5:00 PM
Saturday 10 October 2020
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Books – Sayed Metwally
Scientists have discovered that having more immune cells that fight bacteria in the nose and throat may be the reason for the increased likelihood of some people contracting respiratory viruses.
According to “MedicalXpress”, the bacteria-resistant cells in the airways increase the risk of infection with viruses, according to a study led by a team from Imperial College London and published in the journal Science.
Researchers found that volunteers who had been exposed to a respiratory syncytial virus (RSV) infection had more specialized white blood cells called neutrophils in the airways prior to exposure to the virus, compared to those who avoided the infection.
According to researchers, this type of inflammation caused by neutrophils in the nose and throat, which is usually associated with fighting bacterial infections, may impair our ability to fight viruses and make us more vulnerable to viral infections.
The results can help researchers understand why people respond differently to the same viral threat, predict who is most vulnerable to infection, and even lead to preventive treatments to protect against respiratory syncytial virus and other respiratory viruses, including influenza and coronaviruses.
Same virus … different response
Dr Ryan Thwaites, of the National Heart and Lung Institute in Imperial and the author of the study, said: ‘If we think of a group of 10 people who were all exposed to the same RSV strain under similar conditions, we would expect about six of them to become infected and show symptoms, but the rest might not be affected, yet. We were not able to explain exactly why and why, under the same circumstances, some people are more susceptible to contracting a viral infection in the respiratory system, but the study provides exciting insights into how to improve our defenses against respiratory viruses, and perhaps even Covid-19.
RSV is a common respiratory virus that usually causes symptoms of the common cold in healthy adults, but for infants and the elderly, this can lead to the risk of thousands of hospitalizations every year, and can be fatal.
Unlike other respiratory viruses, such as influenza or rhinovirus, people can be infected with the same strain of RSV more than once, people can also react differently when exposed to the virus in the same circumstances, some may develop mild infections while others develop full symptoms. Some people may avoid the infection completely.
In the last study, the team sought to investigate the mechanisms underlying subjects succumbing to RSV infection and the factors of varied immune responses.
The healthy adults in the study were examined and exposed to RSV in a safe and controlled clinical environment where they were closely monitored.After receiving nasal drops containing the virus, 57% of the volunteers became infected, and analysis of blood samples showed that the presence of protective antibodies, B and T cells can. It only partially explains who got infected.
However, when they analyzed samples from the participants’ airways prior to exposure to the virus, the team found evidence of neutrophil activation in the nasal mucosa – the cells that line the inside of the nose – in those who had contracted the virus.
These immune cells are known to release proteins that help create an anti-bacterial environment in response to the threat, but researchers believe that this antibacterial immune response may pose a risk, making a person more vulnerable to viruses by effectively turning off the early warning system, and letting them pass. Inside the body to cause infection.
Professor Peter Openshaw, professor of experimental medicine at Imperial and co-lead author of the study, said: “The variable transmission we see with respiratory viruses depends partly on the dose and duration of exposure, and also on a person’s autoimmune defenses. We may assume that the cause is due to the presence of protective antibodies. Specific, but despite tremendous efforts over many years, we have never understood what makes someone vulnerable to RSV and another person resistant, our discovery that mucosal condition before arrival of the virus is the main determining factor is a real breakthrough, it seems as if The presence of activated neutrophils in the lining of the airways causes the mucous lining to fail to respond to the virus and get rid of the infection at its start, perhaps what happens is that the willingness to fight the bacteria makes it more likely that viruses will acquire a spread, and once the virus enters, our studies continue to show that the disease is an opportunity to end the infection But only if an early defensive response from the mucosa escalates. “
He added: “People who had colds did not show any evidence of an initial response; those who rejected the infection showed an immediate response before symptoms appeared, these are the results that could only come from experimental studies on volunteers. We would never have discovered this if people waited. People with natural infections, so that they can reveal the matter to us.
Human challenge studies
Dr Christopher Chiu, clinical researcher in infectious diseases at Imperial College and co-author of the study, said: “Our data highlight the complexity of the immune system, which has different arms that provide layers of protection separated by anatomical location (such as the nose, lung or circulation) and timing. These different mechanisms of focus on a specific type of infection but this may come at the expense of protection against other pathogens. Controlled human infection challenge studies have a unique ability to elicit these complex interactions and indicate identifying potential targets for prevention or treatment that are not seen in patients with Of infections caused by various viral strains, in different quantities, in addition to a wide range of other conditions that may affect their immunity.
To confirm the idea, the researchers used animal models to test the effect of the neutrophil pathway on RSV infection in mice without neutrophilic inflammation, and the immune system recognized the virus as a threat and released immune agents that cleared the infection with few symptoms.
However, in mice with a neutrophil-rich nasal mucosa, this early detection of the virus was poor, under these antibacterial conditions the virus was better able to invade mucous cells causing infection, exacerbating symptoms, and secreting the virus to further spread it.
The researchers say that if they can demonstrate that the same mechanism occurs in groups of patients who are most at risk of developing RSV (children younger than 12 months old and adults over age 65 who have chronic conditions, such as COPD or asthma), This may help identify subgroups of patients at greatest risk.
It extends to other viruses
The team is set to explore the mechanism in larger groups of patients as well as investigate whether the same immune mechanisms affect other viral respiratory infections, such as influenza and coronavirus.
Dr Thwaites added: “Our preliminary studies show that in healthy people, inflammation in the airways is associated with RSV infection, and if we can show the same mechanism that plays a role in those most at risk, it could provide opportunities to reduce the damage caused by RSV and organ viruses. Other respiratory, severe bacterial respiratory infections are very rare in healthy adults, so, in theory, it might be beneficial to push the immune response toward virus control during the seasonal winter peaks. It might be possible to design treatments to temporarily suppress some aspects of the inflammation. Such as a simple nasal spray, to enhance protection against viruses circulating, and this can be used in high-risk places, such as hospitals, to enhance protection against respiratory viruses, prevent their spread and reduce the effects of infection on vulnerable groups.
Dr Cecilia Johansson, author of the study at Imperial College, says: “Understanding the underlying mechanisms of sensitivity and protection against respiratory viruses is key to developing treatments, by studying RSV infection in both human volunteers and in mice we are now approaching defining the fine balance of infection resistance. Viral and lung diseases that can be caused by these viruses. “
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