Human is not equal to human. This was shown once again in the corona pandemic. While some became seriously ill with Covid-19, the virus could hardly harm others. Studies have shown that at least one in five people infected with SARS-CoV-2 was asymptomatic, i.e. without recognizable symptoms. What is it about these people that others don't?
A research team from the USA and Australia has set itself the task of solving this mystery. 1,428 people who had been shown to be infected with the coronavirus were examined, including 136 asymptomatically infected people. It turned out that a specific gene variant could be responsible for the increased protection factor. The researchers were able to detect HLA-B*15:01 in up to 25 percent of those infected without symptoms. The study was recently published in the journal "Nature".
HLA is the short form for human leukocyte antigens. It is a gene complex. The HLA genes belong to the immunoglobulins, i.e. to the antibodies, and play a major role in the immune system in recognizing and fighting pathogens. It is already known that some HLA variants protect against certain pathogens. It has been proven, for example, that HLA-B*27 can slow down the progression of AIDS.
"HLA variants have been associated with hundreds of diseases, including infections," write the scientists, who had already suspected before the start of the study that HLA genes could also have an influence on the course of a corona infection and themselves had focused on this during the investigation. In fact, they were able to show that every fifth asymptomatic infected person carried HLA-B*15:01 in their bodies, but only every ninth patient with symptoms.
People who carried the gene variant on both alleles, i.e. inherited from mother and father, were even better protected against the corona virus. They "remain asymptomatic eight times more often than people with other gene variants," the researchers report. An estimated ten percent of all people of European descent are carriers of HLA-B*15:01.
But what can this gene variant do better than others? To put it simply: she is a specialist in cold coronaviruses. Scientists from the Charité, the Berlin Institute of Health in the Charité and the Max- Planck Institute for Molecular Genetics demonstrated in a study. They found that some people have memory immune cells from previous colds that are able to recognize SARS-CoV-2, even though they have never been in contact with the pathogen. Key word: cross immunity.
Based on this, the research team from the USA and Australia examined the immune cells of people who carried the HLA gene variant but who said they had never been infected with SARS-CoV-2 - and found a special protein: NQK-Q8. It turned out that three quarters of those examined had this protein. HLA-B*15:01 therefore seems to ensure that the production of the coronavirus protein is increased. This enables the immune system to react faster and better to SARS-CoV-2. The results underscored the importance of "pre-existing immunity that leaves a memory pool of cross-reactive T cells ready to fight infection," the scientists said.