Findings could pave the way for new vaccines, drugs for SARS-CoV2
At least 20 per cent of COVID–positive patients remain asymptomatic. File photo: Vikas Choudhary / CSE A mutation in a gene linked to the immune system may explain why some who get the novel coronavirus COVID-19 show no symptoms of it, according to a new study published in journal Nature.
At least 20 per cent of COVID-19 patients remain asymptomatic. Scientists don’t yet understand why many individuals do not face major complications after infection while others develop a severe disease even if they do not have pre-existing conditions that make them vulnerable.
A gene, the human leukocyte antigen (HLA), might have some answers. HLA codes for a protein that helps the body differentiate between self and foreign cells. The mutated version of this gene, HLA-B*15:01, helps a type of immune cell called T cells to quickly recognise and attack SARS-CoV2.
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“If you have an army that is able to recognise the enemy early, that is a huge advantage,” the study’s lead researcher, Jill Hollenbach from the University Of California, San Francisco, the United States, said in a statement.
“It is like having soldiers that are prepared for battle and already know what to look for and that these are the bad guys,” she added.
These findings could pave the way for new vaccines, the researchers noted.
The role that HLA variants play in disease severity has been investigated in previous studies. But there is no clear consensus yet, the researchers wrote in the journal.
To find more concrete answers, researchers used a mobile app called COVID-19 Citizen Science Study to recruit infected individuals for the study. Data on the HLA gene variants were collected from The National Marrow Donor Program / Be The Match, the largest registry of HLA-typed volunteer donors in the United States.
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Their analysis found at least one copy of the mutated version of the gene was present in 20 per cent of the asymptomatic patients and 9 per cent of the symptomatic people. This shows the former was more than twice as likely to not fall sick.
Also, people possessing two copies of the variant were over eight times more likely to never develop symptoms, the researchers explained. More experiments revealed that people who contracted COVID-19 for the first time still reacted to a part of SARS-CoV2 called the NQK-Q8 peptide.
Some related coronaviruses, too, possess the NQK-Q8 peptide. This prior exposure, according to the researchers, could be helping T cells quickly respond and launch an attack on the invading SARS-CoV2.
“By studying their immune response, this might enable us to identify new ways of promoting immune protection against SARS-CoV-2 that could be used in future development of vaccines or drugs,” Stephanie Gras, a professor and laboratory head at La Trobe University, said in a statement.
However, the study suffers from a few limitations. One, the data in the study comes from self-reports, which could introduce errors. Second, the study was also limited to individuals who self-identified as white.
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“It is impossible to conclude whether our results for HLA-B*15:01 [the variant’s] association with asymptomatic disease are applicable in other ancestries,” the researchers wrote in their study.
However, the researchers stress that their findings have demonstrated a strong and significant link between the mutated HLA gene and asymptomatic infection of SARS-CoV-2.
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