The Upside of Food Poisoning

A QUANTUM OF SCIENCE

In the future, food poisoning might keep you from developing cancer

Food poisoning occurs when a microbial pathogen enters the food supply and multiplies, leading to a high enough concentration of viable cells to cause an infection when the food is consumed. Most frequently this is a gastrointestinal infection, leading to nausea and diarrhea as the body tries to flush the invader out of its system. In severe cases, especially among the very young and very old, severe cases of dehydration can result in death. This was the case during the recent outbreak of Salmonella in peanut butter, where hundreds were sickened around the US. But is there any upside to food poisoning?

Surprisingly, yes. One particular food-borne pathogen is a common bacterium known as Staphylococcus aureus. Most strains of this microbe are harmless and actually help protect you by competing with the more sinister strains and effectively out-growing them. A few strains are deadly, however, such as the growing frequency of hospital infections of MRSA (multiply-resistant S. aureus, strains that are resistant to all but the newest antibiotics). In between these two extremes are those strains of S. aureus that produce a special protein called staphylococcal enterotoxin. This protein, belonging to a class known as superantigens, is the immune system equivalent of shouting "BOMB!" in an airport. All the body’s defensive systems are activated and a red alert is sounded, sending active T-cells scrambling to produce antibodies and hopefully fight off whatever invader has come calling. But recent research has shown that this is not always a bad thing, at least in small, controlled doses. Enterotoxins have been shown to stimulate the immune system in novel ways, even to generating protective antibodies against unusual targets – targets such as the body’s own cancerous cells.

In their review article "Superantigens: The Good, the Bad, and the Ugly," researchers at Duke and the University of Florida tested the protective effect of superantigens when healthy mice were vaccinated with melanoma cells that had been chemically inactivated – making them unable to grow and become tumors, but allowing the mouse immune system to make antibodies against them. Some of these mice were then given a dose of superantigen (equivalent to a case of food poisoning, roughly speaking) and all the mice were exposed to live, infective melanoma cells. The usual result of this is death after 14 days from massive skin cancer tumors. In this study, however, the results were startling: 100% of the untreated mice in the study expired after 14 days; 100% of vaccinated mice after 17 days; but after 136 days only 40% of the vaccine+superantigen mice had expired, and none of these mice displayed any sign of melanoma tumors. The mice who survived to this stage were given another dose of live melanoma cells and 80% of them survived for another 50 days, showing that the protective antibodies were now a permanent part of their immune repertoire.

Does this mean you should go eat some potato salad that has sat at room temperature on the counter overnight? Well, no. First of all, only the T-cells that are actively making antibodies are stimulated by the superantigen; all others are switched off, the better to concentrate the body’s resources on making protective antibodies. This means that unless you are currently being exposed to an invader and making antibodies against it, receiving a dose of superantigenic staphylococcal enterotoxin isn’t going to do you any good (and while food poisoning won't kill you, the symptoms are far from pleasant). On the other hand, superantigen therapy has the potential to help the human body fight off infections that even modern antibiotics are helpless against. Imagine a patient infected with MRSA – now, his own immune system could be revved up by administration of superantigen and potentially mount a much stronger offense against the current, active infection. The irony here is that MRSA is also a member of the S. aureus species from which the superantigenic enterotoxin is derived, meaning that the invader itself has helped teach us how to fight off its more virulent sibling.

The potential for superantigenic anti-cancer vaccine therapies in humans is still a ways off, but not so far that it cannot be seen. Many researchers are looking for the most effective way to balance the protection gained from superantigenic treatment against the potential harms – which include a range of autoimmune diseases (such as multiple sclerosis and other degenerative disorders). Clearly the potential exists to improve human health and longevity against one of the most prevalent causes of mortality; and with a healthy dollop of caution, the downside of superantigens can be avoided.

Pass the potato salad.



Want to know more? Full text of the cited article can be found here:

http://www.ebmonline.org/cgi/reprint/226/3/164


© A Quantum of Science / Peter Smalley, 2009
Redistribution with attribution is appreciation!