The “silver-bullet” for infectious diseases

An interview with Kary Mullis at Seed:

Seed: Why do we need to rethink the way we treat infectious diseases?

Kary Mullis: Many pathogens are becoming resistant to our antibiotics. Consider penicillin, for example. We took it from a fungus that grew in the soil and killed bacteria for food. Because of this warfare, some bacteria had developed a resistance via DNA, to penicillin. Over time, they passed this resistance via DNA up to the pathogens that infect our bodies. So now many organisms—like Staphylococcus aureu, the cause of Staph infections—are, in large part, unaffected by penicillin. In this way a lot of bacteria have mutated around our antibiotics.

The standard pharmaceutical response is to go stomping through the jungle trying to find extracts of all the organisms and see if one of them will inhibit the growth of particular bacteria. And that of course will get more and more difficult as time goes on. It is clear that we need another solution.

Seed: What is your solution?

KM: A long time ago they used to speculate that there might be what they called a “silver bullet” for cancer. The idea was that if you could find some molecule that would bind to a cancerous cell but not to a non-cancerous cell and attach a radioactive atom—or some sort of poison—to that molecule, you could cure cancer. It turned out cancer didn’t work that way, but you can take a similar approach to fighting infectious diseases.

My work with PCR allowed for the invention by Craig Tuerk of nucleic aptamers, which are tiny binding molecules that can be designed to attach themselves to harmful bacteria. However, instead of attaching a poison to the other end of the aptamer—as the silver-bullet strategy would call for—I put something on there that is a target for our immune system, a chemical compound with which the immune system is already familiar and to which it is very strongly immune. What you end up with is a drug that will drag this thing to which you are highly immune over to some bacteria you don’t want in your body. And your immune system will attack and kill it.

Seed: Do you have any proof that it works?

KM: Yes, we cured anthrax in mice. If you infect a mouse with anthrax and then wait 24 hours and treat it with a penicillin-type drug, you get about a 40 percent survival rate. But using our drug you get a 100 percent survival rate. Of course, it is unlikely that you are going to get anthrax, but that is sort of a model system.

That is only the first half of the interview; go, read the full thing — because it is worth it!


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