Scientific discovery reveals why some people do not get infected with Covid-19

The search for the answer to why some people, even exposed to the virus, did not become infected, or at least did not appear to have been infected, has been an aspect of the disease that has always left scientists puzzled, since the beginning of the Covid-19 pandemic, in 2020. It is estimated that at least 20% of people are asymptomatic. It is normal to know someone who, in these more than three years, has never reported a complaint associated with the disease.

A new study published in the scientific journal Nature provides an answer for the first time. Researchers from the Universities of North Carolina and California, in the United States, and the University of La Trobe, in Australia, investigated the genetics of about 1,428 people who tested positive for Covid-19 and had donated blood years before the pandemic.

_{Measurement of heat in the population. (Photo: Reproduction/Marcelo Camargo/Agência Brasil)}

case analysis

The researchers worked on the analysis of a group of genes called human leukocyte antigens (HLA), which encode proteins read by the immune system to recognize harmful external agents, such as viruses and bacteria, and develop defenses against them. For this reason, they play an essential role in the response to an infection.

They observed that people with a genetic variant called HLA-B*15:01 were twice as likely to develop a symptom-free condition when infected with Sars-CoV-2. The mutation is relatively common, recurrent in about 10% of the population, also noted that the mechanism that protects these individuals.

The HLAs produce pieces of the virus, making the immune system notice them and initiate the production of antibodies and defense cells. In the case of patients with the HLA-B*15:01 variant, the study showed that, even before Covid-19 spread across the planet, they had already produced memory T cells for a very specific part of the virus that causes the illness.

Conclusions

The individuals’ blood was collected before the pandemic, proving that they never had any contact with the new coronavirus. However, they have been exposed to other coronaviruses before, which have circulated in the past causing common colds. Contact with these ancient viruses does not protect against Sars-CoV-2. However, thanks to the genetic variant, the exposure caused a kind of cross-protection.

In these people, this fact occurs because, infection with one of the seasonal coronaviruses caused the immune system to recognize a specific part of them that the new coronavirus also has in common, called NQK-Q8. Thus, the organism immediately identifies the infection with Covid-19 as an invader and begins to fight it.

Featured Photo: Immunizer against COVID 19. Reproduction/Marcelo Camargo/Agência Brasil