Allan Kirk, MD, PhD, FACS David C. Sabiston, Jr. Distinguished Professor and Chairman Department of Surgery Duke University School of Medicine …
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– Good afternoon.
My name is Paul Wischmeyer,
and I'm the Director of
Perioperative Research here
for the DCRI.
And it is my great honor
and pleasure to introduce
our speaker this
afternoon, Dr. Allan Kirk.
For those of you who don't know Dr. Kirk,
he's probably best known,
as he's now our Chair of
Surgery (microphone silence) – 2014,
but has an illustrious background before,
obviously, he came here, as well.
He trained here at Duke,
so he's not totally new to our place.
Did his MD,
and his PhD,
and his surgical residency here, as well.
And then, ultimately went on to work
at the Walter Reed Army Medical Center,
as a Transplant Surgeon,
after doing a Fellowship
in Transplant at the University
of Wisconsin Madison.
And then also he went on to also be
the Chief of Transplant Surgery,
and the Chief Senior Investigator
of the Transplantation
Branch of NIH, and NIDDK,
prior to going to Emery, where he served
as the Professor of
Surgery and Pediatrics,
and ultimately the Vice Chair of Research
for the Surgical Department there.
That led him here, in 2014.
He has an illustrious
background and career with
really seminal discoveries
in the world of Transplant Immunology,
Transplant Drug Intervention,
Immunosuppressive Intervention.
He has over 200 published articles.
His work's been cited 10,000 times,
and for those of you, we
talked about those last week.
He has an H-index of 53,
which shows a credible
impact on our field.
It's truly an honor and a
pleasure, to have Dr. Kirk
talk to us today about
Organ Transplantation
and Federal Immigration Reform Practices.
Dr. Kirk, thank you.
(audience applause)
– So we'll start talking
about Transplantation
at the beginning.
Transplantation is actually
pretty straightforward.
It was, the techniques for sewing organs
in were worked out in the early 1900s,
and we follow the same
rubric that has been followed
for over a hundred years.
Red to red, blue to blue,
and that's about it, really.
The hard part
is that if you sew an organ
from one person into another,
that there's this thing called rejection.
That the body attacks the organ,
and it is not the transplantation
that is the hard part,
it's the rejection that's the hard part.
So scientifically, that brings us
to the most important
question in transplantation.
Why is it, that we reject
other people's organs,
but we don't reject our own?
Now actually, we do reject our own,
we just have different names for it.
We may call it Type 1 Diabetes,
when we reject our islets,
or Multiple Sclerosis,
when we reject our brain,
or any number of autoimmune diseases.
So rejection happens not infrequently.
But it happens much more
frequently for transplanted organs.
So why is that?
Most people will say,
that we reject things
because they're foreign,
and that that is the basis
for determining whether
you have an immune response
against something, or not.
Of course, that doesn't take into account
the fact that we do reject
things that aren't foreign.
So that doesn't seem to work.
And it's interesting to
understand that the biology of
transplantation emerged
during the McCarthy era.
That if you look at all of
the important seminal events,
to determine how transplantation came out,
they were all coming
out in the early 1950s,
about the time when
post-World War II
foreignness was something
certainly to be
opposed.
And it was clearly wrong,
that you don't accept
things that are foreign,
you accept things that are alike.
So the question comes up, do
we really have to reject things
that are foreign?
Is it that dichotomous?
So I would ask a question, to start.
This gets into a little PHI,
so if you're embarrassed,
you don't have to answer.
But how many of you are
products of a pregnancy?
(laughing)
Yeah, most.
Yeah, so, it is important
to recognize that not only
do we not have to reject
things that are foreign,
that our species, in fact, depends
on not rejecting alloimmune tumors,
at least for nine months.
That if we had a hair-trigger
to reject everything
that was allogeneic, we would
have never gotten out of
the evolutionary shoots.
Now we reject our children
when they're 13, but
that's a different biology.
So the first intuitive
point that I want to make,
is that we don't need to
reject things that are foreign,
indeed, our species depends
on us not rejecting
things that are foreign.
Alright, so.
For every complex problem,
there's a simple solution
that is simple, and neat, and wrong.
And that one is one of those.
So, next point.
You all know what this word means.
Yes.
And you know what this word means.
No.
Very defined dichotomous principles.
Which one's right?
You don't know.
Of course you don't know,
because you don't know
what the question is.
So, the problem is, is
that this is the way
our immune system is built.
Our immune system develops
before we are born,
and before we encounter
the rest of the world.
Our repertoire of T cells is established
before we are certainly
pregnant, but before we
generate all sorts of
interesting molecules
that we would have never seen in utero.
And in fact, this all happens
before the first day we're born.
So if there was a
hair-trigger that was set
on some dichotomous principle,
of you must reject things
that look like this, and
you must accept things
that look like that, this wouldn't work.
This first started getting figured out,
again, in the 1950s by a
guy named Peter Medawar.
Peter Medawar did some
really beautiful experiments,
where he took neonatal
mice, and he injected cells
from another strain of mouse,
into the neonatal mouse
and then let them develop.
And he, for the first
time, showed that if you
mess with the thymus at the
time of birth of a mouse,
that you can get animals to accept grafts
from other animals.
Now this is a paper you
could talk about for hours,
but I will just point out
one thing from this paper.
And that is that…
First of all, it was
published in the McCarthy era.
So he,
he used the word tolerance to define this.
Because tolerance, if you
look it up in the dictionary,
is an acquiescence to
something that is wrong.
So clearly, it's wrong that
we accept foreign things,
so this must be that we're
tolerating some wrong thing.
And when asked about why women
didn't reject their children,
he said that their
immune system was wrong,
and that it had been screwed up somehow.
And I think somehow, if half
the population is a certain way
then that's normal,
not abnormal.
But anyway.
He noticed that in his experiments,
the conferment of tolerance was
not an all-or-nothing thing.
Some mice went out and lived forever,
and some mice only had just
a few days of survival,
and there was everything in between.
So that, again, it was
not a digital type thing,
it was analog.
And the biology of that analog structure
is the most interesting part
of transplantation biology,
and what I have studied.
So intuitive point number two:
tolerance is not dichotomous,
anymore than rejection is dichotomous.
And tolerance requires action.
Now in this set of experiments,
when he gave the mice steroids
and inhibited their immune
system from functioning,
it actually inhibited tolerance.
So, it is something that is
active, that makes us accept
other organs.
Very shortly after this, the
very first human transplant
was performed, between identical twins,
which sort of is a special circumstance.
It's interesting that
the twin did not have
acute rejection of the
kidney, but he redeveloped
autoimmune disease later on.
So he did reject his kidney,
just not based on MHC mismatches.
And over time, since the
immune system was involved
in rejection,
that stomping out the immune system became
the clear approach to
preventing organ rejection.
And this just shows,
all of transplant history
for the next 50 years,
that survival went up
and rejection went down,
as we accumulated more and more ways
of paralyzing the immune system.
So, yes, you can prevent rejection by
shutting off the immune
system in a wholesale way.
But when you do this, you
also shutoff tolerance.
And so that any time somebody
takes these medications,
and then stops taking
them, then they reject.
Indeed, the most common
cause of rejection nowadays,
is non-adherence.
It's not that the drugs don't work,
it's that they either can't get them,
because they don't have
insurance, or, oh yeah,
the Federal Government cuts
off funding for insurance
after three years, once
you've had a transplant.
That's the number one cause
of transplant rejection.
And so, this is what a
patient looks at every day,
when they get up in the
morning, to have a transplant.
It seems like there could be a better way.
So, let's figure out biologically
how we can do this better.
You always start from
the fundamental concepts
of an immune response,
and I would say that
an immune response against
a graft or anything else,
is just a decision, that has to be made.
And so, how do you make
decisions every day?
First of all, you have to have
some aspect of specificity.
You have to recognize
what it is you're going to
make a decision about.
And then there needs to be some context
that you put that in.
For example, if I wanted to go around you,
I could go to the left,
and then to the right,
then I'd be around you.
Or I could go to the
right, and then the left.
But once I went to the
right, I couldn't go
to the right again,
because that wouldn't work.
Contextually, the exact same decision,
would lead to the wrong answer.
And every decision has
that contextual dependence.
And then there needs to be a magnitude.
You can do things that are
based on the right specificity,
the right context, but if
it is too big or too little,
it doesn't work very well.
So biologically, a lymphocyte
determines specificity
through it's antigen receptors,
either B cell receptors,
or T cell receptors.
Context is determined
by a number of things,
in the immune synapse, including
costimulation molecules
and adhesion molecules.
And magnitude is determined by things,
soluble molecules like cytokines.
This is simplified, but the rubric works
through most of the discussion.
So three points in space.
Specificity,
context,
and then a magnitude.
And that brings you to
whether you're going to make
an appropriate decision, or an
appropriate immune response.
Let's talk about specificity first.
How does specificity
come about, in immunity
and in transplantation?
The first thing I'll point
out, is that specificity
does not tell you what's going to happen.
If I recognize somebody's
alloantigen, it does not mean
that I have to attack it.
Because it could be a pregnancy.
It could be a part of me
that I did not see in utero.
If there's no context,
just having a perfect ID on
something doesn't give you
a way forward.
In fact, this is an
intuitive point number four:
identity does not determine intent.
What you need is to figure
out, once you've made identity,
what you're going to do with it.
And costimulation
molecules are the molecules
that help us do that.
They can turn the system on, like CD28.
When CD28 is bound with a T cell receptor,
the cell goes on, and it
assumes a positive stance,
or it can be negative, like CD152.
And in fact, a checkpoint
inhibition in cancer is all about
blocking these negative
costimulatory molecules.
And then of course,
as you start turning these
molecules into things
that you can
manipulate, we find that this
biology works pretty well.
The first really good evidence of this was
shown by Chris Larsen, where
he did heart transplants
in mice, and he did not block recognition.
He used genetically distinct
mice, but he blocked
two costimulatory molecules, CD154
and CD28 through this molecule CTLA4-Ig.
And he demonstrated that he
could do a heart transplant,
or skin transplant in a
mouse, blocking the context
at the time the mouse first saw the graft,
and then stop the drugs, and the mouse
would never reject the heart.
So presenting the antigen
without the context of
inflammation, made the decision
to accept the graft.
Interestingly, if you use the
drugs that were typically used
and are still typically
used in transplantation,
it prevented the tolerance.
Demonstrating that if you
freeze the immune system,
it can't function, and
functioning properly requires
this interpretation of contextual signals.
One of the first studies
that I was able to do,
was taking this biology
into primates, and showing
that you could block CTLA4-Ig, or
hu5c8,
or CD40 ligand,
and achieve a very similar
result in outbred primates.
But also pointing out, that this did not,
and I won't go into the details
of the experiment so much,
but this did not prevent
the animal from ever
rejecting the graft at a future date.
It could change it's mind.
It just, unless it had a
reason to change it's mind,
it didn't.
This
gained some attention,
and moved very quickly
into the clinic, such that eventually
a drug named Belatacept was born.
Belatacept is a fusion protein that blocks
B7 molecules, CD28 interaction,
it is a context blocker,
a costimulation blocker.
About ten years ago, the seminal
clinical trials were done
to show that you could
replace Cyclosporine
with this context blocker,
and prevent organ rejection
without having to take drugs every day.
Now the problem with that,
is that even though the
outcome
of the kidney transplants
treated with Belatacept
was better than the outcome
treated with Cyclosporine,
and this is just showing renal function.
And the,
even the humans that
rejected on Belatacept
had better renal function than the people
that didn't reject on Cyclosporine.
The fact was, is that
Belatacept patients rejected
a lot more than patients on Cyclosporine.
It didn't mean they lost
their graft, it just meant
that this was a very
metastable introduction.
And it is, as you would expect,
that if you are introducing
something new into the system,
there are many decisions
that have to be made, and
that introduces uncertainty, and
a metastable nature.
And this is a problem, if
you're a transplant surgeon,
because you don't want
to have to think about
whether your patient's
gonna reject or not.
You just don't want them to reject.
So I can transplant
somebody, with a heavy dose
of immunosuppression,
and be almost assured
that they won't reject.
Or, I can transplant them with something
that will allow them to
begin accepting the graft,
but the chance of them having
an early rejection is higher.
And that problem, is the problem
that people are dealing with
in transplantation right now.
One of the reasons for this,
is related to this issue
of magnitude.
So when you're blocking a immune response
against a single antigen, the
magnitude of that response
is quite small.
One in a million, one in ten million cells
will respond to that.
When you're responding
against another human,
the precursor frequency
is about one in 10.
So it's about 100 times, to 1,000 times
beyond what biology would
normally assume is a appropriate.
And then I ask you one physics question.
Can I
determine an appropriate place
in space by three dimensions?
No.
Because the issue of time
has to be taken into consideration.
Now so this shows
the magnitude of the immune response
against an aligraphed versus
a viral antigen, log fold higher.
And this issue of time,
is something we're always
dealing with immunity, too.
Every time you have an
immune response to anything,
you can't get bigger.
You're immune system has to stay the same,
you're lymphocyte count stays the same,
your antibody levels stay the same.
So every time you respond to something,
you have to kick something else out.
And so your immune system,
every time you respond
to anything, is changing to
your response to everything.
This importance of when
you see an organ in time,
is pointed out by this experiment.
So this is an experiment
that Fadi Lakkis did,
where he took mice, he did
heart transplants in them.
He did this in mice that had
no secondary lymphoid organs.
So they had no lymph nodes, no spleen.
You have plenty of T cells, but they can't
generate an immune response from that.
And naive T cells cannot
reject a heart, no rejection.
If you take the same mouse,
you expose those T cells
to the heart.
You give them a lymph node to structure
and then you pull those T
cells out that now have memory
of that response, and you
put them in the same mouse.
And those reject in seven days.
So in this experiment, the
specificity is unchanged,
exactly the same graft.
The context is actually unchanged.
The trauma of surgery, the
new graft, it's all the same.
The magnitude of the response,
the number of T cells
exactly the same.
But when the encounter occurred,
whether it's a memory
response, or a naive response,
changes the result completely.
So intuitive point five:
tolerance is context dependent,
and context is influenced
by memory, immune memory
in this circumstance.
And memory comes across in
a lot of different ways.
This is a flow cytometry plot.
If you look at it and
understand it, great.
If you don't, you'll just
have to ask a friend.
This is some work done by by Denise Lo,
who was a surgery resident in my lab,
who was able to figure out
that when you gain memory to something,
you lose the molecule CD28.
Because CD28's necessary
to acquire context,
to determine if immune
response is appropriate.
But once you have an immune
response, and you survive,
the default becomes, oh,
that was the right decision.
So you don't need to ask again.
You acquire memory.
CD28 is the molecule
that Belatacept blocks.
If you are exposed to an
alloantigen for the first time,
then this works really well.
If you're exposed to an
alloantigen for a second time,
this doesn't work at all,
because the whole pathway
is now off the lymphocyte.
This is another somewhat complicated slide
done by Hu Xu in my lab,
which points out that
as you rise in memory,
as you gain more polyfunctionality
your
relationship to how well you
are blocked by Belatacept…
And on the
x-axis here, is logged fold increases
in Belatacept, decreases
such as a molecule or a cell
that is known to have seen CMV,
and has memory to CMV, is
unblockable by Belatacept.
Whereas, a cell that has
never seen the antigen before,
completely blockable in
a dose dependent fashion.
There's some other phenotypic changes
that happen with immune experience.
One is called exhaustion.
In other words, if you respond
to something frequently
and over, and over again,
you basically exhaust.
And this happens when you see a molecule,
a molecule called PD1
comes up on the cell,
and you can tell exhausted T
cells from non-exhausted ones.
And there's senescence,
cells that have basically
beat their head against
the wall long enough,
eventually reach a point where they can't
do much of anything.
And as we follow individuals over time,
we find that with time, they lose CD28,
their CD28 negative cells go up,
and their number of naive cells decreases.
So that by the time you're 90 years old,
there is no way you
can be considered naive
to any antigen.
Intuitive point six: with experience
we become more exhausted, more
senescent, and less tolerant.
Again, we all intuitively understand this.
This molecule CD57 has
become interesting to us.
It is a,
a carbohydrate moeity
that is stuck on the end
of another adhesion molecule.
We are interested into
it, because although
it is not very prevalent in normal people,
in people with kidney failure,
it is actually quite prevalent.
And we don't really understand why.
It is perhaps because of
the senescence brought about
by exposure to dialysis membranes,
or the continuous inflammation of uremia,
or some other immune upheaval.
But kidney transplant patients
are somehow quite different.
I am starting to look at
patients with artificial hearts
and find that this molecule is also
upregulated in that.
The reason that's important, is because
this molecule has become a
marker for the immune phenotype
that is Belatacept resistant.
It is sort of the last molecular change
that happens on a T cell,
when it reaches that state
where costimulation is no
longer necessary to fire.
We have been able to find,
that if we check this marker
in patients before they get transplanted,
it will segregate people into a
who is likely to reject,
and who is likely to accept,
on a costimulation based regimen.
We've done some degree of
genotyping of this cell type.
And interestingly, the
most powerful pathway
upregulated in this cell type,
is a pathway called allograft
rejection signaling,
which was very convenient
when we looked it up.
It seems that everything these cells make,
are all the molecules
that have historically
been associated with rejection.
And it is our premise now,
that when you have developed a
extreme bias toward an alloantigen,
and reached this molecular configuration,
that you're going to reject that organ,
regardless of any sort
of contextual coaxing.
Cells that gain this molecule,
gain other molecules like CD2.
This is a experiment that another resident
in my lab did, Tim Weaver.
So this is a CSFE plot that shows cells
that have not divided,
and then each generation of division.
And you can interrogate
each generation of division,
and then measure a molecule of choice.
And you can see that as the cells divide,
they pick up this adhesion molecule CD2.
Similarly, as they become
more polyfunctional,
they do the same thing.
This brings up the thought,
well can we just go in,
find the cells that are
expressing CD57, or have memory,
and just eliminate the memory?
And then do the transplantation.
In fact, you can.
So this is an experiment that
we did with Rhesus Monkeys,
where we went in and we used
a molecule called Alefacept,
that binds to CD52,
pulls out the
memory cells of the monkey,
and then do the transplant.
And what it shows, is
that animals that have
not had their memory pulled
out, reject on therapy.
And animals that have had
their memory pulled out,
don't reject until you
stop all their therapy.
The problem with pulling
an animal's memory out,
is that you've pulled their memory out.
So in this circumstance,
these animals became
grossly overcome by Cytomegalovirus.
And in fact, all the things
that memory is good for go away.
So again, intuitive point number seven:
eliminating memory
usually causes more harm
than it causes good.
There are other ways of
dealing with memory cells.
One is to deal with their
nutritional properties.
And there's a pathway
called the mTOR pathway
that is right in the
center of understanding
how cells work, when they
are in nutritionally replete,
or nutritionally
starved conditions.
If you do
this same experiment adding in Sirolimus,
which is an mTOR
inhibitor with Belatacept,
you actually achieve an
extraordinarily good result.
So this is
an experiment that Mike
Mulvihill, who's a resident
in our lab has done using Rhesus monkeys
that have received Belatacept,
that have had their memory preserved,
but the metabolic response of that memory
is impaired, by blocking the mTOR pathway.
This is sort of like letting the context
and the specificity be there,
but inhibiting the magnitude,
so that these cells cannot,
memory cells cannot respond
to the antigen.
And in the blue line, are animals that are
treated with Belatacept and Sirolimus.
The red line is the
animals that are just
treated with Belatacept.
Interestingly, the green
line is taking the animals
that have been treated with
Belatacept and Sirolimus
and depleting all their T cells.
Now you're wait, wait a
minute, depleting their T cells
makes them reject, why would that be?
Well, because whenever
you create a vacuum,
it has to be filled.
And so, yes, when you deplete
T cells, you deplete T cells.
But then they wanna grow back.
And when they grow back, they
activate through a pathway
that is mTOR independent.
And so, again, you get this
counterintuitive finding,
that reducing the immune system,
actually increases rejection.
And allowing the immune
system to stay intact,
allows you to make a more nuanced approach
toward the allograft.
One of these issues, is that
when you deplete the T cells,
you also deplete T regulatory cells.
Another point we can discuss.
We're currently working now
with monkeys that are
drinking BRDU everyday.
BRDU gives an ability to
look at lymphocyte turnover.
We have found that probably the best thing
we can do with depletion, is
to provide just a little bit
of depletion, to allow cells
to turnover, to make them
have to have these decisions more quickly,
while the context of
immunity is being blocked,
And that gets them to
a final decision more
promptly, so you don't have
to treat for quite as long.
We can discuss that a little bit,
but it brings us to a
final intuitive point.
And that is that lasting
change of perspective
comes from education,
not from erasure of memory.
So can we put all this
stuff together into a trial
that will work for people?
Taking everything that we've
talked about into consideration
how should we approach
a transplanted organ?
I would argue first, that
we not block specificity.
You cannot teach something
that you're not exposed to.
You cannot make a decision,
unless you see what it is
you're going to make a decision about.
Second,
I would certainly attack
costimulation and magnitude,
in particular
blocking the costimulatory signals CD28,
and reducing the capacity
for cells that escape
this contextual blockade
through memory, to expand.
And when a cell is
given an antigen signal,
and can't expand,
it senesces and dies.
And so the theory would be,
if we came up with a
therapy that did this,
people would become less likely
to reject grafts over time,
and instead of needing more
immunosuppression over time,
they would need less
immunosuppression over time.
All right, so this is the
trial that we started,
through an FDA-sponsored RO1,
and it's actually pretty simple.
You deplete T cells a little bit,
just to get T cell cycling going.
You treat with Belatacept,
and you treat with Sirolimus.
And instead of trying to
dampen the ability of the organ
to be seen, we actually put
extra antigen into the system,
and this with bone marrow.
So we are forcing the
system forward quickly,
in a context of non-inflammation,
and a lack of an ability
for memory to respond.
So this is the first 20
patients we did in this,
this is their creatinine level.
And the first 20 patients
went through this trial,
treated in this fashion,
with no rejection episodes
and excellent renal function.
The important thing, though,
is that can they really
reduce their immunosuppression?
And this is the algorithm that
the trial was built around.
After a year, which everyone got through,
they were offered an
opportunity to come off of
some of their immunosuppression,
to see how it went.
Three patients didn't meet
the criteria for that,
so they were declined, and
they moved down into the
stay on Belatacept and Sirolimus forever.
And they've done quite well.
17 of them were offered
the opportunity to wain,
and seven of them said,
"Look, I take one pill a day,
"and one shot a month,
"I'm good".
And they decided not to
proceed with the trial.
And they moved over into the other group,
and have done very well.
But 10 people said, "Okay, we're game.
"We'll come off of our Sirolimus".
And five of those patients came
off Sirolimus and did fine.
And so, those patients proceeded
on once-a-month Belatacept,
and now we're eight years into that trial,
and have patients now that
take one shot, some of them
once every other month,
and that's all they take.
Five of those patients initially failed,
they had biochemical
changes in their lymphocytes
that met stopping rules.
They didn't have a clinical rejection,
but they had to go back in that bucket.
Two of those people decided
to retry, and made it,
and the other three
said, "No, we're good.",
and stayed with that.
So from 20 patients, we had
a rejection rate of zero,
a graft survival rate of
100%, and seven patients
that are now on once-a-month
therapy with a single drug,
without steroids, or
calcineurin inhibitors.
So it's a good start.
As we watch their immune systems change,
things happen that are as
we would have anticipated.
So as we look at naive
cells, cells that have CD28,
that are sensitive to Belatacept.
Those cells are increasing with time.
They're going back through the thymus.
The thymus, even in adults,
is sufficiently active
to push out a few naive cells.
And so the cells that are coming out,
as they repopulate from their depletion,
are cells that are
actually willing to learn.
And the cells that we identified
as being unwilling to learn
actually decrease over time.
As we look at the cells
that we want to be there,
regulatory cells, they are
all bursting into activity
as the population, as
the cells repopulate.
So we've got T regs, and D regs,
and gamma delta regulatory
cells, all burst up
and then come back down.
In a way, so as to say,
that okay we are trying
to figure out what to do with this graft,
it looks like it's okay,
and then backing off.
These are all cells that don't exist
in an immunosuppressive environment,
because they're all blocked
by calcineurin inhibitors
and steroids.
We've now tested this regimen
against standard regimens,
and the gray are the people
that get the Belatacept regimen
and the light tan are people that don't.
And you can see that all
these dynamic changes
happen in this regimen,
but they don't happen
in regular immunosuppression.
The immune system is fixed in place,
it won't change it's mind.
And importantly, as we look at
the
protective immunity of
these patients long-term,
they have lost the ability
to respond to their donor,
but they have not lost
their ability to respond
to Cytomegalovirus, or Epstein Barr virus.
So they are explicitly
and specifically choosing
not to reject the graft, while remaining
appropriately postured
to reject the things
that you need to reject.
So what do you do when
an experiment works?
Do it again, that's exactly right.
And so, we did this on
another 20 patients,
only this time we took the gloves off.
The first trial was
very selected patients,
living donors, no sensitization.
The next 20 patients was,
okay, anyone who comes.
They could have
alloantibody, they could have
you know, extended criteria
donors, deceased donors,
same result.
All patients responded to therapy.
And in fact, as we followed
the next 20 patients
over a period of two
years, their renal function
is getting better with
time, not worse with time.
Because you're not on
the nephrotoxic agents
that we typically use for transplantation.
Now the question then comes,
well, do these people
even need Belatacept?
Are they truly tolerant to their graft?
And so, we've done that experiment too.
And this is the first patient
that went into that trial.
So this an African American male,
that received a mismatched allograft.
He would be considered
a high-risk individual,
transplant wise.
He was treated with Belatacept,
a single dose of Elotuzumab and Sirolimus.
You see that before the transplant,
these are resting cells.
He responds vigorously against his donor,
he responds vigorously against
other people too, right?
So after 12 months,
he now has lost his response to his donor,
but not to other people.
He's
specifically now chosen not
to respond to his donor,
but people that he hasn't seen yet,
or had this contextual
change, no big deal.
So in between Month 12 and Month 24,
he now comes off of his
Rapamycin.
And still, 24 months now, he's taking
just a dose of Belatacept once a month.
No response when he's unstimulated.
No response to his donor.
Normal response to other people.
And so, then we take him
off of his Belatacept.
And now he's six months,
and he has not taken
any medication at all.
And his creatinine is one,
and he doesn't respond
to his donor, and he
responds to other people.
Well that's pretty good.
And so, we were dusting off
our tickets to Stockholm,
and all that stuff.
And then, he caught the flu.
And with an immune response, he pulled in
a response to his donor.
Now that's because, alloimmunity
is just cross-reactivity.
So anytime you respond to
anything, you can pull in cells
that are going to respond to other people.
Now their naive, and they're
easily blocked by Belatacept,
but if Belatacept's not around,
every time you have a big viral infection,
you pull in a rejection response.
So we've still got some stuff to work out,
but we're working on it.
It is interesting to note,
that as these patients
retool their repertoire,
this cell type,
this CD57 positive cell type that we think
is sort of the harbinger
of all the problems,
goes away over time.
So there may be just a matter of time
that we can wait on this.
It's likely related, for the
immunologists in the room,
to the fact that this cell population
doesn't express the IL7 receptor.
And IL7 is what drives
lymphocyte repopulation
after lymphopenia.
And because of this, there's
a selective advantage
to naive cells over memory cells.
And if you deplete and repopulate
a certain number of times,
you can selectively pull
out these memory cells.
We can talk about that later.
In summary,
transplantation currently, as it states,
still remains encumbered
by its association
with non-specific immunosuppression.
These costimulation
pathways can be manipulated,
to allow for fine, antigen-driven
control of immunity,
including alloimmunity.
But they have to be used
in ways that control
these costimulation
independent cell populations.
The regimen that I described
here, seems to work,
and prevent allograft rejection,
or alloantibody formation
in humans that are mismatched,
receiving kidney transplants
without need for calcineurin
inhibitor or steroids.
It seems to be reasonably
tolerable, and over time,
gets stronger, not weaker.
So the need for immunosuppression
decreases over time.
It allows some people to go
on to monotherapy Belatacept.
And we think that this
CD57 positive cell is still
at the center of it, so
we're doing a lot of work
in that space.
We think that knowledge of a
patient's immune repertoire
before transplantation,
can help us figure out
who this is gonna work for,
and who it's not gonna work for.
And there's a lot of work
going on in that space.
We're just starting now, a
clinical trial here at Duke,
that takes this to the next level.
So we're doing the same trial,
but instead of just giving
a dose of bone marrow,
we're actually taking
donor-derived Mesenchymal cells,
expanding them, and then
repeatedly dosing the patient
every month, when they
get their Belatacept,
with Mesenchymal stem cells.
We're using Mesenchymal stem cells,
because they express all
the antigens of the donor,
but they can't cause
graft versus host disease.
And so, this eliminates
the risks that you have
with bone marrow transplantation,
and things along those lines.
And so, we should be
enrolling our first patient
in the next month or so.
We're collaborating with
Joanne Kurtzberg's lab,
to build the Mesenchymal
stem cells, for us on this.
Transplantation allows a foreign organ
to save dying people.
Rejection can be prevented
by blocking engagement
with that foreign organ, but if you do so,
it also blocks adaptation,
and it blocks acceptance.
As soon as the blockade is gone,
rejection comes right back.
Tolerance is achieved by
actually engaging the graft,
seeing it, and taking
the contextual signals
of inflammation away.
That initial first impression,
without costimulation,
is very powerful in
helping the immune system
decide to take a softer
approach toward the allograft.
It is inherently metastable,
and can be disrupted
by inflammatory events like the flu.
So it must be maintained, it's not
a set-it-and-forget-it type of thing.
But over time,
new antigens prevented
in a beneficial context,
without a fuel of inflammation,
eventually exhaust
remnant graft-specific cells,
and a situation of tolerance ensues.
Tolerance becomes
increasingly stable with time,
and what was previously
foreign, then becomes something
that we see as ourself.
Not everything that is
foreign, is harmful.
Beneficence and risk
are context dependent.
You need to engage what is foreign,
without the context of inflammation.
Even an appropriate response
in the right context,
is wrong if its magnitude is off.
So that needs to be managed for sure.
Tolerance takes action, it's metastable,
but it strengthens with time.
And to every
complex problem, there is
a solution that is simple,
and neat, and wrong.
Thank you, very much.
(audience applause)
Questions?
None, good.
– [Paul] Thank you, Dr. Kirk.
Please let questions from the audience
into the microphone,
if you could use them,
that would be wonderful.
– It's a foreign concept,
they're not willing to engage.
It's okay, I completely get it.
– [Paul] I find it was
explicitly well described,
a most clear description
of immune tolerance
in transplants.
For some of you, it's
not (noise interruption)
but dabbles within the lab.
So is the future then
going to be to move away
from the standard transplantation drugs,
and will this Belatacept, and Sirolimus,
and some of these other techniques
that you've been doing your trials on,
become more ingrained to standard care?
Because, you know, we
still watch in our ICU
and even with youth people,
kind of their rejection there
tragically devastated by what happens
when this occurs.
– Yeah, so we were really
starting to get some
headway with this.
Belatacept was starting to
be used more frequently.
We did a couple of trials at Emery,
had done some multi-center trials.
We're short of dabbling into this approach
toward immune minimization, as opposed to
using Belatacept with
a bunch of other drugs,
which is how it had to be
rolled out for the FDA.
We were using so much
of it, they had to build
a new factory, to make Belatacept.
And they built it in, wait for it,
– Puerto Rico.
– Puerto Rico, exactly.
And there's no Belatacept now,
because the hurricane came
through, shut Puerto Rico down,
and now you can't get the drug.
So the trials have been put on hold,
until we can get the supply
of drug back up and going.
You know, it's always something.
I think that over time,
when we can make it
sufficiently anticipatable,
that there will not be an early rejection,
Belatacept will take off.
As it was initially
licensed, it had to be used
with steroids or Mycophenolate.
Don't get me started on that.
But that's how the FDA licensed it,
which means it's a
great immunosuppressant,
not a great tolerogen.
And so this metastable
issue is one that clinicians
really don't want to deal with.
If we were able to use
it with a small dose
of Alemtuzumab, that would be great.
The problem with Alemtuzumab,
is that when you use
a small single dose of a
drug, it is not monetizable.
And so, Alemtuzumab is now being marketed
as a maintenance therapy
for Multiple Sclerosis,
where you can make $80,000 a year on it.
If you give a third of a dose one time,
you can't make any money on it.
And so it is not being
pursued for transplantation,
it's being pursued for Multiple Sclerosis.
We're fortunate, in that
the amount that we need
is so small, the company
is just letting us use it.
But we are gonna have to come up with
a way around the economics of
the drugs that are being used, as well.
There
is a truism in
in medicine and biology,
that if you develop a drug
that treats a chronic disease,
you will make lots of money.
But if you develop a cure,
you cannot monetize it.
And if you develop a prevention,
the only thing you get is liability.
And that's the way the system works.
As we learn to use less and less medicine,
for shorter, and shorter periods of time,
the interest of companies
becomes decreased,
because they can't make money on it.
And that's, they gotta
make money, it's not like
a bad thing about companies,
that's what they gotta do.
But we have to find ways to
do trials that lead to
cures, as opposed to trials
that lead to chronic therapies.
– [Woman In Audience] Thank
you, it's a great talk,
and I particularly enjoyed the ending.
But I did wanna ask, it was
interesting that the patient,
you're almost Stockholm-worthy patient,
wound up with the flu.
What's the affect of costimulatory blockade
on an immunization?
– So, not that big.
You would expect it to be much
more important.
And the only way I can
make sense out of that,
is first of all, that
cognate antigen responses
are very high affinity.
And alloreactivity is largely
just cross-reactivity.
The affinity for a T cell
receptor to an MAC molecule,
is much less, than the
affinity to an antigen
that is really locked into self MHC.
And so that's one possible explanation.
The second, is we've had millions
and millions of years to evolve,
to not let a single pathway
take us down for viruses.
But transplantation just
showed up 50 years ago.
There's nothing that we've
evolved in transplantation,
it's all a fluke.
And we're just sort of trying
to work our way through this weird
evolutionarily,
unanticipatable experiment.
And so I think that it is much easier
to block an alloimmune response,
than it is to block a
viral immune response.
You had a question?
– [Woman In Audience] I
was wondering, how far away
do you think we are from
applying this to other organs?
– Yeah, it's a great question.
So the good thing about
kidneys, is if the kidney fails
you have dialysis.
You have biopsies, you have a creatinine,
it's a great experimental model.
Heart transplant, you know, not so much.
If your kidney doesn't work for a day,
you know, that's okay.
If your heart doesn't work
for a minute, you die.
And that is hard to move this model into
heart transplantation,
or lung transplantation,
where biopsying is more difficult.
There's no easy thing to follow,
with regard to rejection.
The liver transplant is
an interesting situation.
But the reasons people come
to liver transplantation
are very different.
And the inflammatory
milieu of someone dying
of liver failure, is quite
different than the milieu
of someone that has got kidney failure.
And so, trying to work this
into a liver transplant regimen,
I think it's doable,
but it is gonna be,
there are gonna be new challenges
that come up with that.
The really interesting thing about livers,
is that a third of people
can come off their
immunosuppression anyway.
And very few people need triple
immunosuppression long-term
for a liver transplant,
because the liver is postured
to prevent immune
responses, not to make them.
Where as the lung, which
is outwardly facing,
is postured to make immune responses,
not the other way around.
So is the kidney, which is also
exposed to the world.
The liver is exposed to your gut,
and so every time it sees an antigen,
it thinks it's the steak
you had this morning,
and tries to shut it down.
And so that you don't
have an immune response
every time you have a bowel movement.
– [Paul Wischmeyer] Speaking of the gut,
what about the gut for this?
In terms of improving,
disparaging (noise interruption).
You can control the
situation, (mumbled words).
– So, you know, the body
hedges it's bets.
If you're in the gut,
likely what you see is a pathogen,
relative to whether you're in the
kidney, or in the heart.
And so, the resident
immune system in the gut,
seems to have much more problems
shutting its costimulation
down, than an immune system
that's floating within the,
the circulation.
– [Paul Wischmeyer] Figure
all the normal food antigens
have to happen.
– Well, they do.
But normal food antigens
are not MHC molecules,
and so they are presented
in a different manner.
– [Paul Wischmeyer] The microbiome is tolerized.
– Yeah, yeah, well.
It is very, very difficult to figure out
what the gut's gonna
do, when you put it in.
Some individuals
develop a tolerogenic
phenotype, which actually
flips over into being too
tolergenic, and you get septic.
Sometimes it sets up a
situation where it is
the ischemia-reperfusion injury
sets the immune system off,
and you have horrible rejections.
It is,
there is something unnatural about sewing
a tube full of poop into people.
And we have not figured that out yet.
(mumbled words from audience)
(laughing)
(mumbled words from audience)
Yeah, well, I think that
there's all sorts of,
there's job security
in studying this stuff,
because we're not gonna
figure it out anytime soon.
All right, thank you guys, very much.
(audience applause)
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