SARS-CoV-2 IgG seroprevalence surveys in blood donors before the vaccination campaign, France 2020-2021.

We conducted a cross-sectional study for SARS-CoV-2 anti-S1 IgG prevalence in French blood donors (n = 32605), from March-2020 to January-2021. A mathematical model combined seroprevalence with a daily number of hospital admissions to estimate the probability of hospitalization upon infection and determine the number of infections while correcting for antibody decay. There was an overall seroprevalence increase over the study period and we estimate that ∼15% of the French population had been infected by SARS-CoV-2 by January-2021. The infection/hospitalization ratio increased with age, from 0.31% (18-30yo) to 4.5% (61-70yo). Half of the IgG-S1 positive individuals had no detectable antibodies 4 to 5 months after infection. The seroprevalence in group O donors (7.43%) was lower (p = 0.003) than in A, B, and AB donors (8.90%). We conclude, based on seroprevalence data and mathematical modeling, that a large proportion of the French population was unprotected against severe disease prior to the vaccination campaign.

Inflammatory markers and auto-Abs to type I IFNs in COVID-19 convalescent plasma cohort study.

BACKGROUND: COVID-19 convalescent plasma (CCP) contains neutralising anti-SARS-CoV-2 antibodies that may be useful as COVID-19 passive immunotherapy in patients at risk of developing severe disease. Such plasma from convalescent patients may also have additional immune-modulatory properties when transfused to COVID-19 patients. METHODS: CCP (n = 766) was compared to non-convalescent control plasma (n = 166) for soluble inflammatory markers, ex-vivo inflammatory bioactivity on endothelial cells, neutralising auto-Abs to type I IFNs and reported adverse events in the recipients. FINDINGS: CCP exhibited a statistically significant increase in IL-6 and TNF-alpha levels (0.531 ± 0.04 vs 0.271 ± 0.04; (95% confidence interval [CI], 0.07371-0.4446; p = 0.0061) and 0.900 ± 0.07 vs 0.283 ± 0.07 pg/mL; (95% [CI], 0.3097-0.9202; p = 0.0000829) and lower IL-10 (0.731 ± 0.07 vs 1.22 ± 0.19 pg/mL; (95% [CI], -0.8180 to -0.1633; p = 0.0034) levels than control plasma. Neutralising auto-Abs against type I IFNs were detected in 14/766 (1.8%) CCPs and were not associated with reported adverse events when transfused. Inflammatory markers and bioactivity in CCP with or without auto-Abs, or in CCP whether or not linked to adverse events in transfused patients, did not differ to a statistically significant extent. INTERPRETATION: Overall, CCP exhibited moderately increased inflammatory markers compared to the control plasma with no discernible differences in ex-vivo bioactivity. Auto-Abs to type I IFNs detected in a small fraction of CCP were not associated with reported adverse events or differences in inflammatory markers. Additional studies, including careful clinical evaluation of patients treated with CCP, are required in order to further define the clinical relevance of these findings. FUNDING: French National Blood Service-EFS, the Association "Les Amis de Rémi" Savigneux, France, the "Fondation pour la Recherche Médicale (Medical Research Foundation)-REACTing 2020".

Reduced neutralizing antibody potency of COVID-19 convalescent vaccinated plasma against SARS-CoV-2 Omicron variant.

BACKGROUND AND OBJECTIVE: The SARS-CoV-2 Omicron variant displays increased infectiveness as well as mutations resulting in reduced neutralizing activity of antibodies acquired after vaccination or infection involving earlier strains. To assess the ability of vaccinated COVID-19 convalescent plasma (CCP-V) collected before November 2021 to seroneutralize Omicron, we compared neutralizing antibody (nAb) titres of 63 samples against Omicron and earlier B.1 (D614G) strains. METHODS AND FINDINGS: Relationship between anti-Omicron titres and IgG anti-S1 levels (binding arbitrary unit: BAU/ml) was studied. Although correlated, anti-Omicron titres were significantly lower than anti-B.1 titres (median = 80 [10-1280] vs. 1280 [160-10,240], p < 0.0001). Omicron nAb titres and IgG anti-S1 levels were correlated (Spearman's rank correlation coefficient = 0.67). Anti-S1 IgG threshold at 7000 BAU/ml may allow to discard CCP-V without anti-Omicron activity (nAb titre <40). Conversely, only those with highest titres (≥160) had systematically anti-S1 IgG levels >7000 BAU/ml. CONCLUSION: A fraction of CCP-V collected before November 2021 retains anti-Omicron seroneutralizing activity that may be selected by quantitative anti-IgG assays, but such assays do not easily allow the identification of 'high-titre' CCP-V. However, collecting plasma from vaccinated donors recently infected with Omicron may be the best option to provide optimal CCP-V for immunocompromised patients infected with this variant.

COVID-19 convalescent plasma: Evolving strategies for serological screening in France.

Quantitation of anti-SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) neutralizing antibodies (Nabs) is a key parameter in determining the effective dose for treatment with COVID-19 convalescent plasma (CCP). Interpretation of results from clinical trials conducted worldwide requires comparison of Nabs titres obtained from different methods. As virus neutralization tests (VNTs) are not standardized scalable or commercially available, strategies based on intensity of ELISA (Enzyme Linked Immunosorbent Assay) or chemiluminescent binding serological tests were implemented to allow comparisons and establish criteria for determining 'high-titres' of anti-SARS-CoV-2 antibodies (Abs). To this end, the FDA (Food and Drug Administration) has proposed criteria to define high-titre plasmas using different serological assays, including the one used in France for the CCP SARS-CoV-2 Abs screening (Euroimmun anti-S1 IgG). A retrospective study revealed that when using the FDA criteria (ELISA signal-to-cut-off [S/C ratio] ≥3.5), 91% of CCP had Nabs titres ≥40 as assessed with an in-house VNT. French strategy to ensure sufficient stocks of CCP of increasing titre has evolved over time. Recently, we improved our strategy by collecting only plasma from vaccinated convalescent donors as we confirmed that the mean IgG antibody level (ELISA S/C ratio) was significantly higher in plasma from vaccinated convalescent donors compared to donations from unvaccinated convalescent donors: 9.31 (CI 95%: 8.46-10.16) versus 3.22 (CI 95%: 3.05-3.39) (p < 0.001).

The Quality of Anti-SARS-CoV-2 T Cell Responses Predicts the Neutralizing Antibody Titer in Convalescent Plasma Donors.

Convalescent plasma therapy has been described as an attractive approach to treat critically ill patients with COVID-19 (Coronavirus disease 2019). The selection of convalescent plasma donors (CPD) is commonly based on neutralizing antibody titer. A better understanding of the quality of immune responses following COVID-19 will enable the optimization of convalescent donors' selection in convalescent plasma programs. The involvement of SARS-CoV-2 specific T cells in the induction and persistence of high affinity anti-SARS-CoV-2 neutralizing antibody is still poorly investigated. In this study, 115 CPD who presented SARS-CoV-2 and who were eligible for plasma donation were included. Comprehensive analysis of T cells together with humoral responses were performed in regards of sex, age and blood group type. High frequency of T cell responses against SARS-CoV-2 related protein such as spike glycoprotein (80.0%), nucleocapsid (NCAP) (70.4%) and membrane protein (VME1) (74.8%) were detected in CPD by ex vivo IFN-γ and TNF-α ELISpot assays. Among CPD responders, most exhibited poly-specific T cell responses (75%) defined by the ability to mount responses against at least two SARS-CoV-2 antigens. We found a positive correlation between the magnitude and the poly-specificity of anti-SARS-CoV-2 T cell responses in CPD. Notably, both the magnitude and poly-specificity of SARS-CoV-2 T cell responses were highly correlated with neutralizing antibody titer in CPD. The present study highlights that the poly-specificity and strength of SARS-CoV-2 specific T cell responses predicts neutralizing antibody titer following COVID-19. These observations show the interest to combine T cell assays and antibody titer for the selection of CPD and to a latter extend to assess COVID-19 vaccine efficacy in at-risk patients.

SARS-CoV-2 and post-donation information: a one-year experience of the French haemovigilance network.

BACKGROUND: There is growing evidence to support the hypothesis that SARS-CoV-2 is probably not transmissible by blood transfusion. In this study, we use the data gathered over one year by the French haemovigilance network on post-donation information related to SARS-CoV-2, and virological investigations on corresponding plasma to explore viral transmission by transfusion. MATERIALS AND METHODS: Whenever a donor reported COVID-19 symptoms and/or a positive SARS-CoV-2 nasopharyngeal (NP) PCR test, information regarding diagnosis and symptoms was collected using a specific questionnaire, and repository plasmas were screened using the SARS-COV-2 R-GENE® assay (Biomérieux). RNA sequencing (Sanger and deep sequencing) and virus isolation on Vero E6 cells were applied in plasma from donors testing positive. RESULTS: We investigated 1,092 SARS-CoV-2-related post-donation information (PDI) reports. PDI donors were younger than the global donor population and donated more often in the Paris region. Sixty-eight percent reported a positive NP real-time (RT)-PCR or antigenic testing and 22% of these also had symptoms at the time of testing. Thirty-seven (3.4%) donations tested positive for SARS-CoV-2 RNA, 11 (30%) were confirmed by another molecular assay, and 7 (19%) by sequencing, confirming low viral level. Most RNAemic blood donors donated in southern regions and in Paris. There was no difference in demographic data or duration parameter between RNAemic and non-RNAemic donors. Duration parameter was determined as the time elapsed between donation and: i) the onset of symptoms; ii) a positive NP RT-PCR; and iii) PDI. Cell culture experiments did not show any infectivity related to RNAemic plasmas. DISCUSSION: SARS-CoV-2 RNA can be detected in a small fraction of blood donors with PDI, reporting very low levels of RNA. The corresponding plasma is probably not infectious. These findings highlight the value of haemovigilance and PDI to guide blood safety strategies.

Préservation de l'efficacité neutralisante des anticorps anti-SARS-CoV2 dans le PFC-IA

L'efficacité thérapeutique du plasma de sujets convalescents, transfusés à des malades atteints de COVID-19, est en cours d'exploration dans différentes études cliniques et des protocoles d'utilisation thérapeutiques (PUT) sont réalisés pour des patients atteints de formes graves présentant des déficits immunitaires. Le traitement par amotosalen/UVA (INTERCEPT) (IA) des plasmas augmente la sécurité transfusionnelle en réduisant le risque de transmission d'agents pathogènes, dont le SARS-CoV-2, et permet la mise à disposition rapide de ces plasmas thérapeutiques anti-COVID. Étudier l'effet du traitement IA sur l'efficacité neutralisante des anticorps (Ac) anti-SARS-CoV-2 contenus dans les plasmas convalescents (PFC-IA). Au total, 650 mL de plasma est prélevé par aphérèse chez des donneurs guéris du COVID-19 (n = 59) puis traité IA pour obtenir 3 unités de PFC-IA. L'efficacité neutralisante des Ac anti-SARS-CoV-2 est mesurée avant et après IA selon une méthode de référence pour la séroneutralisation (SN) virale. Les valeurs obtenues sont discrètes et les titres définis (10, 20, 40, 80, ≥ 160) sont corrélés au taux de dilution pour lequel le plasma conserve encore son pouvoir neutralisant (une différence de 1 titre est non significative pour ce type de technique de SN utilisant du virus vivant). Sur 59 plasmas testés (Tableau 1), 37 ont conservé leur titre initial, 7 ont augmenté d'un titre ou deux (respectivement 7 et 2) et 13 ont diminué de titres (respectivement 10 et 3). Le traitement IA des plasmas de donneurs guéris du COVID-19 n'altère pas le pouvoir neutralisant des Ac anti-SARS-CoV-2 présents dans ces plasmas. (French) [ABSTRACT FROM AUTHOR] Copyright of Transfusion Clinique et Biologique is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

DGVRetroDon : contribution à l'évaluation du risque de transmission du SARS-CoV-2 par transfusion par un dépistage de l'ARN viral plasmatique dans des dons de sang en France

Lors de l'émergence de l'épidémie de SARS-CoV-2, la question d'une possible transmission par transfusion du virus a été évoquée avec la mise en évidence d'ARN dans le plasma de donneurs de sang. Une étude rétrospective a été réalisée à partir d'échantillons de biothèque transfusionnelle issus de dons de sang prélevés au pic épidémique en France (du 23 au 28 mars 2020), dans les régions les plus impactées (NORD et EST). Selon plusieurs hypothèses de prévalence, la taille d'échantillon minimale a été estimée à 6000. Le dépistage a été réalisé sur des pools de 4 échantillons (P4) par une méthode automatisée (Procleix SARS-CoV-2, Panther System, Grifols). 9672 échantillons ont été testés sous la forme de 2418 pools (P4). Cinq pools ont été dépistés positifs. Sur les 20 échantillons unitaires composant ces pools expertisés au CNR RIT (INTS), 1 seul a été confirmé par 2 méthodes différentes de RT-PCR, avec de faibles intensités réactionnelles suggérant une très faible charge virale. La mise en culture du plasma correspondant n'a pas permis d'isoler le virus. Cet échantillon provenait d'une donneuse ayant décrit rétrospectivement des symptômes évocateurs de COVID-19 dans les jours suivant son don (sans avoir été testée). Aucun EIR n'a été mis en évidence lors de l'enquête d'hémovigilance réalisée chez les receveurs du CGR et du MCP issus du don ARN SARS-CoV-2 positif. Cette étude confirme la possible présence d'ARN du virus SARS-CoV-2 dans le plasma de donneurs de sang asymptomatiques, à taux très faible, avec une prévalence d'environ 1/10 000 dons en période épidémique, sans que le caractère infectieux n'ait été démontré. (French) [ABSTRACT FROM AUTHOR] Copyright of Transfusion Clinique et Biologique is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

SARS-CoV-2 neutralising antibody testing in Europe: towards harmonisation of neutralising antibody titres for better use of convalescent plasma and comparability of trial data.

We compared the performance of SARS-CoV-2 neutralising antibody testing between 12 European laboratories involved in convalescent plasma trials. Raw titres differed almost 100-fold differences between laboratories when blind-testing 15 plasma samples. Calibration of titres in relation to the reference reagent and standard curve obtained by testing a dilution series reduced the inter-laboratory variability ca 10-fold. The harmonisation of neutralising antibody quantification is a vital step towards determining the protective and therapeutic levels of neutralising antibodies.

Convalescent plasma therapy for B-cell-depleted patients with protracted COVID-19.

Anti-CD20 monoclonal antibodies are widely used for the treatment of hematological malignancies or autoimmune disease but may be responsible for a secondary humoral deficiency. In the context of COVID-19 infection, this may prevent the elicitation of a specific SARS-CoV-2 antibody response. We report a series of 17 consecutive patients with profound B-cell lymphopenia and prolonged COVID-19 symptoms, negative immunoglobulin G (IgG)-IgM SARS-CoV-2 serology, and positive RNAemia measured by digital polymerase chain reaction who were treated with 4 units of COVID-19 convalescent plasma. Within 48 hours of transfusion, all but 1 patient experienced an improvement of clinical symptoms. The inflammatory syndrome abated within a week. Only 1 patient who needed mechanical ventilation for severe COVID-19 disease died of bacterial pneumonia. SARS-CoV-2 RNAemia decreased to below the sensitivity threshold in all 9 evaluated patients. In 3 patients, virus-specific T-cell responses were analyzed using T-cell enzyme-linked immunospot assay before convalescent plasma transfusion. All showed a maintained SARS-CoV-2 T-cell response and poor cross-response to other coronaviruses. No adverse event was reported. Convalescent plasma with anti-SARS-CoV-2 antibodies appears to be a very promising approach in the context of protracted COVID-19 symptoms in patients unable to mount a specific humoral response to SARS-CoV-2.

Lower prevalence of antibodies neutralizing SARS-CoV-2 in group O French blood donors.

We investigated the distribution of antibodies neutralizing SARS-CoV-2 according to age, sex or blood group in French blood donors. In 464 samples collected before the emergence of SARS-CoV-2 (2017 and 2018), our virus neutralization assay had a 100% specificity. It was used to test 998 samples collected from blood donors during the last week of March or the first week of April 2020. As expected at this stage of the outbreak, the prevalence was low (2.7%) and, importantly, criteria for blood donation imply that the vast majority of seropositives had asymptomatic or pauci-symptomatic SARS-CoV-2 infections. Seroprevalence values did not differ significantly among age groups (but were slightly higher in donors <30yo and ≥60yo), and between males and females (2.82% vs 2.69%), unlike what has been observed regarding hospitalizations admission to ICU and death rates in France. By contrast, we observed that the proportion of seropositives was significantly lower in group O donors (1.32% vs 3.86% in other donors, p = 0.014). We conclude that virus infection seems to occur with a similar incidence in men and women among French blood donors, but that blood group O persons are less at risk of being infected and not only of suffering from severe clinical presentations, as previously suggested.

Collecting and evaluating convalescent plasma for COVID-19 treatment: why and how?

Plasma provided by COVID-19 convalescent patients may provide therapeutic relief as the number of COVID-19 cases escalates steeply worldwide. Prior findings in various viral respiratory diseases including SARS-CoV-related pneumonia suggest that convalescent plasma can reduce mortality, although formal proof of efficacy is still lacking. By reducing viral spread early on, such an approach may possibly downplay subsequent immunopathology. Identifying, collecting, qualifying and preparing plasma from convalescent patients with adequate SARS-CoV-2-neutralizing Ab titres in an acute crisis setting may be challenging, although well within the remit of most blood establishments. Careful clinical evaluation should allow to quickly establish whether such passive immunotherapy, administered at early phases of the disease in patients at high risk of deleterious evolution, may reduce the frequency of patient deterioration, and thereby COVID-19 mortality.