A “pregnancy test” for chest infections?
The technology found in pregnancy tests has some unexpected uses. New research suggests that it could even assess your risk of getting a chest infection.
The science behind pregnancy tests is based on a simple idea — detecting the presence of a hormone (in this case human chorionic gonadotropin or HCG) which is present in pregnant women but absent in the normal menstrual cycle. These steps rely on antibodies, proteins which bind to the target hormone (HCG) and activate a chemical dye which allows you to see, within a few minutes, if you are pregnant or not. More expensive tests can also examine the amount of chemical dye produced and estimate how many weeks pregnant someone is.
So far, so good. But what if this technology could be adapted to detect other health issues you might want to know about?
First, a little background: antibodies are part of the body’s natural response to infection. They are proteins produced by white blood cells with the specific ability to recognise antigens, which are proteins found on the surface of various microbes, such as bacteria and viruses. To put it simply, antigens are luggage tags and antibodies the baggage handlers — once the baggage handler recognises the luggage tag, it decides where to send the luggage to make sure it reaches the right destination. Only, instead of sending them to sunnier climes, these baggage handlers cook up different ways to destroy the microbes, such as swallowing the invading microbe whole (phagocytosis) or smashing it into tiny little pieces (lysis).
Antibodies are versatile and can bind to a huge number of different proteins because their chemical structures are readily modifiable. By changing the part of the antibody which recognises the antigen (known as the epitope), you open up the possibility of having antibodies bind to any known protein sequence ever created — an infinite number of luggage tags, all with different messages on each of them, ready to match up to the right baggage handler.
The incredible ability of antibodies to attach themselves to any protein has greatly expanded the tools available to molecular biologists to understand how proteins work. Engineering antibodies to recognise and bind to any protein you want is now routinely used in labs across the world.
But, in translating these amazing techniques to the real world, a significant challenge remains — finding those unique proteins that can tell us something meaningful about someone’s medical condition and that we can extract from the human body.
Enter neutrophil elastase. This enzyme is part of the body’s immune system and is produced by a type of white blood cell called a neutrophil. It tries to kill bacteria by cutting up the proteins on the surface of their cells. But unlike many other enzymes which do this job, neutrophil elastase only works when you have a chest infection, as it is specifically sent to the lungs to tackle those pesky bacteria and viruses that grow in the lungs. If you find yourself coughing up phlegm, chances are it will have some neutrophil elastase in it.
So we have an enzyme that we know works only in the lungs, which is produced in large quantities when we have a chest infection and can be easily taken from patients — a prime candidate for a new test to diagnose chest infections.
Scientists at the University of Dundee decided to try a new device containing antibodies which detect neutrophil elastase — the neutrophil elastase airway test stick (NEATStik). They found that it works as well as current methods to test patients for chest infections — yet it takes seconds to test and minutes to get a result.
Hopes are high that this test could rapidly diagnose people at risk of a chest infection. Professor James Chalmers, GSK/British Lung Foundation Professor of Respiratory Research at the University of Dundee, explains:
“For people living with lung disease, getting a chest infection is a serious issue which could result in a visit to hospital. We decided to test people living with a condition called bronchiectasis, as these people are more likely than to get a chest infection.
“We found that the NEATStik could deliver far quicker results, as well as giving an indication of how severe the patient’s chest infection would be. To our knowledge, this is the first demonstration of the clinical applications for this test.
“We are excited by the prospect that we could quickly identify the patients who are in most need of urgent treatment. NEATStik tests could save doctors valuable time in assessing patients and give patients greater control by allowing them to check out their symptoms at home.”
This research was published in the European Respiratory Journal and funded by the British Lung Foundation. Read the full paper here.
