Influenza A H1N1 mediated pre-existing immunity to SARS-CoV-2 predicts COVID-19 outbreak dynamics

Susceptibility to SARSCoV2 infections is highly variable, ranging from asymptomatic and mild infections in most, to deadly outcome in few. Here, we present evidence that antibodies induced by currently circulating influenza A H1N1 (flu) strains cross react with the most critical receptor binding motif of the SARSCoV2 spike protein that interacts with the ACE2 receptor. About 58 to 68% of blood donors in Stockholm had detectable antibodies to this cross-reactive peptide, NGVEGF, and seasonal flu vaccination trended to enhance binding of inhibitory antibodies to SARSCoV2. This peptide also activated CD8 T cells in 20% of healthy subjects. Eleven additional CD8 T cell peptides that cross react with flu and SARSCoV2 were identified that potentially protect against SARSCoV2 in 40 to 71% of individuals, depending on their HLA type.

Recombinant ADAMTS13 for Patients with Sickle Cell Disease: Design of a Phase 1 Safety, Tolerability, Pharmacokinetics, and Pharmacodynamics Study

Background Sickle cell disease (SCD) is an autosomal recessive hemoglobinopathy associated with chronic hemolysis and vaso-occlusive crises (VOCs) resulting in pain, organ damage, and a shortened lifespan. Current treatment options are limited, and many individuals with SCD continue to experience VOCs despite receiving therapy. Although the precise cause of VOCs is not clear, evidence suggests that cell adhesion is involved. Von Willebrand factor (VWF) is a multimeric glycoprotein that mediates the adhesion of platelets to each other and to other cell types, including vascular endothelium and leukocytes. An emerging hypothesis is that VWF contributes to the pathophysiology of VOCs through the formation of hyper-adhesive ultra-large VWF multimers. VWF activity is regulated by the metalloprotease ADAMTS13, which specifically cleaves ultra-large VWF multimers in an extended conformation. Patients with SCD have been shown to have higher levels of VWF multimers and lower levels of ADAMTS13 activity during VOCs. This imbalance could be caused either by the increased generation and release of ultra-large VWF multimers or by the inhibition of ADAMTS13 activity by plasma free hemoglobin or thrombospondin-1. Increasing the plasma concentration of ADAMTS13 using a recombinant ADAMTS13 (rADAMTS13; TAK-755, Takeda Development Center Americas, Inc., Lexington, MA, USA) may be therapeutically beneficial by enhancing cleavage of ultra-large VWF multimers. Here, we report the design and enrollment status of the Recombinant ADAMTS13 In Sickle Cell Disease (RAISE-UP) study (NCT03997760), the first clinical study of a recombinant ADAMTS13 in patients with SCD. Study Design and Methods This phase 1, randomized, double-blind, placebo-controlled, multicenter, ascending single dose study will assess the safety (including immunogenicity), tolerability, pharmacokinetics (PK), and pharmacodynamics (PD) of rADAMTS13 in patients with SCD. This study is planned to be conducted in 2 parts (part A and part B). Here we present the study design for part A which is being conducted initially and will enroll approximately 20 patients aged between 18 and 65 years with a documented history of SCD (HbSS or HbSβ 0 thalassemia). Concurrent treatment with a stable dose of hydroxyurea is allowed. Exclusion criteria include an acute VOC in the preceding 21 days and a blood transfusion either within the last 30 days or on ≥2 occasions in the last 90 days. Ethics committee approval and patient consent were obtained. Patients will be randomized 3:1 to receive a single intravenous infusion of either rADAMTS13 or placebo in 3 sequential dose cohorts. Patients in cohort 1 (n=4) will receive a 40 IU/kg dose, cohort 2 (n=8) will receive an 80 IU/kg dose, and cohort 3 (n=8) will receive a 160 IU/kg dose (Figure). In cohorts 2 and 3, 6 patients will receive rADAMTS13 and 2 patients will receive placebo. The first 3 patients enrolled in each cohort will be dosed with a separation time of at least 14 days. Enrollment into the next higher dose cohort will only be allowed following review of safety data and authorization by a dose escalation committee. Enrollment will be paused if anaphylaxis, binding or inhibitory antibodies, a life-threatening condition, or death are reported. All patients will complete an end-of-study visit on day 28 following infusion. Primary safety endpoints include adverse events, serious adverse events (SAEs), adverse changes in vital signs and laboratory parameters, and incidence of binding and inhibitory antibodies against rADAMTS13 occurring during the study. A secondary objective is to assess the PK of single-dose rADAMTS13 in each dose cohort, including an assessment of ADAMTS13 antigen and ADAMTS13 activity. Secondary PD objectives are to assess the effect of rADAMTS13 on VWF and platelet count and to study the correlation of plasma free hemoglobin and thrombospondin-1 with rADAMTS13 activity and VWF. Enrollment has been completed for cohort 1. In the review of safety data by the dose escalation committee, no drug-related SAEs were reported and no binding or inhibitory antibodies to ADAMTS13 were observed. On the basis of these findings, cohort 2 has been opened for enrollment. Figure 1 Figure 1. Disclosures Patwari: Takeda Development Center Americas, Inc.,: Current Employment. Nguyen: Takeda Development Center Americas, Inc.,: Current Employment. Bhattacharya: Takeda: Current equity holder in publicly-traded company; Takeda Development Center Americas, Inc.: Current Employment. Jain: Takeda Development Center Americas, Inc.,: Current Employment; Takeda: Current equity holder in publicly-traded company.

Administration of FVIII-Expressing Human Placental Cells to Juvenile Sheep Yields Multi-Organ Engraftment, Therapeutic Plasma FVIII Levels and Alter Immune Signaling Pathways to Evade FVIII Inhibitor Induction

We have previously reported that normal juvenile sheep that received weekly intravenous (IV) infusions of human (n=3) or an expression/secretion-optimized, bioengineered human/porcine hybrid (ET3) FVIII protein (n=3) for 5 weeks (20 IU/kg) developed anti-FVIII inhibitory antibodies (10-116 BU, and IgG titers of 1:20-1:245) by week 3 of infusion. By contrast, the IV infusion, or IP administration, of human placental mesenchymal cells (PLC) transduced with a lentiviral vector encoding a myeloid codon-optimized ET3 transgene (PLC-mcoET3) to produce high levels of ET3 protein (4.9-6IU/10^6 cells/24h) enabled the delivery of FVIII without eliciting antibodies, despite using PLC-mcoET3 doses that provided ~20-60 IU/kg ET3 each 24h to mirror the amount of FVIII protein infused. In addition, we showed that the route of PLC-mcoET3 administration (IP vs IV) did not impact the resultant plasma FVIII levels, with animals in these two groups exhibiting mean increases in FVIII activity (quantified by aPTT) of 30.9% and 34.2%, respectively, at week 15 post-treatment. Here, we investigated whether the sites and levels of PLC-mcoET3 engraftment were dependent upon the route of administration and performed s sheep-specific multiplexed transcriptomic analysis (NanoString) to define the immune signaling pathways that thwarted FVIII/ET3 protein immune response when ET3 was delivered through PLC. Tissue samples were collected from various organs at euthanasia and RT-qPCR performed using primers specific to the mcoET3 transgene, to the human housekeeping transcript GAPDH, and to sheep GAPDH, to quantify PLC-mcoET3 tissue engraftment, and normalize the results. RT-qPCR demonstrated PLC-mcoET3 engrafted, in both IP and IV groups, in all the organs evaluated (liver, lung, lymph nodes, thymus, and spleen). Animals that received PLC-mcoET3 via the IP route displayed higher overall levels of engraftment than their IV counterparts. The spleen was the preferential organ of engraftment for both IP and IV groups (IP:2.41±1.97%; IV: 0.64±0.54%). The IP group exhibited significantly higher engraftment in the left lobe of the liver (IP: 1.36±0.35%; IV: 0.041±0.022%), which was confirmed by immunohisto-chemistry (IHC) with an antibody to the human nuclear antigen Ku80 and ImageJ analysis (IP:5.24±3.36%; IV: 0±0). Of note is that the IP route resulted in higher levels of engraftment in the thymus, while IV infusion yielded higher levels of PLC-mcoET3 in lymph nodes. Analysis of H&E-stained tissues demonstrated they were devoid of any abnormal histologic changes and exhibited no evidence of hyperplasia or neoplasia, supporting the safety of the cell platform, irrespective of the route of administration. To date, NanoString analysis of PBMC collected at day 0, week 1, and week 5 post-infusion demonstrated that animals who received FVIII protein had upregulation of UBA5 and BATF, genes involved in antigen processing and Th17 signaling pathways, respectively. Although both IV and IP recipients of PLC-mcoET3 also had an increase in BATF, the IV group exhibited upregulation of BTLA, a gene involved in immune-tolerance, and downregulation of NOTCH and DDL1, involved in T cell differentiation, as well as MAPK12 and PLCG1, genes involved in proinflammatory cytokine regulation and T signaling within the Th17 signature. In IP recipients, BTLA, NOTCH, and DLL1 were all downregulated. Since ET3-reactive Th 1 cells were not present in any of the treated animals, it is possible that the Th17 cells are responsible for the inhibitory antibodies seen in the juvenile sheep treated with FVIII/ET3 protein, while in animals receiving PLC-mcoET3, downregulation of genes involved in T cell differentiation and proinflammatory cytokine signaling keeps the immune system in check to avoid an immune response. Disclosures Doering: Expression Therapeutics: Divested equity in a private or publicly-traded company in the past 24 months. Spencer: Expression Therapeutics: Divested equity in a private or publicly-traded company in the past 24 months.

In Utero Transplantation of FVIII-Expressing Human Placental Cells Upregulates Gene Pathways Associated with Immune Tolerance, Altering the Response to Postnatal FVIII Infusion

We have previously reported that in utero transplantation (IUTx) of sheep fetuses (n=14) with human placental cells (PLC) transduced with a lentiviral vector encoding mcoET3, an expression/secretion-optimized, bioengineered fVIII transgene (PLC-mcoET3) increased plasma FVIII activity levels by 57%, 42%, and 35% at 1, 2, and 3 years post-IUTx, respectively, without the development of FVIII/ET3 inhibitors. We also demonstrated that immune tolerance to the cell/gene product was maintained after postnatal administration of PLC-mcoET3 (cells producing 20 IU/kg/24h were administered i.v. for 3 consecutive weeks). However, when IUTx-treated animals received weekly i.v. infusions of purified ET3 protein (20IU/kg) for 5 weeks, all recipients developed a robust ET3-specific IgG response that appeared at week 3 of infusion at titers ranging from 1:70 to 1:857 and inhibitory antibodies that ranged from 3-36 BU. Here, we investigated differences in the immune responses of animals that received IUTx with PLC-mcoET3 and were boosted postnatally with PLC-mcoET3 (IUTx-PLC-mcoET3) vs. ET3 protein (IUTx-ET3) to define the pathways by which the immune system differentially responds to protein vs. cell-secreted ET3. A sheep-specific multiplex gene expression analysis with 165 genes involved in immune cell signaling pathways (NanoString) was used to evaluate mRNA isolated from peripheral blood mononuclear cells collected at Weeks (W) 0, 1, and 5 of postnatal infusions. Significant fold-change expression in these mRNA targets was determined using NanoString nSolver 4.0 software. Animals in the IUTx-PLC-mcoET3 group (known to be devoid of inhibitors to ET3 post-boosting) showed that immunoregulation and immune tolerance gene clusters were among the top three clusters that increased expression from W0 to W5 (adj. p-value<0.01). Differential expression of genes in pathways involved in Th1, Th2, and Th17 responses was also found, at differing levels, in the IUTx-PLC group, suggesting a balance between immunity and tolerance was maintained. Surprisingly, the IUTx-ET3 group, which developed inhibitory antibodies after ET3 boosting, also showed significantly increased expression of immune tolerance genes, and downregulation of Th1 and Th17 cell signaling, when evaluated by direct global significance score. Nevertheless, 66% of these animals had a significant upregulation of Th2 cell signaling by W1 vs W0. To determine if the increase in expression of immune tolerance genes was due to the IUTx treatment, we also evaluated a group of aged-matched, non-transplanted sheep that received ET3 protein under the same dose and schedule. Results from Gene Set Analysis (GSA) demonstrated significant upregulation of genes involved in interferon signaling, class I MHC antigen processing, and Th17 signaling in these animals, suggesting the potential involvement of Th17 cells in the immune response in this group. In conclusion, IUTx with PLC-mcoET3 induces the upregulation of genes associated with immune tolerance, providing an explanation for the long-lasting elevation in plasma FVIII levels in these animals in the absence of inhibitors. Nevertheless, despite the continued expression of tolerogenic genes, administration of purified ET3 protein to these IUTx recipients induced upregulation of Th2 signaling, a pathway that was not observed in animals that only received ET3 protein, demonstrating that the mechanism by which tolerance is broken in IUTx recipients differs from that by which an immune response to ET3 occurs in animals with no prior exposure. Of note is that animals that develop inhibitors by the Th17 pathway had considerably higher inhibitor titers than the IUTx recipients that responded to ET3 infusion by the Th2 pathway. These studies underscore the need for a more complete understanding of the mechanisms by which immune tolerance to FVIII develops during ontogeny. Disclosures Doering: Expression Therapeutics: Divested equity in a private or publicly-traded company in the past 24 months. Spencer: Expression Therapeutics: Divested equity in a private or publicly-traded company in the past 24 months.

Targeting ErbB3 Receptor in Cancer with Inhibitory Antibodies from Llama

The human ErbB3 receptor confers resistance to the pharmacological inhibition of EGFR and HER2 receptor tyrosine kinases in cancer, which makes it an important therapeutic target. Several anti-ErbB3 monoclonal antibodies that are currently being developed are all classical immunoglobulins. We took a different approach and discovered a group of novel heavy-chain antibodies targeting the extracellular domain of ErbB3 via a phage display of an antibody library from immunized llamas. We first produced three selected single-domain antibodies, named BCD090-P1, BCD090-M2, and BCD090-M456, in E. coli, as SUMO fusions that yielded up to 180 mg of recombinant protein per liter of culture. Then, we studied folding, aggregation, and disulfide bond formation, and showed their ultimate stability with half-denaturation of the strongest candidate, BCD090-P1, occurring in 8 M of urea. In surface plasmon resonance experiments, two most potent antibodies, BCD090-P1 and BCD090-M2, bound the extracellular domain of ErbB3 with 1.6 nM and 15 nM affinities for the monovalent interaction, respectively. The receptor binding was demonstrated by immunofluorescent confocal microscopy on four different ErbB3+ cancer cell lines. We observed that BCD090-P1 and BCD090-M2 bind noncompetitively to two distinct epitopes on the receptor. Both antibodies inhibited the ErbB3-driven proliferation of MCF-7 breast adenocarcinoma cells and HER2-overexpressing SK-BR-3 cells, with the EC50 in the range of 0.1–25 μg/mL. BCD090-M2 directly blocks ligand binding, whereas BCD090-P1 does not compete with the ligand and presumably acts through a distinct allosteric mechanism. We anticipate that these llama antibodies can be used to engineer new biparatopic anti-ErbB3 or bispecific anti-ErbB2/3 antibodies.

Cryo-EM structures of inhibitory antibodies complexed with arginase 1 provide insight into mechanism of action

Human Arginase 1 (hArg1) is a metalloenzyme that catalyzes the hydrolysis of l-arginine to l-ornithine and urea, and modulates T-cell-mediated immune response. Arginase-targeted therapies have been pursued across several disease areas including immunology, oncology, nervous system dysfunction, and cardiovascular dysfunction and diseases. Currently, all published hArg1 inhibitors are small molecules usually less than 350 Da in size. Here we report the cryo-electron microscopy structures of potent and inhibitory anti-hArg antibodies bound to hArg1 which form distinct macromolecular complexes that are greater than 650 kDa. With local resolutions of 3.5 Å or better we unambiguously mapped epitopes and paratopes for all five antibodies and determined that the antibodies act through orthosteric and allosteric mechanisms. These hArg1:antibody complexes present an alternative mechanism to inhibit hArg1 activity and highlight the ability to utilize antibodies as probes in the discovery and development of peptide and small molecule inhibitors for enzymes in general.