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Malaria-associated atypical memory B cells exhibit markedly reduced B cell receptor signaling and effector function

ABSTRACT: Plasmodium falciparum malaria is a deadly infectious disease for which we have no licensed vaccine. Antibodies confer protection against malaria and individuals exposed to P. falciparum acquire protective antibodies, but only after years of repeated infections. We recently showed that malaria exposure is associated with a large expansion of a population of atypical memory B cells (MBCs) that phenotypically resemble B cell populations expanded in chronic viral infections, including HIV. At present the relationship of atypical MBCs to classical MBCs and their function are not known. We provide evidence that the expressed VH gene repertoires and somatic hypermutation rates of atypical and classical MBCs are indistinguishable, indicating the two populations are closely related developmentally. Atypical MBCs can be distinguished by their expression of multiple inhibitory receptors, including Fc receptor-like-5. B cell receptor (BCR) signaling is stunted in atypical MBCs, resulting in impaired Ca2+ mobilization, proliferation and cytokine production. Atypical MBCs do not spontaneously secrete antibodies and cannot be stimulated to differentiate into antibody-secreting cells in vitro. These results suggest that in individuals chronically exposed to malaria, atypical MBCs differentiate from classical MBCs and assume a phenotype refractory to BCR-mediated activation, potentially contributing to the inefficient acquisition of immunity to malaria.

ORGANISM(S): Homo sapiens

PROVIDER: GSE65928 | GEO | 2015/05/07

SECONDARY ACCESSION(S): PRJNA275428

REPOSITORIES: GEO

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Malaria-associated atypical memory B cells exhibit markedly reduced B cell receptor signaling and effector function

Project description:Plasmodium falciparum malaria is a deadly infectious disease for which we have no licensed vaccine. Antibodies confer protection against malaria and individuals exposed to P. falciparum acquire protective antibodies, but only after years of repeated infections. We recently showed that malaria exposure is associated with a large expansion of a population of atypical memory B cells (MBCs) that phenotypically resemble B cell populations expanded in chronic viral infections, including HIV. At present the relationship of atypical MBCs to classical MBCs and their function are not known. We provide evidence that the expressed VH gene repertoires and somatic hypermutation rates of atypical and classical MBCs are indistinguishable, indicating the two populations are closely related developmentally. Atypical MBCs can be distinguished by their expression of multiple inhibitory receptors, including Fc receptor-like-5. B cell receptor (BCR) signaling is stunted in atypical MBCs, resulting in impaired Ca2+ mobilization, proliferation and cytokine production. Atypical MBCs do not spontaneously secrete antibodies and cannot be stimulated to differentiate into antibody-secreting cells in vitro. These results suggest that in individuals chronically exposed to malaria, atypical MBCs differentiate from classical MBCs and assume a phenotype refractory to BCR-mediated activation, potentially contributing to the inefficient acquisition of immunity to malaria. Comparison of human atypical B cell versus classical B cell versus naïve B cell.

2015-05-07 | E-GEOD-65928 | biostudies-arrayexpress

Shared transcriptional profiles at the single cell level of atypical memory B cells suggest common drivers of expansion and function in malaria, HIV and autoimmune diseases [HIV scRNA-seq]

Project description:Human chronic infectious diseases, including malaria and HIV and autoimmune diseases, notably SLE, are accompanied by a striking expansion of a subpopulation of B cells termed atypical memory B cells (MBCs). We compared the single cell transcriptional profiles of B cells in malaria and HIV, characterizing and uncovering heterogeneity within each B cell subset. Remarkably, atypical MBC clusters in these two diseases showed significant similarities to each other as well as to atypical MBCs in autoimmune diseases, suggesting a common driver of their expansion and shared functions. Focusing on atypical MBCs in malaria we identified an IgD+IgMlo subpopulation that expanded in children upon the onset of febrile malaria, showed a distinct V gene usage characteristic of antigen-driven B cell populations and unexpectedly, had acquired high antigen-affinity thresholds for activation. We speculate that in malaria IgD+IgMlo atypical MBCs expand to limit responses to low-affinity self-antigens, a function that may be shared by atypical MBCs in other chronic infections and autoimmune diseases.

2020-09-30 | GSE157966 | GEO

Plasmodium-specific atypical memory B cells upregulate markers of activation and co-stimulatory molecules indicative of cellular interaction with T cells in response to a febrile malaria infection in children and adults.

Project description:In naturally acquired immunity to malaria, antibodies that reliably protect are only acquired after years of repeated Plasmodium falciparum (Pf) infections. We have shown in Mali that this inefficiency in humoral immunity to malaria is associated with a large expansion of CD21loCD27- ‘atypical’ B cells (atBCs). The function of atBCs remains elusive, as they exhibit altered B cell receptor (BCR) signaling and when activated fail to secrete cytokines and antibodies. We set out to study the participation and function of malaria-specific atBCs during the immune response to a febrile malaria infection. Here, we show in a Mali cohort spanning infants to adults, that atBCs frequencies within the malaria and influenza-specific MBC compartment are comparable to the overall atBC frequency, showing that atBCs are not predominantly expanded within Pf-specific B cells. We performed a transcriptional analysis of Pf- and influenza-specific atBCs, actBC and MBCs and show that CXCL16, IL-6, IL-10, TNFα, IL12R and IL12R are uniquely upregulated in Pf-specific atBCs. Comparative transcriptomic and flow cytometric analysis before and after an acute malaria infection showed that after malaria, Pf-specific atBCs are transcriptionally most like the actBC subset, sharing many common features, such as activation of intracellular signaling pathways and expression of high levels of T-bet, FcRL5, Ki67 and CD86. Unique to Pf-specific atBCs was an upregulation of IL-5RA, CD38, CXCR3, TLR7, 9 and 10 after a febrile malaria episode. Our data shows that atBCs exhibit a surface marker profile that could facilitate cellular interaction with T cells in secondary lymphoid tissues.

2022-06-01 | GSE183744 | GEO

Chronic Malaria drives functional heterogenity in B cell subpopilations and expansion of unswitched atypical memory B cells [Malaria scRNA-seq]

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

2020-09-30 | GSE149728 | GEO

Chronic Malaria drives functional heterogenity in B cell subpopulations and expansion of unswitched atypical memory B cells [Malaria bulkRNA-seq]

2020-09-30 | GSE149727 | GEO

Shared transcriptional profiles at the single cell level of atypical memory B cells suggest common drivers of expansion and function in malaria, HIV and autoimmune diseases [Malaria VDJ+GEX scRNA-seq]

2020-09-30 | GSE157967 | GEO

Molecular profiling reveals features of clinical immunity and immunosuppression in asymptomatic P. falciparum malaria

Project description:To define the impact of asymptomatic malaria, we pursued a systems approach integrating antibody responses, mass cytometry, and transcriptional profiling of individuals experiencing symptomatic and asymptomatic P. falciparum infection. Defined populations of classical and atypical memory B cells and a TH2 cell bias were associated with reduced risk of clinical malaria. Despite these protective responses, asymptomatic malaria featured an immunosuppressive transcriptional signature with upregulation of pathways involved in the inhibition of T cell function, and CTLA-4 as a predicted regulator in these processes.

2022-02-21 | GSE181179 | GEO

Plasmodium-specific atypical memory B cells are short-lived activated B cells

Project description:Chronic infections such as HIV, tuberculosis and malaria in humans are associated with the appearance of atypical memory B cells in peripheral blood. It has been suggested that these B cells do not function normally as memory cells, and thus may be responsible for poor acquisition of immunity and maintenance of chronic infections. Studies on these cells in human infections are limited by the lack of accessibility to lymphoid organs, and relevant mouse models would be valuable to investigate their development, functional capacities, and role. To investigate Plasmodium-specific memory B-cell responses during malaria, we generated an immunoglobin heavy chain knock-in mouse with a B-cell receptor that recognizes the merozoite surface protein (MSP)-1 of the rodent malaria parasite, Plasmodium chabaudi. Using this mouse and a P. chabaudi infection initiated by infected mosquito bites we show that antigen-specific B cells with many characteristics of human atypical memory B cells are generated. These cells are immunoglobulin class-switched and express, among others, the cell surface molecules CD11c, CD11b, FCRL5, and some inhibitory receptors including PD1 and LAIR-1, as well as the transcription factor T-bet. Antigen-specific atypical memory B cells are detected side-by-side with classical memory B cells during chronic blood-stage infection. Whereas classical memory B cells persist after complete infection clearance, atypical memory B cells are short-lived and disappear from the spleen at the resolution of chronic infection. Short-lived Plasmodium-specific atypical B cells also appear transiently after immunization with a TLR7/8 ligand and MSP-1. Our data suggest that these atypical memory B cells are not a subset of memory B cells, but rather antigen-experienced activated cells, and part of a normal ongoing response. Their persistence over weeks in malaria and other infections may be a consequence of continued and chronic antigenic stimulation.

2018-11-01 | GSE115155 | GEO

Expansion of an FCRL5+ B cell subset resembling atypical memory B cells in an animal model of malaria

Project description:Background: In human malaria, parasites of the genus Plasmodium elicit expansion of atypical memory B cells (atMBCs), which lack the classical markers CD21 and CD27. We have identified a putative population of analogous B cells in a murine model of infection with P. chabaudi, delineated by the marker FCRL5. We performed RNA-Seq on FCRL5+ and FCRL5- B cells sorted from infected mice, so as to characterize the transcriptional profile of these cells and permit comparison to atMBCs in humans. Results: FCRL5+ B cells were found to have distinct transcriptional profiles from FCRL5- B cells, with approximately 400 genes exhibiting significant differences between the two groups. Additionally, about 25% of these differentially expressed genes were also differentially expressed in human atMBCs versus classical MBCs, as previously described by Sullivan et al (PLoS Pathogens 2015). Conclusions: FCRL5+ class-switched B cells are a transcriptionally distinct subset arising in P. chabaudi infection, with transcriptional similarities to human atMBCs that develop in chronic malaria settings.

2019-04-16 | GSE85205 | GEO

Transcription profiling of PfSPZ Malaria Vaccine trial subjects receiving a 3-dose regimen in a malaria endemic region

Project description:The Sanaria® PfSPZ Vaccine can confer sterilizing protection against liver stage infection by Plasmodium falciparum (Pf) in malaria naïve individuals. The vaccine consists of aseptically purified irradiated Pf sporozoites. Vaccinees received 3 doses of 1.8 X 106 irradiated sporozoites. Efficacy was measured by challenged by controlled human malaria infections (CHMI), and against naturally occurring Pf Infections in Malian adults during the malaria transmission season

2022-08-20 | GSE211599 | GEO

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