Neanderthals & COVID-19: a genetic risk factor

Scientists have discovered that a piece of genetic code in some people that makes them more likely to get severe COVID-19 actually comes to us directly from Neanderthals. This genetic variant is about 50,000 letters of DNA long, and a study across the whole human genome identified it as the only major genetic risk factor for serious coronavirus infections. And when Hugo Zeberg at the Max Planck Institute for Evolutionary Anthropology heard about it, he discovered the Neanderthal link...

Hugo - This is a variant on chromosome 2, and there's a lot of genes in this region. So we don't really know what gene it is, but we see the effects. People carrying this variance are more likely to end up in the hospital with Covid-19 and end up in the intensive care unit.

Phil - Oh, really? Do we know how much more likely?

Hugo - Yeah. So the latest studies put this risk at 100% risk increase.

Phil - A hundred percent?

Hugo - Yes. So for a genetic variant, this is a quite strong effect.

Phil - How many people have got this?

Hugo - In Europe, one in six. Or people with European ancestry, that's one in six. And people in South Asia, one in two. It's missing in East Asia and it's missing in Africa.

Phil - So this gene variant comes to us directly from Neanderthals?

Hugo - Yes. That's true.

Phil - Not to question you of course Hugo, but how do you know?

Hugo - We have three really good genomes from Neanderthals. So we extract DNA from bones. And then we have the genome of people living today and we can just compare the genome to the Neanderthal genome.

Phil - And that's what you did. You saw this variant and you just looked through the Neanderthal genome and then you saw, "Oh my God, they're exactly the same".

Hugo - Yes. I fell off my chair when I saw it! I should say that the finding of this risk variance is not my doing, but what I did was to see that, "Oh gosh, this is a Neanderthal variant."

Phil - Tell me how unlikely do you think this is. Because obviously we're not, we don't come from Neanderthals. So what are the chances of us having this gene that's from them?

Hugo - Yes, that's a very good question. Each individual with ancestry outside Africa carry 1 to 2% Neanderthal variant. So it's not super likely that it would be a Neanderthal variant. But I think that in terms of pandemics, they might be more important. So if you separate groups, they develop their immune system to the local environment. And Neanderthals and modern humans were separated for half a million years. And then they met. So the immune system might be somewhat different.

Phil - You seem to be sort of hinting at what this gene variant might do. Are you suggesting there's a chance it might have something to do with the immune system?

Hugo - Yes. Yes. There are several receptors that modulate the immune system in this region. And we know that some of the people who have gotten very sick with Covid-19, they are characterized by an overactive immune response. So this is one hypothesis. There is also another good hypothesis. And there's another gene in this region that encodes a protein that forms a complex with the receptor for the virus. So how the virus gets into the cell. So that's another good hypothesis. We're trying to figure that out, but it probably modulates the immune response somehow. I should say, it's also striking that it is so common in some parts of the world that we believe that it couldn't have been that bad for 50,000 years. Almost like it must have been quite good because it's more common than the other Neanderthal genetic variants.

Phil - So, so it's possible then maybe if this is something that helps your immune system react more strongly, that's something that's previously been good. And it's just backfiring now.

Hugo - Exactly. One can think that it might protect against some pathogens, and now you get a too good response and this overactive immune response.