Written by Himanshu Kaul from the Zandstra lab, Michael Smith Laboratories.
Follow Himanshu on Twitter @HDKaul.
Asthma afflicts over 300 million people worldwide. In a recently published article in Immunity, researchers suggest that the microbes in our bodies can play a critical role in regulating asthma. This review article presents and discusses evidence of how our microbiota can mediate asthma.
“The microbiota consists of all of the invisible microbes in and on our body surfaces,” says Rozlyn Boutin, a co-author on the review and a graduate student in the laboratory of Dr. Brett Finlay. “Though it primarily includes bacteria, there are a host of other organisms such as fungi, viruses, and archaea that make up our microbiota.” While the cell is the functional unit of human life, it is estimated that we have as many non-viral microbes in and on our body as cells. Boutin adds, “The number of non-viral microbes is further dwarfed by the number of viruses in and on our bodies.”
Protecting the body with ‘good’ bacteria
There is an increasing appreciation of how our microbiota impacts human health. Typically, these microorganisms are not harmful, rather, they are quite central to the optimal functioning of the human body. The article highlights how bacteria tend to be protective in nature and can induce beneficial immune responses. However, in disease, certain strains of the ‘good’ microorganisms – whether it is bacteria, fungi, or viruses – get wiped out, allowing the inflammatory phenotype to prevail and promoting an allergic reaction in the case of asthma. An initiative called the Human Microbiome Project, launched by the National Institute of Health in the USA, aimed to characterize the microorganisms found in both healthy and diseased humans.
Fungi are part of the microbiota too
The role of gut bacteria on asthma is relatively well studied. However, this article points to the critical role of the microbiota in other organs, such as the lungs, and particularly other microorganisms beyond bacteria, specifically fungi, in regulating asthma pathology. Boutin emphasizes that lots of epitopes and antigens that trigger allergic reactions in asthma are found in fungi and fungi are also used to induce asthma in animal models.
“Fungal dysbiosis, or imbalance in the fungal communities in the gut, has been found to be a more striking signature associated with the development of high-risk asthma phenotypes in childhood. This is certainly a key message in our article,” stresses Boutin.
Towards treating asthma by addressing the microbiota
If our microbiota is central to mediating asthma, it raises the question of whether we can treat asthma by targeting the microbiome? Boutin suggests that if there is dysbiosis that can be associated with an asthma phenotype, then the disease has the potential to be prevented, especially if the dysbiosis precedes the onset of disease symptoms.
Live Biotherapeutic Products are an emerging therapeutic alternative that work by enabling the colonisation of ‘good’ microorganisms and correcting the microbial imbalance or dysbiosis. Live Biotherapeutic Products have the potential to be beneficial in adults and children according to Boutin. However, before this type of treatment can be considered, researchers must identify the right biomarkers, understand the microbiota-driven cellular and molecular mechanisms underpinning asthma pathology, and include microbiome analyses to determine whether the microbiota features correlate with responses to treatment.
“Currently, we are looking at a very limited snapshot and tons of work still needs to be done in terms of leading to some sort of effective therapy,” explains Boutin. “Though, it is promising to see that the tools needed to undertake this challenge are rapidly evolving.” This thought is further echoed by Dr. Brett Finlay who notes that “It is quite remarkable that we now know that microbes, including bacteria and fungi, found on the body early in life can influence asthma. This is a paradigm shift in our understanding of the disease, and has real potential to develop ways to decrease asthma.”
This article was supported by funds from the Canadian Institute of Health Research, the University of British Columbia, Vancouver Coastal Health, and the Swiss National Science Foundation.