THEY have a fearsome reputation, but could sharks soon be helping to save many more human lives than the 10 or so they take each year?
Over 400 million years of evolution, sharks' immune systems have developed into finely-tuned defences, much more precise than humans' and which are capable of seeing off almost any dangerous virus or life-threatening tumour.
It's thought to be one of the main reasons why some species, such as the great white, can live for up to 70 years. Sharks also have exceptional wound healing capabilities, which mean injuries rarely lead to death.
Now researchers have solved the puzzle of why sharks' immune systems are so effective at warding off disease. And the findings could lead to new medicines to combat illnesses such as cancer and rheumatoid arthritis.
In humans, when the immune system senses the presence of foreign cells (such as a virus, or bacteria) it releases a protein called an antibody. This latches on to a specific molecule on the surface of the virus or bacteria and calls up support from more potent immune system cells, called T-cells, to kill the invader.
Separately scientists have developed man-made antibodies, 'monoclonal' antibodies, which are injected into the body to home in on certain rogue cells, such as cancerous ones.
Once they've docked with their target, these synthetic antibodies switch on the immune system to attack the tumour cells (Herceptin, the drug used to treat some forms of breast and stomach cancer, is a monoclonal antibody).
But human and man-made antibodies tend to be bulky, Y-shaped molecules which, because of their size, are usually only able to bind to a small number of targets on invading cells. This helps explain why the human immune system and antibody-based medicines are not always 100 per cent effective at seeing off the enemy.
In sharks, antibodies are less than one-tenth the size of those found in humans, allowing them to penetrate deeper into tiny cracks found on the surface of bacteria or cancer cells - improving the chances of them 'sticking' and the immune system destroying the invader.
What's more, tests have shown shark antibodies are very tough. Scientists claim to have boiled them and dipped them in corrosive acid - yet they survived.
"Sharks are among the planet's oldest living creatures so scientists wanted to see if their disease-fighting toolbox was the same as humans'," says Dr Caroline Barelle, chief executive officer of Elasmogen Ltd, a spin-out company from Aberdeen University that's developing synthetic versions of shark antibodies for human medicine.
"They soon found sharks had antibodies which are small and simple, with potentially enormous benefits over large human antibodies that are very complex and can only bind to one target."
Elasmogen is testing synthetic shark antibodies against triple negative breast cancer, an aggressive form of the disease. The idea is that man-made versions of tiny shark antibodies, injected into the bloodstream, will have a better chance of binding to breast cancer cells by squeezing into tiny gaps on the surface and alerting the immune system.
The other option is loading the shark molecules with chemotherapy drugs which they can smuggle inside cancer cells.
Trials using shark antibodies to treat cancer could take place in the next five to 10 years.
Another target is rheumatoid arthritis, a condition that can cause crippling pain. Laboratory tests suggest man-made shark antibodies could carry medication that then homes in on a receptor on the surface of cells in the inflamed joints.
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