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CD40/anti-CD40 antibody complexes which illustrate agonist and antagonist structural switches.

ABSTRACT: BACKGROUND:CD40 is a 48?kDa type I transmembrane protein that is constitutively expressed on hematopoietic cells such as dendritic cells, macrophages, and B cells. Engagement of CD40 by CD40L expressed on T cells results in the production of proinflammatory cytokines, induces T helper cell function, and promotes macrophage activation. The involvement of CD40 in chronic immune activation has resulted in CD40 being proposed as a therapeutic target for a range of chronic inflammatory diseases. CD40 antagonists are currently being explored for the treatment of autoimmune diseases and several anti-CD40 agonist mAbs have entered clinical development for oncological indications. RESULTS:To better understand the mode of action of anti-CD40 mAbs, we have determined the x-ray crystal structures of the ABBV-323 (anti-CD40 antagonist, ravagalimab) Fab alone, ABBV-323 Fab complexed to human CD40 and FAB516 (anti-CD40 agonist) complexed to human CD40. These three crystals structures 1) identify the conformational CD40 epitope for ABBV-323 recognition 2) illustrate conformational changes which occur in the CDRs of ABBV-323 Fab upon CD40 binding and 3) develop a structural hypothesis for an agonist/antagonist switch in the LCDR1 of this proprietary class of CD40 antibodies. CONCLUSIONS:The structure of ABBV-323 Fab demonstrates a unique method for antagonism by stabilizing the proposed functional antiparallel dimer for CD40 receptor via novel contacts to LCDR1, namely residue position R32 which is further supported by a closely related agonist antibody FAB516 which shows only monomeric recognition and no contacts with LCDR1 due to a mutation to L32 on LCDR1. These data provide a structural basis for the full antagonist activity of ABBV-323.

SUBMITTER: Argiriadi MA

PROVIDER: S-EPMC6683420 | biostudies-literature | 2019 Aug

REPOSITORIES: biostudies-literature

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CD40/anti-CD40 antibody complexes which illustrate agonist and antagonist structural switches.

Argiriadi Maria A MA Benatuil Lorenzo L Dubrovska Ievgeniia I Egan David A DA Gao Lei L Greischar Amy A Hardman Jennifer J Harlan John J Iyer Ramesh B RB Judge Russell A RA Lake Marc M Perron Denise C DC Sadhukhan Ramkrishna R Sielaff Bernhard B Sousa Silvino S Wang Rui R McRae Bradford L BL

BMC molecular and cell biology 20190805 1

<h4>Background</h4>CD40 is a 48 kDa type I transmembrane protein that is constitutively expressed on hematopoietic cells such as dendritic cells, macrophages, and B cells. Engagement of CD40 by CD40L expressed on T cells results in the production of proinflammatory cytokines, induces T helper cell function, and promotes macrophage activation. The involvement of CD40 in chronic immune activation has resulted in CD40 being proposed as a therapeutic target for a range of chronic inflammatory diseas ...[more]

PMID: 31382872

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Project description:CD40 is a potent activating receptor expressed on antigen-presenting cells (APCs) of the immune system. CD40 regulates many aspects of B and T cell immunity via interaction with CD40L expressed on activated T cells. Targeting antigens to CD40 via agonistic anti-CD40 antibody fusions promotes both humoral and cellular immunity, but current anti-CD40 antibody-antigen vaccine prototypes require co-adjuvant administration for significant in vivo efficacy. This may be a consequence of dulling of anti-CD40 agonist activity via antigen fusion. We previously demonstrated that direct fusion of CD40L to anti-CD40 antibodies confers superagonist properties. Here we show that anti-CD40-CD40L-antigen fusion constructs retain strong agonist activity, particularly for activation of dendritic cells (DCs). Therefore, we tested anti-CD40-CD40L antibody fused to antigens for eliciting immune responses in vitro and in vivo. In PBMC cultures from HIV-1-infected donors, anti-CD40-CD40L fused to HIV-1 antigens preferentially expanded HIV-1-specific CD8+ T cells versus CD4+ T cells compared to analogous anti-CD40-antigen constructs. In normal donors, anti-CD40-CD40L-mediated delivery of Influenza M1 protein elicited M1-specific T cell expansion at lower doses compared to anti-CD40-mediated delivery. Also, on human myeloid-derived dendritic cells, anti-CD40-CD40L-melanoma gp100 peptide induced more sustained Class I antigen presentation compared to anti-CD40-gp100 peptide. In human CD40 transgenic mice, anti-CD40-CD40L-HIV-1 gp140 administered without adjuvant elicited superior antibody responses compared to anti-CD40-gp140 antigen without fused CD40L. In human CD40 mice, compared to the anti-CD40 vehicle, anti-CD40-CD40L delivery of Eα 52-68 peptide elicited proliferating of TCR I-Eα 52-68 CD4+ T cells producing cytokine IFNγ. Also, compared to controls, only anti-CD40-CD40L-Cyclin D1 vaccination of human CD40 mice reduced implanted EO771.LMB breast tumor cell growth. These data demonstrate that human CD40-CD40L antibody fused to antigens maintains highly agonistic activity and generates immune responses distinct from existing low agonist anti-CD40 targeting formats. These advantages were in vitro skewing responses towards CD8+ T cells, increased efficacy at low doses, and longevity of MHC Class I peptide display; and in mouse models, a more robust humoral response, more activated CD4+ T cells, and control of tumor growth. Thus, the anti-CD40-CD40L format offers an alternate DC-targeting platform with unique properties, including intrinsic adjuvant activity.

Project description:BackgroundA novel [64Cu]Cu-NOTA-aCD40 immunoPET tracer was developed to image a CD40+ pancreatic tumor model in C57BL/6 mice and to study the biodistribution profile of the agonist CD40 (aCD40) monoclonal antibody (mAb) alone or combined with other mAbs.ProceduresCopper-64 ([64Cu]Cu) labeled NOTA-aCD40 and NOTA-IgG (10 μg; 7 MBq) were injected intravenously into C57BL/6 mice with subcutaneous mT4 tumors to assess specificity 48 h post injection (p.i.) through positron emission tomography/computed tomography (PET/CT) imaging and biodistribution studies (n = 5). [64Cu]Cu-NOTA-aCD40 was injected alone or simultaneously in combination with a therapeutic mass of cold aCD40 (100 μg), aPD-1 (200 μg) and aCTLA-4 (200 μg) mAbs. A group of mice with or without tumor received the second round of injections 1 or 3 weeks apart, respectively. PET/CT imaging and biodistribution studies were performed at 48 h p.i. The organ dose for [64Cu]Cu was estimated based on biodistribution studies with 2 μg [64Cu]Cu-NOTA-aCD40 (corresponds to 5 mg patient dose) in non-tumor bearing mice.Results[64Cu]Cu-NOTA-aCD40 accumulation was 2.3- and 7.8-fold higher than [64Cu]Cu-NOTA-IgG in tumors and spleen, respectively, indicating the specificity of aCD40 mAb in a mouse pancreatic tumor model. Tumor accumulation of [64Cu]Cu-NOTA-aCD40 was 21.2 ± 7.3%ID/g at 48 h after injection. Co-injection of [64Cu]Cu-NOTA-aCD40 with cold aCD40 mAb alone or with PD-1 and CTLA-4 mAbs reduced both spleen and tumor uptake, whereas liver uptake was increased. With the second round of injections, the liver was the only organ with substantial uptake. With a 2 μg administered dose of [64Cu]Cu-NOTA-aCD40 in a dosimetry study, the liver to spleen ratio was greater compared to the 10 μg dose (2.8 vs 0.37; respectively). The human equivalent for the highest dose organ (liver) was 198 ± 28.7 μSv/MBq.ConclusionsA CD40-immunoreactive [64Cu]Cu-NOTA-aCD40 probe was developed. The ratio of spleen to liver accumulation exceeded that of the IgG isotype and was greatest with a single small, injected mass. The safety of human patient imaging with [64Cu]Cu was established based on extrapolation of the organ specificity to human imaging.

Dataset Information

CD40/anti-CD40 antibody complexes which illustrate agonist and antagonist structural switches.

Publications

CD40/anti-CD40 antibody complexes which illustrate agonist and antagonist structural switches.

Similar Datasets

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