It stands up, looks you in the eyes and fires: Spitting cobras like the Nubian spitting cobra seen here can spray their venom at the speed of a water pistol. They are extremely accurate at a distance of up to 2.40 meters; there is no chance for a human to avoid them. The snakes aim for the eyes of their victims, where their toxins cause burning pain, which in the worst case can lead to blindness.
Although spitting cobras use this tactic as a very effective defense measure, like all cobras, they kill through their bite. The injected poison causes painful swelling, redness and necrosis – i.e. dead skin – and an untreated victim dies shortly afterwards as a result. But survivors also have to expect amputations and lifelong stigmatization due to the necrosis that occurs.
Researchers led by Greg Neely from the University of Sydney have now made a surprising discovery. Using CRISPR gene editing, the group was able to identify the gene sequences that the poison needs to kill cells. Some of the enzymes that are preferentially attacked are responsible for the synthesis of heparin and heparan in the body. Heparins have been known in the pharmaceutical industry for years as blood-thinning compounds and are prescribed, for example, to treat thrombosis.
But the polysaccharides apparently have even more to offer: if you flood a cobra’s new bite wound with heparins, the chances of severe necrosis are significantly reduced. The polysaccharides serve as “bait”. The snake venom attaches itself to them and is no longer able to kill the cells.
Such a preparation would therefore have several advantages over conventional antibody therapy, which is based on the antibodies of naturally immune animals such as horses. Such active substances are very complex to produce and are not always readily available. “Heparin is cheap, readily available and a WHO-listed ‘essential medicine’. After successful trials on humans, it could relatively quickly become a cheap, safe and effective drug for treating cobra bites,” says lead author Tian Du, also from the University of Sydney.