Quirks & Quarks

Scientists are trying to find out why some people don't get COVID-19

Researchers are recruiting subjects who were exposed to COVID-19 and whose immune systems show no sign of encountering the coronavirus. The people who show resistance to infection could be the key to treatments in the future.

A small number of people could be completely resistant to the coronavirus

Scientists are searching for genes that may give some a superhuman ability to resist contracting COVID-19. (Evan Buhler/The Canadian Press)

An international team of researchers is hoping to identify individuals in the population who, for reasons that are not yet understood, don't get infected by the coronavirus that causes COVID-19. They want determine whether these people have unique genes that could be studied to develop new treatments against the disease.

These are people who are distinct from those whose immune systems can successfully fight off the virus if they are infected, people who experience low grade or asymptomatic infections or those who've been immunized with vaccines.

If the virus cannot attach to our cells and inject its genetic payload to make more copies of itself, the immune system doesn't even see the virus. This is what scientists suspect could be happening in COVID-19 resistant people.

"We want to find out who are those superpeople, the supermen and the superwomen, who are resistant and why are they resistant?" said Dr. Don Vinh, an infectious disease specialist and medical microbiologist at the McGill University Health Centre.

Vinh is the only Canadian investigator in an international team that has started recruiting people who were exposed to SARS-CoV-2, the virus that causes COVID-19, but who didn't get sick, and whose immune systems show no signs of encountering the virus. They described their project in a study published in the journal Nature Immunology

The first candidates for this study are relatives of people who became very ill, but who themselves never tested positive, said Vinh. 

"There are these people who come to the hospital sick, sometimes deathly sick, with life-threatening COVID-19 and they have a family member or several family members who are totally, totally well — who themselves got tested and found out they weren't infected." 

Scientists can tell by studying a person's antibodies and T-cells if their immune systems have ever encountered the virus through a natural infection.

A woman has her temperature taken as she arrives at the Roberta Place Long Term Care home in Barrie, Ont. in January 2021. By studying exposed family members of people who got sick, researchers hope to find genes that can prevent COVID-19 infection in the first place. (Frank Gunn/The Canadian Press)

In an interview with Quirks & Quarks host Bob McDonald, Vinh said one goal of this project is to develop treatments that can interrupt an infection even earlier and more completely than a vaccine. Vaccines are excellent at protecting us against disease, but people who are vaccinated can still get infected and transmit the virus, albeit for a shorter period of time.

"If we could abort that initial process, the infection part, through this kind of work, I think that will hopefully be a groundbreaker in our fight against this pandemic," said Vinh. 

Finding the right people

By testing for a person's antibodies and T cells, the researchers hope to identify people who were exposed, but whose immune system show no signs of ever encountering the virus. (Simon Dawson/The Associated Press)

Vinh said that his team has already recruited 1,000 exposed individuals who they suspect are resistant to infection. 

The plan is to scan their genomes and compare the group to people who were exposed and infected, to identify any gene variants that can prevent the virus from establishing itself.

Once the team identifies genes that are heavily represented in those who are resistant, they will shift their focus to the proteins the genes make, and whether they offer any protection against infection.

Usefulness of this type of investigation

Throughout human history, there are other examples of people who are exposed to viruses like malaria, HIV and norovirus but don't get infected, said Vinh.

"In all of these infections, what we've seen are clusters of people who are exposed, but uninfected and then the molecules responsible for that resistance have been identified and some have even been transformed into drug therapies," said Vinh.

A man walks by a sign for a COVID-19 testing centre in Montreal in October 2021 as the pandemic continues in Canada and around the world. (Graham Hughes/The Canadian Press)

A good example of how this information can be useful for fighting off infections came from a group of sex workers in Kenya who, though exposed to the virus, were found to have a natural resistance to HIV-1 infection

By investigating the genetic basis for that immunity, scientists discovered one unexpected gene that, in its mutated form, protected the sex workers from getting infected, said Vinh.

That led to the development of a highly-effective antiviral that suppresses the HIV-1 virus by inhibiting its ability to enter and infect cells, which Vinh said is what they're hoping to do for the SARS-CoV-2 virus.

Produced and written by Sonya Buyting. Click on the link at the top of the page to hear the interview with Dr. Don Vinh.