Exposure to the virus that causes common cold can protect against infection by the SARS-CoV-2 virus behind Covid-19, according to a study.

The research, published on Tuesday, June 5,  in the Journal of Experimental Medicine, found that rhinovirus, the common respiratory virus, jump-starts the activity of interferon-stimulated genes.

These genes trigger early-response molecules in the immune system which can stop reproduction of the SARS-CoV-2, the virus that causes Covid-19, within airway tissues infected with the cold, the researchers said.

Triggering these defenses early in the course of Covid-19 infection holds promise to prevent or treat the infection, said senior study author, Ellen Foxman, assistant professor at the Yale School of Medicine in the US.

One way to do this, Foxman said, is by treating patients with interferons, an immune system protein that is also available as a drug.

“But it all depends upon the timing,” she said.

Previous work showed that at the later stages of Covid-19, high interferon levels are associated with worse disease outcomes, and may fuel overactive immune responses.

However, recent genetic studies show that interferon-stimulated genes can also be protective in cases of Covid-19 infection.

The researchers wanted to study this defense system early in the course of Covid-19 infection.

They decided to study whether rhinoviruses would have a beneficial impact against the SARS-CoV-2 virus. The team infected lab-grown human airway tissue with the virus and found that for the first three days, viral load in the tissue doubled about every six hours.

However, the researchers found that reproduction of the Covid-19 virus was completely stopped in tissue that had been exposed to rhinovirus.

If antiviral defenses were blocked, the SARS-CoV-2 could reproduce in airway tissue previously exposed to rhinovirus.

The same defenses slowed down SARS-CoV-2 infection even without rhinovirus, but only if the infectious dose was low.

Source: PTI