Basically vaccines work because they mimic actual pathogens (viruses, bacteria, etc - anything that makes us sick). These fake pathogens fool our immune systems into making antibodies, which we can use to fight off the real germs if they ever show up.
Normally when we get sick it takes about two weeks of trial and error for our systems to evolve effective antibodies against the disease. But if we've been immunized so that we've already made those antibodies once, or immune systems remember how to make them again, and we can fight off the disease right away.
All of this works because our bodies can recognize a particular virus and call up the proper antibody to fight it off.
The problem with a virus like HIV is that it keeps changing. If you have HIV virus in your body, and it takes two weeks to come up with an antibody, by the end of that time you'll have hundreds of new HIV variations and the new antibody will not be able to fight them off. Basically your immune system can never catch up with all that rapid change!
Abbie's idea for getting around this seems pretty simple on the surface. Just put lots of variations of fake HIV into a vaccine, so that our systems will learn how to make lots of different HIV antibodies!
But here's the rub: in order to cover all the possible HIV variations in one vaccine, you would need to put in a mind-boggling number of different fake viruses. That number is something like a one with 61 zeros after it! (And that's only one way of counting them - other types of variation are possible too!)
If you were to get a vaccine shot containing just one of each possible variation of fake HIV in it, you would need to use a gallon-sized syringe!
Luckily if you can make an antibody for one type of HIV, your system can quickly come up with antibodies for similar types. That means we don't need ALL the possibilities to go into one vaccine, just a relatively small portion of them.
Abbie is working on how to create a mixture of fake HIV types that might work as a vaccine. She has been testing her methods to make sure that all the different variations she put in actually work to produce different antibodies. She is just about ready to start testing the vaccine on mice to find out if it really provides protection against HIV.
Maybe we'll be able to get her to visit again one day and let us know how that turned out!
Since Abbie's work involves a lot of time spent manipulating DNA (to create and test all those different fake HIVs!), we ended the program with a hands-on activity that lets you actually see your own DNA in a test tube!!
You can do this yourself at home - it's really easy. Here are instructions (thanks to the Science Museum of Minnesota).
And here are photos from our program. We hope to see YOU at the next one!
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| Abbie Smith explains how viruses work. |
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| Me swishing water vigorously to dislodge cheek cells. This is the first step in our activity, which allowed each participant to extract and view their own DNA! |
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| Second step - add soap and mix gently. This bursts open the cells and sets the DNA free. |
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| The third step is to add some chilled alcohol. This forces the DNA out of solution. |
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| See that cloudy bit dangling beneath the cap? That's a glob of my very own DNA! |
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| Show us your DNA! Cheers! |
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| Abbie is extracting the DNA from the top of the test tube to put it in a small capsule for safekeeping. It lasts longer if you freeze it. |
Our next program:
October 15
The Intrepid White-footed Mouse
How Toxic Waste Affects Animal Populations and Diversity
Dr. Karen McBee, Curator of Vertebrates with the Department of Zoology at Oklahoma State University, will speak about her research into what makes some animal species more resilient than others at the Tar Creek Superfund Site.
See you then!
