Immune memory is influenced by the frequency and type of antigenic challenges. Here, we performed a cross-sectional comparison of immune parameters following a BA.1 breakthrough infection in individuals with prior hybrid immunity (conferred by infection and vaccination) versus those solely vaccinated in a cohort of health care workers in Lyon, France. The results showed higher levels of serum anti-receptor binding domain (RBD) antibodies and neutralizing antibodies against BA.1 post-infection in the vaccine-only group. Individuals in this group also showed a decrease in memory B cells against the ancestral strain but an increase in those specific and cross-reactive to BA.1, suggesting a more limited immune imprinting. Conversely, hybrid immunity prevents the decrease in antibody dependent cellular cytotoxicity (ADCC) response, possibly by limiting IgG4 class-switching and enhanced anti-N responses post-infection. This highlights that BA.1 breakthrough infection induces different immune responses depending on prior history of vaccination and infection, which should be considered for further vaccination guidelines.

Kidney transplant recipients (KTRs) are highly vulnerable to COVID-19. An intensified scheme of vaccination offers short-term protection to the 50%-75% of KTRs able to develop a germinal center reaction, required for the generation of neutralizing titers of antibodies (NAbs). However, the duration of this vaccinal protection is unknown. In-depth longitudinal analysis of the immune response to vaccination of 33 KTRs demonstrates that the low peak of IgGs, the progressive decline in antibody titers, and the emergence of a variant of concerns (VOC) of SARS-CoV2, synergize to let 2/3 of responders to vaccine without NAbs after only a few months. Yet, a retrospective study of an independent cohort of 274 KTRs, revealed that the risk of severe COVID-19 in the latter was low, similar to that of patients with serum neutralizing capacity against VOC. Our work links this late vaccine protection with the presence of memory B cells, which are generated during the initial vaccine-induced germinal center reaction, have a wide repertoire directed against conserved spike epitopes, and rapidly differentiate into IgG-producing plasma cells upon antigenic rechallenge. We conclude that in contrast with a serological layer that goes fading rapidly, the cellular layer of humoral memory provides an efficient long-term protection against VOC to KTRs. This illustration of the complementary roles of the two layers of the humoral memory has implications in immunopathology beyond the COVID-19 in KTRs.

Patients on maintenance hemodialysis (MHD) are at high risk of both infection by SARS-CoV-2 and death from COVID-19,1 justifying the early prioritization of this vulnerable population for vaccination. It is widely accepted that the protection induced by vaccination against symptomatic COVID-19 , in both the general population2 and immunocompromised patients,3 is due to neutralizing antibodies. Cellular immunity, which is able to limit the risk of severe COVID-19 in the absence of neutralizing antibodies, appears to be a second step of immune protection,.

Idiopathic nephrotic syndrome (INS) is the most frequent glomerular disease in childhood. There is overwhelming evidence that INS is immune mediated. INS is mainly attributed to the impaired function of T cells resulting in increased plasma lymphocyte-derived permeability factors even if the precise mechanisms remain unknown. Unfortunately, none of the avail-able drugs (corticosteroids, calcineurin inhibitors, mycophenolate mofetil, levamisole and B cell–targeted drugs) proposed by the lat-est clinical practice recommendations lead to persistent remission in every patient [ 1 , 2 ]. Today,INS in children is classified based on response to corticosteroid treatment. Although 90% of children exhibit a favorable response to steroids, only 25% of these children will effectively be cured and will not undergo further relapses after an initial course of steroids. Therefore, one of the major current challenges in INS is to identify which patients will have a persistent response to therapy, and which patients will relapse [ 3 ]. Indeed, using classical indicators such as clinical parameters or renal biopsies does not help in the prediction of the individual response

The diversity of vaccination modalities and infection history are both variables that have an impact on the immune memory of individuals vaccinated against SARS-CoV-2. To gain more accurate knowledge of how these parameters imprint on immune memory, we conducted a long-term follow-up of SARS-CoV-2 spike protein–specific immune memory in unvaccinated and vaccinated COVID-19 convalescent individuals as well as in infection-naïve vaccinated individuals. Here, we report that individuals from the convalescent vaccinated (hybrid immunity) group have the highest concentrations of spike protein–specific antibodies at 6 months after vaccination. As compared with infection-naïve vaccinated individuals, they also display increased frequencies of an atypical mucosa-targeted memory B cell subset. These individuals also exhibited enhanced T H 1 polarization of their SARS-CoV-2 spike protein–specific follicular T helper cell pool. Together, our data suggest that prior SARS-CoV-2 infection increases the titers of SARS-CoV-2 spike protein–specific antibody responses elicited by subsequent vaccination and induces modifications in the composition of the spike protein–specific memory B cell pool that are compatible with enhanced functional protection at mucosal sites.

Les patients hémodialysés chroniques présentent un risque accru d’infection par le SARSCoV2 et de décès en cas de COVID-19. Pour atteindre un titre d’anticorps protecteur permettant une seroneutralisation virale, les hémodialysés naïfs pour le virus nécessitent un schéma vaccinal intensifié (3 doses de vaccin à ARNm). La persistance dans le temps de cette protection et notamment l’impact du statut d’hémodialysé, d’une infection préalable par le virus et l’efficacité d’un rappel vaccinal ne sont pas connus. L’évolution de la réponse humorale (titre d’IgG anti-RBD et capacité de seroneutralisation virale in vitro) et cellulaire (interferon gamma releasing assay, IGRA) a été évaluée chez 62 patients hémodialysés naïfs pour le virus (HD_naïf) entre le pic de la réponse vaccinal et 6 mois après la dernière dose. La réponse à un rappel a été évaluée chez les 33 patients ayant reçu une nouvelle dose de vaccin. Ces données ont été comparées à celles de 21 volontaires sains (VS) et de 9 hémodialysés ayant développé une immunité hybride (infection puis vaccin ; HD_hybride). Six mois après la dernière dose vaccinale, seuls 13/62 (21 %) des HD_naïf ont conservé une capacité de neutralisation virale. Ce résultat est similaire à celui des VS, 6/21 (29 %), mais diffère nettement des HD_hybride 9/9 (100 %). Par ailleurs, 29/39 (74 %) des HD_naïf, qui présentaient une réponse cellulaire détectable au pic la conservait à M6, contre 18/21 (86 %) des VS, et 9/9 (100 %) des HD_hybride. Le rappel a permis de restaurer une capacité de séroneutralisation virale chez 100 % (33/33) des patients HD_naïfs l’ayant reçu. Contrairement à la réponse cellulaire, le titre d’anticorps vaccinal décroît rapidement mais de manière similaire chez les hémodialysés et les VS. En dehors d’un contact avec le virus, la majorité des individus (hémodialysés ou pas) n’est plus correctement protégé après 6 mois et doit recevoir une dose de rappel.

Kidney pathology is frequently reported in patients hospitalized with COVID-19, the pandemic disease caused by the Severe acute respiratory coronavirus 2 (SARS-CoV-2). However, due to a lack of suitable study models, the events occurring in the kidney during the earliest stages of infection remain unknown. We have developed hamster organotypic kidney cultures (OKCs) to study the early stages of direct renal infection. OKCs maintained key renal structures in their native three-dimensional arrangement. SARS-CoV-2 productively replicated in hamster OKCs, initially targeting endothelial cells and later disseminating into proximal tubules. We observed a delayed interferon response, markers of necroptosis and pyroptosis, and an early repression of pro-inflammatory cytokines transcription followed by a strong later upregulation. While it remains an open question whether an active replication of SARS-CoV-2 takes place in the kidneys of COVID-19 patients with AKI, our model provides new insights into the kinetics of SARS-CoV-2 kidney infection and can serve as a powerful tool for studying kidney infection by other pathogens and testing the renal toxicity of drugs.

Tetanic stimulation at 50 Hz elicited long-term potentiation (LTP) in the hippocampal CA1 region of 28-day-old control animals. In contrast, no significant potentiation was seen following the same tetanus in animals chronically exposed to 1000 ppm of lead acetate during development. Gender differences were observed in animals exposed to 500 ppm of lead. In females, LTP was significantly attenuated, while in males the LTP was identical to that of controls.

The level of protection achieved by the standard two doses of COVID-19 mRNA vaccines in patients receiving maintenance hemodialysis (MHD) remains unclear. To study this we used the French Renal Epidemiology and Information Network (REIN) Registry to compare the incidence and severity of 1474 cases of COVID-19 diagnosed in patients receiving MHD after none, one or two doses of vaccine. Vaccination significantly reduce COVID-19 incidence and severity, but 11% of patients infected after two doses still died. Lack of vaccinal protection in patients naïve for SARS-CoV-2 could be due to defective Tfh response [38% of patients with negative spike-specific CD4+ T-cell interferon gamma release assay] and failure to generate viral neutralizing titers of anti-spike receptor binding domain (RBD) IgGs (63% of patients with titer at or under 997 BAU/ml, defining low/no responders) after two doses of vaccine. To improve protection, a third dose of vaccine was administered to 75 patients [57 low/no responders, 18 high responders after two doses] from the ROMANOV cohort that prospectively enrolled patients receiving MHD vaccinated with BNT162b2 (Pfizer). Tolerance to the third dose was excellent. High responders to two doses did not generate more anti-RBD IgGs after three doses but had more side effects. Importantly, 31 (54%) of low/no responders to two doses reached neutralizing titers of anti-RBD IgGs after three doses. A positive interferon gamma release assay and/or suboptimal titer of anti-RBD IgGs after two doses were the only predictive variables for response to three doses in multivariate analysis. Thus, the standard scheme of vaccination insufficiently protects patients receiving MHD. Anti-RBD IgG and specific CD4+ T-cell response after two doses can guide personalized administration of the third dose, which improves the humoral response of SARS-CoV-2-naïve patients receiving MHD.

Transplant recipients, who receive therapeutic immunosuppression to prevent graft rejection, are characterized by high coronavirus disease 2019 (COVID-19)–related mortality and defective response to vaccines. We observed that previous infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), but not the standard two-dose regimen of vaccination, provided protection against symptomatic COVID-19 in kidney transplant recipients. We therefore compared the cellular and humoral immune responses of these two groups of patients. Neutralizing anti–receptor-binding domain (RBD) immunoglobulin G (IgG) antibodies were identified as the primary correlate of protection for transplant recipients. Analysis of virus-specific B and T cell responses suggested that the generation of neutralizing anti-RBD IgG may have depended on cognate T-B cell interactions that took place in germinal center, potentially acting as a limiting checkpoint. High-dose mycophenolate mofetil, an immunosuppressive drug, was associated with fewer antigen-specific B and T follicular helper (T FH ) cells after vaccination; this was not observed in patients recently infected with SARS-CoV-2. Last, we observed that, in two independent prospective cohorts, administration of a third dose of SARS-CoV-2 mRNA vaccine restored neutralizing titers of anti-RBD IgG in about 40% of individuals who had not previously responded to two doses of vaccine. Together, these findings suggest that a third dose of SARS-CoV-2 mRNA vaccine improves the RBD-specific responses of transplant patients treated with immunosuppressive drugs.

The analysis of immune cell signaling is critical for the understanding of the biology and pathology of the immune system, and thus a mandatory step for the development of efficient biomarkers and targeted therapies. Phosflow, which has progressively replaced the traditional western blot approach, relies on flow cytometry to analyze various signaling pathways at a single-cell level. This technique however suffers a lack of sensitivity largely due to the low signal/noise ratio that characterizes cell signaling analysis. In this study, we describe a new technique, which combines the use of biofunctionalized nanospheres (i.e., synthetic particulate antigens, SPAg) to stimulate the immune cells in suspension and imaging flow cytometry to identify homogenously-stimulated cells and quantify the activity of the chosen signaling pathway in selected subcellular regions of interest. Using BCR signaling as model, we demonstrate that SIBERIAN (SPAg-assIsted suB-cEllulaR sIgnaling ANalysis) allows assessing immune cell signaling with unprecedented sensitivity and specificity.

Introduction Les patients transplantés rénaux (TxR), à haut risque de développer une infection grave par le SARS-Cov2, bénéficient d’une priorité pour la vaccination. Cependant, comme les TxR reçoivent un traitement immunosuppresseur, ils sont connus pour présenter des réponses vaccinales défectueuses. Description Les TxR ayant des antécédents de COVID ne présentent pas de réinfection par le SARS-Cov2, indiquant qu’ils sont efficacement protégés par leur immunité, contrairement aux TxR ayant reçu 2 doses de vaccin à ARNm-1273 (Moderna Therapeutics). Méthodes Afin de comprendre pourquoi l’infection offre une protection plus robuste que le vaccin ARNm, nous avons comparé les réponses humorales et cellulaires anti-SARS-Cov2 chez les patients TxR après infection (n = 22, TxR COVID) ou vaccination (n = 29, TxR Vacc). Résultats Contrairement aux réponses lymphocytaires T CD8+, qui sont similaires, presque tous les TxR COVID (91 %) développent des IgG anti-RBD, contre seulement 41 % des TxR Vacc (p < 0,001). Ce défaut de réponse humorale corrèle avec un nombre plus faible de lymphocytes Tfh1 et Tfh17 spécifiques de la spicule virale chez les TxR Vacc non-répondeurs. L’incapacité à générer un nombre suffisant de lymphocytes Tfh capables d’aider les cellules B semble lié aux doses plus élevées d’antimétabolites (MMF) chez ces patients. Cependant, les TxR COVID ont développé des taux satisfaisant d’IgG anti-RBD malgré des doses identiques aux TxR Vacc non-répondeurs, suggérant que le blocage induit par le MMF peut être surmonté si l’immunogénicité (virus>vaccin) est suffisante. Conformément à cette hypothèse, l’administration d’une troisième dose de vaccin induit une séroconversion en IgG anti-RBD chez 54 % des patients non-répondeurs après deux doses. Conclusion Ces données suggèrent qu’une meilleure protection vaccinale des TxR pourrait être obtenue en adaptant transitoirement l’immunosuppression et/ou en augmentant l’immunogénicité du vaccin par l’administration d’une troisième dose.

Transplant recipients, which receive therapeutic immunosuppression to prevent graft rejection, are characterized by high COVID-19-related mortality and defective response to vaccines. Having observed that previous infection by SARS-CoV-2 but not the standard 2 doses scheme of vaccination, provided complete protection against COVID-19 to transplant recipients, we undertook this translational study to compare the cellular and humoral immune responses of these 2 groups of patients. Neutralizing anti-Receptor Binding Domain (RBD) IgG were identified as the critical immune effectors associated with protection. Generation of anti-RBD IgG was dependent upon spike-specific T follicular helper (Tfh) CD4+ T cells, which acted as limiting checkpoint. Tfh generation was impeded by high dose mycophenolate mofetil in non-responders to vaccine but not in infected patients, suggesting that increasing immunogenicity of vaccine could improve response rate to mRNA vaccine. This theory was validated in two independent prospective cohorts, in which administration of a 3rd dose of vaccine resulted in the generation of anti-RBD IgG in half of non-responders to 2 doses.

Introduction Les patients hémodialysés chroniques (HD) présentent un défaut de réponse immunitaire après 2 doses de vaccin ARNm anti SARS-Cov2, ayant conduit les autorités de santé françaises à recommander l’injection d’une 3e dose vaccinale. Description Notre objectif était d’évaluer : – la nécessité clinique ; – la tolérance ; – l’immunogénicité d’une 3e injection vaccinale chez les patients HD. Méthodes Nous avons comparé la gravité des maladies COVID des patients HD non vaccinés, après 1 dose ou 2 dose vaccinale issues du registre national français REIN. Nous avons ensuite mesuré les taux d’IgG anti-RBD et la réponse interféron gamma des lymphocytes T CD4 et CD8 spécifiques 10 à 14jours après la 3e injection vaccinale chez 56 patients hémodialysés ayant un défaut de réponse après 2 doses. Résultats obtenus ou attendus Entre le 01/02/2021 et le 18/05/2021, 105 cas de COVID-19 sont survenus chez des HD après 2 injections vaccinales, 179 après 1 dose et 1094 chez des HD non vaccinés. Si la vaccination diminue la sévérité de la maladie COVID(p < 0,0001), la mortalité reste élevée même après 2 doses(12 %), justifiant la réalisation d’une troisième dose aux patients non protégés. La tolérance de la 3e dose vaccinale était identique à celle de la 2e dose(effets indésirables mineurs à modérés chez 0 à 30 % des patients). La 3e dose permettait d’augmenter le taux d’IgG anti-RBD de 106,0 BAU/mL[IQR 9,7-458,0] à 1463 BAU/mL[IQR 207,5-2665], p < 0,0001. En analyse multivariée, une réponse CD4 après 2 doses était associée à une réponse optimale après 3 doses (OR=7,89 ;[IC95 % 1,31–68,7], p = 0,034). Conclusion Deux doses de vaccin ARNm anti-SARS Cov2 sont insuffisantes pour protéger totalement tous les patients HD. Chez les non répondeurs, une 3ème dose vaccinale est bien tolérée, et permet d’augmenter le taux d’IgG anti-RBD chez une majorité de patients.

Background/objectives: Acute Kidney Injury (AKI), induced by Checkpoint Inhibitors therapies (CPI-induced AKI), is an uncommon but severe Immune-Related Adverse Event (IRAE). The aim was to describe the epidemiology, risks factors, clinical, and laboratory characteristics of these renal adverse events (AEs) in a real-life cohort treatment. Design/participants: Consecutive patients undergoing a checkpoint inhibitor (CPI) therapy at the Hopital Lyon Sud from January 2015 to July 2017 were included. A systematic retrospective analysis of medical files was performed, monthly serum creatinine levels, associated treatments, and occurrence of other IRAEs data were collected. AKI episodes explained by classic AKI aetiologies (prerenal, obstructive, septic) were excluded from the analysis. Results: CPI-induced AKI incidence was 3.7% (13/ 352) and appeared to be time- dependent (7.7% (11/143) for patients with >3 months of CPI exposure), ranging from 1 to 16 months. All cases with available histology were acute tubulointerstitial nephritis (ATIN), with poor urinary sediment. The severity of AKI was mild (stage 1 in 50% of cases), with no need for renal-replacement therapy. Although CPI-induced AKI patients had more frequently other IRAEs (77% versus 39%), this was not associated with a greater risk of AKI. Pre-existing chronic kidney disease (defined as an estimated glomerular filtration rate (eGFR) <60 ml/ min) was not associated with a greater risk of CPI-induced AKI. Treatments of CPIinduced AKI were heterogeneous, with discontinuation of CPIs, and inconstant systemic corticosteroid therapy. Conclusion: The monitoring of renal function and early identification of AKI during CPIs treatment is essential. The optimal management of CPI-induced AKI remains unclear and requires a close collaboration between the oncology and nephrology departments. (C) 2021 Elsevier Ltd. All rights reserved.

Only a minority of kidney transplant recipients (KTRs) develop protective neutralizing titers of anti-receptor binding domain of spike protein (RBD) IgG after two doses of mRNA COVID-19 vaccine. Administration of a third dose of mRNA vaccine to KTRs with sub-optimal response increase anti-RBD IgG titers but with high inter-individual variability. Patients with the higher response rate to the third dose of vaccine can be identified by the presence of low anti-RBD IgG titers and spike-specific CD4+ T cells in their circulation 14 days after the second dose.

Les patients hémodialysés chroniques (HD) sont à haut risque d'infection par le SARS-CoV2 et de décès en cas de COVID-19, justifiant la priorisation de la vaccination dans cette population. Cependant, ces patients étaient exclus des études pivots, et sont connus pour avoir un défaut de réponse vaccinale. Il est donc urgent d'établir si les patients HD sont protégés après un schéma vaccinal « standard » par 2 doses de vaccin ARNm. Nous avons mesuré le taux d'IgG dirigé contre le domaine de fixation de la protéine Spike (IgG anti-RBD) ainsi que la réponse interféron-gamma (IFNγ) des lymphocytes T CD4 et CD8 spécifiques 10 à 14 jours après la 2nde injection vaccinale chez 106 patients hémodialysés chroniques (dont 14 avec un antécédent de COVID-19). En l'absence de corrélat de protection, nous avons utilisé une cohorte de 30 volontaires sains comme référence. Dix à 14 jours après la 2nde injection, 19/106 (18 %) des patients n'avaient pas d'IgG anti-RBD, 47/106 (44 %) des IgG anti-RBD détectables mais inférieurs aux volontaires sains, et 40/106 (38 %) un titre d'IgG anti-RBD similaire aux volontaires sains. En analyse multivariée, les facteurs indépendamment associés à une réponse IgG anti-RBD optimale étaient une absence d'immunosuppression (OR = 0,16, p = 0,05), un antécédent de COVID-19 (OR = 9,55 ; p = 0,004) et de meilleurs paramètres d'hémodialyse (OR = 6,11 ; p = 0,014). Les réponses CD4 étaient corrélées aux IgG anti-RBD (p < 0,0001). Les réponses CD8 étaient plus faibles que chez les volontaires sains (p < 0,01). Au total, seulement 14/92 (15 %) des patients hémodialysés naïfs pour le SARS-Cov2 présentaient des niveaux d'IgG anti-RBD, LT CD4+ et CD8+ similaires à des volontaires sains (Fig. 1). Les réponses humorales et cellulaires chez les patients hémodialysés chroniques sans antécédent de COVID-19 sont diminuées par rapport à celle de la population générale après 2 doses de vaccin ARNm anti-SARS-CoV2.