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What makes the plague so deadly? -

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Norman Swan: As you heard, bubonic plague gets its name from buboes, grossly swollen and infected lymph nodes in the groin and under the arm. Soman Abraham is Professor of Pathology at Duke University School of Medicine in North Carolina and he's been using advanced technology to find out how the plague germ, Yersinia pestis, has had the power to cause such devastation over the centuries.

Soman Abraham: The fleas carry the bacteria and the bacteria then traffic into the lymph nodes, and then from the lymph nodes it's thought to go out into the circulation.

Norman Swan: Why did you start studying it?

Soman Abraham: We got into it just by the fact that when we undertook some studies in mice comparing the growth in the lymph nodes between Salmonella and E. coli, and then introduced Yersinia as a kind of a control, we found that the lymph nodes of mice infected by Yersinia was so much larger than the other mice that were infected with Salmonella or E. coli. So we were fascinated by that, and we were then curious to know why you had these buboes, it was never clear from the literature what role these buboes had. And so we initiated our studies.

Norman Swan: They looked at what happened to the plague bacteria in mice and found that the Black Death was scarily like the AIDS virus in the way it causes havoc, but thousands of years earlier. Plague finds its way into white blood cells called macrophages and hides from the immune system, taking over the lymph nodes and using the macrophages to traffic around the body, lymph node to lymph node. Soman Abraham thinks this gives a clue to new treatments because antibiotics don't always work.

Soman Abraham: So in seeing what the macrophages were doing, we then thought an effective way to reduce the spread of the bacteria was to try and find ways to block this movement of macrophages from one node to the next. And there are drugs that lock some of the receptors that are on macrophages that determine their movement from one lymph node to the other. And so when we used these drugs we were able to show that we could dramatically reduce the infection and protect the mice from death. Even without adding antibiotics we could actually protect 70% of the mice from death by just blocking the migration of the macrophages from one lymph node to the next.

Norman Swan: Soman Abraham is Professor of Pathology at Duke University's School of Medicine in North Carolina.

I'm Norman Swan and this has been the Health Report. I look forward to your company next week.