This evidence review was compiled by members of the CITF Secretariat with the input from experts affiliated with the CITF and does not necessarily reflect the views of all CITF members.

By Varun C. Anipindi

People infected with SARS-CoV-2 can experience a wide range of outcomes, ranging from asymptomatic infection to severe disease and death. While emerging evidence indicates that antibodies may represent a major correlate of protection, the specific mechanisms by which they influence overall disease outcomes is unknown.  In this pre-print, not yet peer-reviewed, Kaplonek et al. conducted an in-depth profiling of the humoral immune response to infection in a large cohort of individuals with asymptomatic, moderate, or severe disease during the acute phase of infection (0-12 days post-symptom onset)1.

Key points

  • Those who survived severe COVID-19 generated robust and highly coordinated acute antibody responses early post-infection, compared to patients that succumbed to COVID-19.
  • Antibodies generated against the conserved S2 subunit (non-RBD binding portion of the spike protein) may represent a key biomarker in distinguishing survivors and non-survivors of COVID-19.
  • Cross-reactive immunity to the S2 subunit of seasonal coronaviruses, such as OC43, (an immune response raised against the proteins of a virus that provides some level of immunity to a different virus) may be associated with the rapid maturation of SARS-CoV-2 specific antibodies, which was linked to better disease outcomes.
  • These S2-specific antibodies have the capacity to interact with Fc receptors (receptors on the surface of phagocytes involved in clearance of pathogens from the body) and may represent a key correlate of protection against death or symptomatic COVID-19 disease.

Kaplonek P, Wang C, Bartsch Y, et al. Early cross-coronavirus reactive signatures of protective humoral immunity against COVID-19. bioRxiv. 2021;2021.05.11.443609. Published 2021 May 12. doi:10.1101/2021.05.11.443609