Free Radicals - Michael Brooks [35]
Keen to ingest the wisdom of their forebears, the Fore in their funeral rituals ate their dead ancestors. The ritual cannibalism began with the women stripping muscle from the body to give to the male members of the family. Having handed over the choice cuts, the women fed themselves, their children and elderly relatives on the internal organs, including – especially, in fact – the brain.
In an experiment that was to win him a Nobel Prize, Gajdusek showed that injecting chimpanzees with material from the mashed-up brain of a kuru victim brought out kuru-like symptoms in the chimps. Kuru, he said, was infectious: the result of an as yet unidentified ‘slow virus’ that lived in the organs the women and children ate, but not in the muscle that the men consumed.
Gajdusek’s breakthrough paper was published in 1966. He and his colleague Joe Gibbs spent the next few years testing whether dozens of other human neurological diseases could be transmitted in the same way. Only one gave a positive result: Creutzfeldt–Jakob disease, or CJD. That result was published in 1968, the same year that Stanley Prusiner, the anarchist who stands at the centre of this chapter, received his MD.
Stanley Prusiner first encountered CJD when he was working as a resident in neurology at the University of California, San Francisco. It was 1972, and one of his patients was suffering a slow and agonising death. The typical symptoms of CJD are confusion, blindness, jerking spasms and an inability to communicate. These patients, we can safely assume, die lonely, frightened and in darkness. Fascinated and appalled, Prusiner began to read the scientific literature on the disease. From this he learned that his patient had succumbed to a mysterious slow-acting virus that no one had ever been able to isolate or identify. It was a mystery that would define the rest of his career.
Kuru and CJD are now known to be two of a select group of diseases that includes bovine spongiform encephalopathy (BSE, also known as mad cow disease) and the sheep and goat disease scrapie, so called because its symptoms include a desperate itching that causes the animals to scrape off patches of their wool or hair. Prusiner began his research with a programme of reading about scrapie, the disease in the group that had been studied the most. Almost immediately he came across what he later called an ‘astonishing’ report by Tikvah Alper, then at the Hammersmith Hospital in London. In 1967, Alper and her colleagues had shown that the mysterious virus might not be a virus at all.
Viruses multiply by coercing a host cell into reproducing the virus’s genes. But genes are composed of chains of molecules known as nucleic acids, and these are fragile. If you subject them to ultraviolet or ionising radiation, the chains break up. For organisms like us, that often results in life-threatening cancer. For viruses it is even more catastrophic: radiation kills them. So when Alper’s team took the brains of scrapie-infected sheep and irradiated them, they fully expected the viruses to be killed and the brain material to be rendered safe.
It was not. Even after irradiation, the brain material remained infectious. It wasn’t a difficult step to suggest that, whatever the infectious agent was, it didn’t contain the nucleic acids that make up genetic material. That is, it wasn’t a virus.
Alper had already thrown some cold water on the virus idea. She had weighed the minimum amount of material that would cause an infection, and shown that its molecular weight was too low for it to be a virus or a bacterium. What’s more, no one had ever found the nucleic acids. So, if not a virus, what was the infectious agent? The English mathematician John Stanley Griffith had come up with an answer to that in a September 1967