In the early dark days of the pandemic, when vaccines for what was then still sometimes referred to as the novel coronavirus were just a hope, researchers around the world started noticing a strange phenomenon.
A family member would come into the hospital with their loved one, who was struggling to breathe, or hooked up to a ventilator. But instead of also getting ill, this person seemed to have somehow dodged the virus altogether.
“Wait a minute. You live in the same house, in the same bed, you do everything together — he’s in the ICU and you’re not?” said Dr. Donald Vinh, an infectious-disease specialist and medical microbiologist at the McGill University Health Centre.
“It became very clear that there were people who were exposed without getting severe disease,” Vinh recalls, but the “burning question” was, did they just not have symptoms, or had they escaped the infection? And if so, how?
The sixth wave has brought an explosion of COVID in some Ontario communities, including Toronto, with for many, more friends and family members getting sick than ever before in the pandemic.
But for every story of someone out with the virus, it seems like there’s another of someone who was spared, despite an exposure, or even living in the same house as multiple people who tested positive. If you’ve sidestepped COVID so far, you probably have vaccines, masks, and luck on your side, experts say.
There is, however, a very small group of people who appear to have innate immunity to the virus. There’s actually a precedent for this with other diseases, and Canadian researchers hope that unlocking the mystery of these “COVID resistors” can help develop more effective treatments and vaccines.
For the average person who hasn’t been infected, “it’s probably because you’re doing all the right public health things,” said Dawn Bowdish, the Canada research chair in aging and immunity and a professor of medicine at McMaster University.
There are people out there, though, probably less than one per cent of the population, Bowdish estimates, who are “highly exposed but seronegative” — health-care workers, for example, who were in COVID wards without proper masks before vaccines. Unlike individuals who got it and were asymptomatic, this elite group never develop antibodies in their blood to the virus (and scientists can tell whether those antibodies are from the disease or the vaccine), possessing some kind of natural immunity.
Bowdish is a co-lead on a large study about COVID in long-term care and hypothesizes that certain individuals may have developed immunity after repeated exposure to other seasonal coronaviruses that cause the common cold.
“When they’re exposed to SARS-CoV-2 they pull up that immune response, and sort of help protect themselves,” she said. “Ninety-nine-point-nine per cent of us, we have to rely on our antibodies to do some of that work, whereas these other people use what we call T-cells” — another part of the immune system — that saw something very similar months or years ago and “jump into action and clear it out before it can even get started.”
McGill’s Vinh is the Canadian site lead for an international investigation looking at so-called “COVID resistors” that started as an effort to determine why some people get a severe bout of the disease. The team has identified about 700 people worldwide who qualify as exposed, test negative (with polymerase chain reaction (PCR) or rapid tests) and never developed antibodies.
“We’re hunting for the genetic basis for why people are resistant to COVID infection,” said Vinh.
“If we can actually understand the molecular basis by which humans are naturally resistant to infection, that first step, when the virus tries to get into our cells, it can guide logically and rationally the development of therapies,” he added.
If you’re still convinced you’re one of this tiny elite group, Vinh and his team are still actively recruiting for their study.
In Britain, one research group has taken this a step further in what’s called a human challenge study, where they deliberately exposed 36 healthy, young unvaccinated adults with the virus. The main aim was to find the infectious dose necessary for infection, but they also found that “interestingly, 50 per cent of volunteers did not become infected,” said Dr. Andrew Catchpole, chief scientist at hVIVO, the company that ran the study, recently published in Nature Medicine, in partnership with Imperial College London and the British government. Although they never expected everyone to become infected when using low doses, they are currently studying the immune responses of those who did get infected vs those who did not in the hope that this could help find future drugs, he added in an email.
After two years of “shots in the dark” with treatments, the idea with this kind of work is to start something that’s already happening in humans and go from there, said Vinh.
“Some people say, well isn’t that a bit far-fetched, it is, except that’s what science is supposed to be, it’s supposed to be far-fetched,” he said.“But it’s not unproven.”
Hundreds of years ago when the plague was decimating Europe, there were cases of people who simply never got it, despite sometimes losing their entire families to the disease.
One theory is that people who survived the Black Death had a “specific mutation in one of their immune cells that made them less likely to support the bacteria that caused the plague,” said McMaster’s Bowdish. Another famous example is a group of sex workers in Nairobi, Kenya who were exposed to HIV many times but never became infected.
The message for most people who have avoided COVID so far, is don’t rely on this innate immunity as some kind of hidden superpower, Bowdish added. “But I think the inspiring part about finding people like this is that it kind of gives immunologists who are making vaccines a hint about what they should be targeting those for.”
Her colleagues at McMaster, for example, are working on developing an inhaled vaccine that would ideally provide broader immunity against multiple variants of COVID, rather than racing to develop a specific vaccine each time the virus mutates.
“In a perfect world, our vaccines would do exactly what these people naturally do, shut down that infection before it even got started and you’d never carry it and you’d never transmit it,” Bowdish said. “And we’d all be able to go back to our 2019 life.”
May Warren is a Toronto-based breaking news reporter for the Star. Follow her on Twitter: @maywarren11
Everyone has COVID but you? Could you be immune? - Toronto.com
Read More
No comments:
Post a Comment