Are Viruses Keeping us Healthy?
Once found killing bacteria in the faeces of World War I soldiers, the viruses known as bacteriophages, or more simply, phages may have a new role within the human body.
Science writes, with a new study suggesting that people absorb up to 30 billion phages every day through their intestines, scientists have been left pondering whether they might be influencing our physiology, by regulating our immune systems.
Researcher Jeremy Barr, from Monash University in Melbourne, Australia, explained, “Basic biology teaching says that phages don’t interact with eukaryotic cells.” But, he now believes that statement is absolute rubbish.
His work shows that phages might naturally help protect us from pathogens. Studying animals ranging from corals to humans, he discovered that phages are more than four times as abundant in mucus layers, for example, the ones that protect our gums and gut, as they are in the adjacent environment. The protein shell of a phage can in fact, bind mucins, large secreted molecules that together with water, make up, mucus.
Being able to stick to mucus allows the phages to obtain more of their bacterial prey. In a series of in vitro studies, the viruses protect the underlying cells from potential bacteria pathogens, providing an additional layer of immunity.
Since then he has found evidence that these viruses can travel from the guts mucus into the body. In a petri dish, his team demonstrated that epithelial cells such as those that line our guts, lungs, and the capillaries surrounding the brain take up phages and transport them across their interior. Although the transport mechanism remains unknown, the researchers spotted the viruses enclosed in vesicles within the cells.
Even more interestingly, the cells took up phages on the side that in the body faces outward. From the rate at which the epithelial cells took up phages in the lab, the researchers estimated that a person might absorb up to 30 billion in a day.
Molecular biologist, Krystyna Da Browska of the Polish Academy of Science’s Institute of Immunology and Experimental Therapy in Wroclaw, explains however, that a lab dish is very different from the gut of a living animal.
If phages do manage to get into our tissues, what do they do when they get there. A few studies have addressed this, one in particular led by Dr Browska claimed that a specific type of phage can bind the membrane of cancer cells, reducing tumour growth and spread in mice.
Barr believes that in humans, a steady influx of the viruses creates an “intrabody phageome,” which may modulate immune responses. Work by Belgium-based researchers may support this idea. A group led by immunologist, Herbert Virgin at Washington University of Medicine in St. Louis in Missouri discovered that people with two autoimmune conditions, type 1 diabetes and inflammatory bowel disease, have altered gut phageomes.
With Barr speculating whether the phageome may alert the immune system to the presence of potential pathogens, once scientists understand the role of the human phageome, they can begin learning how phages could be used to manipulate the bacterial communities within our body and potentially even control our own cells.