A study has found that DNA variation that affects the immune system may increase a person’s chances of surviving COVID-19 symptoms. The work, published Wednesday in the journal Nature, helps explain why some people infected with the virus that causes COVID-19 don’t get sick.
The researchers said that the T cells of some people with the variation can find and kill the virus without first seeing it. This is because the part of the virus that their T cells take home is very similar to the common coronavirus they have already encountered.
“There are people who have got strong prior immunity from their normal coronavirus exposure,” said Danny Altman, professor of immunology at Imperial College London, who was not involved in the study. This work could help researchers design better vaccines. Altman said.
The researchers found that people with a copy of the genetic variation were more than twice as likely to avoid symptoms than people without it. For those with two copies, the odds of avoiding symptoms increased by more than eightfold.
Federal data shows weekly reported COVID-19 deaths and hospitalizations in the US are at record lows. The concentration of virus detected in wastewater has recently increased from a low base. Health authorities and hospitals have shied away from reporting and monitoring.
Yet researchers are still discovering mysteries about the virus, including why some people become infected and transmit it without becoming ill. Age, underlying health problems, vaccination status and quality of health care all affect how a person fares against infection.
Jill Hollenbach, senior author of the study, wanted to focus on what are known as HLA genes that make human leukocyte antigens, immune-signaling molecules that sit on the surface of cells. These molecules hold fragments of foreign proteins for T cells to observe. A person’s HLA type determines which pieces of the pathogen are sent to T cells.
“There’s a lot of variation in that mix,” said Hollenbach, professor of neurology, epidemiology and biostatistics at the University of California, San Francisco.
Hollenbach and colleagues enrolled nearly 30,000 volunteers from a national registry of bone-marrow donors that matched them to transplant recipients based on HLA-type. From February 2020 to April 2021, more than 1,400 unvaccinated donors reported via a smartphone app that they had tested positive for the virus and 136 said they had no symptoms.
The researchers found that a variant called HLA-B*15:01 was associated with asymptomatic infections. The researchers found that nearly a fifth of participants who were symptom-free had at least one copy, compared to 9% of those with symptoms. This finding was reproduced with data from two other groups of patients.
Paula Cannon, professor of molecular microbiology and immunology at USC’s Keck School of Medicine, who was not involved in the research, said, “That’s not saying that if you have it, you don’t have to worry.” ” To be honest, I’d love to have these genes. If that happens, I’ll sleep better at night.”
The researchers also looked at T cells from people who had the HLA variant but had not been exposed to the virus. Their T cells still react to a fragment of the COVID-19 virus that is similar to those found in other common cold coronaviruses.
For some people with HLA-B*15:01, the piece of virus that T cells are exposed to resembles a piece of the normal coronavirus they’re already familiar with, which makes it easier to fight off, Canon Said: “It’s just kind good luck.”
Hollenbach said the study’s final analysis was limited to people who said they were white because the number of participants from other groups was not large enough to confirm a link.
The researchers found that another HLA variation exerted a protective effect when a person had both. Ludmila Prokunina-Olson, director of the Translational Genomics Laboratory at the National Cancer Institute, who was not involved in the study, said many factors, including genetics, play a role in when the body fights an infection.
“The combination of all these factors will determine how this will happen,” Prokunina-Olson said.