We have all heard of families where some people have never tested positive, even if all their relatives were infected., says Dr. Donald Vinh, infectious disease specialist and medical microbiologist at the McGill University Health Center (MUHC).
Dr Vinh is the only Canadian researcher in this team who has started studying (New window) the genomes of some 2,000 participants, all of whom have had direct and prolonged contact with an infected person, but who have never tested positive.
SARS-CoV-2 infects human cells by interacting with several proteins on their surface. These researchers believe that people who are resistant to COVID-19 have genetic mutations that prevent the virus from infecting human cells.
It is believed that some people are born with variants or mutations in one or more genes that are important for SARS-CoV-2, he says. These mutations would prevent the virus from attaching itself to human cells and injecting its genetic make-up to make copies of itself – the way a virus spreads through an organism.
Finding out exactly which mutation is involved here will still be complex, says Dr. Vinh, since there are hundreds of proteins that could be involved.
We do not yet know which of these proteins is encoded in our genome and which is critical to have this resistance.
Thus, by sequencing the genome of each participant, we hope to identify the polymorphisms (variations between individuals in the sequence of genes) that make these people resistant to COVID-19. The researchers will also compare the genomes of these potentially resistant people with those of people who have been infected.
There are many examples of people exposed to viruses such as malaria, HIVand noroviruses that have never been infected, says Dr Vinh. For example, while investigating the genomes of female sex workers, researchers notably discovered a mutation in a gene that protected them from infection with the sex worker. HIV . This discovery led to the development of a very effective antiviral which prevents the virus from entering and infecting cells.
It is possible that these mutations also protect these people from other respiratory infections, adds Dr Vinh. On the other hand, it is also possible that a mutation offers protection against COVID-19, but that it is the cause of another disease. For example, people with sickle cell anemia, a genetic disease caused by a mutation in a gene encoding part of hemoglobin, are protected from malaria.
By having participants from all over the world, researchers will also be able to analyze whether certain populations, because of their genetic history, are more resistant than others to COVID-19.
We could perhaps find a mutation in a gene that is specific to French-speaking Quebecers or to Argentines from a certain region, for example. This could partly explain the difference [des taux d’infection] between countries, believes Dr. Vinh.
Find a treatment that blocks the infection
These researchers believe their research will not only help better define how SARS-CoV-2 infects people, but also develop drugs that could stop the infection.
Remember that with the vaccine, designed first and foremost to reduce the severe symptoms of COVID-19, a person can still be infected. The treatments that are available only relieve the severe symptoms of the disease and cannot stop the infection or transmission.
: we could block the infection process “,” text “:” Instead of targeting the replication of the virus, as is done with drugs [présentement utilisés contre la COVID-19], we could target the intervention further upstream: we could block the infection process “}}”>Instead of targeting virus replication, as is done with drugs [présentement utilisés contre la COVID-19], we could target the intervention further upstream: we could block the infection process. Such a drug could have a major impact on the transmission of COVID-19 and would be another tool in the fight against this virus, believes Dr. Vinh.
The team hopes to have preliminary results within six months.