A respirator instead of a fluorogram
Scientists from Pushchino have developed a way to diagnose tuberculosis by breathing
Scientists from the Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences, in collaboration with colleagues from the Central Research Institute of Tuberculosis and with the support of the Russian Science Foundation, have developed a method for noninvasive diagnosis of tuberculosis at an early stage through the air that a person exhales. Their article was published in the Journal of Breath Research (Morozov et al., Non-invasive approach to diagnosis of pulmonary tuberculosis using microdroplets collected from exhaled air).
"In this study, for the first time, we were able to non-invasively collect samples of pulmonary fluid from exhaled air and detect antibodies specific to the so-called secreted antigens of mycobacteria that cause tuberculosis in the samples. Of course, we were all vaccinated against tuberculosis in childhood, but it is precisely such antibodies that do not appear in humans during vaccination. The antibodies that we find in the samples appear if mycobacteria that secrete these antigens multiply in a person's lungs. They can also be observed when a person has been caring for a tuberculosis patient for a long time and received this antigen from the outside," said the head of the study, Viktor Morozov, head of the laboratory of nanostructures and nanotechnology at ITEB.
Tuberculosis has two forms: latent and active acute form. Carriers of tuberculosis are about a third of the world's population. These people are infected, but they do not develop the disease in an acute form and they do not infect others. When tuberculosis becomes active, its symptoms, such as cough, fever, changes in the lungs that can be seen on an X-ray, may not appear immediately, so that at an early stage the patient may already be contagious, but not yet notice his illness.
Tuberculosis is caused by mycobacteria, intracellular parasites that live in macrophages. Macrophages are cells that protect the body by absorbing and destroying cells of microbes and viruses. However, the causative agents of some diseases have learned to avoid death inside macrophages, settling and multiplying in them themselves. During the reproduction of mycobacteria, they secrete certain proteins into a liquid that covers the surface of the lung with a thin layer. By the presence of such marker proteins in the pulmonary fluid, it is possible to determine the moment of the beginning of the active development of tuberculosis. However, unlike blood or urine, it is not easy to get a sample of pulmonary fluid. For example, there is a method of bronchoalveolar lavage, in which a person's lungs are washed with a saline solution. This is a very unpleasant procedure. Scientists have suggested that this complex procedure can be avoided by capturing and analyzing that part of the pulmonary fluid that enters the exhaled air in the form of microscopic droplets.
To capture drops of pulmonary fluid, specialists from ITEB used an analog of the Petryanova filter. Filters were developed in the USSR in the middle of the last century to purify the air from radioactive dust in the nuclear industry. In the new work, the researchers modified this technology and created filters for collecting and analyzing particles in the air. A nozzle with such a filter can be put on a household vacuum cleaner, run air through the filter, and then wash off the particles collected by it from the filter and study their composition. For the purposes of non-invasive diagnostics, scientists have designed a simple and cheap disposable device for collecting microdrops in exhaled air.
A snapshot from an article in the Journal of Breath Research – VM.
The device was tested by the Tuberculosis Institute. Forty-two patients from those who had just entered the clinic and had not yet been treated, breathed for 10 minutes through a nylon filter in the device, after which the institute staff determined whether there were biomarkers of tuberculosis in the collected material. It turned out that there are no live mycobacteria, Mycobacteria DNA and mycobacteria antigens in the exhaled air, but there are antibodies specific to the secreted mycobacteria antigens. These antibodies in very small quantities (only a few thousand or tens of thousands of molecules) are found in samples in most patients. Such small amounts were detected by the method of ultrasensitive immunoassay, also developed by ITEB employees. This immunoassay is performed on a multicomponent microchip and allows you to quickly (in 5-10 minutes) determine several antibodies or antigens at once. Thus, for the first time it was possible to show that specific markers of the disease are present in the exhaled air – antibodies produced for an actively multiplying pathogen of infection.
In addition to the material collected at the Tuberculosis Institute, scientists examined exhaled air samples taken from 13 healthy volunteers. It turned out that by the presence of antibodies specific to Mycobacterium pathogens, it is possible to diagnose the presence of an active form of tuberculosis with sensitivity and specificity of about 60-70%. Diagnosing tuberculosis with greater accuracy is hindered by the fact that some healthy people who have been in contact with patients for a long time have the same antibodies in their lungs as in patients.
The problem of increasing specificity can be solved by supplementing the antibody analysis with a check for another sign of infection – inflammation in the lungs, which can be determined by the presence of special regulatory proteins – interleukins in the exhaled air. Such verification will be the next task of the researchers if the project receives further funding.
Thus, for the first time it was shown that it is possible to painlessly and noninvasively collect samples from exhaled air and diagnose infection. ITEB specialists believe that the method they have developed can be used not only for the diagnosis of tuberculosis, but also for the diagnosis of other lung diseases, for example, chronic obstructive pulmonary disease – a disease that is now ranked third in the world among the causes of death.
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