scholarly journals A public antibody class recognizes a novel S2 epitope exposed on open conformations of SARS-CoV-2 spike

2021 ◽  
Author(s):  
Mathieu Claireaux ◽  
Tom G Caniels ◽  
Marlon de Gast ◽  
Julianna Han ◽  
Denise Guerra ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Cell Repertoire ◽  
Fold Enrichment ◽  
B Cell Repertoire ◽  
High Fraction ◽  
Antibody Class

AbstractDelineating the origins and properties of antibodies elicited by SARS-CoV-2 infection and vaccination is critical for understanding their benefits and potential shortcomings. Therefore, we investigated the SARS-CoV-2 spike (S)-reactive B cell repertoire in unexposed individuals by flow cytometry and single-cell sequencing. We found that ∼82% of SARS-CoV-2 S-reactive B cells show a naive phenotype, which represents an unusually high fraction of total human naive B cells (∼0.1%). Approximately 10% of these naive S-reactive B cells shared an IGHV1-69/IGKV3-11 B cell receptor pairing, an enrichment of 18-fold compared to the complete naive repertoire. A proportion of memory B cells, comprising switched (∼0.05%) and unswitched B cells (∼0.04%), was also reactive with S and some of these cells were reactive with ADAMTS13, which is associated with thrombotic thrombocytopenia. Following SARS-CoV-2 infection, we report an average 37-fold enrichment of IGHV1-69/IGKV3-11 B cell receptor pairing in the S-reactive memory B cells compared to the unselected memory repertoire. This class of B cells targets a previously undefined non-neutralizing epitope on the S2 subunit that becomes exposed on S proteins used in approved vaccines when they transition away from the native pre-fusion state because of instability. These findings can help guide the improvement of SARS-CoV-2 vaccines.

scholarly journals Transplanted Long-Term Cultured Pre-Bi Cells Expressing Calpastatin Are Resistant to B Cell Receptor–Induced Apoptosis

2001 ◽  
Vol 194 (3) ◽  
pp. 247-254 ◽  
Author(s):  
Antonio Ruiz-Vela ◽  
Fernando Serrano ◽  
Manuel A. González ◽  
José Luis Abad ◽  
Antonio Bernad ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
B Cell Receptor ◽  
Scid Mice ◽  
Cell Repertoire ◽  
Clonal Deletion ◽  
B Cell Repertoire ◽  
Induced Apoptosis

Long-term cultured pre-B cells are able to differentiate into immunoglobulin (Ig)M-positive B cells (IgM+ cells) when transplanted into severe combined immunodeficient (SCID) mice. Based on previous studies, here we report the development of a reconstitution assay in nonobese diabetic/SCID (NOD/SCID) mice using pre-B cells, which allows us to study the role of calpains (calcium-activated endopeptidases) during B cell development as well as in B cell clonal deletion. Using this model, we show that calpastatin (the natural inhibitor of calpains) inhibits B cell receptor–induced apoptosis in IgM+ cells derived from transplanted mice. We thus hypothesize an important function for calpain in sculpting the B cell repertoire.

scholarly journals Targeted inhibition of eIF4A suppresses B-cell receptor-induced translation and expression of MYC and MCL1 in chronic lymphocytic leukemia cells

2021 ◽  
Author(s):  
Sarah Wilmore ◽  
Karly-Rai Rogers-Broadway ◽  
Joe Taylor ◽  
Elizabeth Lemm ◽  
Rachel Fell ◽  
...  
Keyword(s):  
B Cells ◽  
Chronic Lymphocytic Leukemia ◽  
B Cell ◽  
Mrna Translation ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Lymphocytic Leukemia ◽  
Mrna Levels ◽  
Mrna Stabilization

AbstractSignaling via the B-cell receptor (BCR) is a key driver and therapeutic target in chronic lymphocytic leukemia (CLL). BCR stimulation of CLL cells induces expression of eIF4A, an initiation factor important for translation of multiple oncoproteins, and reduces expression of PDCD4, a natural inhibitor of eIF4A, suggesting that eIF4A may be a critical nexus controlling protein expression downstream of the BCR in these cells. We, therefore, investigated the effect of eIF4A inhibitors (eIF4Ai) on BCR-induced responses. We demonstrated that eIF4Ai (silvestrol and rocaglamide A) reduced anti-IgM-induced global mRNA translation in CLL cells and also inhibited accumulation of MYC and MCL1, key drivers of proliferation and survival, respectively, without effects on upstream signaling responses (ERK1/2 and AKT phosphorylation). Analysis of normal naïve and non-switched memory B cells, likely counterparts of the two main subsets of CLL, demonstrated that basal RNA translation was higher in memory B cells, but was similarly increased and susceptible to eIF4Ai-mediated inhibition in both. We probed the fate of MYC mRNA in eIF4Ai-treated CLL cells and found that eIF4Ai caused a profound accumulation of MYC mRNA in anti-IgM treated cells. This was mediated by MYC mRNA stabilization and was not observed for MCL1 mRNA. Following drug wash-out, MYC mRNA levels declined but without substantial MYC protein accumulation, indicating that stabilized MYC mRNA remained blocked from translation. In conclusion, BCR-induced regulation of eIF4A may be a critical signal-dependent nexus for therapeutic attack in CLL and other B-cell malignancies, especially those dependent on MYC and/or MCL1.

scholarly journals Characterization of B-cell Receptor Heavy Chain Complementarity-determining Region 3 Repertoire Based on the Differences of Symbiotic Microorganisms in the Gut of Mice

2021 ◽  
Author(s):  
Jun Li ◽  
Yurong Pan ◽  
Qingqing Ma ◽  
Long Ma ◽  
Bin Shi ◽  
...  
Keyword(s):  
Small Intestine ◽  
B Cells ◽  
B Cell ◽  
Heavy Chain ◽  
Intestinal Microflora ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Positive Effects ◽  
Significant Difference

Abstract Background Colonization of gut microorganism is related to maturation of B cells in peripheral immune organs. This study aims to investigate the effect of intestinal microflora in Germ-free (GF), Specific Pathogen-free (SPF) and Clean (CL) BALB/C mice to small intestine total B-cell and memory B-cell receptor (BCR) complementary-determining region 3 (CDR3) repertoire. Results The composition and characteristics of intestinal microflora were analyzed by 16S rDNA sequencing. Genomic DNA extracted from small intestine tissue and memory B-cells of GF, SPF and CL mice were conducted via high-throughput DNA sequencing methods. As expected, significant differences of gut microflora diversity were observed in the three mice groups. CL group showed the most diversity, followed by SPF group, and GF group had the lowest diversity. Moreover, anormogenesis of intestinal lymphoid tissue were observed in GF mice. Diversity of the BCR heavy chain CDR3 repertoire in memory B cells were significant difference among three groups, but not in total B cells. The nucleotide polymorphism, usage frequency of gene segments (V, D, J, V–J gene segments) and amino acid of total B cells and memory B cells CDR3 were comparable among three mice groups, and there was significant difference between CL and GF mice groups. Conclusions The results of this study advocate that the colonization of intestinal microorganisms affect the diversity of B cells CDR3 repertoire. Elucidating mechanism of microbiome participated in the function of intestinal mucosal immune system may have positive effects on human health, and it requires further investigation.

scholarly journals Shared HIV envelope-specific B cell clonotypes induced by a pox-protein vaccine regimen

2021 ◽  
Author(s):  
Kristen W. Cohen ◽  
Lamar Ballweber-Fleming ◽  
Michael Duff ◽  
Rachael E. Whaley ◽  
Aaron Seese ◽  
...  
Keyword(s):  
B Cells ◽  
B Cell ◽  
Neutralizing Antibodies ◽  
Rational Design ◽  
Critical Role ◽  
Memory B Cells ◽  
Protein Vaccine ◽  
Cell Repertoire ◽  
B Cell Repertoire ◽  
Specific Igg

An effective HIV-1 vaccine will likely induce potent, broad neutralizing antibodies. No candidate vaccines have elicited these responses presumably because they fail to activate human B cell precursors that can affinity mature to generate broad neutralizing antibodies. To identify the B cell clonotypes that are elicited, we conducted in-depth analyses of the envelope-specific B cell repertoire in recipients of ALVAC-HIV vector (vCP2438) and bivalent subtype C gp120 protein (HVTN100). We observed high frequencies of envelope-specific IgG+ memory B cells with restricted immunogenetic diversity, relative to non-vaccine induced memory B cells, with preferential expansions of distinct variable genes but limited accumulation of mutations. Many envelope-specific clonotypes were shared across vaccinees, but did not overlap with the envelope-negative memory repertoire, within and across subjects. Single-cell sequencing of envelope-specific IgG+ memory B cells often revealed VH1-2*02 and VK3-20 sequence co-expression and in one case, contained a 5 amino acid CDRL3, the canonical signature of VRC01-class antibodies, confirming that these B cells are extremely rare but detectable. Our study provides evidence that immunogens play a critical role in selecting and restricting the responding B cell repertoire and supports the rational design of HIV vaccines targeting specific B cell lineages for induction of broadly-reactive neutralizing antibodies.

scholarly journals Silencing of B Cell Receptor Signals in Human Naive B Cells

2002 ◽  
Vol 196 (10) ◽  
pp. 1291-1305 ◽  
Author(s):  
Niklas Feldhahn ◽  
Ines Schwering ◽  
Sanggyu Lee ◽  
Maria Wartenberg ◽  
Florian Klein ◽  
...  
Keyword(s):  
Gene Expression ◽  
B Cells ◽  
B Cell ◽  
Cell Receptor ◽  
Memory B Cells ◽  
B Cell Receptor ◽  
Functional Assay ◽  
Hematopoietic Stem ◽  
Large Group ◽  
Bcr Signaling

To identify changes in the regulation of B cell receptor (BCR) signals during the development of human B cells, we generated genome-wide gene expression profiles using the serial analysis of gene expression (SAGE) technique for CD34+ hematopoietic stem cells (HSCs), pre-B cells, naive, germinal center (GC), and memory B cells. Comparing these SAGE profiles, genes encoding positive regulators of BCR signaling were expressed at consistently lower levels in naive B cells than in all other B cell subsets. Conversely, a large group of inhibitory signaling molecules, mostly belonging to the immunoglobulin superfamily (IgSF), were specifically or predominantly expressed in naive B cells. The quantitative differences observed by SAGE were corroborated by semiquantitative reverse transcription–polymerase chain reaction (RT-PCR) and flow cytometry. In a functional assay, we show that down-regulation of inhibitory IgSF receptors and increased responsiveness to BCR stimulation in memory as compared with naive B cells at least partly results from interleukin (IL)-4 receptor signaling. Conversely, activation or impairment of the inhibitory IgSF receptor LIRB1 affected BCR-dependent Ca2+ mobilization only in naive but not memory B cells. Thus, LIRB1 and IL-4 may represent components of two nonoverlapping gene expression programs in naive and memory B cells, respectively: in naive B cells, a large group of inhibitory IgSF receptors can elevate the BCR signaling threshold to prevent these cells from premature activation and clonal expansion before GC-dependent affinity maturation. In memory B cells, facilitated responsiveness upon reencounter of the immunizing antigen may result from amplification of BCR signals at virtually all levels of signal transduction.

scholarly journals Ex vivo characterization and isolation of rare memory B cells with antigen tetramers

Blood ◽  
2011 ◽  
Vol 118 (2) ◽  
pp. 348-357 ◽  
Author(s):  
Bettina Franz ◽  
Kenneth F. May ◽  
Glenn Dranoff ◽  
Kai Wucherpfennig
Keyword(s):  
B Cells ◽  
B Cell ◽  
Single Cell ◽  
Ex Vivo ◽  
Cell Receptor ◽  
Memory B Cells ◽  
Cell Repertoire ◽  
Low Frequencies

Abstract Studying human antigen-specific memory B cells has been challenging because of low frequencies in peripheral blood, slow proliferation, and lack of antibody secretion. Therefore, most studies have relied on conversion of memory B cells into antibody-secreting cells by in vitro culture. To facilitate direct ex vivo isolation, we generated fluorescent antigen tetramers for characterization of memory B cells by using tetanus toxoid as a model antigen. Brightly labeled memory B cells were identified even 4 years after last immunization, despite low frequencies ranging from 0.01% to 0.11% of class-switched memory B cells. A direct comparison of monomeric to tetrameric antigen labeling demonstrated that a substantial fraction of the B-cell repertoire can be missed when monomeric antigens are used. The specificity of the method was confirmed by antibody reconstruction from single-cell sorted tetramer+ B cells with single-cell RT-PCR of the B-cell receptor. All antibodies bound to tetanus antigen with high affinity, ranging from 0.23 to 2.2 nM. Furthermore, sequence analysis identified related memory B cell and plasmablast clones isolated more than a year apart. Therefore, antigen tetramers enable specific and sensitive ex vivo characterization of rare memory B cells as well as the production of fully human antibodies.

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