When SARS-CoV-2, the virus that causes COVID-19, first appeared in 2019, medical doctors and scientists started to note a curious affiliation: Sufferers with blood kind A appeared to have an elevated danger of an infection. This was not wholly shocking — blood kind is linked to a number of illness states, and 20 years earlier, in the course of the SARS epidemic, comparable associations have been seen. However the virus infects our lungs, so what does blood need to do with it?
A brand new examine, revealed within the journal Blood on June 27, describes a possible mechanism, offering proof that SARS-CoV-2 preferentially binds to the floor proteins related to blood group A. It appears this blood kind may improve the flexibility for the virus to enter a cell.
A person’s blood cells are principally the identical and so they have the identical perform, however they’re coated in proteins that give rise to the totally different blood varieties: A, B, AB, O and the constructive and damaging varieties related to Rhesus issue, or Rh. These tiny variations play a task in our danger for sure well being situations — together with, as an example, how inclined we is perhaps to coronary heart illness or an infection — as a result of the proteins aren’t simply expressed on blood cells however throughout totally different cells within the physique. It was affordable to suppose the danger of an infection by SARS-CoV-2 may very well be linked to blood kind.
Quite a few research investigated the hyperlink between blood kind and COVID-19 danger, courting again to the earliest days of the pandemic. In Might 2020, Chinese language researchers explored the affiliation between blood teams and danger of COVID-19 and located that folks with blood group A have been contaminated greater than wholesome controls, whereas blood group O was decrease. In October 2020, a examine revealed in Blood Advances, and one other revealed in The New England Journal of Drugs discovered comparable outcomes.
Although the COVID-19 public well being emergency was declared over within the US on Might 11, the virus nonetheless circulates worldwide. In line with the World Well being Group, for the reason that begin of the pandemic virtually 7 million individuals have misplaced their lives. About one in three sufferers battle with lengthy COVID, lingering results from the illness that can lead to muscle weak point or cognitive issues. And lately, a brand new, extremely mutated variant referred to as BA.2.86 has scientists on excessive alert.
COVID and spike proteins
The observational research from 2020 supplied proof that blood group A was related to COVID-19 an infection whereas blood group O was considerably protecting. Nonetheless, a handful of research prompt this may simply be a spurious outcome primarily based on the affected person teams studied, and a mechanism that would give rise to this relationship was elusive.
The newest examine supplies one, and it is all to do with the spike protein.
To contaminate a cell, SARS-CoV-2 makes use of its spike protein to bind to a protein on the floor of a cell, referred to as ACE2. In a lock-and-key state of affairs, the spike protein’s “receptor binding area,” or RBD, acts as a key, recognizing the lock of ACE2. This allows the virus to sneak via the cell membrane and start replicating. Quite a lot of totally different proteins are concerned on this course of, and earlier than unlocking entry by way of the principle lock of ACE2, the virus may attempt a number of totally different keyholes. It seems the protein related to blood kind A is simply the proper measurement to snag the virus.
“This interplay seems to make the blood group A cells extra ‘sticky’ for the spike protein and subsequently the SARS-CoV-2 virus, which finally enhances its skill to have interaction ACE2 and infect cells,” says Sean Stowell, affiliate professor of pathology at Harvard Medical College and writer of the brand new examine.
Stowell and his colleagues have been capable of illuminate this mechanism by genetically engineering hamster cells to specific each ACE2 and quite a lot of totally different blood group antigens together with group A and group O. “We engineered cells to specific the identical ranges of ACE2 and subsequently solely differ within the A or O blood group standing,” notes Stowell. The researchers then added a pressure of SARS-CoV-2 — both the unique Wuhan pressure, the delta variant or the omicron variant — and assessed the extent of an infection of the cells.
They discovered that, in all strains, the cells with blood group A proteins confirmed a lot greater ranges of an infection. As well as, the omicron variant confirmed the very best selectivity for blood group A people. To substantiate the impact they have been seeing, researchers additionally used one other protein to dam blood group A binding by the virus. When blood group A was blocked, there have been no variations in an infection between the group A and group O blood varieties.
“This direct interplay with blood group A might account for the epidemiological knowledge all through the pandemic demonstrating that blood group A people usually tend to get contaminated with SARS-CoV-2 than blood group O people,” says Stowell.
You have acquired blood kind A. What it is best to know
Three years on from the start of the pandemic, we’re nonetheless studying precisely how SARS-CoV-2 turned such a devastating microscopic adversary. Our blood varieties make us barely totally different, however they are not the one danger issue.
Should you’re one of many 30% with blood kind A, the outcomes could seem a little bit regarding. “On common, the whole lot else being equal, people who find themselves blood group A could also be 20% extra more likely to turn into contaminated than blood group O,” explains Stowell. Nonetheless, he says, it is not doable to at the moment assess the danger of an infection, as a result of COVID-19 danger is said to quite a lot of variables together with age, weight, ACE2 ranges, way of life and different underlying medical situations.
Then again, it would look like that is constructive information for individuals with blood kind O blood, however it’s vital to notice this blood group would not make you proof against SARS-CoV-2. You possibly can nonetheless be contaminated.
Getting contaminated can also be associated to the bodily actuality of being near an contaminated particular person for lengthy intervals of time. As a result of SARS-CoV-2 travels by way of air, being in well-ventilated areas or outside and sporting a masks lowers the danger of an infection. Vaccinating your self towards the virus additionally supplies the easiest way to scale back the danger of an infection and, importantly, of extreme issues from the illness, like hospitalization and dying. These precautions needs to be taken no matter your blood group.