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Humoral immunity to COVID-19 in people who are not infected

Scientists have discovered antibodies to coronavirus that suggest humoral immunity in blood samples donated before the pandemic began. It appears that some people may be immune to such an infection, at least to some extent. Nevertheless, the number of new COVID-19 cases is increasing in many regions of the world. But not everyone who comes into contact with SARS-CoV-2 will develop COVID-19.

Indication of humoral immunity to coronaviruses

young woman with protective mask may have humoral immunity to coronavirus

A group of scientists in the UK may have found some clue as to why some people are better at fighting SARS-CoV-2 than others. The research team originally planned to develop a highly sensitive test to detect antibodies against SARS-CoV-2. Scientists can use this type of test to determine if a person has antibodies after COVID-19. This is important information for those who want to determine how long immunity can last after COVID-19 infection. As part of their work, the scientists used blood samples from people without COVID-19. To their surprise, they found antibodies that reacted to SARS-CoV-2 in some samples. In their work, the researchers describe a scientific theory that exposure to one of the most common human coronaviruses, which can cause colds, can result in immunity to the other common human coronaviruses. They call this immune cross-reactivity.

3d illustration of coronaviruses spreading in the organism and cross-reactivity of antibodies

There are four seasonal common human coronaviruses, all of which cause mostly mild illness. The vast majority of people get infected with at least one of these viruses at some point. Scientists already know that the human body does not develop permanent or humoral immunity to these viruses. This is why a person can get infected with the common human coronavirus more than once in their life. So could previous exposure to a common human coronavirus provide at least temporary protection against SARS-CoV-2? Coronaviruses use a protein called spike protein to attach to host cells and infect them. In the new study, the researchers explain how antibodies that recognize part of the spike protein can cause cross-reactivity in the immune system. In their study, they determined the concentrations of antibodies reacting in this way in several sample collections, most of which had been donated before the appearance of the SARS-CoV-2 virus.

Study results

Female dentist wears protective visor while treating patient due to covid 19 pandemic

Using a group of 50 blood samples from pregnant women as of May 2018, the team found that 10% of them had antibodies with cross-reactivity. In a separate cohort of 101 samples as of May 2019, three had these antibodies. In another experiment, the scientists analyzed 13 additional samples from adults who recently had an infection due to coronavirus-related flu. Of these, only 1 sample had cross-reacting antibodies. Overall, the authors reported that 16 of 302 samples or 5.29% had some type of antibody against Sars-CoV-2. The average age of the donors was 51 years. But why did relatively few people have reactive antibodies, despite the high number of infections with common human coronaviruses? This could depend on how often a person has been infected with a common human coronavirus. The frequency is highest in children and adolescents.

social distance in public areas as one of the measures against sars cov 2

The results show that children are much more likely to have these reactive antibodies than adults. However, more research is needed to understand why this is so. But it could be because children are more often exposed to other coronaviruses. These higher scores could also explain why children with COVID-19 are less likely to get seriously ill. However, there is still no evidence that these antibodies prevent SARS-CoV-2 infection. the authors the study emphasize that there are still many unknowns that need further research. For example, how exactly is the humoral immune response to one coronavirus changed by exposure to another? Why does this activity decrease with age? Additionally, people who have recently had a cold shouldn’t believe they are immune to COVID-19.