How sharks could hold the key to our immunity

They have a fearsome reputation, but could sharks soon help save far more human lives than the dozen they take each year?

Over 400 million years of evolution, sharks’ immune systems have evolved into finely tuned defenses that are far more precise than those of humans and capable of fending off almost any dangerous virus or life-threatening tumor.

This is thought to be one of the main reasons why some species, like the great white, can live up to 70 years. Sharks also have exceptional wound healing abilities, which means injuries rarely result in death.

Researchers have now solved the riddle of why sharks’ immune systems are so good at warding off disease. And the discoveries could lead to new drugs to fight diseases such as cancer and rheumatoid arthritis.

They have a fearsome reputation, but could sharks soon help save far more human lives than the dozen they take each year?

In humans, when the immune system detects 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 on support from more powerful immune system cells, called T cells, to kill the invader.

Separately, scientists have developed artificial antibodies, “monoclonal” antibodies, which are injected into the body to target certain rogue cells, such as cancer cells.

Once docked to their target, these synthetic antibodies activate the immune system to attack tumor cells (Herceptin, the drug used to treat some forms of breast and stomach cancer, is a monoclonal antibody).

But human and artificial antibodies tend to be bulky Y-shaped molecules that, due to 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 drugs aren’t always 100% effective in repelling the enemy.

In sharks, the antibodies are less than a tenth the size of those found in humans, allowing them to penetrate deeper into the tiny cracks found on the surface of bacteria or cancer cells, which increases the chances that they “stick” and the immune system destroys the invader.

This is thought to be one of the main reasons why some species, like the great white, can live up to 70 years. Sharks also have exceptional wound healing abilities, meaning wounds rarely result in death.

Moreover, tests have shown that shark antibodies are very resistant. Scientists claim to have boiled them and immersed them in corrosive acid, but they survived.

“Sharks are among the oldest living creatures on the planet, so scientists wanted to see if their disease-fighting toolkit was the same as humans’,” says Dr Caroline Barelle, chief executive of Elasmogen Ltd, a spin-off from the University of Aberdeen that develops synthetic versions of shark antibodies for human medicine.

“They quickly discovered that sharks had small and simple antibodies, with potentially huge advantages over large human antibodies that are very complex and can only bind to a single target.”

Elasmogen is testing synthetic shark antibodies against triple-negative breast cancer, an aggressive form of the disease. The idea is that artificial versions of tiny shark antibodies, injected into the bloodstream, will have a better chance of binding to breast cancer cells by squeezing into tiny cracks on the surface and alerting the immune system.

The other option is to load the shark molecules with chemotherapy drugs that they can smuggle inside cancer cells.

Trials using shark antibodies to treat cancer could take place in the next five to ten years.

Another target is rheumatoid arthritis, a disease that can cause debilitating pain. Lab tests suggest that man-made shark antibodies could carry drugs that would then lodge on a receptor on the surface of cells in inflamed joints.