Archived story from http://www.detnews.com
Wednesday, June 15, 2005
Blood of the lowly horseshoe crab helps save humans
By Dr. Ranit Mishori / Health and Fitness News Service You'll see them on the beach this summer -- the ancient, plodding, otherworldly creature from the sea that is limolus polyphemus -- otherwise known as the horseshoe crab.
Not really a crab at all, it's a member of the spider family. And if you do spot one, stranded, as tends to happen, helpless on its back, drying out in the sun -- do the right thing. Flip it over, gently, carefully, so the crab can get itself back into the water.
You won't just be doing a crab a favor. You'll also be making a small contribution to medical research for humans.
It's about blood. Horseshoe crab blood. It has become an invaluable ingredient in the development and manufacture of all the intravenous drugs and implantable devices on the market today. All of them. If it travels through an IV tube into a patient's body -- if it's designed to live inside a patient, as with artificial heart valves, replacement hips and knees -- then horseshoe crab blood played a part.
Here's why. The blood of these sea creatures is not like ours. For one thing, it runs a bright, milky blue in color. That's because of its high copper content (human blood is high in iron, which colors it red). For another, this blue blood contains a unique substance called LAL (limulus amoebocyte lysate). LAL might as well be colored gold, because extracted from crab blood, and concentrated for medical use, it runs about $15,000 a quart.
LAL is what gives the horseshoe crab a working, though primitive, immune system. Primitive it may be, but it also turns out that the substance is absolutely foolproof at detecting bacteria that can hurt humans, such as E. coli and salmonella. These are the kinds of bacteria that, in the past, have plagued patients getting implants, or receiving drugs via IV tubes. A system was needed to quickly -- and accurately -- screen the IV drugs or the artificial devices to ensure they were bacteria-free to prevent complicating infections.
Scientists discovered that LAL is the perfect alarm system. Normally liquid in form, it clots up or turns yellow when it comes in contact with any of those unwanted bugs. Now it's an FDA requirement. Before it can be packed and shipped, every new implant device must be dipped in water containing LAL.
LAL is also added to every batch of IV drugs to make sure it does not clot or go yellow.
"Virtually the entire world's drug supply is monitored using this material," says Malcolm Finkleman, vice president for Clinical Affairs at Associates of Cape Cod Inc., East Falmouth, Mass., one of three U.S. companies that isolate and sell the product.
All this gets rabbits off the hook. Until the mid-1980s, IV drugs were routinely tested for bacteria by injecting them into rabbits, which were watched for 48 hours for any signs of illness.
Horseshoe crabs can donate blood and go on living, just like humans. In standard practice, they are captured alive, and then tapped for about one-third of their blood via a needle inserted into the heart. Within 72 hours, they are once again returned to the sea.
According to Finkelman, the wound clots naturally, and their blood supply is back up to normal in two to three months.
Horseshoe crabs are native to the Northeast United States, along the Atlantic seaboard from Virginia to Maine. One estimate is that they number 2.3 to 4.5 million on the Atlantic Coast between New Jersey and Virginia alone.
That sounds like a lot of crabs, but given the other uses of their blood that scientists are now looking into -- ways to test for vitamin deficiencies, and as ingredients in new antibiotics -- maybe it's not so many after all.