been very disappointing.
This is Bill Hazeltine upat Sidney Farber up in Boston,
[?] down at Duke,he's not very optimistic.
There are some people at NIHwho are somewhat more optimistic
about being able to produce a vaccine,
but I think this might be a ployto get additional monies for research
and carry out this expensive researchthat needs to be done.
To this date, there really isn't anything
on the horizon that looks likeit's going to be very effective.
There's no questionthat the way to go is right here.
You're talking about viral inhibitors,reverse transcriptase inhibitors.
The immune systemhas already been decimated.
Even if you get rid of the virus,theoretically,
if you could get rid of the virus,
you're still leftwith an immune crippled status.
The patient has
virtually no T4 helper cellsor effector cells.
That isn't going to change.
The best way to gois the vaccine and, hopefully,
a vaccine that we can give to peopleprophylactically in the future.
I think I'm going to stop therebecause, again, I've gone over time,
and I'm sure my wife's goingto give me hell again for doing it.
Let's see.
Yes, I think I'll stop there.
I know it's late and I'm sorry againthat I've gone over time,
but I'll spend some time taking questionsbecause I'm on vacation.
[silence]