SARS-CoV-2 Omicron BA.1 breakthrough infection drives late remodeling of the memory B cell repertoire in vaccinated individuals

How infection by a viral variant showing antigenic drift impacts a preformed mature human memory B cell (MBC) repertoire remains an open question. Here, we studied the MBC response up to 6 months after SARS-CoV-2 Omicron BA.1 breakthrough infection in individuals previously vaccinated with three doses of the COVID-19 mRNA vaccine. Longitudinal analysis, using single-cell multi-omics and functional analysis of monoclonal antibodies from RBD-specific MBCs, revealed that a BA.1 breakthrough infection mostly recruited pre-existing cross-reactive MBCs with limited de novo response against BA.1-restricted epitopes. Reorganization of clonal hierarchy and new rounds of germinal center reactions, however, combined to maintain diversity and induce progressive maturation of the MBC repertoire against common Hu-1 and BA.1, but not BA.5-restricted, SARS-CoV-2 Spike RBD epitopes. Such remodeling was further associated with a marked improvement in overall neutralizing breadth and potency. These findings have fundamental implications for the design of future vaccination booster strategies.

Prolonged response after TPO-RA discontinuation in primary ITP: results of a prospective multicenter study

Sustained response off treatment (SROT) after thrombopoietin receptor agonist (TPO-RA) discontinuation has been reported in immune thrombocytopenia (ITP). This prospective multicenter interventional study enrolled adults with persistent or chronic primary ITP and complete response (CR) on TPO-RAs. The primary end point was the proportion of patients achieving SROT (platelet count >30 × 109/L and no bleeding) at week 24 (W24) with no other ITP-specific medications. Secondary end points included the proportion of sustained CR off-treatment (SCROT, platelet count >100 × 109/L and no bleeding) and SROT at W52, bleeding events, and pattern of response to a new course of TPO-RAs. We included 48 patients with a median age of 58.5 years; 30 of 48 had chronic ITP at TPO-RA initiation. In the intention-to-treat analysis, 27 of 48 achieved SROT, 15 of 48 achieved SCROT at W24; 25 of 48 achieved SROT, and 14 of 48 achieved SCROT at W52. No severe bleeding episode occurred in patients who relapsed. Among patients rechallenged with TPO-RA, 11 of 12 achieved CR. We found no significant clinical predictors of SROT at W24. Single-cell RNA sequencing revealed enrichment of a tumor necrosis factor α signaling via NF-κB signature in CD8+ T cells of patients with no sustained response after TPO-RA discontinuation, which was further confirmed by a significant overexpression of CD69 on CD8+ T cells at baseline in these patients as compared with those achieving SCROT/SROT. Our results strongly support a strategy based on progressive tapering and discontinuation of TPO-RAs for patients with chronic ITP who achieved a stable CR on treatment. This trial was registered at www.clinicaltrials.gov as #NCT03119974.

Human type I IFN deficiency does not impair B cell response to SARS-CoV-2 mRNA vaccination

Inborn and acquired deficits of type I interferon (IFN) immunity predispose to life-threatening COVID-19 pneumonia. We longitudinally profiled the B cell response to mRNA vaccination in SARS-CoV-2 naive patients with inherited TLR7, IRF7, or IFNAR1 deficiency, as well as young patients with autoantibodies neutralizing type I IFNs due to autoimmune polyendocrine syndrome type-1 (APS-1) and older individuals with age-associated autoantibodies to type I IFNs. The receptor-binding domain spike protein (RBD)-specific memory B cell response in all patients was quantitatively and qualitatively similar to healthy donors. Sustained germinal center responses led to accumulation of somatic hypermutations in immunoglobulin heavy chain genes. The amplitude and duration of, and viral neutralization by, RBD-specific IgG serological response were also largely unaffected by TLR7, IRF7, or IFNAR1 deficiencies up to 7 mo after vaccination in all patients. These results suggest that induction of type I IFN is not required for efficient generation of a humoral response against SARS-CoV-2 by mRNA vaccines.

Immune Responses after a Third Dose of mRNA Vaccine Differ in Virus-Naive versus SARS-CoV-2- Recovered Dialysis Patients

BACKGROUND AND OBJECTIVES

After two doses of mRNA vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), patients on dialysis show a defective humoral response, but a third dose could increase anti-SARS-CoV-2 spike IgG titers. Responses could be different in virus-naive and SARS-CoV-2-recovered patients on dialysis. However, characterization of memory B cell response after three doses is lacking.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

We evaluated the dynamics of antireceptor binding domain IgG titers and antireceptor binding domain memory B cells until 6 months after two and three doses (administered within 6 months after the second dose) of mRNA vaccine in SARS-CoV-2-recovered and virus-naive dialysis populations. Results were analyzed by ordinary one-way ANOVA, the Kruskal-Wallis test, or the Wilcoxon matched-pairs test as appropriate.

RESULTS

In total, 108 individuals (59 patients on dialysis and 49 controls) were included. In virus-naive patients on dialysis, antireceptor binding domain IgG response was quantitatively lower after two doses compared with healthy controls, but IgG titers increased by three-fold after three doses (P=0.008). In SARS-CoV-2-recovered patients on dialysis, antireceptor binding domain IgG titers after two doses were significantly higher compared with virus-naive patients on dialysis but did not significantly increase after a third dose. Regarding memory B cell response, we detected receptor binding domain-specific memory B cells at similar proportions in virus-naive patients on dialysis and vaccinated controls after two doses. Moreover, a strong receptor binding domain-specific memory B cell expansion was observed after the third dose in virus-naive patients on dialysis (5.5-fold; P<0.001). However, in SARS-CoV-2-recovered patients on dialysis, antireceptor binding domain memory B cells remained unchanged after the third dose.

CONCLUSIONS

The third dose of mRNA vaccine given within 6 months after the second dose boosts serologic and memory response in virus-naive patients but not in SARS-CoV-2-recovered patients on dialysis.

CLINICAL TRIAL REGISTRY NAME AND REGISTRATION NUMBER

COVID-19: SARS-CoV-2 Specific Memory B and T-CD4+ Cells (MEMO-COV2), NCT04402892.

Le déficit en interféron de type I n’altère pas la réponse lymphocytaire B mémoire contre le SARS-CoV-2 après vaccination par ARNm

Introduction

Les vaccins à ARN messagers ont joué un rôle majeur dans la lutte contre la pandémie de SARS-CoV-2 grâce à une excellente efficacité et sécurité clinique. Ces vaccins ont été développés suite à des années de recherche fondamentale, dont l’une des étapes cruciales a été de remplacer l’uridine de l’ARNm par de la 1-méthyl-pseudo-uridine afin d’éviter la reconnaissance par les récepteurs de l’immunité innée, notamment le toll-like-receptor (TLR) 7. Une hypothèse, très fréquemment défendue mais jamais étayée expérimentalement, est que cet ARN modifié garde une activité immunostimulatrice à bas bruit permettant la production d’interféron de type I, agissant comme un adjuvant du vaccin. Les interférons de type I sont des cytokines antivirales essentielles et les patients ayant un déficit dans les voies de l’interféron de type I sont à haut risque de COVID-19 sévère. Dans ce travail, nous avons analysé la réponse lymphocytaire B au vaccin à ARNm de patients présentant l’absence de signalisation par les interférons de type I. Ceci nous a permis de savoir si les vaccins par ARNm permettaient d’établir une réponse lymphocytaire B robuste en l’absence d’interféron de type I.

Patients et méthodes

Nous avons constitué trois cohortes de patients (i) des patients avec des déficits génétiques sur les voies de l’interféron de type I : 2 patients avec une mutation homozygote d’IRF7 (facteur de transcription responsable de la production d’interférons de Type I, notamment en aval de TLR7) et un patient avec une déficit hémizygote de TLR7 (ii) des patients ayant des auto-anticorps neutralisant les interférons alpha et oméga, dans le cadre d’une polyendocrinopathie auto-immune de type I (APS-1, n = 14) (iii) des patients ayant des auto-anticorps neutralisant les interféron, associés à l’âge, une entité récemment décrite et particulièrement fréquente chez les sujets âgés (n = 8). Ces sujets ont été comparés à 29 contrôles sains. Tous étaient naïfs du COVID-19 et ont reçu 2 doses de vaccin à ARNm (BNT162n2 ou mRNA1273). Les patients ont été prélevés à différents point de temps, dans les 3 premiers mois et entre 3 et 7 mois après la seconde dose. La réponse sérologique a été évaluée par ELISA anti-IgG et IgA RBD (receptor binding domain de la Spike) et la neutralisation sérique a été testée in vitro contre le D614G-SARS-CoV-2. Les lymphocytes B (LB) mémoires CD19 + IgD-CD27± spécifiques du RBD ont été analysés en cytométrie en flux et triés en cellule unique pour séquençage des régions variables de la chaîne lourde de l’immunoglobuline.

Résultats

La réponse sérologique anti-RBD IgG et IgA était comparable aux temps précoces et tardifs de la réponse vaccinale, évoluant de façon similaire chez les patients déficients en interféron de type I et les sujets sains. La capacité de neutralisation des sérums contre le SARS-CoV-2 était également identique dans tous les groupes, et corrélait fortement avec le taux d’IgG anti-RBD, suggérant que le RBD était également la cible de la réponse neutralisante chez les patients déficients en interféron de type I. Des LB mémoires circulants spécifiques du RBD étaient retrouvés dans toutes les cohortes de patients déficients en interféron de type I au cours des 3 mois suivant la vaccination. Ceux-ci se maintenaient dans le temps et étaient encore présents entre 3 et 7 mois après la vaccination (0,18 % des LB IgD-CD27+ chez les sujets sains, 0,24 % chez les sujets avec déficit génétiques, 0,16 % chez les APS-1 et 0,26 % chez les AAB, pas de différence statistiquement significative). Le séquençage de la chaîne lourde des régions variables de l’immunoglobuline des LB mémoires spécifiques du RBD révélait l’accumulation progressive des mutations jusqu’à 7 mois chez les sujets sains, témoignant d’une réaction des centres germinatifs permettant la maturation d’affinité et la génération de lymphocytes B mémoires à longue durée de vie. Chez les patients IRF7 déficients, les LB mémoires spécifiques du RBD acquerraient progressivement des mutations de M1 à M6, et les LB mémoires spécifiques du RBD de patients TLR7 et APS-1 arboraient un nombre élevé de mutation dès M4, témoignant que même en l’absence de réponse à l’interféron de type I, le vaccin permettait la génération des LB mémoire issus des centres germinatifs, comme chez les sujets sains. Enfin, des clones partagés étaient retrouvés entre les sujets sains et les patients déficient en interféron de type I témoignant d’une réponse qualitativement normale.

Conclusion

Notre travail apporte des données rassurantes sur la vaccination de ces patients à haut risque de forme de grave de COVID-19 et suggère que l’ARNm contenu dans les vaccins n’a pas de rôle adjuvant intrinsèque.

High-affinity autoreactive plasma cells disseminate through multiple organs in patients with immune thrombocytopenic purpura

The major therapeutic goal for immune thrombocytopenic purpura (ITP) is to restore normal platelet counts using drugs to promote platelet production or by interfering with mechanisms responsible for platelet destruction. Eighty percent of patients with ITP possess anti–integrin αIIbβ3 IgG autoantibodies that cause platelet opsonization and phagocytosis. The spleen is considered the primary site of autoantibody production by autoreactive B cells and platelet destruction. The immediate failure in approximately 50% of patients to recover a normal platelet count after anti-CD20 rituximab-mediated B cell depletion and splenectomy suggests that autoreactive, rituximab-resistant, IgG-secreting B cells (IgG-SCs) reside in other anatomical compartments. We analyzed more than 3,300 single IgG-SCs from spleen, bone marrow, and/or blood of 27 patients with ITP, revealing high interindividual variability in affinity for αIIbβ3, with variations over 3 logs. IgG-SC dissemination and range of affinities were, however, similar for each patient. Longitudinal analysis of autoreactive IgG-SCs upon treatment with the anti-CD38 mAb daratumumab demonstrated variable outcomes, from complete remission to failure with persistence of high-affinity anti–αIIbβ3 IgG-SCs in the bone marrow. This study demonstrates the existence and dissemination of high-affinity autoreactive plasma cells in multiple anatomical compartments of patients with ITP that may cause the failure of current therapies.

Analysis of mRNA vaccination-elicited RBD-specific memory B cells reveals strong but incomplete immune escape of the SARS-CoV-2 Omicron variant

The SARS-CoV-2 Omicron variant can escape neutralization by vaccine-elicited and convalescent antibodies. Memory B cells (MBCs) represent another layer of protection against SARS-CoV-2, as they persist after infection and vaccination and improve their affinity. Whether MBCs elicited by mRNA vaccines can recognize the Omicron variant remains unclear. We assessed the affinity and neutralization potency against the Omicron variant of several hundred naturally expressed MBC-derived monoclonal IgG antibodies from vaccinated COVID-19-recovered and -naive individuals. Compared with other variants of concern, Omicron evaded recognition by a larger proportion of MBC-derived antibodies, with only 30% retaining high affinity against the Omicron RBD, and the reduction in neutralization potency was even more pronounced. Nonetheless, neutralizing MBC clones could be found in all the analyzed individuals. Therefore, despite the strong immune escape potential of the Omicron variant, these results suggest that the MBC repertoire generated by mRNA vaccines still provides some protection against the Omicron variant in vaccinated individuals.

Nonclassical Monocytes Are Prone to Migrate Into Tumor in Diffuse Large B-Cell Lymphoma

Absolute count of circulating monocytes has been proposed as an independent prognostic factor in diffuse large B-cell lymphoma (DLBCL). However, monocyte nomenclature includes various subsets with pro-, anti-inflammatory, or suppressive functions, and their clinical relevance in DLBCL has been poorly explored. Herein, we broadly assessed circulating monocyte heterogeneity in 91 DLBCL patients. Classical- (cMO, CD14pos CD16neg) and intermediate- (iMO, CD14pos CD16pos) monocytes accumulated in DLBCL peripheral blood and exhibited an inflammatory phenotype. On the opposite, nonclassical monocytes (ncMOSlanpos, CD14low CD16pos Slanneg and ncMOSlanneg, CD14low CD16pos, Slanneg) were decreased in peripheral blood. Tumor-conditioned monocytes presented similarities with ncMO phenotype from DLBCL and were prone to migrate in response to CCL5 and CXCL12, and presented similarities with DLBCL-infiltrated myeloid cells, as defined by mass cytometry. Finally, we demonstrated the adverse value of an accumulation of nonclassical monocytes in 2 independent cohorts of DLBCL.

La vaccination par ARNm des sujets naïfs ou convalescents de la COVID-19 permet la génération de lymphocytes B mémoires capables de reconnaître et de neutraliser les variants du SARS-CoV-2

Introduction

La mémoire immunitaire est un mécanisme qui protège les individus contre la réinfection. Cette stratégie de défense de l’organisme, qui est à la base du succès des vaccins, comprend la production d’anticorps protecteurs dans le sang ainsi que la formation de cellules à mémoire, capables de se réactiver rapidement en cellules productrices d’anticorps lors d’une nouvelle infection. Les vaccins à ARNm, codant pour la protéine Spike du SARS-CoV-2, ont été rapidement déployés dans le monde entier, avec une grande efficacité clinique. Déterminer les caractéristiques de la réponse lymphocytaire B mémoire générée par ces vaccins est d’une importance majeure, notamment dans le contexte de circulation de variants du SARS-CoV-2, porteurs de mutations dans la protéine Spike. Nous avons étudié la dynamique, l’évolution clonale, et l’affinité des cellules B à mémoire chez des patients vaccinés par le vaccin à ARNm, ainsi que leur capacité à reconnaître et à neutraliser les variants du SARS-CoV-2 dans deux cohortes longitudinales de patients, l’une infectée lors de la première vague (convalescents-vaccinés), et l’autre n’ayant pas été infectée (naïfs-vaccinés).

Patients et méthodes

Les patients infectés lors de la première vague de la pandémie ont été inclus dans l’étude MEMO-CoV2. Une partie de ces patients avec une forme sévère hospitalisée, ou une forme modérée ambulatoire ont reçu une dose de vaccin à ANR messager (BNT162b2) un an après l’infection. De façon parallèle, une cohorte de soignants, naïfs de toute infection et avec une sérologie négative, ont été vaccinés avec deux doses de vaccin à ARNm. Ces deux cohortes ont été suivies et analysées (Sérologie, Cytométrie en flux des cellules B) longitudinalement jusqu’à 2 mois après le boost vaccinal (première injection pour les convalescents, deuxième injection pour les naïfs). Les cellules B mémoires spécifiques du domaine RBD de la protéine Spike ont été isolées, triées et cultivées en cellule unique. Pour chaque cellule anti-RBD mémoire, nous avons séquencé la chaîne lourde de l’immunoglobuline et nous avons déterminé l’affinité par Biolayer-interferometry des anticorps produits contre des variants préoccupants(α, β, γ et δ). Nous avons aussi déterminé pour certains clones leur capacité à neutraliser le virus D614G (dominant lors de la première vague) et β in vitro.

Résultats

La vaccination induisait une réponse sérologique IgG anti-RBD robuste chez tous les patients analysés (n = 47). L’activité neutralisante du sérum contre le virus D614G était excellente pour tous les patients. Néanmoins, la neutralisation sérique des variants β et δ était très nettement meilleure chez les patients déjà infectés, suggérant que les plasmocytes mobilisés lors du boost vaccinal proviennent de cellules mémoires matures. L’analyse en cytométrie en flux, a mis en évidence une expansion du pool mémoires chez les patients convalescents à un niveau supérieur à celui des naïfs. L’analyse de plus de 2400 séquences de la chaîne lourde de l’immunoglobuline provenant de cellules B mémoires anti-RBD cultivés en cellule unique, a révélé que la réponse vaccinale anti-RBD mobilise des cellules peu mutées, donc nouvellement générées, chez les individus naïfs. À l’inverse les cellules mémoires mobilisées après le boost chez patients convalescents arboraient de nombreuses mutations somatiques, témoignant de la mobilisation de mémoires préexistantes. L’analyse du répertoire des cellules B mémoires montrait que sa diversité était conservée après la vaccination malgré son expansion. Nous avons ensuite analysé l’affinité de 382 anticorps monoclonaux issus cellules B mémoires mobilisées par le boost vaccinal, contre le RBD de différent variants (α, β, γ, δ, κ). L’affinité des anticorps contre la RBD sauvage était plus forte chez les convalescents que chez les naïfs et corrélait avec le nombre de mutations somatiques dans la chaine lourde de l’immunoglobuline, reflétant le processus de maturation d’affinité. Des clones de très haute affinité contre tous les RBD variants étaient détectés chez tous les individus testés, y compris chez les naïfs, ainsi que des clones neutralisant le variant β, qui a la plus grande capacité à échapper à la réponse immune.

Conclusion

Chez les patients convalescents, la vaccination amplifie un large répertoire de cellules B mémoires matures et génère des plasmocytes neutralisant les variants. Chez les individus naïfs, la vaccination induit un pool de mémoire contenant des clones neutralisants puissants contre tous les variants préoccupants actuels, dont bêta et delta. Nos résultats suggèrent qu’une troisième dose chez les sujets naïfs permettrait de différentier en plasmocytes les lymphocytes B mémoires de grande qualité générés par le schéma vaccinal initial et ainsi d’augmenter l’activité neutralisante des sérums contre les variants du SARS-CoV-2.

mRNA vaccination of naive and COVID-19-recovered individuals elicits potent memory B cells that recognize SARS-CoV-2 variants

In addition to serum immunoglobulins, memory B cell (MBC) generation against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is another layer of immune protection, but the quality of MBC responses in naive and coronavirus disease 2019 (COVID-19)-recovered individuals after vaccination remains ill defined. We studied longitudinal cohorts of naive and disease-recovered individuals for up to 2 months after SARS-CoV-2 mRNA vaccination. We assessed the quality of the memory response by analysis of antibody repertoires, affinity, and neutralization against variants of concern (VOCs) using unbiased cultures of 2,452 MBCs. Upon boosting, the MBC pool of recovered individuals expanded selectively, matured further, and harbored potent neutralizers against VOCs. Although naive individuals had weaker neutralizing serum responses, half of their RBD-specific MBCs displayed high affinity toward multiple VOCs, including delta (B.1.617.2), and one-third retained neutralizing potency against beta (B.1.351). Our data suggest that an additional challenge in naive vaccinees could recall such affinity-matured MBCs and allow them to respond efficiently to VOCs.

Efficacy, safety and immunological profile of combining rituximab with belimumab for adults with persistent or chronic immune thrombocytopenia: results from a prospective phase 2b trial

B-cell activating factor may be involved in the failure of B-cell depleting therapy with rituximab in immune thrombocytopenia (ITP) by promoting the emergence of splenic long-lived plasma cells. From results obtained in mouse models, we hypothesized that combining rituximab with sequential injections of belimumab could increase the rate of response at one year in patients with persistent or chronic ITP by preventing the emergence of these long-lived plasma cells. The study was a single-center, single arm, prospective phase 2b trial (RITUX-PLUS, NCT03154385) investigating the safety and efficacy of rituximab given at a fixed dose of 1,000 mg, two weeks apart, combined with five infusions of belimumab, 10 mg/kg at week 0 (W0)+2 days, W2+2 days, W4, W8 and W12 for adults with primary persistent or chronic ITP. The primary endpoint was the total number of patients achieving an overall response (complete response + response) at W52 according to a standard definition. In total, 15 non-splenectomized adults, nine (60%) with persistent IPT and six (40%) with chronic ITP, were included. No severe adverse event, infection, or severe hypogammaglobulinemia was observed. Thirteen patients achieved an initial overall response. At W52, 12 (80%) patients achieved an overall response, including ten (66.7%) with complete response. When compared with a cohort of patients receiving rituximab alone, the kinetics of B-cell repopulation appeared similar, but the number of circulating T follicular helper cells was significantly decreased with belimumab combination therapy. Combining rituximab and belimumab seems a promising strategy in ITP, with high efficacy and acceptable safety.

Rituximab-resistant splenic memory B cells and newly engaged naive B cells fuel relapses in patients with immune thrombocytopenia

Rituximab (RTX), an antibody targeting CD20, is widely used as a first-line therapeutic strategy in B cell-mediated autoimmune diseases. However, a large proportion of patients either do not respond to the treatment or relapse during B cell reconstitution. Here, we characterize the cellular basis responsible for disease relapse in secondary lymphoid organs in humans, taking advantage of the opportunity offered by therapeutic splenectomy in patients with relapsing immune thrombocytopenia. By analyzing the B and plasma cell immunoglobulin gene repertoire at bulk and antigen-specific single-cell level, we demonstrate that relapses are associated with two responses coexisting in germinal centers and involving preexisting mutated memory B cells that survived RTX treatment and naive B cells generated upon reconstitution of the B cell compartment. To identify distinctive characteristics of the memory B cells that escaped RTX-mediated depletion, we analyzed RTX refractory patients who did not respond to treatment at the time of B cell depletion. We identified, by single-cell RNA sequencing (scRNA-seq) analysis, a population of quiescent splenic memory B cells that present a unique, yet reversible, RTX-shaped phenotype characterized by down-modulation of B cell-specific factors and expression of prosurvival genes. Our results clearly demonstrate that these RTX-resistant autoreactive memory B cells reactivate as RTX is cleared and give rise to plasma cells and further germinal center reactions. Their continued surface expression of CD19 makes them efficient targets for current anti-CD19 therapies. This study thus identifies a pathogenic contributor to autoimmune diseases that can be targeted by available therapeutic agents.

Circulating plasmablasts and high level of BAFF are hallmarks of minimal change nephrotic syndrome in adults

BACKGROUND

The recent success achieved with the use of B cell-depleting agents in some patients with minimal change nephrotic syndrome (MCNS) suggests an unexpected role for B lymphocytes in the pathogenesis of this immune-mediated glomerular disease. Nevertheless, no extensive B-cell phenotyping analysis has ever been performed in untreated adult patients soon after MCNS diagnosis.

METHODS

We investigated the distribution of the different B-cell subpopulations in 22 untreated adult patients with biopsy-proven MCNS [MCNS relapse (MCNS-Rel)]. We compared these data with those for 24 healthy controls, 13 MCNS patients in remission (with no specific treatment) and 19 patients with idiopathic membranous nephropathy (IMN).

RESULTS

Patients with MCNS-Rel or IMN had higher proteinuria and lower serum albumin and gammaglobulin levels (P < 0.0001 for all comparisons) than MCNS patients in remission. Plasmablasts were the only B-cell subsets present at significantly higher levels in MCNS-Rel patients than in the patients of the other three groups (P < 0.05 for all comparisons). The lower albumin levels and higher proteinuria levels were positively correlated with the percentage of circulating plasmablasts (Spearman test's ρ = -0.54, P = 0.01 and ρ = 0.65, P = 0.002, respectively). Similarly, the increase of immunoglobulin M (IgM) and the decrease of IgG levels were significantly associated with the percentage of plasmablasts in MCNS-Rel patients (Spearman's ρ = 0.36, P = 0.01 and Spearman's ρ = -0.60, P = 0.01, respectively). Increased production of interleukin (IL)-21, IL-6 and B-cell activating factor (BAFF) in the serum of MCNS-Rel patients was found significantly correlated with the percentage of plasmablasts (ρ = 0.72, P = 0.0002, ρ = 0.49, P = 0.04 and ρ = 0.62, P = 0.009, respectively).

CONCLUSIONS

An increase in the proportion of circulating plasmablasts seems to be a hallmark of untreated MCNS in adult patients. Further studies are required to more precisely determine the phenotype and functions of these cells.

Maturation and persistence of the anti-SARS-CoV-2 memory B cell response

Memory B cells play a fundamental role in host defenses against viruses, but to date, their role has been relatively unsettled in the context of SARS-CoV-2. We report here a longitudinal single-cell and repertoire profiling of the B cell response up to 6 months in mild and severe COVID-19 patients. Distinct SARS-CoV-2 spike-specific activated B cell clones fueled an early antibody-secreting cell burst as well as a durable synchronous germinal center response. While highly mutated memory B cells, including pre-existing cross-reactive seasonal Betacoronavirus-specific clones, were recruited early in the response, neutralizing SARS-CoV-2 RBD-specific clones accumulated with time and largely contributed to the late, remarkably stable, memory B cell pool. Highlighting germinal center maturation, these cells displayed clear accumulation of somatic mutations in their variable region genes over time. Overall, these findings demonstrate that an antigen-driven activation persisted and matured up to 6 months after SARS-CoV-2 infection and may provide long-term protection.

Early Expansion of Circulating Granulocytic Myeloid-derived Suppressor Cells Predicts Development of Nosocomial Infections in Patients with Sepsis

RATIONALE

Sepsis induces a sustained immune dysfunction responsible for poor outcome and nosocomial infections. Myeloid-derived suppressor cells (MDSCs) described in cancer and inflammatory processes may be involved in sepsis-induced immune suppression, but their clinical impact remains poorly defined.

OBJECTIVES

To clarify phenotype, suppressive activity, origin, and clinical impact of MDSCs in patients with sepsis.

METHODS

Peripheral blood transcriptomic analysis was performed on 29 patients with sepsis and 15 healthy donors. A second cohort of 94 consecutive patients with sepsis, 11 severity-matched intensive care patients, and 67 healthy donors was prospectively enrolled for flow cytometry and functional experiments.

MEASUREMENTS AND MAIN RESULTS

Genes involved in MDSC suppressive functions, including S100A12, S100A9, MMP8, and ARG1, were up-regulated in the peripheral blood of patients with sepsis. CD14^posHLA-DR^low/neg monocytic (M)-MDSCs were expanded in intensive care unit patients with and without sepsis and CD14^negCD15^pos low-density granulocytes/granulocytic (G)-MDSCs were more specifically expanded in patients with sepsis (P < 0.001). Plasma levels of MDSC mediators S100A8/A9, S100A12, and arginase 1 were significantly increased. In vitro, CD14^pos- and CD15^pos-cell depletion increased T-cell proliferation in patients with sepsis. G-MDSCs, made of immature and mature granulocytes expressing high levels of degranulation markers, were specifically responsible for arginase 1 activity. High initial levels of G-MDSCs, arginase 1, and S100A12 but not M-MDSCs were associated with subsequent occurrence of nosocomial infections.

CONCLUSIONS

M-MDSCs and G-MDSCs strongly contribute to T-cell dysfunction in patients with sepsis. More specifically, G-MDSCs producing arginase 1 are associated with a higher incidence of nosocomial infections and seem to be major actors of sepsis-induced immune suppression.

Acute alcohol exposure has an independent impact on C-reactive protein levels, neutrophil CD64 expression, and subsets of circulating white blood cells differentiated by flow cytometry in nontrauma patients

Acute and massive alcohol exposure (blood alcohol concentration of ≥1 g/L) is a common way to consume alcohol. In a prospective study performed in critically ill nontrauma patients, we compared C-reactive protein (CRP) values, circulating subsets of white blood cells, and neutrophil CD64 indexes recorded at admission to the intensive care unit between abstinent or moderate drinkers (n = 173), patients with acute or chronic alcohol exposure (n = 32), and patients with acute exposure but not chronically exposed to alcohol (n = 27). Values for CRP (P < 0.001), circulating neutrophils (P < 0.001), and neutrophil CD64 indexes (P < 0.001) were significantly lower in patients acutely exposed compared with the other patients, whereas values for B lymphocytes (P < 0.001) and cytotoxic (P < 0.001) and noncytotoxic T lymphocytes (P < 0.001) were significantly higher. After multiple regression analysis, alcohol exposure remained independently associated with values of CRP, neutrophils CD4 indexes, cytotoxic and noncytotoxic T lymphocytes, and CD16-negative and -positive monocytes. These results were not affected by the presence or absence of infection at admission. Our results suggest that in nontrauma critically ill patients, acute alcohol exposure diminishes inflammation and increases numbers of circulating B and T lymphocytes.

Polycyclic aromatic hydrocarbons reciprocally regulate IL-22 and IL-17 cytokines in peripheral blood mononuclear cells from both healthy and asthmatic subjects

Pollution, including polycyclic aromatic hydrocarbons (PAH), may contribute to increased prevalence of asthma. PAH can bind to the Aryl hydrocarbon Receptor (AhR), a transcription factor involved in Th17/Th22 type polarization. These cells produce IL17A and IL-22, which allow neutrophil recruitment, airway smooth muscle proliferation and tissue repair and remodeling. Increased IL-17 and IL-22 productions have been associated with asthma. We hypothesized that PAH might affect, through their effects on AhR, IL-17 and IL-22 production in allergic asthmatics. Activated peripheral blood mononuclear cells (PBMCs) from 16 nonallergic nonasthmatic (NA) and 16 intermittent allergic asthmatic (AA) subjects were incubated with PAH, and IL-17 and IL-22 productions were assessed. At baseline, activated PBMCs from AA exhibited an increased IL-17/IL-22 profile compared with NA subjects. Diesel exhaust particle (DEP)-PAH and Benzo[a]Pyrene (B[a]P) stimulation further increased IL-22 but decreased IL-17A production in both groups. The PAH-induced IL-22 levels in asthmatic patients were significantly higher than in healthy subjects. Among PBMCs, PAH-induced IL-22 expression originated principally from single IL-22- but not from IL-17- expressing CD4 T cells. The Th17 transcription factors RORA and RORC were down regulated, whereas AhR target gene CYP1A1 was upregulated. IL-22 induction by DEP-PAH was mainly dependent upon AhR whereas IL-22 induction by B[a]P was dependent upon activation of PI3K and JNK. Altogether, these data suggest that DEP-PAH and B[a]P may contribute to increased IL22 production in both healthy and asthmatic subjects through mechanisms involving both AhR -dependent and -independent pathways.

CCL17 production by dendritic cells is required for NOD1-mediated exacerbation of allergic asthma

RATIONALE

Pattern recognition receptors are attractive targets for vaccine adjuvants, and polymorphisms of the innate receptor NOD1 have been associated with allergic asthma.

OBJECTIVES

To elucidate whether NOD1 agonist may favor allergic asthma in humans through activation of dendritic cells, and to evaluate the mechanisms involved using an in vivo model.

METHODS

NOD1-primed dendritic cells from allergic and nonallergic donors were characterized in vitro on their phenotype, cytokine secretion, and Th2 polarizing ability. The in vivo relevance was examined in experimental allergic asthma, and the mechanisms were assessed using transfer of NOD1-conditioned dendritic cells from wild-type or CCL17-deficient mice.

MEASUREMENTS AND MAIN RESULTS

NOD1 priming of human dendritic cells promoted a Th2 polarization profile that involved the production of CCL17 and CCL22 in nonallergic subjects but only CCL17 in allergic patients, without requiring allergen costimulation. Moreover, NOD1-primed dendritic cells from allergic donors exhibited enhanced maturation that led to abnormal CCL22 and IL-10 secretion compared with nonallergic donors. In mice, systemic NOD1 ligation exacerbated allergen-induced experimental asthma by amplifying CCL17-mediated Th2 responses in the lung. NOD1-mediated sensitization of purified murine dendritic cells enhanced production of CCL17 and CCL22, but not of thymic stromal lymphopoietin and IL-33, in vitro. Consistently, adoptive transfer of NOD1-conditioned dendritic cells exacerbated the Th2 pulmonary response in a CCL17-dependent manner in vivo.

CONCLUSIONS

Data from this study unveil a deleterious role of NOD1 in allergic asthma through direct induction of CCL17 by dendritic cells, arguing for a need to address vaccine formulation safety issues related to allergy.

Pulmonary CCL18 recruits human regulatory T cells

CCL18 is both a constitutively expressed and an inducible chemokine, whose role in the inflammatory reaction is poorly known. The aim of this study was to evaluate whether CCL18 has the capacity to attract human T cells with a regulatory function (regulatory T cells [Treg]). Results from chemotaxis assays performed on different types of Treg showed that CD4(+)CD25(+)CD127(low) cells, but neither T regulatory type 1 clones nor Treg differentiated in vitro with anti-CD3/CD46 mAbs, were recruited by CCL18 in a dose-dependent manner. CCL18-recruited memory CD4(+) T cells were enriched in CD25(high), CD25(+)CD127(low), latency-associated peptide/TGF-β1, and CCR4-expressing T cells, whereas there was no enrichment in Foxp3(+) cells as compared with controls. Stimulated CCL18-recruited memory T cells produced significantly increased amounts of the regulatory cytokines IL-10 and TGF-β1, as well as IL-4, but not IFN-γ and IL-17. Cell surface CCL18 binding was found predominantly on IL-10(+) (26.3 ± 5.8%) and on a few latency-associated peptide/TGF-β1(+) (18.1 ± 1.9%) and IL-4(+) (14.5 ± 2.9%) memory T cells. In an in vivo model of SCID mice grafted with human skin and reconstituted with autologous PBMCs, the intradermal injection of CCL18 led to the cutaneous recruitment of CD4(+), CD25(+), and IL-10(+) cells, but not Foxp3(+) cells. Furthermore, CCL18-recruited memory T cells inhibited the proliferation of CD4(+)CD25(-) effector T cells through an IL-10-dependent mechanism. These data suggest that CCL18 may contribute to maintaining tolerance and/or suppressing deleterious inflammation by attracting memory Tregs into tissues, particularly in the lung, where it is highly and constitutively expressed.