Just microwave that parasite!

The Bill and Melinda Gates Foundation has invested $1 million in a plan to treat malaria by sticking the patient into a microwave. OK, not the whole patient. Probably just an arm or a leg. Not just any microwave oven, but one set at very low power and with the frequency of its electromagnetic field tuned very precisely.

The process is simple: Open special microwave, insert limb, repeat daily. Dr Jose A Stoute, a Penn State microbiologist and his co-inventor, Carmenza Spadafora of the Institute for Advanced Scientific Studies in Panama, were originally given $100,000 by the Gates Foundation after writing a two-page proposal suggesting microwaves could safely kill malaria parasites in the blood. Spadafora proved the idea worked in a petri dish. The new $1 million is to see if it works in mice. “There’s a lot of data on mice exposed to microwaves, so we think we’ll be able to stay well below their level of safety,” Stoute said.

Parasites feeding on haemoglobin

The idea, he said, is based on the fact that malaria parasites invade red blood cells and eat the haemoglobin inside them. Hemoglobin contains iron and it’s a bad idea to microwave metal. Of course, the red cells containing parasites are floating along in arteries right next to healthy red cells, so whatever damage the microwave does to the parasites cannot be visited on the healthy cells, too. And that, Stoute said, is where a crucial difference comes in: When a malaria parasite digests hemoglobin, it converts the iron into an inert crystalline pigment called hemozoin.

The parasite must do that because free iron will tear oxygen atoms off things the parasite wants intact, like its cell membrane. The hemozoin crystals, packed with concentrated iron, are pushed into the parasite’s food vacuole – the empty space where a rudimentary creature that does not have a gut dumps its waste products.

Drifting into an electromagnetic field with a vacuole full of hemozoin is about as brainy as stepping into a microwave with a stomach full of nails. But parasites don’t have brains, either. Stoute and Spadafora have shown that they can finetune a custom-built microwave so that only the parasites are damaged.

Their theory is that the heated-up hemozoin swells the vacuoles till they pop, unleashing an acid bath on the parasite’s innards. The microwave is built from commercially available parts but puts out less than one-thousandth the power of a kitchen model.

Malaria parasites become resistant to every new drug, so the foundation is interested in new ways to kill them. Stoute kept nixing Spadafora’s ideas, he recalled. “She finally said, ‘What do you want – a magic ray?’ And I remembered reading a study about using microwaves on cancer cells after tagging them with iron. I thought, ‘Parasites come with their own iron. Why don’t we try this?”

Even if the approach works in mice, all sorts of problems will have to be worked out before it is tested on humans, Stoute said. Hot spots like those that a microwave creates in liquids must be avoided. And any patient will undoubtedly need treatments for several days in a row, because the parasites hide in the brain, liver and spleen – and microwaving the head or abdomen is probably a bad idea. “But eventually they have to come back out into the blood,” he said, “and that’s when we’ll get them.” Stoute has not discussed his idea widely, but one person he told was Dr Gray Heppner, the former chief of malaria vaccine development at the Walter Reed Army Institute of Research.

“Microwaves are not ionising radiation. They cause heat. If he can get them to cause very local heat, there’s an exquisite differential susceptibility that might make it possible. And if anyone can carry this off, it’s Jose.” Heppner, a retired colonel, said Stoute did “brilliant jobs” running a hospital in the Persian Gulf War and a malaria research project in Kenya.

Stephen Ward, the first Gates Foundation official to see the grant application, said his initial reaction was: “This is an absolutely crazy idea.” “But once you understand the underlying biology,” he added, “it’s a crazy idea that just might work.” A different grant applicant, he said, had proposed a malaria test using hemozoin, which helped him better understand the key role the crystal plays in malaria. Another advantage, said Dr David Brandling-Bennett, head of the foundation’s malaria strategy team, was that if the technology works, it may be practical to use in poor countries.

Low-cost, energy-efficient option

“We want things that, in theory, are low in cost and make reasonable power demands, that might even run on batteries or solar power,” he said.

“We wouldn’t be interested if it was expensive and usable only in a tertiary hospital in the first world, like an MRI.” He could imagine many future uses, he said. The simplest would be a microwave that could be used on bags of donated blood if malaria tests were not available. And his wildest vision was an airport scanner that would cure malaria as immigrants walked through it – and do it so harmlessly that there would not even be a need to test them first.

New York Times News Service