key: cord-348727-o38uplxe
authors: Beaudoin-Bussières, Guillaume; Laumaea, Annemarie; Anand, Sai Priya; Prévost, Jérémie; Gasser, Romain; Goyette, Guillaume; Medjahed, Halima; Perreault, Josée; Tremblay, Tony; Lewin, Antoine; Gokool, Laurie; Morrisseau, Chantal; Bégin, Philippe; Tremblay, Cécile; Martel-Laferrière, Valérie; Kaufmann, Daniel E.; Richard, Jonathan; Bazin, Renée; Finzi, Andrés
title: Decline of humoral responses against SARS-CoV-2 Spike in convalescent individuals
date: 2020-07-09
journal: bioRxiv
DOI: 10.1101/2020.07.09.194639
sha: 
doc_id: 348727
cord_uid: o38uplxe

In the absence of effective vaccines and with limited therapeutic options, convalescent plasma is being collected across the globe for potential transfusion to COVID-19 patients. The therapy has been deemed safe and several clinical trials assessing its efficacy are ongoing. While it remains to be formally proven, the presence of neutralizing antibodies is thought to play a positive role in the efficacy of this treatment. Indeed, neutralizing titers of ≥1:160 have been recommended in some convalescent plasma trials for inclusion. Here we performed repeated analyses at one-month interval on 31 convalescent individuals to evaluate how the humoral responses against the SARS-CoV-2 Spike, including neutralization, evolve over time. We observed that receptor-binding domain (RBD)-specific IgG slightly decreased between six and ten weeks after symptoms onset but RBD-specific IgM decreased much more abruptly. Similarly, we observed a significant decrease in the capacity of convalescent plasma to neutralize pseudoparticles bearing SARS-CoV-2 S wild-type or its D614G variant. If neutralization activity proves to be an important factor in the clinical efficacy of convalescent plasma transfer, our results suggest that plasma from convalescent donors should be recovered rapidly after symptoms resolution.

plasma from convalescent donors should be recovered rapidly after symptoms resolution. 48

Until an efficient vaccine to protect from SARS-CoV-2 infection is available, alternative 52 approaches to treat or prevent acute COVID-19 are urgently needed. A promising approach is the 53 use of convalescent plasma containing anti-SARS-CoV-2 antibodies collected from donors who 54 have recovered from COVID-19 (1). Convalescent plasma therapy was successfully used in the 55 treatment of SARS, MERS and influenza H1N1 pandemics and was associated with 56 improvement of clinical outcomes (2-4). Experience to date shows that the passive transfer of 57 convalescent plasma to acute COVID-19 patients has been shown to be well tolerated and 58 presented some hopeful signs (5-9). In one study, the convalescent plasma used had high titers of 59

IgG to SARS-CoV-2 (at least 1:1640), which correlated positively with neutralizing activity (10). 60

While it remains to be formally demonstrated, neutralizing activity is considered an important 61 determinant of convalescent plasma efficacy (11) and regulatory agencies have been 62 recommending specific thresholds for qualifying convalescent plasma prior to its release. While 63 neutralizing function has been associated with protection against reinfection in rhesus macaques 64 expressing VSV-G. Neutralizing activity against pseudoparticles bearing the SARS-CoV S 120 glycoprotein was detected in only 25% of convalescent plasma and exhibited low potency, as 121 previously reported (Figure 2) (14) . Of note, while we observed enhanced infectivity for the 122 D614G variant compared to its WT SARS-CoV-2 S counterpart ( Figure S3A ), no major 123 differences in neutralization with convalescent plasma were detected at both time-points ( Figure  124 S3B), thus suggesting that the D614G change does not affect the overall conformation of the 125 Spike, in agreement with recent findings (18) . 126 127 The capacity to neutralize SARS-CoV-2 S WT or D614G-pseudotyped particles 128 significantly correlated with the presence of RBD-specific IgG, IgM and anti-S antibodies 129 ( Figure S4 ). Interestingly, we observed a pronounced decrease (20-30%) in the percentage of 130 patients able to neutralize pseudoparticles bearing SARS-CoV-2 S glycoprotein between 6 and 131 10 weeks after symptoms onset. Moreover, with plasma that still neutralized, the neutralization 132 activity significantly decreased between these two time-points ( Figure 2C ). Interestingly, RBD-133 specific IgM and neutralizing activity declined more significantly in convalescent plasma 134 overtime compared to RBD-specific IgG and anti-S Abs ( Figure S5A , B). Moreover, while the 135 loss of neutralizing activity on the WT and D614G pseudoparticles over time correlated with the 136 loss of anti-RBD IgM and IgG antibodies, the correlation was higher for IgM than IgG ( Figure  137 S5C, D), suggesting that at least part of the neutralizing activity could be mediated by IgM, as 138 recently proposed (13, 14) . 139

In summary, our study indicates that plasma neutralization activity keeps decreasing 141 passed the sixth week of symptom onset (14). It is currently unknown whether neutralizing activity is truly driving the efficacy of convalescent plasma in acute Figure S3 . D614G mutation enhances SARS-CoV-2 infectivity but does not affect its susceptibility to plasma neutralization.(A) Reverse Transcriptase normalized levels of pseudoviral particles bearing the SARS-CoV-2 S WT or D614G variant were used to infect 293T/ACE2 cells and infectivity measured 48h later by luciferase activity. Graph shown represents the percentage of infectivity relative to pseudoviral particle bearing the SARS-CoV-2 S WT. Statistical significance was tested using Mann-Whitney U tests (**** p < 0.0001). (B) Comparison between the neutralization ID 50 from pseudoparticles bearing SARS-CoV-2 S WT and SARS-CoV-2 S D614G. Statistical significance was tested using Wilcoxon matched-pairs signed rank test. (ns, not significant). 

SARS-CoV-2 Cell Entry Depends on ACE2 and TMPRSS2 and Is

Human coronavirus NL63 employs the severe acute respiratory syndrome coronavirus 113 receptor for cellular entry

Cross-sectional evaluation of 119 humoral responses against SARS-CoV-2 Spike

The membrane-proximal