Evolution of Antibody Immunity to SARS-CoV-2

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) has infected 78 million individuals and is responsible for over 1.7 million deaths to date. Infection is associated with development of variable levels of antibodies with neutralizing activity that can protect against infection in animal models. Antibody levels decrease with time, but the nature and quality of the memory B cells that would be called upon to produce antibodies upon re-infection has not been examined. Here we report on the humoral memory response in a cohort of 87 individuals assessed at 1.3 and 6.2 months after infection. We find that IgM, and IgG anti-SARS-CoV-2 spike protein receptor binding domain (RBD) antibody titers decrease significantly with IgA being less affected. Concurrently, neutralizing activity in plasma decreases by five-fold in pseudotype virus assays. In contrast, the number of RBD-specific memory B cells is unchanged. Memory B cells display clonal turnover after 6.2 months, and the antibodies they express have greater somatic hypermutation, increased potency and resistance to RBD mutations, indicative of continued evolution of the humoral response. Analysis of intestinal biopsies obtained from asymptomatic individuals 4 months after coronavirus disease-2019 (COVID-19) onset, using immunofluorescence, or polymerase chain reaction, revealed persistence of SARS-CoV-2 nucleic acids and immunoreactivity in the small bowel of 7 out of 14 volunteers. We conclude that the memory B cell response to SARS-CoV-2 evolves between 1.3 and 6.2 months after infection in a manner that is consistent with antigen persistence

Convergent Antibody Responses to SARS-CoV-2 Infection in Convalescent Individuals

During the COVID-19 pandemic, SARS-CoV-2 infected millions of people and claimed hundreds of thousands of lives. Virus entry into cells depends on the receptor binding domain (RBD) of the SARS-CoV-2 spike protein (S). Although there is no vaccine, it is likely that antibodies will be essential for protection. However, little is known about the human antibody response to SARS-CoV-2. Here we report on 149 COVID-19 convalescent individuals. Plasmas collected an average of 39 days after the onset of symptoms had variable half-maximal pseudovirus neutralizing titres: less than 1:50 in 33% and below 1:1,000 in 79%, while only 1% showed titres above 1:5,000. Antibody sequencing revealed expanded clones of RBD-specific memory B cells expressing closely related antibodies in different individuals. Despite low plasma titres, antibodies to three distinct epitopes on RBD neutralized at half-maximal inhibitory concentrations (IC₅₀ values) as low as single digit nanograms per millitre. Thus, most convalescent plasmas obtained from individuals who recover from COVID-19 do not contain high levels of neutralizing activity. Nevertheless, rare but recurring RBD-specific antibodies with potent antiviral activity were found in all individuals tested, suggesting that a vaccine designed to elicit such antibodies could be broadly effective

Regulation of NKp46+ lymphoid cells’ function and development

Il existe différents groupes de cellules lymphoïdes innées (ILC) qui ont été caractérisées en fonction des facteurs de transcriptions indispensables à leur différenciation et des cytokines qu’elles sécrètent. Les ILC1, dont font partie les cellules Natural Killer (NK), expriment T-bet et produisent de l’IFN-γ. Les ILC2 sont caractérisées par GATA-3 et sécrètent de l’IL-5 et de l’IL-13. Quant aux ILC3, elles ont été identifiées par leur sécrétion d’IL-17 et d’IL-22 ainsi que par l’expression de RORγt.Mon travail de thèse m’a amené à étudier différents aspects de la biologie des cellules NK et ILC3 : leur tolérance, leur homéostasie et leur plasticité.Les cellules NK jouent un rôle dans l’élimination de cellules cancéreuses et des cellules infectées par des bactéries et des virus. J’ai mis en évidence le rôle de la phosphatase SHP-1 (Src homology region 2 domain-containing phosphatase-1) dans les mécanismes de tolérance et d’activation des cellules NK. J’ai également montré que la protéine anti-apoptotique Bcl2 (B-cell lymphoma 2) est importante pour l’homéostasie des cellules NK. Seules les cellules en cycle cellulaire peuvent compenser l’absence de Bcl2, notamment du fait de l’augmentation de l’expression d’une autre protéine anti-apoptotique, Mcl1 (Myeloid Cell Leukemia 1). Les ILC3 sont des cellules principalement localisées dans l’intestin et qui peuvent être classées en différents groupes en fonction des marqueurs qu’elles expriment. J’ai montré qu’il existe une plasticité entre les différentes populations d’ILC3, et que cette plasticité est régulée par des facteurs environnementaux tel que le TGF-β et le ligand de Notch, DL1.There are three groups of innate lymphoid cells (ILC), defined notably by the transcriptions factors essential to their differentiation and their cytokines secretion. ILC1, including natural killer (NK) cells, express T-bet and secrete IFN-γ. ILC2 are characterized by GATA3 expression and the production of IL-5 and IL-13. ILC3 secrete IL-17 and IL-22 and express RORγt.My PhD work dealt with different aspects of NK cells and ILC3: their tolerance, homeostasis and plasticity.NK cell are involved in killing tumor cells and bacteria- or virus-infected cells. I found that the phosphatase SHP-1 (Src homology region 2 domain-containing phosphatase-1) has a role in NK cell tolerance and activation.I also showed that the anti-apoptotic Bcl2 protein (B-cell lymphoma 2) is important for NK cell homeostasis. Only cycling NK cells could compensate the Bcl2 deficiency, due to the increase expression of another anti-apoptotic protein, Mcl1 (Myeloid Cell Leukemia 1).ILC3 are mainly located in the gut and are classified in different groups, depending on the markers that they expressed. I showed that there is plasticity between ILC3 populations and that this plasticity is regulated by environmental factors, including TGF-β and the Notch ligand, DL1

Du surfaçage radiculaire au débridement ultrasonore (évolution des concepts)

Les progrès récents dans le domaine de la conception des instruments et les nouvelles philosophies en matière de thérapie parodontale encourageant une réflexion sur le rôle joué par les instruments de détartrage mécanisés dans le débridement parodontal. Jusqu à une période récente, les limites d accès sous-gingival aux instruments ultrasonores et le retrait intentionnel de cément obligeaient les cliniciens à utiliser des instruments manuels. L amélioration de l accès sous-gingival, de l efficacité des instruments et l importance accordée au phénomène de cicatrisation des tissus mous, le souci de préservation du cément et la réduction au minimum des traumatismes créés par les inserts parodontaux offrent un rôle plus important à l utilisation des instruments ultrasonores en thérapie parodontale. L objet de ce travail est de décrire l évolution des concepts de l étiologie des maladies parodontales et le progrès dans les techniques utilisées, c'est-à-dire passage de surfaçage radiculaire au débridement ultrasonore.The recent progress in the conception of instrument and new philosophies in periodontal therapy encourage the reflexion on the role played by the mechanized instruments in the root surface debridement. Until a recent period, the milit of sub-gingival access to theultrasonic instruments and the deliberate retreat of cement, pushed the clinicians to use manuals instruments. The improvement of the sub-gingival access, the efficiency of instruments and the importance granted to the phenomenon of healing of soft tissues, interest in conservation of the cement and the reduction at least traumas created by inserts give a role more important for the use ultrasonics instruments in periodontal therapy. The object of this work is to describe the evolution of the periodontal diseases etiology concepts and the progress in used technology : scaling and root planning to root surface debridement.BORDEAUX2-BU Sci.Homme/Odontol. (330632102) / SudocSudocFranceF

Les cellules lymphoïdes innées

International audienc

Sequencing, cloning, and antigen binding analysis of monoclonal antibodies isolated from single mouse B cells

Summary: The analysis of B cell receptors (BCR) from single B cells is crucial to understanding humoral immune responses. Here, we describe a protocol for the sequencing, cloning, and characterization of antibody genes that encode BCRs. We used this method to analyze the BCRs of different mouse B cell populations for somatic hypermutations, clonal and phylogenic relationships, and their affinity for cognate antigen.For complete details on the use and execution of this protocol, please refer to Viant et al. (2020)

The metabolic checkpoint kinase mTOR is essential for IL-15 signaling during the development and activation of NK cells

International audienceInterleukin 15 (IL-15) controls both the homeostasis and the peripheral activation of natural killer (NK) cells. The molecular basis for this duality of action remains unknown. Here we found that the metabolic checkpoint kinase mTOR was activated and boosted bioenergetic metabolism after exposure of NK cells to high concentrations of IL-15, whereas low doses of IL-15 triggered only phosphorylation of the transcription factor STAT5. mTOR stimulated the growth and nutrient uptake of NK cells and positively fed back on the receptor for IL-15. This process was essential for sustaining NK cell proliferation during development and the acquisition of cytolytic potential during inflammation or viral infection. The mTORC1 inhibitor rapamycin inhibited NK cell cytotoxicity both in mice and humans; this probably contributes to the immunosuppressive activity of this drug in different clinical settings

Transforming growth factor-beta and Notch ligands act as opposing environmental cues in regulating the plasticity of type 3 innate lymphoid cells

International audienceGroup 3 innate lymphoid cells (ILC3s) are composed of subsets that are either positive or negative for the natural cytotoxicity receptor (NCR) NKp46 (encoded by Ncr1). ILC3s are located at mucosal sites, such as in the intestine and lung, where they are exposed to billions of commensal microbes and potentially harmful pathogens. Together with T cells, the various ILC3 subsets maintain the balance between homeostasis and immune activation. Through genetic mapping, we identified a previously uncharacterized subset of NCR- ILC3s in mice that transiently express Ncr1, demonstrating previously undescribed heterogeneity within the ILC3 population. In addition, we showed that sustained Notch signaling was required for the maintenance of the NCR+ phenotype and that the cytokine transforming growth factor-beta (TGF-beta) impaired the development of NCR+ ILC3s. Thus, the plasticity of ILC3s is regulated by the balance between the opposing effects of Notch and TGF-beta signaling, maintaining homeostasis in the face of continual challenges

The microanatomic segregation of selection by apoptosis in the germinal center

B cells undergo rapid cell division and affinity maturation in anatomically distinct sites in lymphoid organs called germinal centers (GCs). Homeostasis is maintained in part by B cell apoptosis. However, the precise contribution of apoptosis to GC biology and selection is not well defined. We developed apoptosis-indicator mice and used them to visualize, purify, and characterize dying GC B cells. Apoptosis is prevalent in the GC, with up to half of all GC B cells dying every 6 hours. Moreover, programmed cell death is differentially regulated in the light zone and the dark zone: Light-zone B cells die by default if they are not positively selected, whereas dark-zone cells die when their antigen receptors are damaged by activation-induced cytidine deaminas