Nearly everyone has been exposed to the highly prevalent seasonal coronaviruses responsible for the common cold. But could this exposure induce antibodies that also recognize certain proteins of the SARS-CoV-2 virus? A study led by University of Ottawa researcher Dr. Marc-André Langlois, now published in EBio Medicine, proposes that some individuals previously infected with certain seasonal coronaviruses may have pre-existing protective immune responses against SARS-CoV-2.

Key points: 

  • Researchers used samples collected prior to 2019, ensuring no exposure to SARS-CoV-2. Of the 580 samples examined, the majority were positive for IgG antibodies against proteins from the seasonal coronaviruses OC43, NL63, and 229E (83%, 75%, and 82% respectively).
  • While less than 5% of these pre-pandemic samples reacted against the SARS-CoV-2 spike protein, 7 to 15% reacted to the SARS-CoV-2 nucleocapsid protein. This can be explained by antibody ‘cross-reactivity’ as these individuals were not exposed to the SARS-CoV-2 virus at the time of sample collection. Antibody cross-reactivity is due to antibodies recognizing areas that are similar between proteins from different coronaviruses.
  • Of the many different seasonal coronaviruses, previous exposure to NL63 seems to be associated with a greater ability to neutralize the interaction between the SARS-CoV-2 spike and its cellular receptor, ACE2.
  • Aside from antibodies, other variables yet to be identified (such as cell-mediated immunity from prior exposures) may also be involved in protection against SARS-CoV-2.

Galipeau Y, Siragam V, Laroche G, Marion E, Greig M, McGuinty M, Booth RA, Durocher Y, Cuperlovic-Culf M, Bennett SAL, Crawley AM, Giguère P, Cooper C, Langlois M-A. Relative Ratios of Human Seasonal Coronavirus Antibodies Predict the Efficiency of Cross-Neutralization of SARS-CoV-2 Spike Binding to ACE2. EBioMedicine 2021 Dec.; doi: https://doi.org/10.1016/j.ebiom.2021.103700