Scientists around the world continue to test countless vaccines and drugs in hopes of finding effective ways to prevent and treat COVID-19.
Among the trials going on in Australia is one my team is about to start, looking at something called OM85.
OM85 is not a conventional drug, but a combination of molecules extracted from the walls of bacteria that commonly cause respiratory infections.
It is not available in Australia, but has been widely used in Europe and South America for 40-50 years, usually under the brand name Broncho Vaxom.
We are now looking at its potential to prevent respiratory infections, including COVID-19. But how does it work?
First, a bit of context
Some of our organs, including the skinthe respiratory tract and lungs, and the gastrointestinal tract, are effectively “open” to the outside world. The cells that line these organs, called mucous membranes, are home to billions of bacteria.
These bacteria, known as “microbiota”, play an essential role in keeping us healthy. This is particularly important in the digestive tractwhere the microbiota “trains” the immune system.
One way to do this is to provide a continuous stream of signals which travel through the mucous membranes to the tissues below, where the immune cells are. Specialized immune cells responsible for detecting the invasion of infectious pathogens recognize and respond to these signals.
We now recognize that these signals from the microbiota act as “immune trainers”, helping to keep the immune system’s frontline defenses on high alert.
OM85 is an immune booster
OM85 appears to enhance some important aspects of this natural “immune formation” process. One of the ways to achieve this is to stimulate the maturation of regulatory T cells (called Tregister) in the lymph nodes of the upper intestine.
Once they have reached full maturity, these Tregister can migrate to other mucosal surfaces of the body to strengthen local anti-inflammatory defenses. This process is particularly important in the lungs and respiratory tract to prevent respiratory infections.
OM85 signals are also leaking in our traffic. There they are recognized by bone marrow cells, which control the production of other types of immune cells.
This results in an increase in immune cells – both in number and function – that move to frontline mucosal surfaces, including the airways, to further bolster our immune defenses.
We strongly suspect that OM85 also influences the composition of the gastrointestinal microbiome itself, although we know very little about how this happens. This in turn helps promote the survival of bacterial strains that stimulate the immune system.
What the evidence tells us
OM85 is a preventive medicine, given to people at risk of more serious consequences of respiratory infections, rather than as a treatment for current infections.
Studies have shown that OM85 reduces the risk of infection-related wheezing in infants and schoolchildren.
It also reduces the incidence of severe flare-ups of chronic obstructive pulmonary disease in adults.
A exam of 35 placebo-controlled studies involving 4,060 children concluded that immune stimulants, including OM85, reduced respiratory infections by an average of 40% in susceptible children.
OM85 has a good security profile. A small proportion of people may experience gastrointestinal upset, but in clinical trials, like the one we conducted in infantsside effects are rarely observed.
So why not use it more widely?
No request has been made to bring OM85 to Australia. We are a small market that is not necessarily attractive to drug manufacturers.
In countries where OM85 is available, doctors can prescribe it, but people can also buy it without a prescription, in the same way as a complementary medicine or dietary supplement.
OM85 was met with a great deal of skepticism in its day, with some people viewing it as “snake oil”.
Scientists are skeptical when we don’t understand why something works, or at least when we don’t have a plausible explanation for how it works. The idea that something swallowed but not absorbed could protect the lungs seems fanciful, especially without solid explanations.
But as we begin to better understand the mechanisms that may explain how OM85 works in the body, and with the accumulation of clinical evidence, we have good reason to be open to exploring its potential further.
What we will do during the trial
Healthcare workers are susceptible to serious respiratory infections associated with other viruses, including influenza, which can cause them to miss work.
We plan to give 1,000 OM85 health workers, half immediately and the other half delayed for three months.
To understand how OM85 works, we will take blood samples and test immune responses.
We will determine which virus caused the respiratory illnesses when sick (COVID-19 or otherwise), whether the immune response is different depending on the virus, and whether OM85 is equally effective against all respiratory viruses encountered.
The trial is due to start this month and the first results should be available by November.
