9 November 2018
An unexpected find by the parasitic disease team has added weight to evidence pointing to the potential human health benefits of certain species of parasitic worm.
The research, published in Mucosal Immunology, found that the presence of intestinal parasites provides long-lasting protection against infection from other species of parasites in other organs. The finding appears to contradict traditional understanding of parasitic worms acting to dampen the immune system, which would predict weaker protection from later infections.
“We found that, quite unexpectedly, if you infect with a gut worm prior to infecting with a hookworm, which migrates through the lung, the gut worm protects against the hookworm infection,” says Dr Kara Filbey, whose paper was the culmination of four years of research.
“Previous work with these gut worms shows that they’re immune-suppressive – the worms induce immune regulation to protect themselves within the body, which can also dampen the response against allergens. For that reason, they’re widely used in autoimmune and allergic disease research. Therefore, we would have predicted that the immune response against the migrating hookworm larvae would have also been suppressed.”
But rather than benefitting from a suppressed immune response, the lung hookworm was quickly killed in the host, with the gut worm remaining. What was perhaps even more intriguing was that the gut worm induced this response in the lung, without ever leaving the host’s gut.
“What’s amazing is that this gut worm spends its whole life in the gut,” says Dr Filbey. “It’s not going anywhere near the lung, but it’s inducing protective mechanisms in this distant organ, and we set out to understand how and why it might have evolved to do this.
“By selectively activating immune cells in the gut which circulate around the body, lodging themselves in different organs, the immune system is primed to act quickly if another worm shows up. Even if you remove the gut worms entirely, those activated cells remain in the body, waiting to protect against a new infection.”
The findings suggest that as well as playing a role in protection against allergic diseases such as allergy and eczema, parasitic worms may also help protect the body from infectious disease. This work opens doors for future research, including whether we’re moving towards a future where living with a ‘friendly’ parasite could protect against infection and autoimmune disease.
However, Dr Filbey explains that it’s not so simple: “You have to look within the context of human health and the bigger picture. In places where worm infection is endemic alongside a range of other diseases and health conditions, the risks of worm infection probably outweigh any potential benefits. Not all worms are created equal, and there are several species that can cause a range of debilitating diseases in humans.
“But you do have to consider what it means to get rid of worms entirely. Will it negatively affect immune response to other things? Consider allergies. It’s well established that people living with worms have less severe allergic responses, which then increase if you remove the worms with drug treatment.
Dr Filbey says there are several groups around the world trialling controlled human worm infection as a treatment for some serious inflammatory diseases.
“Understanding the immune responses triggered by worms is an important area of research, and we still have much to learn.”
Filbey KJ, Camberis M, Chandler J, Turner R, Kettle AJ, Eichenberger RM, Giacomin P, LeGros G (2018) ‘Intestinal helminth infection promotes IL-5- and CD4+ T cell-dependent immunity in the lung against migrating parasites’ Mucosal Immunol
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