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Purpose To investigate the impact of a new class of anti-Ig autoantibodies reactive with variable heavy (V H ) chain framework sequences (human anti-V H autoantibodies) on the pharmacology and safety of an anti-TNFR1 V H domain antibody (GSK1995057) in healthy human subjects. Methods Single-blind, randomised, placebo-controlled dose escalation study in which healthy males ( n  = 28) received a single GSK1995057 intravenous infusion of 0.0004, 0.002 and 0.01 mg/kg. All enrolled subjects were pre-screened for human anti-V H (HAVH) autoantibody status and prospectively stratified accordingly. Serum samples from drug-naïve, HAVH-positive volunteers were used to investigate the effect of HAVH/GSK1995057 complexes on the activation of TNFR1 and cytokine release in vitro. Results Human anti-V H autoantibodies were detected in approximately 50 % of drug-naïve healthy human subjects and clinical and in vitro studies were performed to evaluate their impact on the pharmacology and safety of GSK1995057. We demonstrated that formation of HAVH autoantibody/GSK1995057 complexes activated TNFR1 and caused cytokine release in vitro in some, but not all, of the human cell types tested. When GSK1995057 was administered to healthy subjects, clinical and physiological signs of cytokine release were observed in two HAVH autoantibody-positive subjects following GSK1995057 infusion. In vitro, HAVH autoantibody levels correlated with TNFR1-dependent cytokine release and propensity for cytokine release in humans following GSK1995057 dosing. Conclusions Our data support a greater focus on the impact of pre-existing, drug-reactive autoantibodies on the development of antibody fragments and biotherapeutics targeting cell surface receptors.

Patients with systemic lupus erythematosus (SLE) experience flares of autoantibody secretion. Sanz and colleagues track the plasma cell repertoires of patients with SLE and find a sizeable polyclonal contribution by newly activated autoreactive B cells. Acute systemic lupus erythematosus (SLE) courses with surges of antibody-secreting cells (ASCs) whose origin, diversity and contribution to serum autoantibodies remain unknown. Here, deep sequencing, proteomic profiling of autoantibodies and single-cell analysis demonstrated highly diversified ASCs punctuated by clones expressing the variable heavy-chain region V H 4-34 that produced dominant serum autoantibodies. A fraction of ASC clones contained autoantibodies without mutation, a finding consistent with differentiation outside the germinal centers. A substantial ASC segment was derived from a distinct subset of newly activated naive cells of considerable clonality that persisted in the circulation for several months. Thus, selection of SLE autoreactivities occurred during polyclonal activation, with prolonged recruitment of recently activated naive B cells. Our findings shed light on the pathogenesis of SLE, help explain the benefit of agents that target B cells and should facilitate the design of future therapies.

BackgroundRotavirus-induced diarrhea poses a worldwide medical problem in causing substantial morbidity and mortality among children in developing countries. We therefore developed a system for passive immunotherapy in which recombinant lactobacilli constitutively express neutralizing variable domain of llama heavy-chain (VHH) antibody fragments against rotavirus MethodsVHH were expressed in Lactobacillus paracasei in both secreted and cell surface–anchored forms. Electron microscopy was used to investigate the binding efficacy of VHH-expressing lactobacilli. To investigate the in vivo function of VHH-expressing lactobacilli, a mouse pup model of rotavirus infection was used ResultsEfficient binding of the VHH antibody fragments to rotavirus was shown by enzyme-linked immunosorbent assay and scanning electron microscopy. VHH fragments expressed by lactobacilli conferred a significant reduction in infection in cell cultures. When administered orally, lactobacilli-producing surface-expressed VHH markedly shortened disease duration, severity, and viral load in a mouse model of rotavirus-induced diarrhea when administered both fresh and in a freeze-dried form ConclusionsTransformed lactobacilli may form the basis of a novel form of prophylactic treatment against rotavirus infections and other diarrheal diseases

The vertebrate adaptive immune system modifies the genome of individual B cells to encode antibodies that bind particular antigens 1 . In most mammals, antibodies are composed of heavy and light chains that are generated sequentially by recombination of V, D (for heavy chains), J and C gene segments. Each chain contains three complementarity-determining regions (CDR1–CDR3), which contribute to antigen specificity. Certain heavy and light chains are preferred for particular antigens 2 – 22 . Here we consider pairs of B cells that share the same heavy chain V gene and CDRH3 amino acid sequence and were isolated from different donors, also known as public clonotypes 23 , 24 . We show that for naive antibodies (those not yet adapted to antigens), the probability that they use the same light chain V gene is around 10%, whereas for memory (functional) antibodies, it is around 80%, even if only one cell per clonotype is used. This property of functional antibodies is a phenomenon that we call light chain coherence. We also observe this phenomenon when similar heavy chains recur within a donor. Thus, although naive antibodies seem to recur by chance, the recurrence of functional antibodies reveals surprising constraint and determinism in the processes of V(D)J recombination and immune selection. For most functional antibodies, the heavy chain determines the light chain.  Among naturally occurring antibodies that have adapted to antigen, those with similar heavy chains usually have similar light chains.

Georgiou and colleagues describe a single-cell, emulsion-based approach for the high-throughput determination of the paired antibody variable heavy and light chain (VH-VL) repertoire encoded by the more than 2 × 10 6 B cells in human peripheral blood samples. High-throughput immune repertoire sequencing has emerged as a critical step in the understanding of adaptive responses following infection or vaccination or in autoimmunity. However, determination of native antibody variable heavy-light pairs (VH-VL pairs) remains a major challenge, and no technologies exist to adequately interrogate the >1 × 10 6 B cells in typical specimens. We developed a low-cost, single-cell, emulsion-based technology for sequencing antibody VH-VL repertoires from >2 × 10 6 B cells per experiment with demonstrated pairing precision >97%. A simple flow-focusing apparatus was used to sequester single B cells into emulsion droplets containing lysis buffer and magnetic beads for mRNA capture; subsequent emulsion RT-PCR generated VH-VL amplicons for next-generation sequencing. Massive VH-VL repertoire analyses of three human donors provided new immunological insights including (i) the identity, frequency and pairing propensity of shared, or 'public', VL genes, (ii) the detection of allelic inclusion (an implicated autoimmune mechanism) in healthy individuals and (iii) the occurrence of antibodies with features, in terms of gene usage and CDR3 length, associated with broadly neutralizing antibodies to rapidly evolving viruses such as HIV-1 and influenza.

Colonization by the microbiota causes a marked stimulation of B cells and induction of immunoglobulin, but mammals colonized with many taxa have highly complex and individualized immunoglobulin repertoires 1 , 2 . Here we use a simplified model of defined transient exposures to different microbial taxa in germ-free mice 3 to deconstruct how the microbiota shapes the B cell pool and its functional responsiveness. We followed the development of the immunoglobulin repertoire in B cell populations, as well as single cells by deep sequencing. Microbial exposures at the intestinal mucosa generated oligoclonal responses that differed from those of germ-free mice, and from the diverse repertoire that was generated after intravenous systemic exposure to microbiota. The IgA repertoire—predominantly to cell-surface antigens—did not expand after dose escalation, whereas increased systemic exposure broadened the IgG repertoire to both microbial cytoplasmic and cell-surface antigens. These microbial exposures induced characteristic immunoglobulin heavy-chain repertoires in B cells, mainly at memory and plasma cell stages. Whereas sequential systemic exposure to different microbial taxa diversified the IgG repertoire and facilitated alternative specific responses, sequential mucosal exposure produced limited overlapping repertoires and the attrition of initial IgA binding specificities. This shows a contrast between a flexible response to systemic exposure with the need to avoid fatal sepsis, and a restricted response to mucosal exposure that reflects the generic nature of host–microbial mutualism in the mucosa. A mouse model of systemic versus mucosal exposure to microbial taxa reveals that the former provokes a flexible B cell response with a diverse immunoglobulin repertoire, whereas the latter generates a more-restricted response.

Antibody VRC01 is a human immunoglobulin that neutralizes about 90% of HIV-1 isolates. To understand how such broadly neutralizing antibodies develop, we used x-ray crystallography and 454 pyrosequencing to characterize additional VRC01-like antibodies from HIV-1—infected individuals. Crystal structures revealed a convergent mode of binding for diverse antibodies to the same CD4-binding-site epitope. A functional genomics analysis of expressed heavy and light chains revealed common pathways of antibody-heavy chain maturation, confined to the IGHV1-2*02 lineage, involving dozens of somatic changes, and capable of pairing with different light chains. Broadly neutralizing HIV-1 immunity associated with VRC01-like antibodies thus involves the evolution of antibodies to a highly affinity-matured state required to recognize an invariant viral structure, with lineages defined from thousands of sequences providing a genetic roadmap of their development.

Blimp-1 is known to act as a transcriptional repressor by suppressing genes associated with mature and activated germinal center B cells. Busslinger and colleagues show that Blimp-1 can also directly activate gene expression in plasma cells, including those encoding proteins that regulate the production of membrane-bound immunoglobulin versus secreted immunoglobulin. The transcription factor Blimp-1 is necessary for the generation of plasma cells. Here we studied its functions in plasmablast differentiation by identifying regulated Blimp-1 target genes. Blimp-1 promoted the migration and adhesion of plasmablasts. It directly repressed genes encoding several transcription factors and Aicda (which encodes the cytidine deaminase AID) and thus silenced B cell–specific gene expression, antigen presentation and class-switch recombination in plasmablasts. It directly activated genes, which led to increased expression of the plasma cell regulator IRF4 and proteins involved in immunoglobulin secretion. Blimp-1 induced the transcription of immunoglobulin genes by controlling the 3′ enhancers of the loci encoding the immunoglobulin heavy chain ( Igh ) and κ-light chain ( Igk ) and, furthermore, regulated the post-transcriptional expression switch from the membrane-bound form of the immunoglobulin heavy chain to its secreted form by activating Ell2 (which encodes the transcription-elongation factor ELL2). Notably, Blimp-1 recruited chromatin-remodeling and histone-modifying complexes to regulate its target genes. Hence, many essential functions of plasma cells are under the control of Blimp-1.

Tumor-infiltrating B cells are an important component in the microenvironment but have unclear anti-tumor effects. We enhanced our previous computational algorithm TRUST to extract the B cell immunoglobulin hypervariable regions from bulk tumor RNA-sequencing data. TRUST assembled more than 30 million complementarity-determining region 3 sequences of the B cell heavy chain (IgH) from The Cancer Genome Atlas. Widespread B cell clonal expansions and immunoglobulin subclass switch events were observed in diverse human cancers. Prevalent somatic copy number alterations in the MICA and MICB genes related to antibody-dependent cell-mediated cytotoxicity were identified in tumors with elevated B cell activity. The IgG3–1 subclass switch interacts with B cell–receptor affinity maturation and defects in the antibody-dependent cell-mediated cytotoxicity pathway. Comprehensive pancancer analyses of tumor-infiltrating B cell–receptor repertoires identified novel tumor immune evasion mechanisms through genetic alterations. The IgH sequences identified here are potentially useful resources for future development of immunotherapies. This comprehensive pancancer analysis of RNA-sequencing data from bulk tumors defines the landscape of tumor-infiltrating B cell–receptor repertoires and highlights new mechanisms of tumor immune evasion through genetic alterations.

VRC01-class broadly neutralizing HIV-1 antibodies protect animals from experimental infection and could contribute to an effective vaccine response. Their predicted germline forms (gl) bind Env inefficiently, which may explain why they are not elicited by HIV-1 Env-immunization. Here we show that an optimized Env immunogen can engage multiple glVRC01-class antibodies. Furthermore, this immunogen activates naive B cells expressing the human germline heavy chain of 3BNC60, paired with endogenous mouse light chains in vivo . To address whether it activates B cells expressing the fully humanized gl3BNC60 B-cell receptor (BCR), we immunized mice carrying both the heavy and light chains of gl3BNC60. B cells expressing this BCR display an autoreactive phenotype and fail to respond efficiently to soluble forms of the optimized immunogen, unless it is highly multimerized. Thus, specifically designed Env immunogens can activate naive B cells expressing human BCRs corresponding to precursors of broadly neutralizing HIV-1 antibodies even when the B cells display an autoreactive phenotype. The induction of broadly neutralizing antibodies (bNAbs) is a goal of HIV-1 vaccine research. Here the authors demonstrate the ability of an HIV Env-derived immunogen to bind germline precursors of a class of bNAbs and to activate the corresponding B cells in a knock-in mouse model