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We have recently described the development of a series of small-molecule inhibitors of human tumour necrosis factor (TNF) that stabilise an open, asymmetric, signalling-deficient form of the soluble TNF trimer. Here, we describe the generation, characterisation, and utility of a monoclonal antibody that selectively binds with high affinity to the asymmetric TNF trimer–small molecule complex. The antibody helps to define the molecular dynamics of the apo TNF trimer, reveals the mode of action and specificity of the small molecule inhibitors, acts as a chaperone in solving the human TNF–TNFR1 complex crystal structure, and facilitates the measurement of small molecule target occupancy in complex biological samples. We believe this work defines a role for monoclonal antibodies as tools to facilitate the discovery and development of small-molecule inhibitors of protein–protein interactions. TNF can be inhibited by small molecules that stabilize the TNF trimer in an asymmetric conformation. Here, the authors develop a monoclonal antibody that selectively binds this inactive form of TNF, enabling both target engagement assessment and structural characterization of TNF binding to TNF receptor 1. [ABSTRACT FROM AUTHOR]

Objective: Antibodies against posttranslationally modified proteins are a hallmark of rheumatoid arthritis (RA), but the emergence and pathogenicity of these autoantibodies are still incompletely understood. The aim of this study was to analyze the antigen specificities and mutation patterns of monoclonal antibodies (mAb) derived from RA synovial plasma cells and address the question of antigen cross‐reactivity. Methods: IgG‐secreting cells were isolated from RA synovial fluid, and the variable regions of the immunoglobulins were sequenced (n = 182) and expressed in full‐length mAb (n = 93) and also as germline‐reverted versions. The patterns of reactivity with 53,019 citrullinated peptides and 49,211 carbamylated peptides and the potential of the mAb to promote osteoclastogenesis were investigated. Results: Four unrelated anti–citrullinated protein autoantibodies (ACPAs), of which one was clonally expanded, were identified and found to be highly somatically mutated in the synovial fluid of a patient with RA. The ACPAs recognized >3,000 unique peptides modified by either citrullination or carbamylation. This highly multireactive autoantibody feature was replicated for Ig sequences derived from B cells from the peripheral blood of other RA patients. The plasma cell–derived mAb were found to target distinct amino acid motifs and partially overlapping protein targets. They also conveyed different effector functions as revealed in an osteoclast activation assay. Conclusion: These findings suggest that the high level of cross‐reactivity among RA autoreactive B cells is the result of different antigen encounters, possibly at different sites and at different time points. This is consistent with the notion that RA is initiated in one context, such as in the mucosal organs, and thereafter targets other sites, such as the joints. [ABSTRACT FROM AUTHOR]

Single B cell screening strategies, which avoid both hybridoma fusion and combinatorial display, have emerged as important technologies for efficiently sampling the natural antibody repertoire of immunized animals and humans. Having access to a range of methods to interrogate different B cell subsets provides an attractive option to ensure large and diverse panels of high quality antibody are produced. The generation of multiple antibodies and having the ability to find rare B cell clones producing IgG with unique and desirable characteristics facilitates the identification of fit-for-purpose molecules that can be developed into therapeutic agents or research reagents. Here, we describe a multi-parameter flow cytometry single-cell sorting technique for the generation of antigen-specific recombinant monoclonal antibodies from single IgG+ memory B cells. Both mouse splenocytes and rabbit PBMC from immunised animals were used as a source of B cells. Reagents staining both B cells and other unwanted cell types enabled efficient identification of class-switched IgG+ memory B cells. Concurrent staining with antigen labelled separately with two spectrally-distinct fluorophores enabled antigen-specific B cells to be identified, i.e. those which bind to both antigen conjugates (double-positive). These cells were then typically sorted at one cell per well using FACS directly into a 96-well plate containing reverse transcriptase reaction mix. Following production of cDNA, PCR was performed to amplify cognate heavy and light chain variable region genes and generate transcriptionally-active PCR (TAP) fragments. These linear expression cassettes were then used directly in a mammalian cell transfection to generate recombinant antibody for further testing. We were able to successfully generate antigen-specific recombinant antibodies from both the rabbit and mouse IgG+ memory B cell subset within one week. This included the generation of an anti-TNFR2 blocking antibody from mice with an affinity of 90 pM. [ABSTRACT FROM AUTHOR]

The article focuses findings of a study on development of a therapeutic monoclonal antibody at targets secreted fatty acid–binding protein aP2 to treat type 2 diabetes. It states that Serum aP2 levels are markedly elevated in mouse and human obesity and strongly correlate with metabolic complications, and mentions that the structure of the aP2-CA33 complex and resolved the target epitope. It infers that antibody had no effect in aP2-deficient mice, demonstrating its target specificity.

Abstract: We describe a method for the generation of high-affinity monoclonal antibodies, which combines the power of natural immune responses with in vitro panning, B cell culture, RT-PCR and expression of the recombinant product. B cells from immunised rabbits were incubated at approximately 1000–10,000 cells per well with solid phase antigen coated on the surface of 96-well ELISA plates. Extensive washing removed non-binding cells as well as those B cells, which bound with low affinity. Retained B cells were cultured for 7 days in the presence of activated rabbit splenocyte supernatant and irradiated EL-4-B5 mouse thymoma cells, to induce proliferation and secretion of immunoglobulin. Supernatants were screened to confirm the presence of specific antibody, before the cells were harvested en masse from individual positive wells. Single heavy- and light-chain variable region genes were recovered from individual wells by RT-PCR, critically without the need for isolation of single B cells. Paired VH and VL genes were subsequently expressed as recombinant antibodies and shown to retain the original activity and specificity of the B cell culture supernatants. The method has also been successfully applied to the generation of high-affinity antibodies to antigen expressed on the surface of target cells. [Copyright &y& Elsevier]