Many coronaviruses are also in circulation, including some that cause the common cold. This analysis of antibodies from 11 patients with or without COVID reveals how SARS-CoV-2 infection affects the ability of the immune system to recognize these other coronaviruses. Lead author Dr. Andrew Ward, Professor of Integrative Structural and Computational Biology at Scripps explains that “better understanding how immunity once morest this large family of coronaviruses changes with COVID-19 infection is an important step towards the development better vaccines once morest the coronavirus or even “ pan-coronavirus ».
SARS-CoV-2 cross-immunity factor once morest other coronaviruses
A priori, SARS-CoV-2 is only 1 of the viruses of a large and diverse family of coronaviruses. Some of its close relatives (MERS, SARS of 2002-2004…) are just as contagious and virulent. Overall, many of these coronaviruses have only a quarter to half of their genetic material in common with SARS-CoV-2, but individual sections of their structures, including their spike protein are considered relatively similar between family members.
The cross-immunity hypothesis: Since the start of the COVID-19 pandemic, scientists have questioned whether previous exposure to these “cold coronaviruses” impacts immunity to SARS-CoV-2 and, similarly, whether infection by COVID-19 might change how the immune system recognizes common circulating coronaviruses. Immune system antibodies once morest a coronavirus spike protein might indeed recognize other similar spike proteins. The analysis of serum samples from 11 patients, 8 of whom dated from before the COVID-19 pandemic (therefore never exposed to SARS-CoV-2) and 3 of which came from donors who had recently had COVID-19 allowed to measure the strength with which the samples respond to spike proteins isolated from the different coronaviruses (specifically OC43 and HKU1), both associated with the common cold, as well as from SARS-CoV-1, MERS-CoV and SARS-CoV-2. The analysis reveals that:
- unsurprisingly, only serum from patients who recovered from COVID-19 reacted to SARS-CoV-2 spike proteins;
- more surprisingly, this same serum from COVID-19 patients also reacts more strongly than pre-pandemic samples to other spike proteins.
“Exposure to SARS-CoV-2 increases the levels of these antibodies”, conclude the authors. Further high-resolution structural studies of these serum antibodies from 3 healthy donors and 2 COVID-19 patients reveal that:
- most pre-pandemic coronavirus antibodies recognize a section of the OC43 and HKU1 spike proteins known as the S1 subunit, which tends to vary widely between coronaviruses;
- however, a larger sample of antibodies is identified in COVID-19 patient samples, including antibodies recognizing the S2 subunit, which varies less between different coronaviruses.
This research provides a first basic characterization of people’s antibody responses to endemic coronaviruses before and following exposure to SARS-CoV-2. The ultimate goal remains to design “universal” or “pan-coronavirus” vaccines capable of recognizing many different coronaviruses or most circulating coronaviruses. Finally, this work encourages us to focus on the S2 subunit.
