A new study aims to understand the genetic factors present in people with Down syndrome, making them susceptible to the coronavirus.
Earlier studies have shown a tenfold mortality risk for people with Down syndrome if they contract coronavirus.
Now, the new study, published in the journal Scientific Reports, noted that TMPRSS2, a gene that codes for an enzyme critical for aiding the entry of SARS-CoV-2 in human cells, had 60 per cent higher levels of expression in Down syndrome.
The gene is located on chromosome 21, which people with Down syndrome have three copies of.
The researchers also found higher expression levels for CXCL10, a gene that can trigger a cascade of events. This results in unchecked inflammation -- cytokine storms -- where the body's immune system attacks its own lung cells.
The authors speculated that this might lead individuals with Down syndrome to be more susceptible to late-onset complications such as lung fibrosis.
Furthermore, Down syndrome individuals may also be susceptible to subsequent bacterial infections following Covid-19.
However, the researchers also observed that people with Down syndrome have an overactivated interferon response, an important innate defence that shuts down viral replication within cells. Two of the genes linked to an interferon response - IFNAR1 and IFNAR2 - are found on chromosome 21.
This study can be corroborated by another research recently published study in the Annals of Internal Medicine. The research reported that people with Down syndrome affected by Covid-19 in the United Kingdom are five times more likely to be hospitalized and ten times more likely to die.