Genetically engineered IgG1 and nanobody oligomers acquire strong intrinsic CD40 agonism

Most anti-CD40 antibodies show robust agonism only upon binding to FcγR+ cells, such as B cells, macrophages, or DCs, but a few anti-CD40 antibodies display also strong intrinsic agonism dependent on the recognized epitope and/or isotype. It is worth mentioning, however, that also the anti-CD40 antibodies with intrinsic agonism can show a further increase in agonistic activity when bound by FcγR-expressing cells. Thus, conventional antibodies appear not to be sufficient to trigger the maximum possible CD40 activation independent from FcγR-binding. We proved here the hypothesis that oligomeric and oligovalent anti-CD40 antibody variants generated by genetic engineering display high intrinsic, thus FcγR-independent, agonistic activity. We generated tetra-, hexa- and dodecavalent variants of six anti-CD40 antibodies and a CD40-specific nanobody. All these oligovalent variants, even when derived of bivalent antagonistic anti-CD40 antibodies, showed strongly enhanced CD40 agonism compared to their conventional counterparts. In most cases, the CD40 agonism reached the maximum response induced by FcγR-bound anti-CD40 antibodies or membrane CD40L, the natural engager of CD40. In sum, our data show that increasing the valency of anti-CD40 antibody constructs by genetic engineering regularly results in molecules with high intrinsic agonism and level out the specific limitations of the parental antibodies.

Impact of antibody architecture and paratope valency on effector functions of bispecific NKp30 x EGFR natural killer cell engagers

Natural killer (NK) cells emerged as a promising effector population that can be harnessed for anti-tumor therapy. In this work, we constructed NK cell engagers (NKCEs) based on NKp30-targeting single domain antibodies (sdAbs) that redirect the cytotoxic potential of NK cells toward epidermal growth factor receptor (EGFR)-expressing tumor cells. We investigated the impact of crucial parameters such as sdAb location, binding valencies, the targeted epitope on NKp30, and the overall antibody architecture on the redirection capacity. Our study exploited two NKp30-specific sdAbs, one of which binds a similar epitope on NKp30 as its natural ligand B7-H6, while the other sdAb addresses a non-competing epitope. For EGFR-positive tumor targeting, humanized antigen-binding domains of therapeutic antibody cetuximab were used. We demonstrate that NKCEs bivalently targeting EGFR and bivalently engaging NKp30 are superior to monovalent NKCEs in promoting NK cell-mediated tumor cell lysis and that the architecture of the NKCE can substantially influence killing capacities depending on the NKp30-targeting sdAb utilized. While having a pronounced impact on NK cell killing efficacy, the capabilities of triggering antibody-dependent cellular phagocytosis or complement-dependent cytotoxicity were not significantly affected comparing the bivalent IgG-like NKCEs with cetuximab. However, the fusion of sdAbs can have a slight impact on the NK cell release of immunomodulatory cytokines, as well as on the pharmacokinetic profile of the NKCE due to unfavorable spatial orientation within the molecule architecture. Ultimately, our findings reveal novel insights for the engineering of potent NKCEs triggering the NKp30 axis.

Multivalent antigen display on nanoparticle immunogens increases B cell clonotype diversity and neutralization breadth to pneumoviruses

Nanoparticles for multivalent display and delivery of vaccine antigens have emerged as a promising avenue for enhancing B cell responses to protein subunit vaccines. Here, we evaluated B cell responses in rhesus macaques immunized with prefusion-stabilized respiratory syncytial virus (RSV) F glycoprotein trimer compared with nanoparticles displaying 10 or 20 copies of the same antigen. We show that multivalent display skews antibody specificities and drives epitope-focusing of responding B cells. Antibody cloning and repertoire sequencing revealed that focusing was driven by the expansion of clonally distinct B cells through recruitment of diverse precursors. We identified two antibody lineages that developed either ultrapotent neutralization or pneumovirus cross-neutralization from precursor B cells with low initial affinity for the RSV-F immunogen. This suggests that increased avidity by multivalent display facilitates the activation and recruitment of these cells. Diversification of the B cell response by multivalent nanoparticle immunogens has broad implications for vaccine design.

Dimeric Lectin Chimeras as Novel Candidates for Gb3-Mediated Transcytotic Drug Delivery through Cellular Barriers

Receptor-mediated transcytosis is an elegant and promising strategy for drug delivery across biological barriers. Here, we describe a novel ligand-receptor pair based on a dimeric, engineered derivative of the Pseudomonas aeruginosa lectin LecA, here termed Di-LecA, and the host cell glycosphingolipid Gb3. We characterized the trafficking kinetics and transcytosis efficiencies in polarized Gb3-positive and -negative MDCK cells using mainly immunofluorescence in combination with confocal microscopy. To evaluate the delivery capacity of dimeric LecA chimeras, EGFP was chosen as a fluorescent model protein representing macromolecules, such as antibody fragments, and fused to either the N- or C-terminus of monomeric LecA using recombinant DNA technology. Both LecA/EGFP fusion proteins crossed cellular monolayers in vitro. Of note, the conjugate with EGFP at the N-terminus of LecA (EGFP-LecA) showed a higher release rate than the conjugate with EGFP at the C-terminus (LecA-EGFP). Based on molecular dynamics simulations and cross-linking studies of giant unilamellar vesicles, we speculate that EGFP-LecA tends to be a dimer while LecA-EGFP forms a tetramer. Overall, we confidently propose the dimeric LecA chimeras as transcytotic drug delivery tools through Gb3-positive cellular barriers for future in vivo tests.

eIg-based bispecific T-cell engagers targeting EGFR: Format matters

Bispecific antibodies are molecules with versatile modes of action and applications for therapy. They are commonly developed as T-cell engagers (TCE), which simultaneously target an antigen expressed by tumor cells and CD3 expressed by T-cells, thereby inducing T-cell-mediated target cell killing. There is growing evidence that the molecular composition and valency for the target antigen influence the activity of TCEs. Here, the eIg platform technology was used to generate a set of bispecific TCEs targeting epidermal growth factor receptors (EGFR) and CD3. These molecules either included or lacked an Fc region and exhibited one binding site for CD3 and either one or two binding sites for EGFR (1 + 1 or 2 + 1 formats) utilizing different molecular arrangements of the binding sites. In total, 11 different TCE formats were analyzed for binding to target cells and T cells, T cell-mediated killing of tumor cells, and for the activation of T cells (release of cytokines and proliferation of T-cells). Bivalent binding to EGFR strongly increased binding and T cell-mediated killing. However, the molecular composition and position of the CD3-binding arm also affected target cell killing, cytokine release, and T-cell proliferation. Our findings support that screening of a panel of formats is beneficial to identify the most potent bispecific TCE, and that format matters.

Using quantitative single molecule localization microscopy to optimize multivalent HER2-targeting ligands

Introduction

The progression-free survival of patients with HER2-positive metastatic breast cancer is significantly extended by a combination of two monoclonal antibodies, trastuzumab and pertuzumab, which target independent epitopes of the extracellular domain of HER2. The improved efficacy of the combination over individual antibody therapies targeting HER2 is still being investigated, and several molecular mechanisms may be in play: the combination downregulates HER2, improves antibody-dependent cell mediated cytotoxicity, and/or affects the organization of surface-expressed antigens, which may attenuate downstream signaling.

Methods

By combining protein engineering and quantitative single molecule localization microscopy (qSMLM), here we both assessed and optimized clustering of HER2 in cultured breast cancer cells.

Results

We detected marked changes to the cellular membrane organization of HER2 when cells were treated with therapeutic antibodies. When we compared untreated samples to four treatment scenarios, we observed the following HER2 membrane features: (1) the monovalent Fab domain of trastuzumab did not significantly affect HER2 clustering; (2) individual therapy with either trastuzumab or (3) pertuzumab produced significantly higher levels of HER2 clustering; (4) a combination of trastuzumab plus pertuzumab produced the highest level of HER2 clustering. To further enhance this last effect, we created multivalent ligands using meditope technology. Treatment with a tetravalent meditope ligand combined with meditope-enabled trastuzumab resulted in pronounced HER2 clustering. Moreover, compared to pertuzumab plus trastuzumab, at early time points this meditope-based combination was more effective at inhibiting epidermal growth factor (EGF) dependent activation of several downstream protein kinases.

Discussion

Collectively, mAbs and multivalent ligands can efficiently alter the organization and activation of the HER2 receptors. We expect this approach could be used in the future to develop new therapeutics.

Multispecific, Multivalent Antibody-Based Molecules Engineered on the DART® and TRIDENTTM Platforms

Multispecific antibodies bind two or more different antigens and enable new therapeutic applications that cannot be replicated with conventional monoclonal antibodies, such as bridging different cells or bringing soluble proteins in close proximity. The DART and TRIDENT platforms enable the engineering of such antibodies. A DART molecule combines two independent antigen-binding sites in a stabilized, diabody-like structure. A DART molecule can be expressed with or without an Fc domain and thus can be tailored to have a long or short half-life in vivo and to induce or ablate effector function. Linking two DART units or a DART unit and a Fab domain (the latter structure is called TRIDENT format) via an Fc domain creates a monospecific, bispecific, trispecific, or tetraspecific molecule with up to tetravalent targeting of antigens. This article focuses on the design of DART and TRIDENT molecules that target two or three different antigens. © 2020 by John Wiley & Sons, Inc. Basic Protocol 1: Design and generation of expression plasmids encoding DART and TRIDENT molecules Basic Protocol 2: Expression of DART and TRIDENT molecules by transient transfection of CHO cells Basic Protocol 3: Purification of DART and TRIDENT molecules from CHO cell supernatants.

Multifaceted Effects of Antigen Valency on B Cell Response Composition and Differentiation In Vivo

How antigen valency affects B cells in vivo during immune responses is not well understood. Here, using HIV immunogens with defined valencies ranging from 1 to 60, we investigated the role of antigen valency during different phases of B cell responses in vivo. Highly multimerized immunogens preferentially rapidly activated cognate B cells, with little affinity discrimination. This led to strong early induction of the transcription factors IRF4 (interferon regulatory factor 4) and Bcl6, driving both early extrafollicular plasma cell and germinal center responses, in a CD4⁺ T-cell-dependent manner, involving B cells with a broad range of affinities. Low-valency antigens induced smaller effector B cell responses, with preferential recruitment of high-affinity B cells. Thus, antigen valency has multifaceted effects on B cell responses and can dictate affinity thresholds and competitive landscapes for B cells in vivo, with implications for vaccine design.

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Antigen valency dictates the magnitude and composition of B cell responses

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High valency enables robust activation and effector differentiation of B cells

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Antigen valency alters breadth of B cell affinities recruited

Molecular Insights into the Ligand-Based Six-Proton- and Six-Electron-Transfer Processes Between Tris-ortho-Phenylenediamines and Tris-ortho-Benzoquinodiimines

The global demand for energy and the concerns over climate issues renders the development of alternative renewable energy sources such as hydrogen (H₂ ) important. A high-spin (hs) Fe^II complex with o-phenylenediamine (opda) ligands, [Fe^II (opda)₃ ]²⁺ (hs-[6R]²⁺ ), was reported showing photochemical H₂ evolution. In addition, a low-spin (ls) [Fe^II (bqdi)₃ ]²⁺ (bqdi: o-benzoquinodiimine) (ls-[0R]²⁺ ) formation by O₂ oxidation of hs-[6R]²⁺ , accompanied by ligand-based six-proton and six-electron transfer, revealed the potential of the complex with redox-active ligands as a novel multiple-proton and -electron storage material, albeit that the mechanism has not yet been understood. This paper reports that the oxidized ls-[0R][PF₆ ]₂ can be reduced by hydrazine giving ls-[Fe^II (opda)(bqdi)₂ ][PF₆ ]₂ (ls-[2R][PF₆ ]₂ ) and ls-[Fe^II (opda)₂ (bqdi)][PF₆ ]₂ (ls-[4R][PF₆ ]₂ ) with localized ligand-based proton-coupled mixed-valence (LPMV) states. The first isolation and characterization of the key intermediates with LPMV states offer unprecedented molecular insights into the design of photoresponsive molecule-based hydrogen-storage materials.

Chemical Bonding: The Journey from Miniature Hooks to Density Functional Theory

Our modern understanding of chemistry is predicated upon bonding interactions between atoms and ions resulting in the assembly of all of the forms of matter that we encounter in our daily life. It was not always so. This review article traces the development of our understanding of bonding from prehistory, through the debates in the 19th century C.E. bearing on valence, to modern quantum chemical models and beyond.

Hidden Aspects of Valency in Immune System Regulation

Valency can be defined as the number of discrete interactions a biomolecule can engage in. Valency can be critical for function, such as determining whether a molecule acts as a scaffold for assembling large supramolecular complexes or forms a functional dimer. Here, we highlight the importance of the role of valency in regulating immune responses, with a focus on innate immunity. We discuss some of the ways in which valency itself is regulated through transcriptional, post-transcriptional, and post-translational modifications. Finally, we propose that the valency model can be applied at the whole cell level to study differences in individual cell responses with relevance to putative therapeutic applications.

Avidity and Cell Uptake of Integrin-Targeting Polypeptide Micelles is Strongly Shape-Dependent

We describe a genetically encoded micelle for targeted delivery consisting of a diblock polypeptide with segments derived from repetitive protein motifs inspired by Drosophila melanogaster Rec-1 resilin and human tropoelastin with a C-terminal fusion of an integrin-targeting fibronectin type III domain. By systematically varying the weight fraction of the hydrophilic elastin-like polypeptide (ELP) block and molecular weight of the diblock polypeptide, we designed micelles of different morphologies that modulate the binding avidity of the human wild-type 10th fibronectin domain (Fn3) as a function of shape. We show that wormlike micelles that present the Fn3 domain have a 1000-fold greater avidity for the α_vβ₃ receptor compared to the monomer ligand and an avidity that is greater than a clinically relevant antibody that is driven by their multivalency. The amplified avidity of these micelles leads to significantly increased cellular internalization, a feature that may have utility for the intracellular delivery of drugs that are loaded into the core of these micelles.

Soluble Antigen Arrays for Selective Desensitization of Insulin-Reactive B Cells

Autoimmune diseases are believed to be highly dependent on loss of immune tolerance to self-antigens. Currently, no treatments have been successful clinically in inducing autoantigen-specific tolerance, including efforts to utilize antigen-specific immunotherapy (ASIT) to selectively correct the aberrant autoimmunity. Soluble antigen arrays (SAgAs) represent a novel autoantigen delivery system composed of a linear polymer, hyaluronic acid (HA), displaying multiple copies of conjugated autoantigen. We have previously reported that soluble antigen arrays displaying proteolipid peptide (SAgA_PLP) induced tolerance to this specific multiple sclerosis (MS) autoantigen. Utilizing SAgA technology, we have developed a new ASIT as a possible type 1 diabetes (T1D) therapeutic by conjugating human insulin to HA, known as soluble antigen array insulin (SAgA_Ins). Three types were synthesized, low valency _lvSAgA_Ins (2 insulins per HA), medium valency _mvSAgA_Ins (4 insulins per HA), and, high valency _hvSAgA_Ins (9 insulins per HA), to determine if valency differentially modulates the ex vivo activity of insulin-binding B cells (IBCs). Extensive biophysical characterization was performed for the SAgA molecules. SAgA_Ins molecules were successfully used to affect the biologic activity of IBCs by inducing desensitization of the B cell antigen receptors (BCR). SAgA_Ins bound specifically to insulin-reactive B cells without blocking epitopes recognized by antibodies against the Fc regions of membrane immunoglobulin or CD79 transducer components of the BCR. Preincubation of IBCs (125Tg) with SAgA_Ins, but not HA alone, rendered the IBCs refractory to restimulation. SAgA_Ins induced a decrease in BCR expression and IP3R-mediated intracellular calcium release. Surprisingly, SAgA_Ins binding to BCR on the surface of IBCs induced the observed effects at both high and low SAgA_Ins valency. Future studies aim to test the effects of SAgA_Ins on disease progression in the VH125.NOD mouse model of T1D.

Adsorption mechanism and valency of catechol-functionalized hyperbranched polyglycerols

Nature often serves as a model system for developing new adhesives. In aqueous environments, mussel-inspired adhesives are promising candidates. Understanding the mechanism of the extraordinarily strong adhesive bonds of the catechol group will likely aid in the development of adhesives. With this aim, we study the adhesion of catechol-based adhesives to metal oxides on the molecular level using atomic force microscopy (AFM). The comparison of single catechols (dopamine) with multiple catechols on hyperbranched polyglycerols (hPG) at various pH and dwell times allowed us to further increase our understanding. In particular, we were able to elucidate how to achieve strong bonds of different valency. It was concluded that hyperbranched polyglycerols with added catechol end groups are promising candidates for durable surface coatings.

Ya33 'give' as a valency increaser in Jinghpo nuclear serialization: from benefactive to malefactive

This paper analyzes serial verb constructions in Jinghpo formed by ya³³ 'give', arguing that it has the function of a valency-increasing device in nuclear serialization: the use of ya³³ allows the licensing of an additional beneficiary argument as a core argument to the lexical verb. In a new twist, however, on the evolution of give verbs, we demonstrate that the benefactive usage is extended to malefactive semantics in a distinct, derived structure, conditioned via the expression of possession, a type of malefactive that is not well-documented in current literature on this domain. Furthermore, the existence of two distinct constructions for the benefactive and the malefactive in Jinghpo conforms to Radetzky & Smith's claim (2010: 116) that this is an areal feature comprising the Indian subcontinent, Southeast and East Asia, and thus contrasts strongly with the conflation of both types of construction in many European languages. Finally, we propose that the nuclear type of serialization, integral to the typological profile of Jinghpo, a SOV language, is a determining factor in the reanalysis of ya³³ . This feature is subsequently invoked to explain why the malefactive usage of ya³³ constitutes a separate development from the well-attested pathway for give verbs leading to permissive causative verbs and adversative passive markers, which, while blocked in Jinghpo, is commonly found in many other East and Southeast Asian languages with core serialization. The present analysis is based on the variety of Jinghpo spoken in Luxi county, Yunnan province, China, using in the main natural discourse data collected in the field.

Stimulation of mitogenesis in normal and leukemic human lymphocytes by divalent and tetravalent lima bean lectins

Two hemagglutinating components purified from the lima bean and composed of identical 62,000-molecular-weight subunits have mitogenic activity in normal and leukemic human lymphocyte cultures. Component II (247,000 molecular weight), a tetramer with four saccharide binding sites, is severalfold more active than component III (124,000 molecular weight), a dimer with two binding sites per molecule, as a mitogen for normal lymphocytes. Component II also stimulates mitogenesis in populations of cultured leukemic lymphocytes and appears to have greater activity than phytohemagglutinin-P in leukemic lymphocyte cultures obtained from some patients. Lima bean component III has minimal mitogenic activity toward leukemic lymphocytes. Components II and III appear to compete for the same cell-surface binding sites, but component II has a much greater capacity than component III to trigger DNA synthesis at low concentrations (2.5-25 mug/ml) in normal lymphocyte cultures. These results suggest that the mitogenic activity of lima bean lectin components is directly related to their valence.