It’s still a distant dream, but a Californian chemist and Costa Rican venom expert are reporting progress in a novel effort to make injectable nanoparticles that can neutralize snake venom and can be carried in backpacks.
In a recent study in PLOS Neglected Tropical Diseases, their particles protected mice against tissue damage from spitting-cobra venom without triggering allergic reactions.
In wealthy countries, snakes are an abiding threat to an unlucky few, among them hikers, ranch hands, soldiers, zookeepers and reptile collectors.
In the tropics of Africa, Asia and Latin America, however, they are a major cause of death and disability in rural areas: more than 2 million people are bitten each year. About 100,000 of them die, and another 400,000 are left with serious disabilities, including amputations or nerve damage so extensive that a leg or hand is permanently useless.
There have been reports of electric shocks, including stun guns, used to break down the poisons. But most reports are anecdotal, and there is no accepted explanation about how they work — if they work.
Antivenins have existed for decades, of course, but they are expensive, potentially dangerous and used only rarely in poor countries. The medicines contain antibodies harvested from the blood of sheep or horses that have been injected with diluted venom and allowed to recover.
The process is cumbersome, and the antibodies must be kept refrigerated. Few drug companies bother to make antivenins, so the prices are high.
Because they contain horse or sheep proteins, antivenins also can trigger life-threatening anaphylactic shock or hemorrhaging. They must be given intravenously in an emergency room, and many bite victims die before they can reach hospitals.
“They have a lot of issues, but they’re the only show in town,” said Kenneth J. Shea, a chemist at the University of California, Irvine.
Dr. Shea’s lab is creating hydrogel nanoparticles coated with polymers — the building blocks of plastics — small enough to attach to proteins.
While screening them against common venoms, he isolated some nanoparticles that bind with and neutralize two poisons produced by snakes like cobras, kraits, coral snakes, sea snakes and mambas.
José María Gutiérrez, a venom specialist at the University of Costa Rica, injected dozens of mice with the venom of the black-necked spitting cobra. He found that Dr. Shea’s nanoparticles significantly reduced tissue damage in the mice. Importantly, the nanoparticles did not appear to interfere with normal proteins or to trigger dangerous allergic reactions.
Much more research needs to be done, Dr. Shea said, but the goal is to create a cocktail of particles that could be loaded in an injector like an Epi-Pen.
It would not completely replace antivenins. But since the nanoparticles are relatively easy to make and need no refrigeration, they could be carried in the field and injected into the site of a bite, reducing tissue damage and stopping the poison from spreading. That would buy time to reach better treatment.
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Asked about the source of his funding, Dr. Shea said, “Well, right now I don’t have any money for this.”
The military expressed initial interest, he said, and so has the veterinary industry. But he also hopes to attract the attention of groups that fund global health research, like the Bill and Melinda Gates Foundation or the Wellcome Trust.
The path to regulatory acceptance may be a long one. Use of nanoparticles in medicine is relatively new, and for clinical trials involving snakebites, “there aren’t many volunteers,” Dr. Shea said.