Spider venom could treat a devastating form of childhood epilepsy
Spider venom might not be the first thing you reach for if you're unwell, but that could soon change, with new research suggesting that a peptide in spider venom called Hm1a might be able to help with a type of epilepsy called Dravet syndrome.
This syndrome is a rare but severe type of childhood epilepsy, which is resistant to many types of drugs.
Babies born with the syndrome appear healthy in the first few months after birth, until they begin having seizures at around five to eight months of age.
These seizures come in a range of types, and can occur frequently and unpredictably. They can cause delays in development and sleep disturbances, and are associated with an increased risk of sudden death.
Approximately 1 percent of the population has epilepsy, and about 1.4 percent of all cases of epilepsy in children under 15 are Dravet syndrome. So it's rare, but extremely severe.
"About 80 percent of Dravet syndrome cases are caused by a mutation in a gene called SCN1A," said one of the researchers, Glenn King, from the University of Queensland (UQ).
"When this gene doesn't work as it should, sodium channels in the brain which regulate brain activity do not function correctly."
Hm1a or Heteroscodratoxin-1 is a neurotoxic peptide produced by the venom glands of the Togo starburst tarantula, (Heteroscodra maculata) and it's been shown to mess with sodium channels.
When used on mice that have an equivalent to Dravet syndrome, this spider venom peptide did something amazing.
"In our studies, the peptide from spider venom was able to target the specific channels affected by Dravet, restoring the function of the brain neurons and eliminating seizures," King said.
The team, from UQ and The Florey institute of Neuroscience and Mental Health, used mice that had been bred with the same SCN1A gene mutation seen in humans with Dravet syndrome.
The researchers gave these mice a continuous infusion of Hm1a, which reduced or completely stopped six of the nine animal's seizures.
Those that didn't get the infusion were not so lucky. Only 24 hours after the control infusion had started, 62 percent of the mice had died.
So how is spider venom so effective at fixing these specific sodium channels?
"Spiders kill their prey through venom compounds that target the nervous system, unlike snakes for example, whose venom targets the cardiovascular system," King said.
"Millions of years of evolution have refined spider venom to specifically target certain ion channels, without causing side effects on others, and drugs derived from spider venoms retain this accuracy."
Although it'll still be a few years before we can give Hm1a to kids that have this syndrome, this is an exciting step towards such a treatment.
The team is hoping that Hm1a can be developed into a precision medicine for treating Dravet, giving these kids a better chance to control their seizures.
The research has been published in PNAS.
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