PMC8419417_01
Kinetics of (A) anti-SARS-COV-2 IgG (anti-S + anti-N) and (B) neutralizing titer (MNT90). In parentheses, number of days elapsed since the second negative molecular nasopharyngeal swab.
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As demonstrated in Figure 1, this molecular positivity was not associated with a change in the trend of decline of total IgG or with a boost in NT. The SOFA score was 5-7 immediately before transfusion and reduced, showing improvement, in two out of five patients after transfusion (patients 2 and 3) (Supplementary Figure 1A). The PaO2/FiO2 ratio ranged from 92 to 294 at admission, and from 172 to 182 immediately before CP treatment; they improved after CP transfusion for all patients (Supplementary Figure 1B). Lymphocytopenia improved after CP transfusion in four of the five patients (Supplementary Figure 1C). After the transfusion, the pulmonary lesions in two patients (patients 2 and 4) markedly reduced (Supplementary Figures 1A, 3B), while the remaining patients (patients 1, 3 and 5) had no significant improvement.
Antibody and neutralizing kinetics. (A) IgA, MNT, and RABI titers superimposed to anti-S + anti-N IgG and IgM. IgA, MNT, and RABI are expressed as reciprocal of dilution on a base 2 antilog scale (left "X" axis). IgG and IgM are expressed as AU on a linear scale (right "Y" axis). The chequered boxes highlight the stable profile of MNT (B) and IgA and RABI titer (C), compared with anti-S + anti-N IgG.
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As observed, there is no evident correlation between the steadily decreasing total IgG titer ("xs" on Figure 2) and the even level of MNT (solid squares on Figures 2A, B), indicating that RBD-targeted antibodies (i.e., those relevant to suppression of viral transmission and sterilizing immunity) may have different kinetics and longer persistence than those targeted to non-RBD epitopes. However, their titer, once again, closely matched the profile as obtained both by MNT and RABI test, suggesting that IgA may be a relevant contributor to the neutralizing activity (Figures 2A, C). All patients presented bilateral ground-glass opacity and/or pulmonary parenchymal consolidation (on the chest CT scan), and two of them were carrying pulmonary micro-embolism immediately before CP transfusion (Supplementary Figure 2).