Researchers from Université de Montréal and Héma Québec, led by Dr. Andrés Finzi and Dr. Renée Bazin, and working with collaborators across Canada, are reporting that antibodies against SARS-CoV-2 Spike correlate with COVID-19 severity. This publication is part of their research funded by the Government of Canada through the COVID-19 Immunity Task Force and the Canadian Institutes for Health Research. In their cross-sectional study they analyze samples from over 100 COVID-19 patients with moderate to severe disease that were not hospitalized, at different times post-symptom onset.

In response to infection, different types of antibodies (also known as immunoglobulins or Ig) are made recognizing a variety of viral proteins. The antibodies more commonly studied are three specific types of immunoglobulins; IgG, IgM, and IgA. The spike proteins of SARS-CoV-2 mediate the virus’ entry into human cells. The region of the spike that binds to the cellular receptor to trigger viral entry is known as the Receptor Binding Domain (or RBD for short). Most infected individuals had antibodies recognizing spike within 2 weeks of the onset of symptoms. The levels of IgG antibodies recognizing RBD remained stable over time, but the levels of RBD-specific IgM and IgA antibodies decreased after symptom resolution.

A special type of antibody can bind to the spike protein preventing it from binding to the human receptor and blocking new infections. These are known as neutralizing antibodies. Most individuals developed neutralizing antibodies within 2 weeks of infection, but the level of neutralizing activity significantly decreased over time.

Their results highlight the importance of studying the persistence of neutralizing activity upon natural SARS-CoV-2 infection. Understanding the antibody response directed against SARS-CoV-2 is crucial for the development of vaccine, therapeutic, and public health interventions.


Prévost J, Gasser R, Beaudoin-Bussières G, Richard J, Duerr R, Laumaea A, Anand SP, Goyette G, Benlarbi M, Ding S, Medjahed H, Lewin A, Perreault J, Tremblay T, Gendron-Lepage G, Gauthier N, Carrier M, Marcoux D, Piché A, Lavoie M, Benoit A, Loungnarath V, Brochu G, Haddad E, Stacey HD, Miller MS, Desforges M, Talbot PJ, Maule GTG, Côté M, Therrien C, Serhir B, Bazin R, Roger M, Finzi A. Cross-sectional evaluation of humoral responses against SARS-CoV-2 Spike. Cell Rep Med. 2020 Oct 20;1(7):100126. doi: 10.1016/j.xcrm.2020.100126.