Posted by: Glow-worm PJ6 NOV 2013
Haemocyanins are copper-containing compounds that carry oxygen around the bodies of certain molluscs and arthropods. The haemocyanin of the giant keyhole limpet (Megathura crenulata), known as KLH, is a potent immunoactivator. It has been used for decades in the treatment of certain bladder cancers because it stimulates the human immune system without causing any adverse effects.
The properties of KLH have more recently been used in the world of biotechnology, where it has been employed as a carrier protein in producing antibodies for research, particularly in the development of vaccines.
Haptens are substances with a low molecular weight that, on their own, are not able to trigger antibody production, but when they are attached to KLH, the carrier protein initiates an immune response and antibodies are produced against the hapten.
The properties of haptens can be engineered, and the antibodies produced from stimulation by haptens can be harvested for use in vaccine production. Recent research has concentrated on developing tumour-associated antigens, which stimulate an antitumour immune response that can destroy tumour cells.
KLH is a high molecular weight metalloprotein. Its unusual glycosylation means that it cannot easily be synthesised. It is generally prepared by purification of haemolymph from the limpet.
The species occurs only in southern California, and there is a limited supply. It was formerly harvested with little thought to its ecology or the effect on its sustainable population. In the late 1990s, work began on developing non-lethal extraction techniques, allowing haemolymph to be taken without killing the animal.
Growing the limpets under the controlled conditions required for medical research proved a challenge, but today thousands of limpets live their entire lives in these controlled systems, and haemolymph is extracted several times a year.
KLH is now big business. Fifty animals typically produce 20g of the protein, with a current market value of $100,000.