Vaccines help prevent disease by challenging the immune system to make antibodies—proteins that target particular viruses or bacteria, and help the body fight them off. In this Science Update, you'll hear about efforts to make a better vaccine against anthrax.
Cleaning up anthrax's aftermath. I'm Bob Hirshon and this is Science Update.
Last fall's frightening anthrax attacks put thousands of people on regimens of the drug Cipro. Antibiotics like these kill the anthrax bacteria, but they do nothing to clear the deadly toxin released by the bacteria into the body.
Now, George Georgiou of the University of Texas at Austin and his colleagues are working on a way to help the body get rid of the toxin: they've engineered protein antibodies against it.
When an antibody encounters a toxin molecule and binds to it, it stays latched on to the toxin for at least a hundred minutes. And ultimately the toxin complex is cleared by presumably the kidneys, without having the chance to bind to human cells and cause damage.
The treatment successfully prevented rats from getting sick from an injection of toxin. Since the antibodies were developed from mouse proteins, Georgiou says the next step is to make them more 'human.'
In other words, we change parts of these antibodies so that it resembles more and more the antibodies that our own immune system produces.
He says eventually, antibodies could be a way to treat anthrax infections caught at a late stage—or even given as a vaccine to prevent the disease. For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
The problem with anthrax is that once the disease is diagnosed, it's usually too late to treat it. Symptoms don’t appear until the anthrax bacteria have already released too much of their deadly toxin. The disease can be prevented with antibiotics before symptoms appear, but deciding when to use those antibiotics involves a lot of guesswork. If the antibiotic isn't given when it's needed, people may die. But distributing antibiotics when they're not needed is expensive, logistically difficult, and may promote the growth of drug-resistant bacteria. Plus, it can waste valuable stockpiles of a drug that may be in limited supply.
There is a vaccine against anthrax itself, but currently it's given only to military personnel. The vaccine requires several doses over a long period of time, and carries a risk of serious side effects. Because anthrax exposure was previously considered very unlikely for most people, only limited supplies of the vaccine are available.
That's why this anthrax vaccine would be valuable, if it turns out to work in humans. Patients could be cured of the disease after they showed symptoms of exposure. That would greatly decrease the threat posed by the disease, while also reducing the need to distribute powerful antibiotics unnecessarily.
However, it's important to note that in Georgiou's experiment, the animals had already received the vaccine before they were infected with the anthrax toxin. It remains to be seen whether the drug is powerful enough to neutralize an infection that's already in progress. If the answer is yes, only then will the scientists move on to experiments in more human-like animals.
Incidentally, this isn't the only vaccine that targets a toxin, rather than the bacteria that produce it. The tetanus vaccine, which is distributed in the U.S. to all children and adults, also targets the toxin produced by the disease-causing bacteria.
Now try and answer these questions:
- How does Georgiou's anthrax vaccine work? How does it differ from most other vaccines?
- What are the advantages to this kind of vaccine?
- What has Georgiou's team demonstrated so far? What has yet to be proven?
- It may be difficult to know for sure if this vaccine works in humans, unless a serious outbreak of anthrax occurs. Why do you think that is?
- Suppose a single individual in a major city tested positive for anthrax. What steps would you take to protect other citizens? Under what circumstances would you distribute antibiotics? What if this vaccine were available? Who would get it? Why?
The War on Disease, presented by National Geographic Magazine and introduced by former president Jimmy Carter, discusses the threat posed in the 21st century by the rise in infectious disease, and the scientific measures being taken to forestall epidemics.
The Anthrax page on the Centers for Disease Control website provides information about the disease.
Vaccines and Immunizations, also from the Centers for Disease Control, provides a host of information about vaccines and immunizations.