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Measles, mumps, and polio are things we can prevent with vaccines, but scientists are looking to add a surprising entry to that list: Type 1 diabetes.

Hosted by: Stefan Chin

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Sources:
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Images:
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https://www.istockphoto.com/photo/mature-diabetic-patient-taking-a-blood-test-gm865903474-143856411
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(Intro)

Measles, mumps, and polio.  These are things that we can prevent with a vaccine, but scientists are looking to add a surprising entry to that list: type 1 diabetes, which, unlike the others, is not an infectious disease.  You can't share a sugar-free soda with your diabetic friend and suddenly lose your ability to produce insulin.  It just doesn't work like that, and usually, infectious diseases are the ones that we can target with vaccines, so how would a diabetes vaccine even work?

Well, type 1 diabetes, or T1D for short, is a chronic, irreversible condition, typically diagnosed in children, where certain peoples' bodies do not make the insulin they need to control sugar in their bloodstream, and that's different from type 2 diabetes, where patients' bodies typically become resistant to insulin so it can't effectively manage blood sugar levels.  In type 1, they just don't make it in the first place.  Their immune system has turned on the rest of their body and destroyed the cells in their pancreas responsible for making insulin.

For a long time, the trigger for this destruction has been a big question mark.  In recent years, scientists have identified genetic risk factors that increase a person's risk for T1D, but these factors can't cause the disease alone, nor can they explain all the weird things public health scientists have found when studying T1D, like the fact that there are certain times of year where more people get diagnosed with this chronic disease than other times, not something usually chalked up to genetics.

So with genetic factors failing to explain the full picture, scientists have looked to the environment for additional causes.  They've investigated links to vitamin deficiency, potential dietary causes, and even pancreatic toxins, but one of the most compelling explanations has to do with viruses, specifically, that a class of viruses called enteroviruses, which typically infect your GI tract, could induce T1D. 

It's thought that they could somehow cause an immune response that makes the body destroy those insulin-producing cells, and this could be the key to a T1D vaccine, because while T1D is not infectious, viruses are, and if these viruses induce T1D, it could open the door to using vaccines to grant immunity those viruses, which, in turn, could prevent the development on T1D.  

Over the last 50 years, several studies have been able to show a causal connection between enteroviral infections and the induction of T1D, at least in mice, but this connection has been much harder to show in humans, partly because human subjects are just more difficult to study.  In order to prove that enteroviruses cause T1D, you have to demonstrate that a group of infants who were genetically predisposed to T1D were also infected with enterovirus.  That's before they were diagnosed with T1D, and of course, we can't infect human babies with viruses, so instead, you have to wait until the babies naturally get infected, which is difficult because most enteroviruses don't cause symptoms.

Parents don't generally show up at the doctor when their baby doesn't seem sick.  Neither do doctor usually think to look for a virus that's not doing anything.  Instead you have to routinely collect samples from babies' poop and check them for enterovirus genes, but as researchers soon discovered, entervirus genes can't always be found during an infection.  You need to check a bunch of times to catch them, so in 2017, after a couple successful studies, several more failed ones, and a whole lot of baby poop, the largest study to date settled the score with two important findings.

First, it showed that babies who are genetically susceptible to T1D also have higher rates of enterovirus infection, and second, it found that months after those infections, the T1D predisposed babies started producing certain autoimmune cells which are known to attack the pancreas and cause T1D.  That's a pretty strong case, and now that a strong connection has been shown in multiple studies, it opens the door to vaccine research to prevent these infections.

That research has already begun.  One vaccine being studied in mice targets a specific enterovirus called CVB.  In a small study published in 2018, researchers administered the vaccine to seven mice carrying the genetic risk factors for T1D and all seven were protected from developing it.  News reports have claimed that the CVB vaccine is set to enter human clinical trials soon, but it could be years before they start the study or have results.

With that said, a group of scientists in Finland had the idea to try a shortcut.  See, polio is an enterovirus, and we already have a vaccine for it that we know is safe and effective.  They published a study in 2018 which looked at whether the polio virus vaccine could prevent T1D, but unfortunately, they found it had no protective effect. 

So thus far, we don't have an anti-diabetes vaccine that works in humans, but the CVB vaccine could work out, and maybe someday, we'll be able to look at type 1 diabetes as a disease of the past.  

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