Have you ever been bitten by a mosquito?
Well, yes, I have been too.
Almost everyone around the world has had this experience
at least once in their lives.
But tell me, have you ever wondered
why it's itchy right afterwards?
And the answer might surprise you.
It's actually saliva.
It turns out that, just like you and me,
insects like mosquitoes have saliva
that they use when they eat.
They inject it into our skin,
where it numbs the bite so we don't feel the pain.
And it makes the blood flow freely,
so they can take the biggest meal that they can
before flying away... unless this happens.
But the itch that you feel
is actually our immune system responding
to the different molecules in the saliva.
And there are many molecules in the saliva,
all of which can be classified as
proteins, sugars, lipids,
and other types of components.
Now, a lot of research until now
has focused specifically on the proteins,
and not a lot of attention
has been paid to the sugars.
And that is why I was interested in looking at them.
Now, I'm going to look at the sugars in the saliva
not only of mosquitoes
but of all of these bloodfeeders:
tsetse flies, ticks, sandflies, and kissing bugs.
But why do we care about saliva?
Now, the most important reason
is that they can all transmit disease.
Diseases that can be well known,
like malaria, dengue, or sleeping sickness.
Because saliva is such an important part of the biting process,
it can influence how our bodies
respond to these invaders
and can have an effect on the success, or not,
of an infection in our bodies.
The other reason that we could care about saliva
is because of the allergic responses
that they can induce in some people.
And here, I want to tell you a bit more about ticks.
But let me first start with a story and a question.
What is your favorite food in the whole wide world?
For many people,
it could be this juicy, delicious, 100% beef burger.
Now, imagine taking a bite of this burger
and savoring all those delicious flavors,
finishing your meal,
and going to bed quite happy.
And then waking up in the middle of the night
feeling not so good.
Your body is full of rashes that really itch.
Your throat starts to close and your blood pressure drops.
You could be experiencing a red meat allergy.
And surprisingly enough,
the culprit could actually be a tick.
Ticks feed differently to mosquitoes and other bloodfeeders.
They attach themselves to your skin,
where they remain for several days.
And during all of this time,
they're constantly injecting you with saliva
and other molecules.
Now, for many people,
the bites go completely unnoticed.
But for others, it can have life-changing consequences,
like the development of an allergy to red meat.
The first cases of red meat allergy
were reported in Australia around the 1980s.
But even many years after,
doctors remain puzzled as to why so many people
were developing this severe allergic response
to red meat.
And after a lot of research,
they found that what these patients had in common
was that they all remembered being bitten by ticks.
When they looked at their blood tests,
they showed abnormally high levels
of an antibody called IgE,
which is involved in allergic responses.
And in this case, that IgE
was specific for a sugar called alpha-Gal.
And this was the first suggestion
that there was a link between this alpha-Gal,
the tick bites,
and the allergy to red meat.
But this story of discovery doesn't end there.
In the U.S.,
some patients were reporting really severe allergic reactions
to a cancer drug called cetuximab.
When they looked at the blood of these patients,
they also saw abnormally high levels
of these Ig-E antibodies against the alpha-Gal sugar.
Now, humans don't produce the alpha-Gal sugar,
and that's why our bodies recognize it as foreign
and produce antibodies against it.
It turns out that the cetuximab drug
is produced in a mouse cell line.
And because mice do produce the alpha-Gal sugar,
the drug ended up being decorated
with all of these molecules.
And when it was given to some patients,
they developed a severe reaction against it.
But why only some patients?
Well, a bit more digging found out that
the patients that developed this severe reaction
lived in rural areas of the Southeast U.S.,
rural areas where they could be more exposed to the bites of ticks.
And so all of this evidence started coming together
to suggest and reinforce this strong link
between tick bites and the development of red meat allergy.
As the condition became more well known,
this alpha-Gal syndrome,
doctors started to register it
in different parts of the world.
And in each region,
it could be associated with a different species of tick.
Now we know that thousands
or perhaps more around the world
have developed this alpha-Gal syndrome
and cannot eat meat anymore.
But it's not only beef.
They can be allergic to pork, to milk,
to the gelatin capsules that surround some medications,
and even in some unfortunate cases
to life-saving drugs like cetuximab.
Now, there's... there continues to be a lot of debate
about the source of this alpha-Gal,
but some researchers believe that it is found
in the saliva of the tick.
And this is why these researchers, in Brazil,
have decided to explore this connection
between the tick bite and the red meat allergy,
for the Brazilian tick, Amblyomma sculptum in particular,
which is the most commonly distributed in Brazil.
So, in order to do this in the lab,
they needed to create a model
to be able to study the effects of the tick saliva.
Because humans don't produce alpha-Gal,
they created a mouse model
that also doesn't produce the alpha-Gal sugar.
They then exposed these mice to tick bites,
or to the saliva obtained from these ticks.
And when they looked at the blood of the mice,
they saw that they produced
antibodies against the alpha-Gal sugar.
And this was very nice evidence
that the origin of the sugar was actually the saliva of the ticks.
And at this point, we started a collaboration,
where my job was to find the sugars
in the saliva of the ticks
and confirm that the alpha-Gal was actually there.
And first, I want to tell you a little bit about the sugars here.
Now, sugars can be also known as glycans,
and they are found in all living systems,
inside and outside the cells.
They can have roles in aspects like metabolism,
structure, or cell-cell interactions.
And here we see a classic image
of the surface of a red blood cell,
where all of this fuzz on the surface
is actually glycans that are attached to lipids or proteins.
And these glycans are the ones
that determine your blood group,
so they are actually very well known.
When sugars are attached to proteins, they form glycoproteins
And these are just some types of the structures
that you can find attached to proteins.
And this attachment can actually
influence the protein's folding, interaction,
and immunogenicity.
And by immunogenicity,
I mean the type of strong or weak immune responses
that this combination can generate in our bodies.
And so, the way that I go about
studying the sugars in the saliva of the bloodfeeders
is first by extracting their saliva.
And so, I can...
I have to dissect hundreds of these insects at a time.
As you can see here,
the salivary glands have been extracted from each of them.
I take that saliva into the lab to process,
where I treat it with an enzyme
that allows me to separate the sugar from the protein,
to study each one individually.
Now, for purposes of this talk,
I'm going to focus on the sugars,
because that's what we're interested in right now.
I label the sugars with a fluorescent marker
that allows me to detect them more easily
by liquid chromatography and mass spectrometry.
Now, this is the type of result that I would get after that analysis,
using ticks as an example.
And in this chromatogram,
you can see the profile of salivary sugars,
where each of the peaks corresponds
to a different structure that we now know.
But this gives me a very general idea.
And after further analysis and treatment,
for example with specific enzymes,
I can rebuild each of these structures.
And here, I am showing you
that we found the sugar structure
that contains this alpha-Gal,
which is this portion that we find here.
And so, it's a confirmation that the alpha-Gal sugar
is actually present in the saliva of ticks.
But now that we know that the sugar structure is there,
what is the protein that this alpha-Gal is actually attached to?
So, here I turn to the proteins in the saliva.
And for example,
each of these bands
is representing a different protein in the saliva of ticks,
and I then purify one of these proteins
that has the alpha-Gal,
using a marker that is specific for this sugar,
as you can see here, that is labeled with the asterisk.
I then take this protein
and identify it by mass spectrometry,
and get a list of candidates.
These results, together,
help me to confirm that the alpha-Gal
is actually present in the saliva of ticks,
that it forms part of a glycoprotein,
and that knowing the...
and knowing this structure can actually
help me use these molecules
as tools to improve diagnosis
or even, perhaps, to create better treatments
for the people that are affected by this condition,
the alpha-Gal syndrome.
But the tick story is only a part of a much larger project,
where I'm characterizing the salivary sugars
of all of these bloodfeeders.
And because we know how important sugars
can be to the type of immune responses
that saliva can trigger in our bodies,
this information will allow me
to potentially use each of these structures as a tool
to diagnose, monitor, or better treat diseases in different ways.
And so, the next time you're bitten by a mosquito,
you and I will know what's going on there,
in that little bit of skin,
all the complex reactions that are being started.
You now know that saliva has proteins and sugars.
And you know that somewhere around the world,
there is one scientist looking at how all of this happens.