Zombie CSU (26 page)

 


–
Iatrogenic Creutzfeldt-Jakob disease
(iCJD)


 


 


–
Variant Creutzfeldt-Jakob disease
(vCJD)


 


 


–
Familial Creutzfeldt-Jakob disease
(fCJD)


 


 


–
Sporadic Creutzfeldt-Jakob disease
(sCJD) is the most common prion disease in humans


 

 


Fatal familial insomnia
(fFI) is an autosomal dominant inherited disease


 


 


Sporadic fatal insomnia
(sFI) a noninherited type of fatal insomnia


 


 


Gerstmann-Sträussler-Scheinker syndrome
(GSS) is associated with autosomal dominant inheritance


 


 


Kuru
—the word
kuru
means “trembling with fear” in the language of the Fore people, trembling is a symptom of dying brain tissue


 

Expert Witness

Dr. B. Burt Gerstman, an epidemiologist from San Jose State University, remarks, “Prions represent unknowns…and people fear unknowns. Prions are strange creatures—they have no DNA but are capable of replication (not reproduction). We still know very little about prion transmission and pathogenesis. We do know they are resistant to routine disinfection and can withstand harsh environmental conditions. I believe they can even survive autoclaving, which is sort of the standard for aseptic technique. These are strange creatures…no DNA yet capable of self-replication under circumstances which we understand relatively little about.”

According to Dr. Pawel P. Liberski
⁷
of the Department of Molecular Pathology and Neuropathology at the Medical University of Lodz, Poland, “Prions do not have DNA. According to the prion hypothesis, a prion is a protein (our own) encoded by a cellular gene. In normal situations—you and me for instance—our prion gene (PRNP) encodes for a normal protein called PrPc (from a cellular isoform
⁸
of prion protein). In abnormal situations, this PrPc changes the shape (technically speaking it is
misfolded
) into ‘scrapie’ isoform (PrPSc). In people with mutations within the PRNP gene this misfolding occurs spontaneously. If you eat the brain (as in cases of
kuru
) or you get injected (as in Creutzfeldt-Jakob disease after human growth hormone), the abnormal protein (PrPSc) acts on a normal protein and the normal one is transformed into abnormal protein. It’s a domino effect. How the disease, as in the case of Mad Cow Disease, mutated in humans into variant Creutzfeldt-Jakob Disease (vCJD) nobody really knows. Perhaps passage through an organism (human) different from the original host (cow) somehow change it.”

Dr. Bruno Vincent of the
L’Institut de Pharmacologie Moléculaire et Cellulaire
⁹
tells us: “Prions are strongly supposed to be exclusively composed of one protein named PrPsc (for PrP scrapie) that is an abnormal form of the cellular prion protein (PrPc) which is produced physiologically by mammals and non-mammals—and even yeast and fungi.”

Dr. Vincent adds, “Numerous mutations (that occur randomly) associated with this gene have been reported that lead to the development of spontaneous prion diseases. They confer to the mutated prion protein the ability to form aggregates more efficiently and more rapidly by complex molecular mechanisms. These mutations are rare and account for the so-called inherited prion diseases (genetic forms that are transmitted from parents to children) which represent less than 5 percents of prion pathologies. The remaining cases are either infectious (ingestion of bovine infected meat or cannibalism) or sporadic (that account for 90 percents of prion diseases and for which the cause of PrPc/PrPsc conversion is unknown). The notion of ‘strains’ (several infected brain tissues display distinct incubation times and pattern of neuropathology when injected to mice) is even more puzzling if we referred to the ‘protein only’ hypothesis. This is not due to PrP mutations and is currently under intense investigation in numerous laboratories.”

I asked Dr. Bruno to speculate on whether a prion disease of this kind could be combated. “Numerous pharmacological agents have been shown to slow down or reverse PrPc/PrPsc conversion. Most of these compounds display anti-aggregate properties and prevent the beta-sheet structure of PrPsc. However, the most promising therapeutic against these pathologies is undoubtedly vaccination. Considerable progress has been made in this direction, and, optimistically, a vaccine against prion diseases should be available in the forthcoming fifteen years. Another strategy that could prove useful is to target the cellular prion protein (PrPc) with either PrP RNA antigens or small double-stranded RNA (also called RNAi). In either case, the normal protein is extinguished and the abnormal PrPsc form can no longer replicate because of the lack of the ‘matrix.’”

I asked Dr. Gerstman to help us understand what a “plague” is: “The term
plague
is used in various ways. There is a specific zoonitic disease called plague—the disease that wiped out half of some European populations in the Dark Ages. With this said, I think ‘plague’ is also used loosely to refer to an epidemic that incites fear.” He goes on to discuss the popular view of what an epidemic is. “This depends on the nature of the epidemic. The term
epidemic
is general. An ‘HIV epidemic’ is quite different than an ‘epidemic of teen pregnancies.’ However there are many highly contagious diseases. When environmental conditions are right, just about any contagious disease can spread rapidly.”

If it spreads too fast, it’s an epidemic; if it crosses national lines, it becomes a pandemic.

The Zombie Factor

If zombies could come about as a result of a prion disease, how could the disease be stopped? I put this question to my experts.

Dr. Liberski says, “There is no treatment. Certain drugs can interfere with the conversion of normal into abnormal protein, but they are not very efficient. But if you stop the conversion, perhaps the disease can be cured. The goal has not been achieved, however.”

Dr. Vincent, however, says that there are some advances in “nonzombie” prion diseases. He explains, “The recently described human variant of Creutzfeldt-Jakob disease due to the ingestion of contaminated bovine meat as well as the now eradicated Kuru disease which emerged some decades ago in the Fore linguistic group of the eastern highlands in Papua New Guinea and was due to ritualistic cannibalism are the proofs of such a possibility. Thus, the oral route is one way to inoculate humans with prions. Injection in blood is another way to acquire prion diseases since some people contracted Creutzfeldt-Jakob disease following intravenous injections of contaminated growth hormone prepared from bovine hypothalamus. However, we must take into account that both routes in those cases carry small amounts of infectious prions that lead to disease after a long period of time.”

Both doctors maintain that a cure or treatment is not certain and carries with it some considerable risks.

I asked if humans could be inoculated in some way against transmissible prion diseases, but Dr. Liberski didn’t think so. “You must remember, however, that prion is a misfolded
normal
protein. A vaccine would hurt
all
forms of that protein.”

Many of the zombie stories talk about an “experimental” pathogen that accidentally escapes a lab. I asked Dr. Vincent to comment on whether a prion could be modified or combined with other pathogens to form a more dangerous pathogen. “Of course it would be feasible to combine prions with other pathogens by laboratory process. However, one should keep in mind that the time-course of prion pathologies following infection could be very long (from several months to 30 years in humans). Thus, prions are far from being a short-term weapon and could at best represent a time-bomb.”

In fiction we have the advantage of considering science somewhat elastic. We can speculate that a laboratory has been working on just such an advanced prion disease and our patient zero was a test subject who escaped. We can also speculate on prion research specifically designed to speed up the infection process, down from months or years to hours. That might be within the limits of possibility, but Dr. Vincent says that the superspeed infection shown in
28 Days Later
and the
Dawn of the Dead
remake are not possible. “On a scientific point of view, the immediate change observed in infected people in zombie-themed films is absolutely impossible whatever the infectious agent considered. If the contamination state (by viruses, bacteria or prion) is effective immediately, it takes time before the symptoms appear: several hours to several days for the most virulent pathogens.”