Better immune response to corona from colds
In addition to the currently rampant SARS-CoV-2 coronavirus, there are other coronaviruses that have been circulating in humans for a long time and usually cause cold symptoms. Researchers are now reporting that such previous colds improve the immune response to SARS-CoV-2.
Most people who become infected with the SARS-CoV-2 coronavirus only develop COVID-19 slightly or have no symptoms at all. One reason why the disease progresses slightly could be an earlier infection with a seasonal coronavirus.
Four known coronaviruses
As explained in a joint press release from Charité – Universitätsmedizin Berlin, the Berlin Institute of Health in the Charité (BIH) and the Max Planck Institute for Molecular Genetics (MPIMG), four coronaviruses are known in medicine that have been in the People circulate and which are known as endemic human coronaviruses (HCoV).
These viruses commonly cause cold symptoms and are called HCoV-OC43, HCoV-229E, HCoV-HKU1, and HCoV-NL63. It is estimated that they account for up to 30 percent of colds.
Researchers from Charité – Universitätsmedizin Berlin, BIH and MPIMG are now showing in a study that certain immune cells that people have formed in the past against cold coronaviruses strengthen the immune response against SARS-CoV-2 – both during and after natural infection a vaccination.
However, this “cross-immunity” decreases with increasing age. This could contribute to the fact that older people become more seriously ill with COVID-19 and that their vaccination protection is often weaker than that of younger people.
Memory immune cells recognize new pathogens
According to the information, scientists from the Charité and the MPIMG were the first to make a surprising observation last year: Some people who have never had contact with SARS-CoV-2 have memory immune cells that the pathogen despite its novelty recognize.
The researchers attributed the observation to the fact that these so-called T helper cells had to deal with more harmless cold coronaviruses in the past and, due to their similar structure, especially the spike protein on the virus surface, also attack the new coronavirus. Such cross-reactivity has now been confirmed in a number of studies.
However, the question of how these immune cells influence the course of a later SARS-CoV-2 infection remained unclear.
“We assumed that cross-reacting T helper cells have a protective effect, a previous cold with endemic coronaviruses that have been circulating in the population for many years, so alleviates the symptoms of COVID-19,” explains Dr. Lucie Loyal, scientist at Si-M (Der Simulierte Mensch), a joint research space of the Charité and the Technical University of Berlin, and at the BIH Center for Regenerative Therapies (BCRT).
The first author of the study at that time as well as the current study says: “The opposite could also have been the case. In the case of some viruses, a second infection with a similar virus strain leads to a misdirected immune response, with negative effects on the course of the disease. “
The research team is now presenting indications that support the assumption of a protective effect. According to the data, cross-immunity could be one of several reasons not only for the different severity of COVID-19 courses, but also for the different effectiveness of the vaccinations in different age groups.
Immune system analyzed before and during infection
For the study, which was published in the specialist journal “Science”, the researchers recruited almost 800 people from mid-2020 who had not yet come into contact with SARS-CoV-2 and checked at regular intervals whether they were involved infected the pathogen. This was the case for 17 people.
The research group analyzed their immune system in detail both before and during the infection. They found that the body mobilized T helper cells, which it had formed against endemic cold coronaviruses, also against SARS-CoV-2.
In addition, the quality of the immune response against SARS-CoV-2 was better, the more these cross-reacting cells were present before the infection. The cells particularly often recognized a certain area of the spike protein. As explained in the announcement, the structure of the old and the new coronavirus is “preserved” at this point, that is, it is designed to be particularly similar.
“In the case of colds with more harmless coronaviruses, the immune system builds up a kind of universal, protective coronavirus memory,” explains Dr. Claudia Giesecke-Thiel, head of the flow cytometry service group at the MPIMG and lead author of the study.
“If it comes into contact with SARS-CoV-2, such memory cells are activated again and now also attack the new pathogen. This could contribute to a faster immune response against SARS-CoV-2, which prevents the virus from spreading unhindered in the body at the beginning of the infection and thus presumably has a positive effect on the course of the disease. “
But the expert also emphasizes: “That does not mean that you are definitely protected from SARS-CoV-2 if you have had colds in the past. Vaccination is important in any case. Our study provides one of several explanations for the observation made since the beginning of the pandemic that SARS-CoV-2 infection can develop so differently in different people. “
Immune-boosting effect also with vaccination
In a COVID-19 vaccination with the BioNTech vaccine, the researchers also demonstrated an immune-boosting effect of the cross-reacting T cells. Similar to a natural infection, this vaccine causes the body to produce the spike protein of SARS-CoV-2 – including the preserved fragment – and present it to the immune system.
An analysis of the immune response of 31 healthy people before and after vaccination showed that while normal T-helper cells were activated gradually over a period of two weeks, the cross-reacting T-helper cells responded very quickly to the vaccination within one week.
This also had a positive effect on the formation of antibodies: after the initial vaccination, the body was able to produce antibodies against the conserved site in the spike protein at a rate that is otherwise only observed with booster vaccinations.
“Even with the vaccination, the body can at least partially fall back on an immune memory if it has already suffered colds with endemic coronaviruses,” says Prof. Dr. Andreas Thiel, also the lead author of the study, who conducts research as a Charité scientist at the Si-M and the BCRT.
“That could explain the surprisingly quick and very high protective effect that we observe, at least in younger people, after a first COVID-19 vaccination.”
Cross immunity decreases with age
In a second part of the study, by analyzing the T helper cells in almost 570 healthy participants, the researchers were able to demonstrate that cross-immunity decreases as people get older: Both the number of cross-reacting T cells and their binding strength were found in older test subjects less than younger ones.
The authors of the study attribute the decreasing cross-immunity to natural changes in an aging immune system.
“The advantage that a harmless coronavirus cold often brings younger people in fighting SARS-CoV-2 and also in building up vaccination protection is unfortunately less in older people,” explains Prof. Thiel.
“A third booster vaccination could presumably compensate for the weaker immune response in this more vulnerable population group and ensure adequate vaccination protection.” (Ad)
Author and source information
This text complies with the requirements of specialist medical literature, medical guidelines and current studies and has been checked by medical professionals.
- Charité – Universitätsmedizin Berlin: Joint press release by Charité – Universitätsmedizin Berlin, the Berlin Institute of Health in the Charité (BIH) and the Max Planck Institute for Molecular Genetics (MPIMG): Science: Earlier colds improve the immune response to SARS-CoV-2 , (Accessed: 04.09.2021), Charité – Universitätsmedizin Berlin
- Loyal L et al.: Cross-reactive CD4+ T cells enhance SARS-CoV-2 immune responses upon infection and vaccination; in: Science, (veröffentlicht: 31.08.2021), Science
This article is for general guidance only and is not intended to be used for self-diagnosis or self-treatment. He can not substitute a visit at the doctor.