Impact of Convalescent Plasma Therapy on Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Antibody Profile in Coronavirus Disease 2019 (COVID-19) Patients

Abstract

Convalescent plasma (CP) have been used for treatment of coronavirus disease 2019 (COVID-19), but their effectiveness varies significantly. Moreover, the impact of CP treatment on the composition of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies in COVID-19 patients and antibody markers that differentiate between those who survive and those who succumb to the COVID-19 disease are not well understood. Herein, we performed longitudinal analysis of antibody profile on 115 sequential plasma samples from 16 hospitalized COVID-19 patients treated with either CP or standard of care, only half of them survived. Differential antibody kinetics was observed for antibody binding, immunoglobulin M/immunoglobulin G/immunoglobulin A (IgM/IgG/IgA) distribution, and affinity maturation in "survived" versus "fatal" COVID-19 patients. Surprisingly, CP treatment did not predict survival. Strikingly, marked decline in neutralization titers was observed in the fatal patients prior to death, and convalescent plasma treatment did not reverse this trend. Furthermore, irrespective of CP treatment, higher antibody affinity to the SARS-CoV-2 prefusion spike was associated with survival outcome. Additionally, sustained elevated IgA response was associated with fatal outcome in these COVID-19 patients. These findings propose that treatment of COVID-19 patients with convalescent plasma should be carefully targeted, and effectiveness of treatment may depend on the clinical and immunological status of COVID-19 patients, as well as the quality of the antibodies in the convalescent plasma.

Keywords: COVID-19; SARS-CoV-2; antibody therapy; convalescent plasma; treatment.

Figure 1.

Longitudinal analysis of neutralizing antibody titers, antibody binding titers and antibody affinity maturation before and after CP treatment. (A–-B) SARS-CoV-2 neutralizing antibody titers (PsVNA50; colored lines) in plasma of 16 COVID-19 patients at different days post-onset of symptoms. P: CP treated, F: fatal; in shades of red, and S: survived; in shades of green.A, Day of convalescent plasma (PsVNA50 titer ranged from 160 to 640) treatment for each of the 8 COVID-19 patients is indicated by a dotted line on X-axis. B, Evolution of PsVNA50 titers in 8 COVID-19 patients with no CP treatment. (C–D) Evolution of antibody binding and antibody avidity to SARS-CoV-2 prefusion spike in COVID-19 patients. Serial dilutions of each plasma sample were analyzed for antibody binding and antibody avidity to SARS-CoV-2 prefusion spike. Total antibody binding is represented as SPR maximum resonance units (RU) (colored lines) of 10-fold diluted plasma samples that account for binding of all antibody isotypes. Binding was determined for individual COVID-19 patients: fatal patients (F; red shades) and survivors (S; green shades) for 8 patients treated with convalescent plasma (C) and 8 patients not treated with any antibody therapy (D). Plasma antibody off-rate constants against SARS-CoV-2 prefusion spike are shown in black. All SPR experiments were blindly performed twice. Variation for each sample in duplicate SPR runs was <5%. The data shown are average values of 2 experimental runs. Abbreviations: COVID-19, coronavirus disease 2019; CP, convalescent plasma; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SPR, surface plasmon resonance.

Figure 2.

Impact of CP on antibody isotype composition, binding and antibody off-rates to SARS-CoV-2 prefusion spike and their association with clinical outcome. (A–B) Percentage of each antibody isotype (according to the color codes; IgM, black; IgA, blue; IgG1, red; IgG2 green; IgG3, orange; IgG4, fuchsia) contribution to binding to SARS-CoV-2 prefusion spike. Resonance units for each antibody isotype was divided by the total resonance units for all the antibody isotypes combined to calculate the percentage of each antibody isotype. A, Day of CP treatment is indicated by a dotted line on X-axis for each of the 8 COVID-19 patients (P: plasma; F: fatal; S: survived). B, Evolution of prefusion-spike bound antibody isotype in 8 COVID-19 patients who were not treated with any antibody therapy (F: fatal; S: survived). C, Mean % area under the curve (AUC) of antibody isotypes IgM, IgG, IgA bound to SARS-CoV-2 prefusion spike for the COVID-19 patients who expired (fatal; shades of red) vs survived (green) who were either treated with CP (plasma) or not treated with any antibody therapy. D, AUC of SARS-CoV-2 prefusion spike binding antibody levels (RU) for the COVID-19 patients who expired (red) vs. survived (green). Area under the curve (AUC) for the total binding antibodies (RU values in Figure 1) were calculated for the entire duration of hospitalization for these individuals. Bar chart shows datapoints for each individual and presented as mean values ± SEM. E, Average antibody affinity against SARS-CoV-2 prefusion spike is shown for the final day sample from the COVID-19 patients who expired (red) vs survived (green) who were either treated or not-treated with CP. Bar chart shows datapoints for each individual and presented as mean values ± SEM. The statistical significances between the groups were determined by non-parametric (Kruskal-Wallis) statistical test using Dunn’s multiple comparisons analysis in GraphPad prism. The differences were considered statistically significant with a 95% confidence interval when the P value was <.05. * P < .05, ** P < .01, *** P < .001. Abbreviations: COVID-19, coronavirus disease 2019; CP, convalescent plasma; IgA, immunoglobulin A; IgG, immunoglobulin G; IgM, immunoglobulin M; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2; SEM, standard error of the mean.