18 Jun, 2020

The emerging role of genetics and blood type in COVID-19

New research reveals genes which could influence respiratory failure in severe cases of COVID-19.

Respiratory failure is one of the main causes of death in patients suffering from severe cases of COVID-19 but, although there are now more than 8 million cases of the virus confirmed worldwide, respiratory failure affects less than 10% of infected people.

So far researchers have struggled to identify why some individuals experience severe symptoms and why the vast majority of infected people experience mild or even no symptoms.

In a new scientific paper published earlier this month, researchers from Italy, Spain and Australia discovered new links between cases of respiratory failure in infected individuals and genetic variation in specific areas of the human genome.

Update

In the weeks since this blog was published, other research groups have been unable to replicate an association between blood type and COVID-19 severity, casting doubt on the legitimacy of this particular finding. However, the gene cluster association on chromosome 3 has been widely supported by independent studies.

In the weeks since the scientific paper was published, other research groups including the COVID19HG and UKBiobank have been unable to replicate an association between blood type and COVID-19 severity, casting doubt on the legitimacy of this finding.

Blood type is known to correlate with ethnicity, so if ethnicity is not balanced within the study, or not fully corrected for, a false association between blood type and COVID-19 severity could be produced. However, 23andMe also reported the same association within their DNA database, so further work is required to determine whether blood type plays a role.

Can genetics impact the severity of COVID-19 cases?

The researchers carried out a genome-wide association study (GWAS) on 1,610 patients from Italy and Spain suffering from COVID-19 respiratory failure and compared them with 2,205 healthy individuals from the same geographical regions.

In this study, respiratory failure was defined as the person requiring hospitalisation and needing to be put on a ventilator.

What is a GWAS?

A GWAS is a method which helps scientists identify genes involved in a specific disease or trait. By searching specific areas of the genome (a complete set of DNA) for small genetic variations which occur more frequently in people with a particular disease or trait, scientists can identify genes which may contribute to a person’s risk of developing a particular condition.

The impact of blood type

By using this technique, the researchers were able to identify two key areas of the genome which appear to have an impact on whether a patient experiences respiratory failure. One of these is a section of the genome which codes for an individual’s blood group, the ABO blood group locus. An in-depth analysis of different blood groups revealed that individuals who are A positive have a higher risk of respiratory failure if they contract COVID-19. Conversely, those who are blood group O were shown to have increased protection against respiratory failure.

“There are two reasons why this study is important,” says Patrick Short, Chief Executive Officer at Sano Genetics. “Firstly, any data that helps researchers understand why some individuals are more likely to experience severe symptoms provides really practical, actionable insights. For example in the case of front-line workers, if it’s possible to identify individuals who are more at risk of severe infection due to blood type or other genetic factors, that information can be used to develop clear criteria for who can work on the frontline and who should stay at home.

“Secondly, it’s a step in the right direction for understanding how the disease works biologically, which is really important for developing anti-virals, vaccines and designing and running clinical trials.”

Potential virus receptors

The researchers also identified a second group of genes which could potentially impact severe cases of COVID-19.

One particular gene in the group, SLC6A20, carries the instructions for an protein which interacts with another gene, ACE2, which is known to act as a receptor (docking system) for other coronaviruses including Severe Acute Respiratory Syndrome (SARS).

The cluster also included genes encoding proteins involved in regulating the body’s immune response to airway pathogens, including viruses such as influenza. However, the impact and relationship of these genes to COVID-19 severity remains unclear.

What next?

This work provides an essential start point for researchers investigating the impact of genetics on severe COVID-19 cases.

“Replication of the study will be an important next step in order to verify the findings,” adds Short. “Other research groups such as the COVID-19 Host Genetics Initiative have already been able to replicate the association on Chromosome 3, while the blood type association remains in question. In the coming months there will be even larger studies taking place, using data from tens of thousands of patients. Here at Sano we’re planning to contribute to these data collection initiatives and help expand sample sizes.

“While this study has produced vital new findings, it’s important to remember that this is just the tip of the iceberg. It's highly likely that there are many other genetic variants involved in COVID-19 severity, so I think we’re going to see a much more complex picture emerging as research moves forward.”

The information in this article is accurate as of 10am, June 17, 2020.

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