New discoveries raise hope for the development of a cure for the "mad cow" disease, and will make it possible to determine whether the disease is indeed transmitted to humans by eating beef
The growing fear of humans contracting the "mad cow" disease in Britain this week caused anxiety among red meat lovers all over the world. We were informed of the possibility that more than ten million heads of cattle would be destroyed, with tens of billions of dollars in damage. Israel has not imported beef from England for years, and McDonald's has stopped serving meat from the infected islands. An emergency situation of this kind requires a thorough understanding of the non-simple biological phenomena involved. Most of the diseases known to us belong to one of two main types. The first type includes diseases caused by an external "agent", for example a bacterium or virus, which invades the body and disrupts its normal functioning. The second type is "independent" internal malfunctions of the body, such as genetic diseases that are inherited from parents to their offspring. There is also an intermediate type: diseases that are "sown" by an external factor, but in the Mishkan complex internal processes occur that do not depend on the initial factor. Thus in cancer, the early cause is exposure to radiation or a poison (cigarette smoke, for example), which creates a change in the DNA (hereditary material) of one cell. Later, the mechanisms of cell replication work in a distorted way and uncontrolled division begins, causing a malignant tumor. Another important example of the intermediate type is autoimmune diseases, such as multiple sclerosis. Here it is suspected that a small damage to the tissue due to an external factor triggers a "mistaken" immune response of the body against itself, and the result is the destruction of cells and tissues. The "mad cow" disease belongs to this intermediate type, but it has a peculiarity.
Until recently, it was accepted that the brain degeneration disease of cows and sheep, whose rare equivalent in humans is called Creutzfeldt-Jakob disease, is caused by a slow virus, which attacks the nervous system in a process that lasts for many years. It was found that the damage caused to the brain is irreparable and that the symptoms are somewhat similar to those of the neurodegeneration in Alzheimer's disease. But the researchers were unable to collect actual evidence of contagious transmission, except for one case: in New Guinea, where a sister disease called Kuro was common, infection was proven due to eating human brains in cannibalistic rituals. Interestingly, in clear contradiction to the virus theory, cases were observed among Jews from Libya (in the research of Dr. Ruth Gavizon from the Hebrew University) in which a similar disease is transmitted through genetic inheritance. Untangling the resulting tangle requires a look at the attack mechanisms of viruses. Each virus contains hereditary material, DNA or RNA, surrounded by a protein coat. While the envelope is only used to store the DNA and attach to the attacked cell, the direct cause of the disease is the hereditary material. This fits into the cell's genetic program and forces it to produce new viruses, which destroys the cell and spreads the tiny parasites everywhere. The particle that causes brain degeneration in sheep and laboratory animals was tested with the utmost rigor, and it was found that it consists of protein only and does not contain any hereditary material at all! This result caused a storm in the scientific community and raised one of the most intriguing questions ever faced by biologists: How is disease transmitted by protein alone? Since the entity that causes the disease in animals and humans is fundamentally different from ordinary viruses, it was given a special name - prion. It is known that a foreign protein that enters the body breaks down quickly, and if it does not bring quick death, as in the case of snake venom, it cannot cause damage over months and years. This is in contrast to foreign DNA, which can exist for years and even generations, due to its miraculous ability to replicate. How, then, is fertility in the brain maintained and even multiplied and passed from one creature to another?
It was clear from the first moment that the prion protein is not capable of independently producing copies of itself from building blocks (amino acids). Because as far as science knows, only DNA and RNA fragments are capable of a process in which one string of chemical units (bases) dictates the creation of an identical chain of similar building blocks. The information in the protein is dictated by the DNA bases, which for him are a kind of architectural plan. Indeed, it was discovered that the prion is no different from any other protein in the human body and it is encoded in its own normal gene - the segment of DNA that encodes the prion and dictates the order of its "beads". The healthy brain cells produce the product every day in many copies. Then, rarely, in a process whose details are still being elucidated, the completed fertility string may change and move into a new spatial structure, causing the disease. The transition from the normal form of fertility to the "sick" one is similar to the change that begins in an umbrella when it flips upwards in a strong wind. It is difficult to change the normal form of fertility to a sick one, but when this happens, the way back is also difficult. It is important to note that this is a relatively rare phenomenon and that most proteins exist mainly in one form of structure, as long as they have not undergone a chemical change or been linked to another entity. A key discovery in the field of prions was that a few copies of a diseased prion are enough to catalyze a process in which the other normal copies of the prion become morbid, a phenomenon called autocatalysis. Thus, if one morbid particle penetrates the brain from the outside (or is formed within it), it will in time lead to the creation of many like it. Although the morbid fertility does not dictate the creation of another morbid fertility in the manner of viral replication, its ability to bring about a transformation in normal fertility explains the "snowball" of the spread of the disease. The rare case of genetic transmission in Libyan Jews is explained by the fact that, due to an innate genetic mutation in these people, the first spontaneous reversal of fertility occurs in them with a higher probability, so that the disease appears in several family members even though there was no external infection. The discovery of the connection between the prion particles and degenerative diseases of the brain, and the understanding of the infection process by a pure protein without the involvement of genetic material, are among the outstanding achievements of molecular biology in recent years. For these discoveries, this week in the Knesset, by an interesting coincidence, the prestigious Wolf Foundation Award was awarded to Prof. Stanley Prusiner from the University of California in San Francisco. His discoveries led to a comprehensive understanding of the disease and inspire hope for the development of a cure for it in the foreseeable future. This understanding will also soon make it possible to decide whether the disease is indeed transmitted to humans by eating beef. The researchers have no doubt that the English cows were infected with prions from feed containing the brains of infected sheep. It is also clear that the recent appearance of about ten cases of Creutzfeldt-Jakob disease in young people, something that has not been observed until now, points to a new source of the disease.
Tens of thousands of cows infected with "mad cow" disease throughout the UK are a very possible source of infection. It is also known that the fruit particles are relatively resistant to environmental stresses, and infection by eating meat, even if partially cooked, is not unreasonable. Hence there is a real fear of danger in eating beef from Britain, and it is possible that more people have already been affected and will be found blue in years to come. The hope is that by then a solution to the problem will be found. Opinions were heard that the scientists are to blame for everything - they are the ones who convinced the cattle breeders to switch to artificial feed containing proteins from sheep's brain. Catergists must remember that strange and new diseases appear from time to time, but it is a coincidence that a change in nutritional habits in the barns was the cause in this case. On the other hand, without the basic research that led to an in-depth understanding of the unique and interesting mechanism of prions, we would not have had a clue as to the origin of the disease of brain degeneration in humans, certainly there would have been no hope for diagnosis, prevention and cure. In the overall calculation, basic science came out again this time and had the upper hand when it comes to understanding diseases and the possibility of eradicating them.
