Colds may protect against corona infection

Yale University researchers have found that exposure to rhinoviruses, the most common cause of colds, can protect against infection with the virus that causes Covid-19.

In a new study published in the Journal of Experimental Medicine, researchers found that the common respiratory virus raises the activity of interferon-stimulating genes, and early response molecules in the immune system, which can stop the replication of the (emerging corona) virus within cold-infected airway tissues.

The release of these defenses early in the course of infection (Covid-19) holds promise for preventing infection or treatment, but it all depends on the timing.

Previous work has shown that in the late stages of Covid-19, high levels of interferon are associated with worse disease and may fuel overactive immune responses, but recent genetic studies show that interferon-stimulating genes can also be protective in cases of Covid-19 infection. The Foxman lab wanted to study this defense system early during infection.

Since previous studies by Foxman's lab showed that common cold viruses may protect against influenza, they decided to study whether rhinoviruses had the same beneficial effect against Covid-19.

For the study, the research team infected human airway tissues grown in the laboratory with the emerging corona virus, and they found that during the first three days, the viral load in the tissues doubled approximately every six hours.

However, replication of the emerging coronavirus was completely stopped in tissues that had been exposed to rhinovirus, and they found that when antiviral defenses were blocked, the emerging coronavirus could replicate in airway tissues previously exposed to rhinoviruses.

And the defenses themselves slowed infection of the emerging corona virus even without rhinoviruses, but only if the infectious dose was low, indicating that the viral load at the time of exposure makes a difference in whether the body is able to fight the infection effectively.

The researchers also studied nasal swab samples from patients diagnosed near the onset of infection, and found evidence of rapid growth of the emerging coronavirus in the first few days of infection, followed by activation of the body's defenses.

According to their findings, the virus usually increased rapidly in the first few days of infection, before the defenses of human cells kick in, doubling approximately every six hours, as seen in the laboratory, where the virus grew faster in some patients.

Foxman says interferon therapy shows promise but can be deceptive because it will often be effective in the days immediately following infection, when many people have no symptoms.

In theory, an antiviral treatment could be used prophylactically in people at high risk who have been in close contact with others diagnosed with "Covid-19", so far showing potential benefit early in the infection, but not when it is administered later.

She adds that these findings may help explain why rates of infection with other viruses such as influenza are lower at times of the year when colds are common, as there are concerns that with the relaxation of social distancing measures, cold and influenza viruses, which have been dormant over the past year, You will come back with more force.