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Not all Viruses are Villains

As a viral load builds up in a cell, the host cell is altered, killed, and illness ensues. But what sort of illness depends on the sort of virus. Some viruses cause completely benign conditions such as the common cold, whereas others can be life-threatening, as in the case of COVID-19.

Viruses, by and large, are nasty little organisms. Biologically, they are relatively simple, consisting of nothing more than bits of genetic material wrapped in a protein coat. They can reproduce, which is one of the hallmarks of life, but there is debate about whether or not viruses can be classified as living creatures. Why? Because they cannot reproduce on their own. They are, however, very adept at invading living cells, inserting their genetic material into the cell’s reproductive machinery and forcing it to crank out more viruses. As the viral load builds up, the host cells are altered or killed, and illness ensues. What sort of illness? Well, that depends on the sort of virus. Some viruses may do no more than annoy with benign conditions such as warts, the common cold, or chicken pox. But others can devastate health by triggering smallpox, rabies, cervical cancer, AIDS, and of course, COVID-19.

Should anyone then be surprised that eyebrows were raised when the Food and Drug Administration in the U.S. approved the spraying of a viral cocktail on certain meat products, such as hot dogs and sliced cold cuts? Actually, to say that this has raised eyebrows is an understatement. Some activists, who already regard the FDA as a public enemy, went into frenzied mental gyrations at the prospect of adding viruses to our food supply. Genetic modification is bad enough, they proclaim, but a callous FDA has thrown all caution to the wind regarding food safety. Are they right?

Well, there are viruses, and then there are viruses. Some can infect human cells, others can only attack bacteria. And this is the crux of the matter. The “virus cocktail” approved by the FDA only invades bacteria, and more specifically, only Listeria monocytogenes. And this is one nasty bacterium. Named after Joseph Lister, the British surgeon who first recognized the need to keep microbes out of the operating room, Listeria can turn up in our food supply and cause a great deal of human misery. The bacteria lurk in the soil and in vegetation, so it is easy to see how they can find their way into animals and humans. Unpasteurized milk, soft-ripened cheeses, raw and smoked fish, uncooked hot dogs, cold cuts and raw vegetables can all harbour Listeria.

Once they infect the body, these microbes can be pretty wicked. Lucky people may get away with no more than flu-like symptoms, fever, headache, vomiting, cramps and a touch of diarrhea. But if you are unlucky, the bacteria can vend their way into the bloodstream and cause blood poisoning (septicemia) or, if they invade the brain or spinal cord, meningitis. These conditions can be lethal if not appropriately treated with antibiotics. The young, the elderly, the immune-compromised, and pregnant women are most susceptible to infection. Listeriosis in early pregnancy can cause a miscarriage, later, a stillbirth, which is why pregnant women are often advised to stay away from foods such as sliced packaged meats. To complicate matters further, a victim may not easily connect the symptoms of listeriosis to food because these can present anywhere from a couple of days to three months after consuming a contaminated product. And to top off the concerns, Listeria constitute one of the few bacterial species that can multiply at refrigerator temperatures.

Obviously, controlling Listeria in our food supply is of great importance. Washing vegetables well, cooking meat products thoroughly and avoiding unpasteurized milk (forget the unsubstantiated health claims about the benefits of raw milk) can go a long way, but cannot eliminate all risk. After all, we don’t wash our sliced turkey or chicken after opening the package. And this is where viruses can help. Specifically viruses called “bacteriophages,” the name coined by their discoverer, Felix D’Herelle, from the Greek “phagein,” meaning "to eat." Actually, although Montreal-born D’Herelle gets credit for the discovery, he was not the first to observe these” bacteria-eating” organisms.

As early as 1896, British physician E. Hanbury Hankin passed water from the Ganges River through a fine porcelain filter and noted that the filtrate had antibacterial properties. About twenty years later bacteriologist Frederick Twort actually managed to isolate microscopic entities that destroyed bacterial cultures but never pursued the work. Then in 1917, along came the remarkable French-Canadian, Felix D’Herelle. He had no formal education but managed to set up a laboratory in his home and trained himself as a microbiologist with numerous interests, including the development of yeast strains to make cheap whisky from rotting fruit. His major discovery came when working as a volunteer at the Pasteur institute in Paris, he was asked to investigate an epidemic of dysentery that was raging in a cavalry squadron.

D’Herelle didn’t know exactly how the disease was spread, but suspected that it was through fecal matter. He took samples from the soldiers, placed these in a filter with microscopic pores, and passed water through. The idea was to see if the filtrate had any sort of infectious agent. Much to D’Herelle’s surprise, not only was the liquid free of any such substance, when mixed into a bacterial culture, it caused the formation of clear spots, indicative of bacterial destruction. "In a flash I had understood: what caused my clear spots,” D’Herelle later recalled, “it was in fact an invisible microbe... a virus parasitic on bacteria."

D’Herelle managed to isolate these parasitic viruses and suggested they could be used to treat bacterial infections in humans and animals. Some early successes inspired George Eliava, a colleague of D’Herelle’s at the Pasteur Institute, to return to his native Georgia and with D’Herelles’ help, set up a “bacteriophage” institute. Indeed the Eliava Institute has become a world leader in phage therapy, producing a great deal of research which has basically been ignored in the West. But now bacteriophage preparations may help us control the spread of Listeriosis. Human cells do not have receptors for these viruses, so we cannot be infected. In fact, we are exposed to them all the time; bacteriophages are found wherever bacteria are found, in the soil, in our water, in our food. There are some concerns that viral proteins may cause allergies or that the viruses may affect some of the beneficial bacteria in our gut. Those concerns are theoretical. Here is what is factual: more than 500 people a year in North America die from listeriosis. Bacteriophage treatment can help reduce this. So you see? Not all viruses are nasty.


@JoeSchwarcz

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