Four gut bugs prevent asthma

The presence of four strains of intestinal bacteria might make the difference between a child breathing easily and developing lifelong asthma. Brett Finlay from the University of British Columbia explained his findings to Chris Smith...

Brett - Really, this is the first time we can actually demonstrate certain microbes influence asthma. We did this in children. We've had 319 children from across Canada that were already being studied from birth to age 5. What we did is we collected the faeces from these children at 3 months of age and 1 year of age. And then we began to analyse the microbes in there. Initially, we didn't see any gross differences either at 3 months or 1 year in the total bug population. But when we dug really deep, we started to see signature microbes and we quickly zeroed in on 4 microbes and we abbreviated these things FLVR. This is the first letters of their complex microbial names. The bottom line of this whole study was that if you had these 4 microbes, in your intestine at 3 months of age, you basically had a very decreased risk of asthma. If you didn't have these microbes, or had low level of these microbes, you had a much higher risk of asthma and those kids have now all gone on to develop asthma.

Chris - Now, is this biologically plausible though? Is there some way you can tie the presence or absence of those 4 specific strains of microbe to subsequent asthma or wheezing in these children?

Brett - Right. So there's a strong correlation and we also looked at some of the molecules that might be influencing asthma and there's things called short chain fatty acids which affect  inflammation which could be related to asthma. But I think that the experiment that proved these microbes actually have a role is we took mice and these are what we called 'germ-free' mice, they're born sterile by C-section. They have no microbes in them period. We then took the faeces from a child at 3 months of age. We know that child actually went on to get asthma later in life. We took their child faeces and then put it into these microbe-free mice plus or minus these 4 microbes that we grew in the lab. And the we induced experimental asthma in these mice later in life. What we found is that when you add these 4 microbes, these mice basically don't get experimental asthma. So, those 4 microbes alone in human faeces prevented asthma. So, that's the best correlation we've got so far of proving these 4 actually have some kind of role in influencing asthma.

Chris - So, how do you therefore account for the fact that we get these microbes very early in life by 3 months, they may or may not be there or even earlier? Yet, the asthma problem doesn't kick in until much later. So, how do you account for that time lag if these bacteria are playing a role in the development of the condition?

Brett - What we know is that - and this has really come in the last few years is that the gut microbes play a very central role in how our immune system develops very early in life. And what we think and we've proven it in mice but not in children yet, is that these microbes were actually playing a role in how the immune system is developing in these children and setting it up whether it's going to be allergic or not very early in life. And we think these microbes are pushing it towards a less allergic type immune system. If you don't have these microbes, it will then trend towards more allergic-type system which then leads to increase in asthma later in life. It's not just limited to asthma. We're finding these microbes play a central role in the immune system which affects all sorts of diseases and this is now coming out in many different fields, showing the early life microbes play a central role in how we actually develop immunologically.

Chris - So, would one strategy be to - now you've identified these 4 that seem to be critical players to come up with some kind of supplement that's got them in, rather like a probiotic yogurt for babies that would, if you put these into the babies, reduce their risk of getting asthma regardless of those other risk factors like having a caesarean delivery or not being breast fed.

Brett - Yeah. I think that the two implications of this paper are that one, we can detect children at high risk for asthma at 3 months. So we can go in, look for these 4 microbes and then say, you look you're at risk for asthma. But that doesn't really help the kid all that much. What you could do is, okay, if you have a child that's at risk, you could say, well, maybe you should get a pet and expose your child to more environmental microbes. But what we are really trying to work on now is to deliver these 4 microbes as a probiotic type combination to children that are at risk. So, a 3-month old baby is a very fragile being and would not like to put willy nilly all sorts of different microbes into these very early kids. If we can show you a child at risk, we know that you have a much higher chance of asthma. If we can prove these 4 microbes are safe, we could then think of then adding them back to the child or for example if a 3-month old has a very severe infection and has to be treated with antibiotics. Maybe post antibiotic treatment, we could come in and supplement them with these microbes to then reduce the risk later in life of these types of diseases.