Golden bullet fired in river blindness war

"Nanobullets" made of pure gold, coated with genetically engineered DNA vaccines and fired into the skin using a "gene gun" may sound like some gadget out of a James Bond film, but researchers at the School for Tropical Medicine in Liverpool believe they could cure river blindness, which affects more than 500,000 people living in the tropics.

"River blindness is caused by parasitic nematodes, or filariae - a kind of rigid-bodied worm," explains Ted Bianco, head of the research team and the man with the golden gene gun.

The disease is transmitted by bites from the blackfly. Unlike mosquitoes, blackfly larva cannot survive in polluted waters, so river blindness is found mostly in river valleys, where the water is clean and fast-flowing.

Health workers already have a drug, ivermectin, to combat the disease. Initially developed for veterinary use, its positive effects on the treatment of river blindness were detected as early as 1982 and since then it has been supplied free of charge.

It acts by killing the microfilariae, thus removing the agents of the disease.

"The trouble is it doesn't kill the adults. They can survive for five or ten years in the host, breeding and re-infecting blackfly, and so the problem continues," Professor Bianco says. "This means there has to be a continuous campaign to repeat treatments. The areas affected are usually remote, so the whole exercise is horrendously expensive and a logistical nightmare.

"It is widely felt within the scientific community that the problems associated with the treatment regime prevent it from ever becoming really effective. We have to look at other solutions."

The Liverpool group is attempting a new approach - the process of genetic or DNA immunisation. In 1992, Nature reported the ability to insert DNA into human cells. The altered cells are instructed to produce antigen proteins, which drive an immune response to combat the disease.

"It is possible to use intramuscular injection, but much more exciting is the gene gun," Professor Bianco says. "Once we have produced the DNA we require, we coat it on to tiny particles of gold, each around 1nm in diameter. The gene gun uses a cylinder of compressed helium to fire up to two million particles in to the epidermis.

"The process is random - the gold particle must lodge in the cell without killing it for the DNA to stand a chance of being expressed."

Bianco believes the new technique has a number of clear advantages over conventional treatments.

"Producing protein antigens in the very pure forms required can be incredibly expensive. Also, they do not travel well. It is only recently that polio vaccine has been used successfully in the tropical world. DNA vaccines may be expensive to develop, but they are incredibly cheap and easy to produce, and they are as tough as old boots. You can just pop a vial in your back pocket and away you go," he says.

There are no immediate plans for human trials in the United Kingdom in the near future, but a prototype is being tested on cows, while in the US researchers are attempting to apply similar techniques to more high-profile western diseases such as HIV and influenza.

RESEARCH PAPERS

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