Case Report: Effects of Anti-SARS-CoV-2 Convalescent Antibodies Obtained With Double Filtration Plasmapheresis

Abstract

Passive antibody therapy has been used to treat outbreaks of viral disease, including the ongoing pandemic of severe respiratory acute respiratory syndrome (SARS) coronavirus 2 (SARS-CoV-2) or COVID-19. However, the real benefits of the procedure are unclear. We infused a concentrated solution of neutralizing anti-SARS-CoV-2 antibodies obtained from a convalescent donor with a single session of double filtration plasmapheresis (DFPP) into a 56-year-old woman with long history of unremitting, severe COVID-19. She was unable to establish an adequate antiviral immune response because of previous chemotherapy, including the infusion of the anti-CD20 monoclonal antibody rituximab, administered to treat a diffuse large B-cell lymphoma. The disease promptly recovered despite evidence of no endogenous anti-SARS-CoV-2 antibody production. The observation that passive antibody therapy might prove particularly effective in immunodepressed COVID-19 patients requires evaluation in prospective randomized controlled trial.

Keywords: COVID-19; case report; coagulation biomarkers; convalescent antibodies; double filtration plasmapheresis; hypercoagulability; immunosuppression; rituximab.

Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Copyright © 2021 Curtò, Tomatis, Gastoldi, Galbusera, Noris, Raimondi, Lorini, Falanga, Marchetti, Remuzzi and Ruggenenti.

Figures

Figure 1

Patient outcome from symptoms onset to hospital discharge.

Figure 2

Levels of anti-SARS-CoV-2 N IgG antibodies in the concentrate antibody solution infused to the patient, in antibody donor serum and in recipient sera collected before antibody infusion (day 0) and 7, 14, and 22 days thereafter. The dashed line indicates the threshold for antibody positivity.

Figure 3

Patient serum-induced ex vivo C5b-9 deposition (A) and thrombi formation (B) on cultured Human Microvascular Endothelial Cells (HMEC-1) line immediately before antibody infusion (Day 0), and 1, 7, 14, and 21 days thereafter. (A) HMEC-1 were incubated for 2 h with serum (diluted 1:2 with test medium, HBSS with 0.5% BSA) from the patient or with a control serum pool. At the end of incubation, cells were washed, fixed, and stained with rabbit anti-human complement C5b-9 complex antibody followed by FITC-conjugated secondary antibody. Fluorescence microscopy was used to view the fluorescent staining on endothelial cell surface, and the HMEC-1 area covered by C5b-9 staining was calculated by automatic edge detection (Image J software) in 15 high power fields. For each sample, the highest and the lowest values were discarded and the mean of the other 13 fields was calculated, and values were expressed as the percentage of C5b-9 deposits induced by a pool of sera from 10 healthy controls run in parallel (reference 100%). Dashed lines indicate upper and lower limit of normal range. (B) HMEC-1 were activated with ADP and exposed for 2 h to serum (diluted 1:2 with test medium, HBSS with 0.5% BSA) from the patient or with a control serum pool. Perfusion of heparinized whole blood (heparin 10 U/ml) from an healthy subject (added with the fluorescent dye mepacrine 10 µM, to label platelets) was then performed in a thermostatic flow chamber (37°C) in which one surface of the perfusion channel was a glass slide seeded with a monolayer of endothelial cells at a constant flow rate of 1500 sec-1 (60 dynes/cm2). After 3 min, perfusion was stopped, and the slide with the endothelial cell monolayer was dehydrated and fixed in acetone for 20 min. Slides were examined under confocal inverted laser microscopy. Fifteen fields for each slide were systematically digitized along the surface and the area covered by thrombi was quantified by Image J (NIH, Bethesda, MD), and expressed as pixel2 per field analyzed. For each sample the mean of 15 fields (excluding the lowest and the highest values) was calculated. Dashed lines indicated the area covered by thrombi of control serum pool ± SE. Data are reported as means ± SE. °P<0.0001, °°P<0.001 versus control serum pool; ^P<0.0001 versus day 0; *P<0.0001 versus day 1; #P<0.0001, ##P<0.001 versus day 7. Statistical analysis: ANOVA.

Figure 4

D-Dimer levels in patient plasma samples collected before antibody infusion (Day 0) and 1, 7, 14, and 21 days thereafter. Dashed line represents the upper normal reference value.