Systemic 4-1BB stimulation augments extrafollicular memory B cell formation and recall responses during Plasmodium infection [scATAC-seq]
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ABSTRACT: T-dependent germinal center (GC) output, comprising plasma cells (PC) and memory B cells (MBC), is crucial for the clearance of Plasmodium infection and protection against reinfection. In this study, we examined the effect of an agonistic antibody targeting 4-1BB (CD137), a member of the Tumor Necrosis Factor Receptor Superfamily (TNFRSF), during experimental malaria. We found that exogenous 4-1BB stimulation dramatically enhanced humoral immune memory and protection from reinfection, despite delaying the effector GC response. Although fewer in number, single cell RNA and ATAC sequencing of MBCs from mice that received 4-1BB stimulation revealed clusters with a transcriptional and epigenetic signature indicative of superior recall and proliferative potential. Importantly, our results indicate that these effects are independent of parasite load or the inflammatory milieu but are dependent on IL-9R signaling in B cells. Our study proposes an immunomodulatory approach to enhance the quality of the MBC pool, providing superior protection during infection and vaccination, particularly in the context of malaria.
Project description:T-dependent germinal center (GC) output, comprising plasma cells (PC) and memory B cells (MBC), is crucial for the clearance of Plasmodium infection and protection against reinfection. In this study, we examined the effect of an agonistic antibody targeting 4-1BB (CD137), a member of the Tumor Necrosis Factor Receptor Superfamily (TNFRSF), during experimental malaria. We found that exogenous 4-1BB stimulation dramatically enhanced humoral immune memory and protection from reinfection, despite delaying the effector GC response. Although fewer in number, single cell RNA and ATAC sequencing of MBCs from mice that received 4-1BB stimulation revealed clusters with a transcriptional and epigenetic signature indicative of superior recall and proliferative potential. Importantly, our results indicate that these effects are independent of parasite load or the inflammatory milieu but are dependent on IL-9R signaling in B cells. Our study proposes an immunomodulatory approach to enhance the quality of the MBC pool, providing superior protection during infection and vaccination, particularly in the context of malaria.
Project description:In individuals highly exposed to hepatitis C virus (HCV), reinfection is common, suggesting that natural development of sterilising immunity is difficult. In those that are reinfected, some will develop a persistent infection, while a small proportion repeatedly clear the virus, suggesting natural protection is possible. The aim of this study was to characterise immune responses associated with rapid natural clearance of HCV reinfection. Broad neutralising antibodies (BnAbs) and Envelope 2 (E2)-specific memory B cell (MBCs) responses were examined longitudinally in 15 subjects with varied reinfection outcomes. BnAb responses were associated with MBC recall, but not with reinfection clearance. Strong evidence of antigen imprinting was found, and the B cell receptor repertoire showed a high level of clonality with ongoing somatic hypermutation of many clones over subsequent reinfection events. Single cell transcriptomic analyses showed that cleared reinfections featured an activated transcriptomic profile in HCV-specific B cells that rapidly expanded upon reinfection. MBC quality, but not necessarily breadth of nAb responses, is important for protection against antigenically diverse variants, which is encouraging for HCV vaccine development.
Project description:Naturally-acquired immunity to blood-stage malaria is associated with several effector CD4 + T subsets including germinal centre (GC) Tfh, Th1 and Tr1 cells. Children in malaria-endemic regions can experience repeated Plasmodium infections over short periods of time; yet the effect of reinfection on multiple co-existing effector and memory subsets remains unclear. Here, we tracked antigen-experienced polyclonal CD4+ T cells during Plasmodium re-infection in mice using scRNA-seq/TCR-seq.
Project description:Naturally-acquired immunity to blood-stage malaria is associated with several effector CD4 + T subsets including germinal centre (GC) Tfh, Th1 and Tr1 cells. Children in malaria-endemic regions can experience repeated Plasmodium infections over short periods of time; yet the effect of reinfection on multiple co-existing effector and memory subsets remains unclear. Here, we tracked antigen-experienced TCR-transgenic CD4+ T cells during Plasmodium re-infection in mice using scRNA-seq.
Project description:Activated Foxp3+ regulatory T cells (Tregs) express several TNF receptor superfamily (TNFRSF) members. Here, we analyzed the transcriptome of purified Tregs that were activated with anti-CD3 and anti-CD28 mAbs, IL-2 and with or without agonists of TNFR2, 4-1BB, DR3 and OX40 for 18h and 36h. Triggering these TNFRSF in Tregs induces similar changes in gene expression patterns, suggesting that they engage common signal transduction pathways. Among them, we identified a major role of canonical NF-κB.
Project description:Memory B cells (MBCs) play a critical role in protection against homologous and variant pathogen challenge by either differentiating to plasma cells (PCs) or to germinal center (GCs) B cells. The human MBC compartment contains both switched IgG+ and unswitched IgM+ MBCs and at present the contribution of these MBC subpopulations to protection is incompletely understood. We discovered that intrinsic antigen-affinity thresholds for activation were at least 100-fold higher for IgG+ as compared to IgM+ MBCs and that IgG+ MBCs when challenged responded only to high affinity antigens and differentiated almost exclusively towards PC fates. In contrast, IgM+ MBCs were eliminated by apoptosis by high affinity antigens and responded to low affinity antigens by differentiating towards GC B cell fates. Thus, IgG+ and IgM+ MBCs may play distinct yet complementary roles in response to pathogen challenge to ensure the immediate production of high affinity antibodies to homologous and closely related challenges and the generation of variant-specific MBCs through GC reactions.
Project description:Human chronic infectious diseases have been shown to alter the composition and phenotype of the B cell compartment, which, in part, can attribute to failure to acquire protective immunity. However, the extent of such alterations is poorly understood. Here, using a combination of bulk and single cell RNA-sequencing (scRNA-seq) of B cells in individuals living in malaria-endemic Africa, we characterized changes in naïve B cell, classical memory B cell (MBC) and atypical MBC subsets. Of particular interest were unswitched atypical MBCs that expanded in children upon the onset of febrile malaria. This subpopulation expressed IgD but only low levels of IgM (IgD+IgMlo), high levels of the atypical MBC markers, Tbet and CD11c, as well as the intrinsically autoreactive VH4-34. IgD+IgMlo atypical MBCs were distinguished functionally by their acquisition of high antigen-affinity thresholds for activation, suggesting the IgD+IgMlo atypical MBC expansion during febrile malaria may reduce responses to low affinity self-antigens during acute malaria
Project description:Human chronic infectious diseases have been shown to alter the composition and phenotype of the B cell compartment, which, in part, can attribute to failure to acquire protective immunity. However, the extent of such alterations is poorly understood. Here, using a combination of bulk and single cell RNA-sequencing (scRNA-seq) of B cells in individuals living in malaria-endemic Africa, we characterized changes in naïve B cell, classical memory B cell (MBC) and atypical MBC subsets. Of particular interest were unswitched atypical MBCs that expanded in children upon the onset of febrile malaria. This subpopulation expressed IgD but only low levels of IgM (IgD+IgMlo), high levels of the atypical MBC markers, Tbet and CD11c, as well as the intrinsically autoreactive VH4-34. IgD+IgMlo atypical MBCs were distinguished functionally by their acquisition of high antigen-affinity thresholds for activation, suggesting the IgD+IgMlo atypical MBC expansion during febrile malaria may reduce responses to low affinity self-antigens during acute malaria
Project description:Human chronic infectious diseases have been shown to alter the composition and phenotype of the B cell compartment, which, in part, can attribute to failure to acquire protective immunity. However, the extent of such alterations is poorly understood. Here, using a combination of bulk and single cell RNA-sequencing (scRNA-seq) of B cells in individuals living in malaria-endemic Africa, we characterized changes in naïve B cell, classical memory B cell (MBC) and atypical MBC subsets. Of particular interest were unswitched atypical MBCs that expanded in children upon the onset of febrile malaria. This subpopulation expressed IgD but only low levels of IgM (IgD+IgMlo), high levels of the atypical MBC markers, Tbet and CD11c, as well as the intrinsically autoreactive VH4-34. IgD+IgMlo atypical MBCs were distinguished functionally by their acquisition of high antigen-affinity thresholds for activation, suggesting the IgD+IgMlo atypical MBC expansion during febrile malaria may reduce responses to low affinity self-antigens during acute malaria
Project description:There is little insight into or agreement about the signals that control differentiation of memory B cells (MBC) and long-lived plasma cells (LLPC). By performing BrdU pulse-labeling studies, we found that MBC formation preceded the formation of LLPC in an adoptive transfer immunization system, which allowed for a synchronized Ag-specific response with homogeneous Ag-receptor, yet at natural precursor frequencies. We confirmed observations in wild type (WT) mice and extended them with germinal center (GC) disruption experiments and variable region gene sequencing. We thus show that the GC response undergo a temporal switch in its output as it matures, revealing that the reaction engenders both MBC subsets with different immune effector function and, ultimately, LLPC at largely separate points in time. These data demonstrate the kinetics of the formation of the cells that provide stable humoral immunity and therefore have implications for autoimmunity, vaccine development, and for understanding long-term pathogen resistance. Adoptive transfer of B1-8i+/- genetically targeted BALB/cJ mice B cells into AM14 Transgenic (Tg) x Vκ8R genetically targeted BALB/cJ mice. Naive, memory, early and late GC B cells.