When You Can’t Find a Unicorn

As everyone knows, just as with God (Mark 16:18), unicorn horns will render poisons harmless. But what do you do if you can’t find a unicorn or God is busy? Grab an opossum (but watch out for the teeth). If you’ve ever met an opossum in the wild, you already know they can’t be killed without resorting to extraordinary means.

A blog born from Arizona State University’s Consortium for Science, Policy, and Outcomes recently had an interesting article on opossums (Opossums). One of several interesting parts is that they are immune to many naturally occurring toxins.

Opossums are pretty much immune to snake venom.  And not just the neighborhood riffraff, like the eastern diamondback rattlesnake with which they have co-evolved. We’re talking timber rattlers, cottonmouths, Russell’s vipers and common Asiatic cobras. We know this because scientists rounded up a bunch of nasties and forced them to bite a bunch of unfortunate opossums, the latter of which responded like it was a mild bee sting. 

Using high-pressure liquid chromatography, scientists then sought to identify what makes opossums so damned special. They found it to be a small protein, which they named Lethal Toxin-Neutralizing Factor (LTNF). Like the name suggests, these proteinase inhibitors grab onto and neutralize venoms. Rather like antibodies going after antigens, only LTNF is a naturally occurring opossum protein – not an antibody.

This is pretty rad,” said the scientists, “but it could be radder. Better kill some rats.” (Scientists are always trying to kill rats; no one knows why.)

So they took some rats and injected them with LTNF, then pumped them full of otherwise lethal doses of venom from Thailand cobras, Australian taipans, Brazilian rattlesnakes, scorpions and honeybees. But the rats just laughed in their faces.

Dude,” said one scientist, “we have to kill these rats. Do you watch AMC’s Breaking Bad?” The other scientists nodded of course because everybody watches Breaking Bad. So next they tried to kill the rats with ricin, an extremely lethal poison made from castor beans. (How lethal? Just ask Georgi Markov, the real-life Bulgarian defector killed by a ricin umbrella gun. That’s right, I said ricin umbrella gun.)

Alas, the ricin was a no-go. The now-snooty rats danced Ring Around the Rosie. That’s it!” screeched the lead scientist. “It’s time to release the botulinum toxin. Surely this will conquer the awkward opossum’s super serum!” But after many maniacal laughs and a few bolts of lightning, the rats were still alive.

(The paper does not mention what became of the super rats. I can only assume they went on to write “The Secret of Nimh” while the evil scientists lost their rat-killing grant.)

Similar LTNFs are also found in the mongoose, meerkat, and hedgehog. The article goes on to mention the opossums are “resistant to many viral diseases such as [rabies], distemper, parvovirus and feline hepatitis”. Interesting stuff, but the bit about the LTNF looked a little on the questionable side until I read the original paper at Lethal Toxin Neutralizing Factor. This paper is 13 years old, and we’re still making specialized antivenin from the toxins of each type of poisonous snake?

Synthetic LTNF has been made and tested. It was patented in 1996 (US patent 5744449 and US patent 576297). Why has it taken so long for the news to get out? The patents expire next year, but I’m curious why the major pharmaceutical companies didn’t pounce on this 16 years ago. I haven’t been able find out much about it. There have been a flurry of reports about it recently, but it’s all old information.


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