For as long as there have been humans, there have been human parasitic worms. These opportunistic organisms seek shelter and sustenance in our warm, inviting bodies as part of their reproductive lifecycle. While they take up residence, which can be anywhere between a few weeks to a few decades, they happily graze on the green pastures of our lower intestines, reproduce and lay eggs (which get expelled from the body).
But it’s not just a give and no take relationship, as scientific research can attest to. While in residence, these worms regularly interact with the immune system. Our immune system is an army of cells responsible for identifying and destroying foreign invaders like bacteria, viruses and parasites. One of the remarkable things about parasitic worms is that rather than being identified as a typical infectious agent (and removed accordingly), they somehow suppress this immune response and carry on with their lives largely undisturbed.
So how do worms suppress the immune system to fly under the radar? It’s a question of great interest to scientists like Professor Graham Le Gros, Director of the Malaghan Institute of Medical Research.
"Hookworms are masters at dampening down the human immune system in ways we’re only just beginning to understand," says Professor Le Gros. "This offers huge therapeutic potential. Inflammatory and autoimmune diseases are characterised by an overactive immune system, so subduing this response is an obvious line of treatment. We want to better understand how these hookworms modulate the immune system and how we might manipulate this effect in a positive way to treat a range of diseases."
With this in mind, the Malaghan Institute has embarked on a landmark clinical study to investigate what these ‘beneficial’ worms are doing while they set up shop in healthy volunteers.
The Malaghan Institute hookworm clinical study
So far, the clinical study team has treated six initial participants – from a pool of volunteers who, for various reasons, are keen to help make a difference for those suffering from allergic conditions. Each volunteer is given 20 worm larvae via a patch on the inner arm. The juvenile worms then burrow through the skin, which feels like a mild itch. By the time the worms arrive at the gut they’re mature adults, ready to live out the rest of their days attached to the walls of the lower intestines.
“All participants are showing the hallmark signs of successful infection,” says Malaghan Institute Head of Laboratories Mali Camberis, lead investigator of this study. “It’s a little early to see whether or not these worms will take up a more permanent residence in the gut, but we’re hoping to see this happen soon. Likewise, it’s too early to see any significant changes in our volunteers’ health profiles, but early indicators point to an increase in immune cells associated with parasitic infection, which is a good sign.”
Throughout the course of the study, participants will be regularly examined by a doctor to ensure their worms aren’t negatively affecting their health. They’ve been given a very low dose of worms, much lower than what would make the host sick, and since these worms can’t replicate inside the body, there’s no risk of that number increasing.
During the infection, the research team will collect samples from the participants. By monitoring changes to things like metabolites, antibodies, gut bacteria and immune cells, the team are hopeful that data generated from this study will point to future therapeutic application.
The study is expected to last at least 12 months per participant, with the team aiming to treat up to 15 individuals. Once finished, participants will be given the option to remove their worms by simply taking a pill, or they may choose to keep their new-found friends, as several participants have already indicated.
As to where this research may take them, the team say it’s too early to tell which allergic diseases may benefit from parasitic worms. Likewise, they can’t speak for people who suffer from chronic allergic disease and use worms as a way to self-medicate.
“There are many people who are living with severe allergic conditions that cause life-long suffering,” says Prof Le Gros. “Many turn to self-medication with parasitic worms to manage their symptoms. The problem is, is that many are getting these ‘products’ from unverified sources, in often dubious circumstances, and we don’t know what these worms are doing to the body at a fundamental level. It may be placebo, or there may be significant benefits, but so far it’s all anecdotal.
“We want to get hard evidence behind what these worms are doing in the body, and shine a light on what’s really an exciting area of research with a lot of potential.”
Hamish Cameron, Science Communicator at the Malaghan Institute