A new study conducted in Bergamo, Italy, has found that some people inherited a set of genes from Neanderthals that increased their risk of developing severe COVID-19 symptoms. The study analyzed the DNA of about 10,000 people in the city, which was one of the worst-hit areas by the pandemic in the world.
Neanderthal haplotype associated with severe COVID-19
The researchers identified a genetic variant on chromosome 3, called the Neanderthal haplotype, that was present in most of the people who suffered from severe respiratory illness, such as pneumonia and intensive-care unit admission. The variant consists of three genes that are involved in the immune system response to viral infections.
According to the study, people with the Neanderthal haplotype were twice as likely to develop severe pneumonia from COVID-19 than those who did not have it. They were also three times as likely to be hospitalized in intensive-care units and put on ventilators.
The researchers estimated that the Neanderthal haplotype increased the risk of severe COVID-19 by 60% in people from Europe and by 150% in people from South Asia. The variant is rare in Africa, where Neanderthal interbreeding did not occur.
How did the Neanderthal genes affect COVID-19 severity?
The researchers speculated that the Neanderthal genes may have conferred an evolutionary advantage to ancient humans who faced different pathogens than modern humans. However, they may have become detrimental in the context of COVID-19, which is caused by a novel coronavirus.
One of the genes in the Neanderthal haplotype, called DPP4, encodes a protein that serves as a receptor for some coronaviruses, such as MERS-CoV. The researchers suggested that the Neanderthal version of DPP4 may increase the entry of SARS-CoV-2, the virus that causes COVID-19, into human cells.
Another gene in the Neanderthal haplotype, called OAS1, encodes an enzyme that helps fight viral infections by activating interferons, which are molecules that trigger immune responses. The researchers proposed that the Neanderthal version of OAS1 may impair interferon production or signaling, leading to a weaker or delayed immune response to COVID-19.
The third gene in the Neanderthal haplotype, called CCR5, encodes a protein that acts as a co-receptor for HIV and some other viruses. The researchers hypothesized that the Neanderthal version of CCR5 may alter the expression or function of this protein, affecting the interaction between immune cells and viral particles.
Implications and limitations of the study
The study provides new insights into the genetic factors that may influence COVID-19 severity and outcomes. The researchers suggested that screening for the Neanderthal haplotype could help identify people who are at higher risk of developing severe COVID-19 and provide them with preventive measures or treatments.
However, the study also has some limitations. The researchers acknowledged that they could not rule out other environmental or social factors that may have contributed to the high mortality rate in Bergamo. They also noted that their findings need to be replicated and validated in other populations and regions.
Moreover, the study does not imply that having Neanderthal genes is necessarily bad or good for health. The researchers emphasized that genetic variation is complex and dynamic, and that different genes may have different effects depending on the context and interaction with other factors.