Covid-19 Infection Can Create Antibodies To Fight Common Cold: Study

A Covid-19 infection may boost the number of antibodies one has against common-cold causing coronaviruses, and the SARS-CoV-1 and MERS-CoV viruses, all of which are closely related.

A woman with common-cold. A new study has found that Covid-19 infection can create antibodies to fight common cold | Representative Photo

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New Delhi: When people get sick with a common cold, they do not become immune to Covid-19. However, a Covid-19 infection may boost the number of antibodies one has against common-cold causing coronaviruses, and the SARS-CoV-1 and MERS-CoV viruses, all of which are closely related, according to a new study. 

The findings of the study, led by scientists at Scripps Research Institute, were recently published in the journal Science Advances. The scientists have characterised coronavirus antibodies isolated from 11 people to reveal how Covid-19 impacts the immune system's ability to recognise other coronaviruses. 

Understanding Immunity Against Coronaviruses Will Help Develop Vaccines In Future

In a statement issued by Scripps Research Institute, Andrew Ward, senior author of the new paper, said getting a better understanding of how immunity against this broad family of coronaviruses changes with Covid-19 infection is an important step toward developing better coronavirus vaccines, both for Covid-19 and for future, related pathogens.

How Are Different Coronaviruses Similar?

SARS-CoV-2, the causative virus of Covid-19 is just one in a large and diverse family of coronaviruses. A few of the relatives of SARS-CoV-2 are equally contagious and virulent. These include the virus causing Middle East respiratory syndrome (MERS), and the 2002-2004 SARS outbreak. Meanwhile, other relatives of SARS-CoV-2, which are considered common cold viruses, cause much milder symptoms. Though many of these coronaviruses have only one quarter to one half of their genetic material in common with SARS-CoV-2, individual sections of the viruses' structure, notably the spike protein, are considered relatively similar between family members. 

Can Antibodies Against One Coronavirus Spike Proteins Recognise Other Spike Proteins?

Ever since the onset of the Covid-19 pandemic, scientists have wondered whether people's previous exposure to common cold viruses impacts their immunity to SARS-CoV-2, and whether infection with Covid-19 might change how the immune system recognises the more common coronaviruses. According to the new study, the immune system's antibodies against one coronavirus spike protein could potentially recognise other similar spike proteins as disease-causing. 

Which Coronaviruses Were Considered?

Ward's group studied serum samples from eleven people as part of the study. Eight of the samples dated to before the Covid-19 pandemic in order to ensure that the donors had never been exposed to SARS-CoV-2. Meanwhile, three samples were from donors who recently had Covid-19. The scientists measured how strongly each sample reacted to isolated spike proteins from different coronaviruses, including OC43 and HKU1, both of which are associated with common cold, and SARS-CoV-1, MERS-CoV, and SARS-CoV-2.

Which Serum Reacted To SARS-CoV-2 Spike Proteins?

Only the serum from recovered Covid-19 patients reacted to the SARS-CoV-2 spike proteins, the study found. The Covid-19 patient samples also reacted more strongly than the pre-pandemic samples to the other spike proteins as well. 

Sandhya Bangaru, the first author of the new paper, said most people have this baseline immunity to common coronaviruses and exposure to SARS-CoV-2 increases the levels of these antibodies. 

Which Portions Of Spike Proteins Were Recognised By Different Coronaviruses?

The researchers performed high-resolution structural studies on serum antibodies from three of the healthy donors and two Covid-19 patients to determine where on the spike proteins each antibody attached. The study found that most coronavirus antibodies from before the pandemic recognised a section of the OC43 and HKU1 spike proteins known as the S1 subunit, which tends to vary greatly between coronaviruses. 

However, in Covid-19 patient samples, the researchers identified a broader swatch of antibodies, including ones that recognise the S2 subunit, which varies less between different coronaviruses. According to the study, some antibodies from Covid-19 patients are not only bound to the common cold coronaviruses, but also to SARS-CoV-2 and MERS-CoV spoke proteins.

Are These Antibodies Enough To Provide Full Immunity To Coronaviruses?

The researchers do not know whether the presence of these antibodies, in any of the cases, is enough to provide full immunity to coronaviruses in the more complex setting of the human immune system. This is because the results were done directly on serum antibodies.

Convalescent (period of becoming healthy and well again after an illness) sera have an increased ability to react to common coronaviruses. This happens because of increased production of new antibodies that can recognise several coronaviruses, and also because of an increase in levels of pre-existing antibodies that are specific to each virus. 

The researchers, in the future, aim to compare antibodies from the same individuals pre- and post-infection with Covid-19.