The Relationship Between SARS-CoV-2 Neutralizing Antibody Titers and Avidity in Plasma Collected From Convalescent Nonvaccinated and Vaccinated Blood Donors

Abstract

Convalescent plasma (CP) treatment of coronavirus disease 2019 (COVID-19) has shown significant therapeutic effect when administered early (eg, Argentinian trial showing reduced hospitalization) but has in general been ineffective (eg, REMAP-CAP trial without improvement during hospitalization). To investigate whether the differences in CP used could explain the different outcomes, we compared neutralizing antibodies, anti-spike IgG, and avidity of CP used in the REMAP-CAP and Argentinian trials and in convalescent vaccinees. We found no difference between the trial plasmas, emphasizing initial patient serostatus as treatment efficacy predictor. By contrast, vaccinee CP showed significantly higher titers and avidity, being preferable for future CP treatment. Clinical Trials Registration. NCT02735707 and NCT04479163.

Keywords: COVID-19; IgG; SARS-CoV-2; avidity; convalescent plasma; neutralizing antibody; treatment.

Figure 1.

Comparison of SARS-CoV-2 Wuhan anti-spike IgG titers (A), neutralizing antibody titers (B), anti-spike IgM titers (C), and anti-spike IgG avidities (D) in REMAP-CAP donors (where plasma met criteria for inclusion, REMAP-CAP inc., or was excluded, REMAP-CAP exc.), Argentinian donors (where plasma met criteria for inclusion, Arg inc., or was excluded, Arg exc.) and vaccinated (after first and second dose) convalescent plasma. *P ≤ 1.8 × 10⁻³. Boxplots: Median, thick horizontal line; Wishkers, 1.5×interquartile range from 25th and 75th percentle (box); individual datapoints are overlayed. Abbreviations: GMT, geometric mean titer; Ig, immunoglobulin; Neg., negative; REMAP-CAP, Randomized Embedded Multifactorial Adaptive Platform for Community Acquired Pneumonia; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SeroPos., seropositive.