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Since the outbreak of the deadly corona virus more than three years ago, nearly 7 million people in the world have lost their lives due to infection with Covid-19. However, some people have not experienced any symptoms even after being exposed to the virus. A variant or mutation in the immune response gene may explain the cause and pave the way for more effective vaccines and treatments.
to report Science Alertglobal research led by the University of California, San Francisco (UCSF) found that one in five people with asymptomatic SARS-CoV-2 infection carried a gene variant called HLA-B*15:01.
Additionally, UCSF neurologist Jill Hollenbach and her colleagues found that people with HLA-B*15:01 who had never been infected with the virus had some immune cells that reacted to fragments of the SARS-CoV-2 protein. This suggests that immunity has developed after exposure to other infections.
Research shows that at least 20% of SARS-CoV-2 infections are asymptomatic; So learning more in this area can help scientists deal with this disease, which still exists around the world.
Hollenbach and his team write in their paper, “Most global efforts have focused on severe illness in Covid-19. Investigation of asymptomatic infection provides a unique opportunity to consider early immunological features. These features increase the rapid clearance of the virus.
Human white blood cell antigen (HLA) genes produce proteins that support the immune system. Some HLA molecules are found on cell surfaces. They recognize foreign invaders, such as viruses, and provide miniature pieces to help immune cells, such as T cells, recognize and fight infection or disease.
“If you have an army that can identify the enemy quickly, that’s a huge advantage,” Hollenbach said. It’s like having soldiers trained for battle who already know what to look for. “They can recognize the enemy by their clothes.”
The researchers examined the genetic data of 29,947 bone marrow donors collected in advance to see if HLA variation might predispose individuals to asymptomatic infection with SARS-CoV-2. The Covid-19 data was obtained through a voluntary smartphone-based app in which these donors participated and their infection, symptoms and outcomes were assessed.
1,428 donors who tested positive for SARS-CoV-2 were not vaccinated. Of these, 136 people declared that they had no symptoms. A clue to the genetic link discovered was that 20 percent of infected, asymptomatic donors had at least one copy of the HLA-B*15:01 gene, compared to another 9 percent of those with symptoms.
Having one copy of the protective variant HLA-B*15:01 doubles the chance of people having asymptomatic Covid-19. If a person has two copies of it, this probability will be eight times.
“Asymptomatic individuals may help us identify new ways to enhance protection against SARS-CoV-2,” said Stephanie Gross, a biochemist at Latrobe University in Australia. According to Gross, this could be done by mimicking the immune shield seen in people who have survived Covid-19.
Further analysis showed that T cells from individuals with HLA-B*15:01 who had never been exposed to SARS-CoV-2 (from donated blood collected before birth) had strong immune responses to SARS-CoV-2 protein fragments. These fragments share genetic sequences with other seasonal coronaviruses that cause the common cold. The T cells of these people were able to recognize different variants of Covid-19, including Omicron.
University of North Carolina immunologist Danilo Augusto says that even if viruses change their clothes, T cells can still recognize them by their boots or perhaps the tattoos on their arms. “Our immune memory works this way to keep us healthy.”
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