Covid-19: link between blood type and Covid confirmed

Mild or severe Covid… it is (partially) written in our blood. Previous studies have shown that certain blood types were slightly overrepresented in patients with severe Covid-19, in particular group A. The new study confirms this link between blood type and Covid severity. Research published March 3, 2022 in the journal Plos Geneticsstudied the relationship between the expression of more than 3,000 proteins and the likelihood of developing severe Covid, showing that there is a causal relationship between the level of expression of the protein responsible for blood types (AB0) and the likelihood of having a severe form of the disease.

Large scale genetic analysis

The researchers collected data from more than 5,000 genetic analyzes of proteins found in the blood, highlighting the causal relationship between certain alleles (or genetic variations) and the level of expression of those proteins. “These genetic studies study alleles that are randomly passed down from generation to generation. Since there are no external factors influencing this randomization, we can use these alleles as if they were individuals in a randomized clinical trial. explains Vincent Millischer, researcher at the University of Vienna (Austria) and author of the study. Subsequently, we can see if these alleles are associated with an A or B phenotype, such as the level of protein expression.

They then analyzed the presence of these alleles in patients hospitalized for Covid, as well as in patients requiring mechanical ventilation or who died due to this disease (with sequences available at Covid-19 Host Genetics Initiative, which has nearly 10,000 European Covid patient sequences, including 5,100 very serious or fatal cases). Thus, they emphasized that some proteins in the blood protect against Covid-19, while others, including protein-upregulating transferases of the ABO system, increase the risk of severe Covid-19.

The mechanism of this causal relationship is still a mystery.

This protein is responsible for the blood type: it is he who places the sugars that determine the blood type in red blood cells. This enzyme has three alleles, version A, version B, and a smaller version O, which cannot carry these sugars into blood cells, resulting in the O blood type.” he details. This shorter version (O) was not measured by the tests on which we based our analysis, i.e. a person with this version had lower levels of this protein on those tests. Thereby, we examined the relationship between blood levels of this protein and Covid and saw that versions A or B were more common than version O in people hospitalized for Covid, and in patients with artificial respirators or who died from Covid. ”

Thus, the involvement of blood types in covid seems to be more and more obvious, but this does not mean that we can start thinking about treatment based on this knowledge: “It’s one step closer to causation, but it’s a genetic study rather far from the patient; to truly understand the mechanism by which these blood groups may play a role in covid disease, molecular and cellular studies will be required. nuance Vincent Millisher. This study is a starting point to better understand the mechanism before thinking about developing treatments based on this knowledge.”

Blood type 0 protects against Covid but favors Covid for a long time?

So group O will protect against Covid… but not necessarily against long-term Covid! One preprint (not yet peer-reviewed), uploaded 12 March 2022, studied the involvement of blood types in 121 Covid patients with mild disease, 36 of whom developed Covid protractedly. Surprise: blood type O quadruples the risk of long-term Covid! Again, researchers do not yet know what the mechanism for this greater susceptibility might be. So in the end, blood types certainly play a role in Covid, but it can be a lot more complicated than one might imagine.

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