Covid-19: a little Neanderthal DNA in humans can make the virus more virulent

Is it Voltaire's fault?

No to Neanderthals.

Genes that have crossed the millennia and are still present in part of the world population constitute "the major genetic risk of developing a severe form of Covid-19", concludes an article in the scientific journal Nature, Wednesday, September 30.

"We estimate that approximately 100,000 people died after being infected with the coronavirus because they carried this genetic inheritance," says Svante Pääbo, one of the co-authors of the article and director of the Max Institute -Planck of evolutionary anthropology in Leipzig, Germany, contacted by France 24. 

"We almost fell from our chair"

The one Le Monde nicknamed the "Pope" of the ancient genome (he has been studying that of Neanderthals for twenty years) made this discovery with his colleague Hugo Zeberg from the Karolinska Institute in Stockholm by analyzing the results of 'a large study, published in July, seeking to identify the genetic factors that put some people at greater risk than others for the virus. 

This work made it possible to conclude that a large number of patients developing a severe form of Covid-19 shared the same genetic variance at the level of chromosome 3 (out of the 23 pairs of the human genome).

It was by taking a closer look that these two specialists were able to make their incredible journey into the past: they discovered in this region three genes with the same DNA sequence as that found in Croatia in a Neanderthal who lived there there. is 50,000 years old.

"We almost fell out of our chair when we saw this link," Svante Pääbo recalls.

The implications of this discovery are, indeed, not slim.

If we all have * a little Neanderthal in us - about 2% of the genetic background -, one in six Europeans finds himself through the game of inheritance with the precise constellation of genes of this distant ancestor who seems to favor the most common forms. serious of Covid-19 ", note the authors of the article in Nature. It is even worse in certain countries of South Asia, in particular in Bangladesh" where 63% of the population carries at least one copy of the DNA sequence at risk ", emphasizes Svante Pääbo.

A finding that could help to understand why Bangladeshi nationals in the United Kingdom are twice as likely to die from Covid-19 than the British, as noted by Public Health England, the government agency in charge of health issues public, in a study published in June.

"Exposive cocktail" left by Neanderthals

Ironically, one of the hypotheses to explain the importance of this genetic peculiarity among the inhabitants of South Asian countries is that "these Neanderthal genes played a positive role in the immune defense against certain endemic diseases in this region such as cholera, "says Svante Pääbo.

The bearers of this heritage would thus have resisted better than the others, which allowed them to become the majority ... and to be more in danger today against Sars-Cov-2.

"In my opinion, this genetic aspect is, after age, the second most important risk factor for developing a severe form of Covid-19," says the director of the Max-Planck Institute for Evolutionary Anthropology.

It even places it above comorbidities, like diabetes or other illnesses known to play a role in the virulence of the symptoms of the virus. 

What the two researchers found when analyzing the results of the study on genetic factors and the risks of Covid-19 is that "if you have inherited these genes from your mother and your father, it's as if you were added 20 years in the face of the disease ", summarizes Svante Pääbo.

In other words, a 40-year-old person to whom both parents bequeathed this 50,000-year-old genetic makeup is at the same risk of serious complications from the disease as a 60-year-old.

Not just genetics

That's why Svante Pääbo thinks it's important to try to understand why these Neanderthal genes would amplify the risk.

"We do not always know the role that each gene plays," he admits.

But for two of them, he has assumptions.

One of them would play a role in the body's defenses against viruses and we know that the symptoms of Covid-19 can be worsened by too strong a reaction from the immune system.

The other gene has a direct link with the protein that serves as the receptor for Sars-Cov-2.

"Together, they can form a particularly explosive cocktail in the case of the coronavirus", estimates this researcher.

"It is a very interesting and serious work, which opens up new research perspectives", recognizes a German specialist in questions of evolution who preferred to remain anonymous, contacted by France 24. In the columns of the World, Luis Quintana -Murci, a researcher from the Collège de France, calls for “Neandertalize human cells to study the functional effects” of this DNA sequence.

Clearly, he wants to reproduce this fragment of the genome in the laboratory to better understand what happens when it comes into contact with Sars-Cov-2.

But other researchers call for caution.

"We must be careful not to reduce the question to a simple matter of genetics," said Mark Maslin, researcher at University College London, interviewed by The Guardian.

He reminds us that the body's immune response depends as much on genes as on environmental factors and the general state of health of the patient.

He does not, however, deny that Neanderthals, through the ages, left us a time bomb that may have just exploded.

*

.

The summary of the week

France 24 invites you to come back to the news that marked the week

I subscribe

Take international news everywhere with you!

Download the France 24 application

google-play-badge_FR