This is a summary, written by members of the CITF Secretariat, of:

Coutu J, Ricard P, Djaïleb A, Lavallée E, Rabazanaha H, Stuible M, Durocher Y, Gilbert C, Brousseau N, Santerre, Thériault M, Trottier S, Boudreau D, Langlois MA, Pelletier J, Etchebarne MB, Masson JF. Large-scale validation of a plasmonic sensor for SARS-CoV-2 pseudo-neutralization with a cohort of food and retail workers. ChemRxiv. 2023 December 15. doi: 10.26434/chemrxiv-2023-3cwjs

The results and/or conclusions contained in the research do not necessarily reflect the views of all CITF members.

A CITF-funded study, published as a preprint and not yet peer-reviewed, found that a surface plasmon resonance (SPR) sensor, which can provide quantitative biomolecular information and can be used in point-of-care settings, is a viable alternative for monitoring SARS-CoV-2 humoral immune responses. This ability of SPR to track biomolecular changes related to SARS-CoV-2 infection in a population over the course of a longitudinal study has not been demonstrated before. This study was led by Julien Coutu, Pierre Ricard, Dr. Joelle N. Pelletier, and Dr. Jean-Francois Masson (all from Université de Montréal), and CITF-funded researchers Dr. Denis Boudreau (Université Laval) and Dr. Marc-André Langlois (University of Ottawa).

A few studies have demonstrated the performance of SPR sensors, but a large sample cohort was needed to validate them for clinical settings. This study aimed to detail the challenges and opportunities of using plasmonic sensors in clinical practice with over 1,000 clinical samples from a longitudinal study of 304 food and retail workers in Quebec.

The SPR sensor assessed the level of neutralizing antibodies by measuring the inhibition of the SARS-CoV-2 spike protein interaction with the ACE-2 receptor following exposure of the spike protein to naïve and immune (from vaccination and/or infection) sera. Participants provided blood samples at three-month intervals for up to five visits from April 2021 to early October 2022.

A percent inhibition (%I) score was calculated for the SPR sensor and validated against an ELISA (to detect antibody titers) and a live virus microneutralization assay (to detect neutralizing capacity). Values for %I closer to 100% indicate the presence of neutralizing antibodies due to vaccination and/or infection.

Key findings:

  • The response of the SPR sensor in detecting “neutralization” was shown to correlate well (r=0.74) with the live virus microneutralization assay — patients with a higher %I tended to have higher neutralizing capacity.
  • The %I increased progressively between visits two (three months) and four (nine months) for the ancestral spike protein, and between visits three (six months) and four, for the Omicron BA.1 spike protein.
  • While a second vaccine dose increased %I, three doses were required for a sustained humoral response and high %I (for both spike proteins).
  • Patients fully vaccinated with two or more doses and infection (hybrid immunity) had higher %I than individuals fully vaccinated and naïve to the virus.
  • Virus naïve individuals showed lower %I compared to individuals with hybrid immunity, who showed a sustained level of %I throughout the study period (up to 400 days post-vaccination).
  • A longitudinal trend of increased %I coinciding with vaccination campaigns and changes in circulating SARS-CoV-2 strains was seen.