Neanderthal genes could reduce the risk of severe COVID-19 in some people

• Some people may have genes inherited from Neanderthals that reduce their risk of severe COVID-19 by 22%, study finds.
• But the same researchers previously found that Neanderthal DNA may also put people at a higher risk of respiratory failure from COVID-19.
• Inherited genes are more common in Europe and Asia.
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As an emergency room doctor, Hugo Zeberg has seen first-hand how COVID-19 infections can vary in severity. So he started looking for answers in a place he was familiar with: the Neanderthal genome.

Zeberg works at the Karolinska Institute in Sweden and, for the past few years, has been studying the extent to which Neanderthals – an extinct human species that died around 40,000 years ago – passed genes to modern humans through crossbreeding.

Scientists believe that Neanderthal DNA makes up 1% to 2% of the genomes of many people of European and Asian descent. This small fraction of people’s genetic codes can hold important clues about our immune responses to pathogens.

In a study published this week, Zeberg and his colleague Svante Pääbo from the Max Planck Institute for Evolutionary Anthropology suggest that some people may have inherited a genetic advantage that reduces their risk of developing severe COVID-19 by 22%.

The benefit comes from a single haplotype – or long block of DNA – on chromosome 12. The same haplotype has been shown to protect people against West Nile, hepatitis C, and SARS (another coronavirus that shares many genetic similarities with the new one, SARS -CoV-2).

“The protective effect of this haplotype is probably not unique to SARS-CoV-2, but to a more general part of our immune system,” Zeberg told Insider.

Some Neanderthal genes are helpful, others are harmful

Reuters

Zeberg and Pääbo found that the inherited Neanderthal haplotype may have become more common in humans over the past 1,000 years. One possible explanation for this, Zeberg said, is the role of genes in protecting people from other diseases caused by RNA viruses.

For their new study, the team drew on the genomes of three Neanderthals – two whose remains were found in southern Siberia and one from Croatia. DNA dates back 50,000 to 120,000 years. They compared these Neanderthal genomes to the DNA of thousands of people with severe COVID-19.

The less severe COVID-19 associated haplotype was found in all three Neanderthal genomes. It codes for proteins that activate enzymes that help break down RNA viruses.

However, an earlier study by Zeberg and Pääbo, published in September, showed that not all Neanderthal DNA confers a benefit. In this research, they found that some modern humans have inherited a haplotype on chromosome 3 that puts them at a higher risk of respiratory failure from COVID-19. This particular group of genes was found in the Croatian Neanderthal.

“If you have this variant, you have twice the risk of becoming seriously ill with COVID-19 – maybe even more,” Zeberg said.

Zeberg’s research suggests that around 25% to 30% of people in Europe and Asia carry the protective haplotype, while up to 65% of people in South Asia and 16% of people in Europe carry the haplotype. dangerous. Unfortunately, he said, the protective haplotype does not outweigh the risk of harm to those who have both.

Persistent mysteries of how genes influence COVID-19

Nicolas Tucat / AFP via Getty Images

For the most part, Africans do not appear to have inherited Neanderthal genes.

“Neanderthals went to Europe and Asia and lived there before modern humans,” Zeberg said. “Then modern humans came 100,000 years ago and they probably mingled 60,000 years ago. So Africa has never met a Neanderthal ”.

He added, however, that it is possible that Africans have inherited other genetic variants from different ancestors which confer their own protection against COVID-19.

“There are variations in Africa that we and others are looking at,” Zeberg said.

Brendan McDermid / Reuters

Scientists are still not sure to what extent our protection against disease was inherited from ancient ancestors compared to a more recent acquisition. Understanding this is made more difficult by the fact that part of the Neanderthal genome is still missing.

But studying old genes could still help reveal more about how the body responds to the coronavirus. A December study, for example, identified eight locations on human chromosomes where particular genetic variants were more common in critically ill COVID-19 patients.

“If we can better understand how our evolutionary history has shaped our immune system, it can be valuable,” Zeberg said.

It is possible, for example, that human ancestors relied on specific genes to protect them from viruses that have since disappeared. This may explain why some people’s immune systems overreact to the new coronavirus, triggering inflammation that can prove fatal.

Zeberg said scientists have just started to scratch the surface of these findings.