In Deadly Feasts, Pulitzer Prize-winning journalist Richard Rhodes explores the story behind prions and the neurodegenerative diseases they appear to cause. Prions are, apparently, nothing more than naked proteins, sans the nucleic acid blueprints that accompany viruses and bacteria. Although prions arrive with no owner's manual, they recruit normal host prions to adopt their pathogenic shape, and eventually deposits of the abnormal proteins - called amyloid plaques - appear in the brains of victims.

Though Rhodes' apparent mission is to detail how epidemiologists puzzled out the existence and structure of prions - and he does a fantastic job - there is clearly another motive: to alarm the reader. The book's subtitle alone, "Tracking the Secrets of a Terrifying New Plague," is enough to give pause to any veteran observer of the popular medical press. "Evidence accumulates that it [the prion] is a bad seed, a mistake of protein, a misshapen crystal that forces the brain to poison itself. If so, it's a new kind of disease agent that can never be eradicated," Rhodes states in his introduction. His description of the prion is eloquent and accurate as far as it goes - but the dire warning he closes with seems exceedingly alarmist. After all, it's not hard to imagine specially engineered proteases that could home in on prions and break them down, or therapeutic antibodies that might help the stricken host eliminate the invader. Furthermore, since the prion appears to be recruiting a normal protein in the host, the budding field of antisense - which uses strands of nucleic acid derivatives to lock up messenger RNA and block the production of specific proteins - could lend a hand.

Although Rhodes has not written a scholarly treatise on the chemistry and biology of prions, he has written an excellent chronicle of the scientific process, in the vein of James Watson's The Double Helix. Although Deadly Feasts isn't a first-person account, as is Watson's, Rhode's depth of research and rich description of cases and cultural practices gives the reader the feeling of looking right over the researchers' shoulders.

With a vivid account of cannibalism among New Guineans in the 1950s, the book immediately thrusts its audience into the epidemiologist's world. Rhodes recounts the ritual, sparing no particulars, as a dead woman's daughters partake of their fallen forbear. Within months, most of these women are dead of a mysterious "sorcery" the native New Guineans called kuru. The condition begins with disorientation, then progresses to difficulty walking and eating, and finally to coma and death. Only women and children are affected by the malady, leading the women to suspect men as perpetrators of the sorcery. Not coincidentally, the women and children are also the only ones who took part in cannibalism.

Epidemiologist and Nobel laureate Carlton Gajdusek first arrived on the scene in 1957, on his way back to the United States from a visit with an Australian colleague. He became so intrigued by the mysterious disease in New Guinea that he felt compelled to study it. Gajdusek scratched the cannibalism connection early on because patients showed no sign of inflammation, removing the likelihood of any kind of infectious agent. After an exhaustive search for a toxicological cause, he and his colleagues then considered a genetic factor. They found nothing. It wasn't until a neuropathologist at the National Institutes of Health, Igor Klatzo, examined kuru-victim brains sent to him by Gajdusek that the first hard evidence of a cause surfaced. Protein deposits reminiscent of aging and Alzheimer's appeared in the diseased brains. The deposits raised more questions than answers, though, since no one had ever found them in the brain of a child.

The plaques reminded Klatzo of an extremely rare neurological disorder called Creutzfeldt-Jakob disease, which followed a similar degenerative path as kuru. Like kuru, Creutzfeldt-Jakob disease is fatal. The rest of Rhodes' book traces a fascinating path as epidemiologists wound through historical cases, failed experiments, and disbelieving colleagues to lay claim to the discovery of a new infectious agent - naked proteins, or prions (proteinaceous infectious particles; pronounced "pree-ahns").

Prions are generally held to be perverted forms of a protein widely distributed among many species. In its normal three-dimensional shape or conformation, the protein is benign, but the pathologic prion form - identical in amino acid sequence - is misfolded, assuming a unique structure. The trouble apparently arises when enough of the abnormal prion accumulates, forming an insoluble crystal, which in turn catalyzes the conversion of normal protein into the misfolded form. The growing deposits are believed to be the cause of the neurological symptoms. These "seed crystals," in the form of brain tissue, were the infectious agents that plagued the New Guinean women and children Gajdusek and his colleagues studied. It also explains the lack of inflammation that threw Gajdusek off track: The host presents no immune response because the responsible agent is its own protein! This protein is highly conserved across many species, and some form of the disease has apparently made its way from sheep to cows through the use of sheep carcasses in protein supplements for cattle. This "industrial cannibalism," as Rhodes refers to it, is at the root of "mad cow disease," which causes cows to lose motor control with a very grim prognosis. In the past few years an alarming number of British children have developed and perished from a kuru-like condition, leading many to suspect tainted British beef.

The possibility is certainly disturbing, and Rhodes has done an admirable job in describing the history and mechanism of this unique infectious threat. It's a fascinating story, told at times with perhaps just a little too much flair and zeal. If you want to gain insight into the lives and challenges of epidemiologists working on today's most difficult disease problems, this is a worthy read. The reader looking for a penetrating scientific analysis of prions and mad cow disease had best look elsewhere.

Jim Kling writes in Washington State about science and the environment. His work has appeared in Science, Nature Biotechnology, The Scientist, and Popular Science magazine's Web site.

Excerpt

Infection - the alien protein of foreign organisms invading the human body - causes inflammation as the body's lymph and immune systems respond defensively to destroy the invader. With inflammation comes fever, increased numbers of lymph cells in the cerebrospinal fluid that bathes the spinal cord and the brain, and other physical changes. To their astonishment, the two doctors found none of these signs in their kuru patients. "It's hard to explain to a nonmedical person how strange it is not to see inflammation," Gajdusek told me the first time I interviewed him. "And with kuru there was none. Absolutely none."

Virus X: Understanding the Real Threat of the New Pandemic Plagues, which reports on the Ebola Zaire and hantavirus, was recently reviewed in HMS Beagle

Prions - an overview of prion diseases.