October 5, 2020COVID-19
The following if from Dr. Francis Collins' Blog, Posted on June 18th, 2020.
As reported, many people who contract COVID-19 have only a mild illness, or sometimes no symptoms at all. But others develop respiratory failure that requires oxygen support or even a ventilator. This happens more often in men than in women, as well as in people who are older or who have chronic health conditions. Thus, why does respiratory failure also sometimes occur in people who are young and seemingly healthy? A recent genome-wide association (GWAS) study, published online in the New England Journal of Medicine (24 February 2020), observed that gene variants in two regions of the human genome are associated with severe COVID-19 and correspondingly carry a greater risk of COVID-19-related death. The findings suggest that people with blood type A face a 50% greater risk of needing oxygen support or a ventilator should they become infected with the novel coronavirus. In contrast, people with blood type O appear to have about a 50% reduced risk of severe COVID-19. The study included 1,980 people undergoing treatment for severe COVID-19 and respiratory failure at seven medical centers in Italy and Spain.
The study analyzed patient genome data for more than 8.5 million so-called single-nucleotide polymorphisms, or SNPs. The vast majority of these single letter nucleotide substitutions found all across the genome are of no health significance, but they can help to pinpoint the locations of gene variants that turn up more often in association with particular traits or conditions?in this case, COVID-19-related respiratory failure. To find these SNPs, the authors compared SNPs in people with severe COVID-19 to those in more than 1,200 healthy blood donors from the same population groups. Study results identified two places that turned up significantly more often in the individuals with severe COVID-19 than in the healthy folks. One of them is found on chromosome 3 and covers a cluster of six genes with potentially relevant functions. For instance, this portion of the genome encodes a transporter protein known to interact with angiotensin converting enzyme 2 (ACE2), the surface receptor that allows the novel coronavirus that causes COVID-19, SARS-CoV-2, to bind to and infect human cells. It also encodes a collection of chemokine receptors, which play a role in the immune response in the airways of our lungs.
The other association signal was found on chromosome 9, over the area of the genome that determines blood type. Whether a person is classified as an A, B, AB, or O blood type, depends on how one's genes instruct blood cells to produce (or not produce) a certain set of proteins. The authors did find evidence suggesting a relationship between blood type and COVID-19 risk, and that this area also includes a genetic variant associated with increased levels of interleukin-6, which plays a role in inflammation and may have implications for COVID-19 as well.
The hope is that these and other findings yet to come will point the way to a more thorough understanding of the biology of COVID-19, and that a genetic test and a person's blood type might provide useful tools for identifying those who may be at greater risk of serious illness.