G1 Domain Research Articles

A novel hotspot of gelsolin instability triggers an alternative mechanism of amyloid aggregation

Gelsolin comprises six homologous domains, named G1 to G6. Single point substitutions in this protein are responsible for AGel amyloidosis, a hereditary disease causing progressive corneal lattice dystrophy, cutis laxa, and polyneuropathy. Although several different amyloidogenic variants of gelsolin have been identified, only the most common mutants present in the G2 domain have been thoroughly characterized, leading to clarification of the functional mechanism. The molecular events underlying the pathological aggregation of 3 recently identified mutations, namely A551P, E553K and M517R, all localized at the interface between G4 and G5, are here explored for the first time. Structural studies point to destabilization of the interface between G4 and G5 due to three structural determinants: β-strand breaking, steric hindrance and/or charge repulsion, all implying impairment of interdomain contacts. Such rearrangements decrease the temperature and pressure stability of gelsolin but do not alter its susceptibility to furin cleavage, the first event in the canonical aggregation pathway. These variants also have a greater tendency to aggregate in the unproteolysed forms and exhibit higher proteotoxicity in a C. elegans-based assay. Our data suggest that aggregation of G4G5 variants follows an alternative, likely proteolysis-independent, pathway.

Versican: A Dynamic Regulator of the Extracellular Matrix.

Versican is a large chondroitin sulfate/dermatan sulfate proteoglycan belonging to the aggrecan/lectican family. In adults, this proteoglycan serves as a structural macromolecule of the extracellular matrix in the brain and large blood vessels. In contrast, versican is transiently expressed at high levels during development and under pathological conditions when the extracellular matrix dramatically changes, including in the inflammation and repair process. There are many reports showing the upregulation of versican in cancer, which correlates with cancer aggressiveness. Versican has four classical splice variants, and all the variants contain G1 and G3 domains at N- and C-termini, respectively. There are two glycosaminoglycan attachment domains CSα and CSβ. The largest V0 variant contains both CSα and CSβ, V1 contains CSβ, V2 contains CSα, and the shortest G3 variant has neither of them. Versican degradation is initiated by cleavage at a site in the CSβ domain by ADAMTS (a disintegrin and metalloproteinase with thrombospondin motifs) proteinases. The N-terminal fragment containing the G1 domain has been reported to exert various biological functions, although its mechanisms of action have not yet been elucidated. In this review, we describe the role of versican in inflammation and cancer and also address the biological function of versikine.

Ameliorated Autoimmune Arthritis and Impaired B Cell Receptor-Mediated Ca2+ Influx in Nkx2-3 Knock-out Mice.

B cells play a crucial role in the pathogenesis of rheumatoid arthritis. In Nkx2-3-deficient mice (Nkx2-3−/−) the spleen’s histological structure is fundamentally changed; therefore, B cell homeostasis is seriously disturbed. Based on this, we were curious, whether autoimmune arthritis could be induced in Nkx2-3−/− mice and how B cell activation and function were affected. We induced arthritis with immunization of recombinant human proteoglycan aggrecan G1 domain in Nkx2-3−/− and control BALB/c mice. We followed the clinical picture, characterized the radiological changes, the immune response, and intracellular Ca2+ signaling of B cells. Incidence of the autoimmune arthritis was lower, and the disease severity was milder in Nkx2-3−/− mice than in control BALB/c mice. The radiological changes were in line with the clinical picture. In Nkx2-3−/− mice, we measured decreased antigen-induced proliferation and cytokine production in spleen cell cultures; in the sera, we found less anti-CCP-IgG2a, IL-17 and IFNγ, but more IL-1β, IL-4 and IL-6. B cells isolated from the lymph nodes of Nkx2-3−/− mice showed decreased intracellular Ca2+ signaling compared to those isolated from BALB/c mice. Our findings show that the transcription factor Nkx2-3 might regulate the development of autoimmune arthritis most likely through modifying B cell activation.

Budget impact analysis of extended half-life recombinant factor IX (rFIXFc) in the treatment of haemophilia B.

Prophylaxis with factor IX (FIX) concentrates, produced by recombinant DNA technology (rFIX) or human plasma-derived concentrates, is the treatment of choice for haemophilia B (HB); rFIX covalently fused to the Fc domain of human immunoglobulin G1 (rFIXFc) allows for prophylaxis/treatment with one infusion every 7-14 days. The purpose of this study is to quantify the financial impact of prophylaxis with rFIXFc vs. other approved rFIX and reimbursed for treatment of HB in Italy. The number of patients was estimated according to Italian epidemiological data and use of rFIX. Dose and frequency of administration used for weekly prophylaxis were those recommended in the Summary of Product Characteristics (SPC), while clinical trials and literature data were used to calculate bleeding rates and management. Drug costs were calculated using regional ex-factory net prices. In the model, a reference scenario (Reference) vs. an alternative scenario (Alternative) were created to account for introduction of rFIXFc, estimating an increasing trend of the market share of rFIXFc in a 3-year timeframe. The analysis was developed in the perspective of the National Health Service and included healthcare costs related to rFIX for prophylaxis and resolution of bleeding events. The model estimated an overall cumulative expenditure (years 1-3) of €209,453,646 for the Reference and €207,465,568 for Alternative scenarios, with calculated cumulative savings of €1,988,068. The increasing use of rFIXFc as a substitute for other rFIX concentrates in the treatment of HB can represent a financially viable choice for the Italian National Health Service while ensuring effective control of bleeding.

Versican G1 Fragment Establishes a Strongly Stabilized Interaction with Hyaluronan-Rich Expanding Matrix during Oocyte Maturation.

In the mammalian ovary, the hyaluronan (HA)-rich cumulus extracellular matrix (ECM) organized during the gonadotropin-induced process of oocyte maturation is essential for ovulation of the oocyte-cumulus complex (OCC) and fertilization. Versican is an HA-binding proteoglycan that regulates cell function and ECM assembly. Versican cleavage and function remain to be determined in ovarian follicle. We investigated versican expression in porcine ovarian follicles by real-time (RT)-PCR and western blotting. The aims of the present work were to determine whether 1) versican was produced and cleaved by porcine OCCs during gonadotropin stimulation; 2) these processes were autonomous or required the participation of mural granulosa cells (MGCs); and 3) versican cleavage was involved in the formation or degradation of expanded cumulus ECM. We demonstrate two cleavage products of G1 domain of versican (V1) accumulated in the HA-rich cumulus ECM. One of them, a G1-DPEAAE N-terminal fragment (VG1) of ~70 kDa, was generated from V1 during organization of HA in in vivo and in vitro expanded porcine OCCs. Second, the V1-cleaved DPEAAE-positive form of ~65 kDa was the only species detected in MGCs. No versican cleavage products were detected in OCCs cultured without follicular fluid. In summary, porcine OCCs are autonomous in producing and cleaving V1; the cleaved fragment of ~70 kDa VG1 is specific for formation of the expanded cumulus HA-rich ECM.

Human laminin α3 chain G1 domain is a receptor for plasminogen Kringle 5 on human endothelial cells by biological specificity technologies and molecular dynamic

Human plasminogen Kringle 5 is known to pose a more potent anti-angiogenesis effect by inducing endothelial cell apoptosis. Our previous studies have identified the peptide IGNSNTL as a binding sequence of Kringle 5 using Ph.D.-7 phage display peptide library and enzyme-linked immunosorbent assay. Here, eleven proteins were screened and summarized by BLAST, laminin α3 chain G1 domain (LG1) was considered as the most potential receptor based on E value and domain function. The specific interaction of them was directly revealed through ligand blot and a strong concentration-dependent manner occurred between them (Ka 4.30 × 105 L mol−1) in frontal chromatography observation. Moreover, R10A/P83R substitution Kringle 5 decreased the affinity capacity to LG1. Furthermore, a remarkable conformational change from random coil3 to α helix and α1 helix to random coil were observed to the structural compactness and stability for LG1. Surface loops and coils also showed fluctuations up to some extent, giving the binding surface greater flexibility and correspondingly allowing for induced-fit binding, which was −23.87 kcal mol−1 of the free energy with electrostatic force as a main driver. Taken together, not only effective theoretical prediction and experiment validated that LG1 is receptor of Kringle 5, but also give an new perspective of the binding mechanism of Kringle 5 and its specific receptor and could facilitate the development of novel agent targeted toward pathologic angiogenesis.

The synthesis and secretion of versican isoform V3 by mammalian cells: A role for N-linked glycosylation

Versican is a large extracellular matrix (ECM) chondroitin sulfate (CS) proteoglycan found in most soft tissues, which is encoded by the VCAN gene. At least four major isoforms (V0, V1, V2, and V3) are generated via alternative splicing. The isoforms of versican are expressed and accumulate in various tissues during development and disease, where they contribute to ECM structure, cell growth and migration, and immune regulation, among their many functions. While several studies have identified the mRNA transcript for the V3 isoform in a number of tissues, little is known about the synthesis, secretion, and targeting of the V3 protein. In this study, we used lentiviral generation of doxycycline-inducible rat V3 with a C-terminal tag in stable NIH 3T3 cell lines and demonstrated that V3 is processed through the classical secretory pathway. We further show that N-linked glycosylation is required for efficient secretion and solubility of the protein. By site-directed mutagenesis, we identified amino acids 57 and 330 as the active N-linked glycosylation sites on V3 when expressed in this cell type. Furthermore, exon deletion constructs of V3 revealed that exons 11–13, which code for portions of the carboxy region of the protein (G3 domain), are essential for V3 processing and secretion. Once secreted, the V3 protein associates with hyaluronan along the cell surface and within the surrounding ECM. These results establish critical parameters for the processing, solubility, and targeting of the V3 isoform by mammalian cells and establishes a role for V3 in the organization of hyaluronan.

Disparate Phenotypes Resulting from Mutations of a Single Histidine in Switch II of Geobacillus stearothermophilus Translation Initiation Factor IF2

The conserved Histidine 301 in switch II of Geobacillus stearothermophilus IF2 G2 domain was substituted with Ser, Gln, Arg, Leu and Tyr to generate mutants displaying different phenotypes. Overexpression of IF2H301S, IF2H301L and IF2H301Y in cells expressing wtIF2, unlike IF2H301Q and IF2H301R, caused a dominant lethal phenotype, inhibiting in vivo translation and drastically reducing cell viability. All mutants bound GTP but, except for IF2H301Q, were inactive in ribosome-dependent GTPase for different reasons. All mutants promoted 30S initiation complex (30S IC) formation with wild type (wt) efficiency but upon 30S IC association with the 50S subunit, the fMet-tRNA reacted with puromycin to different extents depending upon the IF2 mutant present in the complex (wtIF2 ≥ to IF2H301Q > IF2H301R >>> IF2H301S, IF2H301L and IF2H301Y) whereas only fMet-tRNA 30S-bound with IF2H301Q retained some ability to form initiation dipeptide fMet-Phe. Unlike wtIF2, all mutants, regardless of their ability to hydrolyze GTP, displayed higher affinity for the ribosome and failed to dissociate from the ribosomes upon 50S docking to 30S IC. We conclude that different amino acids substitutions of His301 cause different structural alterations of the factor, resulting in disparate phenotypes with no direct correlation existing between GTPase inactivation and IF2 failure to dissociate from ribosomes.

Interactions between Yersinia pestis V-antigen (LcrV) and human Toll-like receptor 2 (TLR2) in a modelled protein complex and potential mechanistic insights

BackgroundYersinia pestis, the etiological pathogen of plague, is capable of repressing the immune response of white blood cells to evade phagocytosis. The V-antigen (LcrV) was found to be involved in this process by binding to human Toll-like Receptor 2 (TLR2). The detailed mechanism behind this LcrV and TLR2 mediated immune response repression, however, is yet to be fully elucidated due to the lack of structural information.ResultsIn this work, with protein structure modelling, we were able to construct a structure model of the heterotetramer of Y. pestis LcrV and human TLR2. Molecular dynamics simulation suggests the stability of this structure in aquatic environment. The LcrV model has a dumbbell-like structure with two globule domains (G1 at N-terminus and G2 away from membrane) connected with a coiled-coil linker (CCL) domain. The two horseshoe-shape TLR2 subunits form a V-shape structure, are not in direct contact with each other, and are held together by the LcrV homodimer. In this structure model, both the G1 and CCL domains are involved in the formation of LcrV homodimer, while all three domains are involved in LcrV-TLR2 binding. A mechanistic model was proposed based on this heterotetrameric structure model: The LcrV homodimer separates the TLR2 subunits to inhibit the dimerization of TLR2 and subsequent signal transfer for immune response; while LcrV could also inhibit the formation of heterodimers of TLR2 with other TLRs, and leads to immune response repression.ConclusionsA heterotetrameric structure of Y. pestis LcrV and human TLR2 was modelled in this work. Analysis of this modelled structure showed its stability in aquatic environments and the role of LcrV domains and residues in protein-protein interaction. A mechanistic model for the role of LcrV in Y. pestis pathogenesis is raised based on this heterotetrameric structure model. This work provides a hypothesis of LcrV function, with which further experimental validation may elucidate the role of LcrV in human immune response repression.

Cryo-EM Structure of BIVV001 Reveals Coagulation Factor VIII-Von Willebrand Factor D'D3 Interaction Mode

Introduction Coagulation Factor VIII (FVIII) is a serine protease cofactor that directly interacts with coagulation factors IXa and X on activated platelets, and enhances FIXa activity toward FX by 105. von Willebrand Factor (VWF), via its D'D3 domains, interacts with FVIII and prevents premature deposition on phospholipids until activation by thrombin. Thrombin cleavage at Arg1689 of FVIII promotes VWF dissociation by disrupting the FVIII a3 high affinity interaction with the VWF D' domain. VWF extends the half-life of circulating FVIII from less than 3 hours to ~11 hours in humans. While crystal structures of FVIII and VWF D'D3 alone have been solved, the atomic details of a formed complex are unknown. We sought to determine the FVIII-VWF D'D3 complex structure by using BIVV001, our investigational new drug currently in clinical trials for the treatment of Hemophilia A. BIVV001 (rFVIIIFc-VWF-XTEN) is a novel fusion protein consisting of single chain B-domain deleted (BDD) human FVIII, the Fc domain of human immunoglobulin G1 (IgG1), the FVIII-binding D'D3 domain of human von Willebrand factor, and 2 XTEN polypeptide linkers. The Fc, VWF, and XTEN linker portions of the molecule are each designed to extend the half-life of FVIII. We anticipated that the tethering of FVIII to D'D3 through the Fc dimer in BIVV001 would stabilize the complex for structural studies. Given the large size of BIVV001, at 312 kDa, we thought it an ideal target for structure determination by single particle cryo-EM. Methods We collected a total of 3955 micrographs of BIVV001 embedded in vitreous ice at 81,000x magnification using a Titan Krios electron microscope equipped with a Gatan BioQuantum K3 energy filter and camera operating in super-resolution mode. Preferential particle orientation was a major challenge that was overcome through a variety of methods. Micrograph movies were motion-corrected and summed, and over 2 million candidate particle coordinates were extracted. Repeated rounds of reference-free 2D classification resulted in a set of 1.2 million particles that generated a reasonable ab initio/de novo 3D model. Initial full 3D refinements of this model produced a map at approximately 5 Å resolution, into which available crystal structures can be readily fit. Subsequent iterative 3D refinement and 3D classification resulted in a final map at high resolution, into which an atomic model was built. Results The structure of BIVV001 was solved by single particle cryo-EM. D' of VWF interacts with the front face of the C1 and A3 domains of FVIII, consistent with a lower resolution, negative stain EM map (Yee et al. 2015. Blood). Interface residues on FVIII identified in an HDX-MS dataset (Chiu et al. 2015. Blood.) largely correspond to this high affinity interaction. D' protrudes upward from the VWF D3 domain, which sits centrally located between the C1 and C2 domains of FVIII at a 45° tilt. By occupying this position, D3 likely sterically blocks the FVIII C domains from binding to membrane. The VWD3 module of the D3 domain contacts the base of the C1 domain, whereas C8-3 binds to the bottom of the C2 domain. The conserved Ca2+ site in VWD3 identified previously (Dong et al. 2019. Blood.) is in the interface with C1. This is consistent with Yee et al., where docking placed D3 below the C domains. In that study, a lack of density between FVIII and VWF D3 in the 3D reconstruction, due to flexibility, prevented the detailed analysis that is possible here. In this study, flexibility in this region is also apparent, as C2 is less well ordered than the rest of FVIII and VWF D3 is the least well-ordered portion of the resolved structure. The XTEN linkers are not visible in the final map and were not apparent in any 2D class averages. The Fc is absent in most 2D class averages, due to a lack of consistent positioning relative to FVIII. In the rare cases where the Fc is visible, it adopts a preferred position on the back side of FVIII below the A3 protrusion. Conclusions The structure of BIVV001 has been solved by cryo-electron microscopy to high resolution. Alignment with previous results and the averaging out of BIVV001 elaborations suggests the structure obtained here likely represents WT FVIII-D'D3. This structure demonstrates how VWF D'D3 prevents premature FVIII deposition on phospholipids. The structural basis of type 2N von Willebrand Disease mutations in D'D3 can be readily interpreted. Next steps include solving a FVIII-D'D3 dimer structure at high resolution. Disclosures Fuller: Sanofi: Employment. Batchelor:Sanofi: Employment. Knockenhauer:Sanofi: Employment. Biemann:Sanofi: Employment. Peters:Sanofi: Employment.

Phase 1 Repeat Dosing with BIVV001: The First Investigational Factor VIII Product to Break through the Von Willebrand Factor-Imposed Half-Life Ceiling

Introduction The use of factor VIII (FVIII) replacement products enables comprehensive management (prophylaxis, acute bleed control, and perioperative hemostasis) of patients with severe hemophilia A. Prophylaxis with standard half-life FVIII replacement therapies requires frequent administration, and low FVIII activity levels between infusions lead to an increased risk of bleeds. FVIII replacement products that achieve optimal bleed protection with once-weekly dosing intervals remain an unmet need for people living with severe hemophilia A. BIVV001 (rFVIIIFc-VWF-XTEN) is a novel FVIII therapy composed of single-chain FVIII, the Fc domain of human immunoglobulin G1, the FVIII-binding D′D3 domain of von Willebrand factor (VWF), and 2 XTEN polypeptides. BIVV001 is designed to be a next-generation FVIII therapy that circulates independently of endogenous VWF, thereby breaking the VWF-imposed half-life ceiling. Single-dose BIVV001 was well tolerated and provided sustained FVIII activity in a first-in-human trial (Konkle et al, Blood, 2018). Here, we report final data for an open-label Phase 1 trial to assess the safety, tolerability, and pharmacokinetics (PK) of repeat dosing with BIVV001 in subjects with severe hemophilia A (<1 IU/dL [<1%] endogenous FVIII) (EudraCT No: 2018-001535-51). Methods Eligible subjects were 18-65 years of age, had severe hemophilia A, and ≥150 exposure days to prior FVIII products. After screening and washout, subjects received 4 once-weekly doses of BIVV001 (Days 1, 8, 15, and 22) at either 50 IU/kg (Cohort 1) or 65 IU/kg (Cohort 2). The safety observation period extended for 28 days after the last dose of BIVV001. Primary endpoints were the occurrence of adverse events and clinically significant abnormalities in laboratory tests, including inhibitor development. Secondary endpoints were PK parameters derived from FVIII activity evaluated using a one-stage activated partial thromboplastin time clotting assay. PK blood samples were collected immediately before BIVV001 infusion on Days 1, 8, 15, and 22 and at multiple times after dosing on Days 1 and 22. Results All subjects enrolled in Cohort 1 (n=10) and Cohort 2 (n=14) completed the study. Mean (range) age of subjects was 35 (25-55) years for Cohort 1 and 41 (24-58) years for Cohort 2. BIVV001 was well tolerated. No inhibitor development to FVIII was detected, and there were no events of hypersensitivity or anaphylaxis reported. Baseline-corrected PK data were available for 9 subjects in Cohort 1 and all subjects in Cohort 2. Consistent with the single-dose study, the geometric mean (range) half-life for 50 IU/kg and 65 IU/kg BIVV001 was 41.3 (34.2-50.1) hours and 37.3 (28.9-43.8) hours, respectively. After 4 weekly doses of BIVV001 (Day 22), geometric mean (range) area under the activity-time curve from hour 0 over the dosing interval (AUC0-tau) and maximum concentration at steady state (Cmaxss) of BIVV001 were 8290 (5810-10,300) hr × IU/dL and 131 (96-191) IU/dL for Cohort 1 and 11,200 (7040-15,800) hr × IU/dL and 171 (118-211) IU/dL for Cohort 2, respectively. Mean (standard deviation) FVIII activity immediately prior to the final dose of BIVV001 (Ctrough) was 9.9 (2.8) IU/dL in Cohort 1 and 11.7 (5.5) IU/dL in Cohort 2. The mean (range) Day 22-Day 1 accumulation index was 1.07 (1.03-1.11) for Cohort 1 and 1.05 (1.02-1.08) for Cohort 2. At 5 and 7 days after the final BIVV001 infusion, mean steady-state FVIII activity was 22% and 10% for Cohort 1 and 27% and 12% for Cohort 2, respectively (Figure). Geometric mean (range) incremental recovery after the first dose of BIVV001 was 2.3 (1.6-2.8) IU/dL per IU/kg for Cohort 1 and 2.4 (1.6-3.3) IU/dL per IU/kg for Cohort 2. Conclusions Four weekly infusions of 50 IU/kg or 65 IU/kg BIVV001 were well tolerated with no identified safety concerns. FVIII activity levels were sustained and nonaccumulating between doses. By breaking through the VWF-imposed half-life ceiling, BIVV001 prophylaxis may lead to more optimal, extended protection against bleeds for patients with severe hemophilia A than standard FVIII therapies. These results support the continued development of BIVV001 in a Phase 3 clinical trial program. Disclosures Lissitchkov: Roche: Consultancy, Equity Ownership, Honoraria, Speakers Bureau; Sanofi: Equity Ownership, Research Funding; Bayer: Consultancy, Equity Ownership, Honoraria, Other: Principal investigator for clinical trials, Research Funding; Sobi: Consultancy, Equity Ownership, Honoraria; Shire: Consultancy, Equity Ownership, Honoraria, Speakers Bureau; Octapharma: Equity Ownership, Research Funding. Rice:Sanofi: Employment. Katragadda:Sanofi: Employment. Willemze:Sanofi: Employment. Benson:Sanofi: Employment. Knobe:Sanofi: Employment.

The structure of N184K amyloidogenic variant of gelsolin highlights the role of the H-bond network for protein stability and aggregation properties.

Mutations in the gelsolin protein are responsible for a rare conformational disease known as AGel amyloidosis. Four of these mutations are hosted by the second domain of the protein (G2): D187N/Y, G167R and N184K. The impact of the latter has been so far evaluated only by studies on the isolated G2. Here we report the characterization of full-length gelsolin carrying the N184K mutation and compare the findings with those obtained on the wild type and the other variants. The crystallographic structure of the N184K variant in the Ca2+-free conformation shows remarkable similarities with the wild type protein. Only minimal local rearrangements can be observed and the mutant is as efficient as the wild type in severing filamentous actin. However, the thermal stability of the pathological variant is compromised in the Ca2+-free conditions. These data suggest that the N to K substitution causes a local disruption of the H-bond network in the core of the G2 domain. Such a subtle rearrangement of the connections does not lead to significant conformational changes but severely affects the stability of the protein.

Context-dependent bioactivity of versican fragments.

Versican (VCAN) proteolysis and the accumulation of VCAN fragments occur in many developmental and disease processes, affecting extracellular matrix (ECM) structure and cell phenotype. Little is known about the significance of proteolysis and the roles of fragments, or how this ECM remodeling affects the microenvironment and phenotype of diseased cells. G1-DPEAAE fragments promote aspects of epithelial-mesenchymal transitioning in developing and diseased cells, resulting in cell migration. Enhanced proliferation and invasion of tumor and endothelial cells is directly associated with G1 domain deposition and G1-DPEAAE localization respectively. These tumorigenic and angiogenic roles could explain the disease exacerbating effect often associated with G1-containing fragments, however, the pathogenicity of G1 fragments depends entirely upon the context. Overall, VCAN fragments promote tumorigenesis and inflammation; however, the specific cleavage site, the extent of cleavage activity and the microenvironment in which cleavage occurs collectively determine how this pleiotropic molecule and its fragments influence cells.

Therapeutic vaccination by two DerG LEAPS conjugates incorporating different PG (aggrecan) epitopes protect by different immune mechanisms in the PG G1 domain induced mouse model of rheumatoid arthritis

Abstract Background Development of a therapeutic vaccine for rheumatoid arthritis (RA) requires modulating antigen specific inflammatory T cell responses that drive disease. RA can be initiated and driven by responses to multiple antigens but peptide vaccines usually contain few epitopes. The challenge is to elicit the appropriate responses by these vaccines. Method We used the proteoglycan (PG, aggrecan) G1 domain-induced arthritis model of RA. Mice were immunized with either one or two different DerG LEAPS vaccines containing PG epitopes (PG70 or PG275Cit) in Seppic ISA51vg adjuvant subcutaneously after signs of arthritis were noted. Mice were examined trice weekly for arthritis progression. At study end serum antibodies to the vaccine epitopes and splenic T-cell responses to PG G1 domain were determined. Results Immunization with DerGPG70 or DerGPG275Cit conjugate, alone or in combination, stopped the progression of disease. DerGPG275Cit was effective in protection but did not induce significant serum antibodies whereas DerGPG70 (alone or with DerGPG275Cit) induced both protection and antibodies. Spleen cells from DerGPG70-immunized mice had an anti-inflammatory response to PG G1 in vitro. Conclusions Immunization with DerG LEAPS conjugates of different epitopes of PG alone or together were effective at modulating the inflammatory response and stopping disease progression. As observed previously, the DerGPG70 conjugate modulated disease through up-regulation of Th2, and down-regulation of Th1 and Th17 responses. Results suggest mechanistically different immune responses to the two vaccines. Combination of them provided not only broader epitope coverage, but also a greater therapeutic effect than either vaccine alone.

FPT155-001: A phase Ia/Ib study of FPT155 (CD80-FC) in patients with advanced solid tumors.

TPS42 Background: Despite recent advances in immunotherapy, many patients with advanced solid tumors are refractory to available therapies or eventually relapse. Novel immune therapies are needed with differentiated mechanisms of action that result in improved response rates and durability across a broad range of tumors. FPT155 is a first-in-class therapeutic being developed to meet this need. FPT155 is a recombinant fusion protein composed of the extracellular domain of human CD80 fused with the Fc domain of human immunoglobulin G1. It is designed to act as a potent stimulator of anti-tumor immunity through CD28 and thereby co-stimulate T cell responses only in the presence of antigenic T cell receptor (TCR) signaling. FPT155 alone does not induce spontaneous cytokine release by primary human immune cells, in contrast to a CD28 superagonist antibody that exerts TCR stimulus-independent activity. FPT155 also blocks CTLA-4 from competing for endogenous CD80, allowing CD28 signaling to prevail in T cell activation. A murine surrogate of FPT155 is a potent inhibitor of tumor growth that induces complete tumor regression in multiple tumor models, including models that are insensitive to anti-PD1 or anti-CTLA4. Methods: The FPT155-001 study is a Phase 1a/1b open-label, multicenter, dose escalation and expansion study to evaluate the safety and tolerability of FPT155 monotherapy. Phase 1a dose escalation includes an accelerated titration design followed by a standard 3+3 design until the recommended dose for Phase 1b is determined by evaluation of all available safety, pharmacokinetic (PK), and pharmacodynamic (PD) data. Eligible patients with advanced solid tumors who are refractory to all standard therapy for their malignancy will be enrolled in Phase 1a. Phase 1b dose expansion will enroll patients with select tumor types. The primary endpoint is safety in both phases. Key secondary endpoints in Phase 1a include characterization of the FPT155 PK profile and immunogenicity. Key secondary endpoints in Phase 1b include objective response rate, duration of response, progression free survival, and disease control rate. The FPT155-001 trial opened for enrollment in October 2018 and is in progress. Clinical trial information: Submitted - awaiting registration number.

Novel attacin from Hermetia illucens: cDNA cloning, characterization, and antibacterial properties

In this study, we report a novel member of the attacin family from Hermetia illucens. The cDNA clone encoding the attacin-like protein was isolated by screening a cDNA library prepared from immunized fat body. The complete 510 bp cDNA of HI-attacin was predicted to encode a protein of 169 amino acids with a molecular weight of 17.7 kDa. The putative mature protein of H. illucens attacin (HI-attacin) had 50% identity with that of Bactrocera dorsalis attacin B. Phylogenetic analysis revealed that the HI-attacin was separated from the other dipteran attacins with a high bootstrap percentage. Compared to that in the other dipteran attacins, the G1 domain of HI-attacin was shorter and the sequence of the G2 domain of HI-attacin was more conserved than that of the G1 domain. We produced the recombinant attacin (rHI-attacin) protein using a prokaryotic expression system to confirm its antibacterial character. The rHI-attacin was produced as inclusion bodies and refolded by on-column refolding. rHI-attacin exhibited antibacterial activity against both Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Using real-time PCR, the expression of HI-attacin was was barely detected before the immunization, but was mostly evident in the fat body after immunization.

Nanobody interaction unveils structure, dynamics and proteotoxicity of the Finnish-type amyloidogenic gelsolin variant

AGel amyloidosis, formerly known as familial amyloidosis of the Finnish-type, is caused by pathological aggregation of proteolytic fragments of plasma gelsolin. So far, four mutations in the gelsolin gene have been reported as responsible for the disease. Although D187N is the first identified variant and the best characterized, its structure has been hitherto elusive. Exploiting a recently-developed nanobody targeting gelsolin, we were able to stabilize the G2 domain of the D187N protein and obtained, for the first time, its high-resolution crystal structure. In the nanobody-stabilized conformation, the main effect of the D187N substitution is the impairment of the calcium binding capability, leading to a destabilization of the C-terminal tail of G2. However, molecular dynamics simulations show that in the absence of the nanobody, D187N-mutated G2 further misfolds, ultimately exposing its hydrophobic core and the furin cleavage site. The nanobody's protective effect is based on the enhancement of the thermodynamic stability of different G2 mutants (D187N, G167R and N184K). In particular, the nanobody reduces the flexibility of dynamic stretches, and most notably decreases the conformational entropy of the C-terminal tail, otherwise stabilized by the presence of the Ca2+ ion. A Caenorhabditis elegans-based assay was also applied to quantify the proteotoxic potential of the mutants and determine whether nanobody stabilization translates into a biologically relevant effect. Successful protection from G2 toxicity in vivo points to the use of C. elegans as a tool for investigating the mechanisms underlying AGel amyloidosis and rapidly screen new therapeutics.

BIVV001: The First Investigational Factor VIII Therapy to Break Through the VWF Ceiling in Hemophilia A, with Potential for Extended Protection for One Week or Longer

Introduction: The standard of care for patients with severe hemophilia A is prophylactic factor VIII (FVIII) replacement. Conventional recombinant FVIII products are efficacious but require frequent administration because of their short half-life, which reflects the dependence of FVIII on von Willebrand factor (VWF). Recombinant FVIII Fc fusion protein (rFVIIIFc) provides an extended dosing interval, as well as joint protection and improved quality of life (Oldenburg et al, Haemophilia, 2018; Wang et al, Blood, 2016), with a well-characterized safety profile. While rFVIIIFc reduces the required administration frequency, longer prophylactic dosing intervals that also offer maximum overall protection are still an unmet need for patients with severe hemophilia A. Increasing the half-life of rFVIII is ultimately dependent upon decoupling FVIII and endogenous VWF.BIVV001 (rFVIII-VWF-XTEN) is a novel investigational rFVIII therapy with single-chain FVIII, the Fc domain of human immunoglobulin G1, 2 XTEN polypeptides, and the FVIII-binding D′D3 domain of VWF, designed to circulate in plasma independently of VWF, thereby breaking the VWF half-life ceiling. Here, we present the low-dose cohort results of EXTEN-A, a Phase 1/2a study assessing the safety and tolerability of a single dose of BIVV001, and the pharmacokinetic (PK) characteristics of a single dose of BIVV001 compared with rFVIII.Methods: EXTEN-A (NCT03205163) is an open-label, dose-escalation, multicenter study. Previously treated adult males with severe hemophilia A (<1 IU/dL [<1%] endogenous FVIII activity) with ≥150 exposure days to FVIII products were included. Patients were assigned to either the low-dose cohort (25 IU/kg of rFVIII and 25 IU/kg of BIVV001; n≥6) or the high-dose cohort (65 IU/kg of rFVIII and 65 IU/kg of BIVV001; n≥8). Escalation from the low-dose cohort, and enrolment of patients to the high-dose cohort was undertaken after assessment of available data from the low-dose cohort.After a screening and washout period of up to 28 days, patients received a single dose (25 or 65 IU/kg) of rFVIII. After a 3- to 4-day washout period, patients received a single dose of BIVV001 at the same dose level as rFVIII. Blood samples for PK analysis were collected for 3 days after dosing of rFVIII and up to 14 days after dosing of BIVV001. Inhibitor testing was performed 14 and 28 days following BIVV001 administration. Adverse events, clinical abnormalities in laboratory tests (including inhibitor development), and PK parameters were assessed. An interim analysis is planned, including the first 2 patients of the high-dose cohort.Results: Out of 7 patients enrolled in the low-dose cohort (25 IU/kg), 6 patients were dosed with BIVV001. Patients in this group were primarily white, with 1 patient of Asian descent, and 1 of Hispanic/Latino ethnicity. Patient ages ranged from 19 to 60 years. Low-dose BIVV001 was well tolerated and no inhibitors were detected through 28 days after BIVV001 dosing. Low-dose BIVV001 demonstrated an extended half-life of 37.6 hours, compared with a 12.1-hour half-life for rFVIII. Average FVIII activity post-infusion of BIVV001 was 12.2% at 5 days and 5.3% at 7 days.At least 8 patients will be enrolled in the high-dose cohort (65 IU/kg); preliminary data for the first 2 patients will be reported.Conclusions: BIVV001 was well tolerated in 6 patients with severe hemophilia A who were treated with a single low dose (25 IU/kg). No patient developed an inhibitor to FVIII. Low-dose cohort data demonstrated a breakthrough in the half-life of rFVIII therapy, with BIVV001 providing sustained FVIII levels that could potentially allow for more optimal, extended protection for patients. DisclosuresKonkle:Genentech: Consultancy; Spark: Consultancy, Research Funding; Pfizer: Research Funding; Gilead: Consultancy; CSL Behring: Consultancy; Bioverativ: Research Funding; BioMarin: Consultancy; Sangamo: Research Funding; Shire: Research Funding. Shapiro:Shire: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; BioMarin: Research Funding; Prometic Life Sciences: Consultancy, Research Funding; Bioverativ, a Sanofi Company: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Sangamo Biosciences: Consultancy; Genetech: Membership on an entity's Board of Directors or advisory committees, Research Funding, Speakers Bureau; Bayer Healthcare: Other: International Network of Pediatric Hemophilia; OPKO: Research Funding; Octapharma: Research Funding; Kedrion Biopharma: Consultancy, Research Funding; Bio Products Laboratory: Consultancy; Daiichi Sankyo: Research Funding; Novo Nordisk: Membership on an entity's Board of Directors or advisory committees, Research Funding. Quon:Bioverativ, a Sanofi Company: Speakers Bureau; Octapharma: Consultancy; Genetech: Consultancy, Speakers Bureau; Bayer: Consultancy; NovoNordisk: Consultancy, Speakers Bureau; Shire: Speakers Bureau. Staber:uniQure: Honoraria; NovoNordisk: Consultancy; Bayer: Honoraria. Suzuki:Chugai Pharmaceutical Co., Ltd: Research Funding, Speakers Bureau. Poloskey:Bioverativ: Employment. Rice:Bioverativ: Employment. Katragadda:Bioverativ: Employment. Rudin:Bioverativ: Employment, Equity Ownership. Fruebis:Bioverativ: Employment, Other: Clinical Development.

Impairment of the Stromal SDF-1-Mediated Hematopoietic Support By GDF-11 in MDS Is Rescued By Luspatercept

Introduction:Myelodysplastic syndromes (MDS) are characterized by ineffective hematopoiesis due to genetic and functional abnormalities of hematopoietic stem and progenitor cells (HSPCs). Accumulating evidence now also points to the bone marrow microenvironment (BMME) as a key mediator of MDS pathophysiology.Increased levels of transforming growth factor beta (TGF-β) superfamily ligands, including growth differentiation factor 11 (GDF-11), in the bone marrow have been linked to ineffective erythropoiesis and activation of SMAD2/3 signalling in MDS. Luspatercept (ACE-536) is a novel recombinant fusion protein containing modified activin receptor type IIB linked to the fragment crystallisable (Fc) domain of human immunoglobulin G1 and is a first-in-class erythroid maturation agent. Luspatercept binds to selected TGF-β superfamily ligands, including GDF-11 and activin B, restoring late-stage erythropoiesis in MDS mice and patients. Whether luspatercept modulates the BMME is unknown.Aim:We investigated the potential impact of luspatercept on the biology of mesenchymal stromal cells (MSCs).Methods:MSCs from patients with either high-or low-risk MDS and age-matched healthy donors (HD) were treated with GDF-11 in the presence or absence of RAP-536, a homologue of luspatercept harboring the same activin receptor IIB domain. Subsequently, Smad signaling pathway activation was analyzed by Western blot. Moreover, MSC phenotype, stromal derived factor-1 (SDF-1/CXCL12) expression and secretion as well as the osteogenic differentiation potential were recorded. To study the impact on the hematopoietic support, MSCs were pre-treated for one week with GDF-11 ± RAP-536 before freshly isolated CD34+ HSPCs were seeded on the stromal layer. The colony formation (CAF-C) was analyzed weekly. After four weeks, the HSPCs were seeded in methylcellulose medium to perform a CFU-GEMM assay. Further, engraftment and migration potential of co-cultured HSPCs was analyzed in zebrafish embryos in vivo.Results:GDF-11/RAP-536 treatment did not impact viability, proliferation, and growth pattern of MSCs. The osteogenic differentiation was significantly improved by RAP-536 treatment which was shown by a 2.3-fold increase of ALP activity. GDF-11 induced Smad2/3 phosphorylation in MSCs which was inhibited by RAP-536 to about 50% of activity. The MSC phenotype characterized by the expression of CD73, CD90, CD105, CD146, CD29 and CD44 was not significantly influenced by RAP-536 treatment.Interestingly, the chemokine SDF-1 which plays an important role for the interaction and support of HSPCs was significantly up-regulated in MDS and HD MSCs by RAP-536 at both the mRNA (1.9-fold) and the protein level (2.1-fold; 313.0±35.0 vs. 649.7±76.8 pg/ml, *p< 0.05, n=3). This restored SDF-1 secretion of MSCs resulted in functional effects of HSPCs when co-cultured with MSCs. The number of CAF-C was significantly higher after two, three, and four weeks of HSPCs cultured on pre-treated MSC layers (12.0-fold / 3.4-fold / 1.75-fold). The phenotypical analysis of HSPCs demonstrated increased expression levels of CXCR4 in the adherent fraction. Addition of the CXCR4 antagonist AMD3100 blocked enhanced colony formation by RAP-536 confirming the previous observation on SDF-1 modulation. Clonal growth of CAF-C-derived HSPCs after four weeks of co-culture on un- or pre-treated MSC monolayers was analyzed in a secondary colony-forming cell assay (CFU) for an additional 14 days. The frequency of CFUs was increased in all lineages with significant differences in total colony numbers (15±5.8 vs. 35.8±14.7, *p< 0.05, n=6).These results were validated in vivo in a zebrafish model. HSPCs were co-cultured with GDF-11 and RAP-536 pre-treated MDS-MSCs for one week before injection into the zebrafish circulation. One and two days post-injection, a significantly higher cell proportion could be detected in the caudal hematopoietic (CHT) region as a result of RAP-536 pre-treatment (Fig.1).Conclusion:These data provide first evidence that RAP-536 has also the capacity to modulate MSCs which might contribute to the restoration of hematopoiesis in MDS. DisclosuresPlatzbecker:Celgene: Research Funding.

FlhF(T368A) modulates motility in the bacteriophage carrier state of Campylobacter jejuni.

SummaryThe carrier state is an alternative bacteriophage life cycle by which virulent bacteriophage can persist in association with host bacteria. Campylobacter jejuni carrier state strains exhibit growth phase dependent motility due to a truncated flagella phenotype. Genome sequencing identified a T368A substitution in the G3 domain of the SRP‐like GTPase FlhF from C. jejuni PT14CP30A carrier state strains, which we hypothesized to be the cause of the complex motility phenotype. We have analyzed the role of this mutation in C. jejuni PT14 and demonstrated that flhF(T368A) leads to a large proportion of cells unable to synthesize flagella, while the remaining cells form a single flagellum at one pole leading to significantly reduced motility. The flhF(T368A) mutation causes a reduction in the phage adsorption constant, which leads to a decrease in infection efficiency. Down‐regulation of σ28 and σ54 dependent flagellar genes were observed as responses to the flhF(T368A) mutation. FlhF(T368A) protein is impaired in GTPase activity and exhibits reduced stability. C. jejuni carrying flhF(T368A) are less sensitive to bacteriophage infection and formation of the carrier state. The acquisition of flhF(T368A) in carrier state strains acts to prevent super‐infection and maintain association with the bacteriophage that provoked the interaction.