Structure-guided glyco-engineering of ACE2 for improved potency as soluble SARS-CoV-2 decoy receptor

Infection and viral entry of SARS-CoV-2 crucially depends on the binding of its Spike protein to angiotensin converting enzyme 2 (ACE2) presented on host cells. Glycosylation of both proteins is critical for this interaction. Recombinant soluble human ACE2 can neutralize SARS-CoV-2 and is currently undergoing clinical tests for the treatment of COVID-19. We used 3D structural models and molecular dynamics simulations to define the ACE2 N-glycans that critically influence Spike-ACE2 complex formation. Engineering of ACE2 N-glycosylation by site-directed mutagenesis or glycosidase treatment resulted in enhanced binding affinities and improved virus neutralization without notable deleterious effects on the structural stability and catalytic activity of the protein. Importantly, simultaneous removal of all accessible N-glycans from recombinant soluble human ACE2 yields a superior SARS-CoV-2 decoy receptor with promise as effective treatment for COVID-19 patients.

MUC1 ectodomain is a flagellin-targeting decoy receptor and biomarker operative during Pseudomonas aeruginosa lung infection

We previously reported that flagellin-expressing Pseudomonas aeruginosa (Pa) provokes NEU1 sialidase-mediated MUC1 ectodomain (MUC1-ED) desialylation and MUC1-ED shedding from murine lungs in vivo. Here, we asked whether Pa in the lungs of patients with ventilator-associated pneumonia might also increase MUC1-ED shedding. The levels of MUC1-ED and Pa-expressed flagellin were dramatically elevated in bronchoalveolar lavage fluid (BALF) harvested from Pa-infected patients, and each flagellin level, in turn, predicted MUC1-ED shedding in the same patient. Desialylated MUC1-ED was only detected in BALF of Pa-infected patients. Clinical Pa strains increased MUC1-ED shedding from cultured human alveolar epithelia, and FlaA and FlaB flagellin-expressing strains provoked comparable levels of MUC1-ED shedding. A flagellin-deficient isogenic mutant generated dramatically reduced MUC1-ED shedding compared with the flagellin-expressing wild-type strain, and purified FlaA and FlaB recapitulated the effect of intact bacteria. Pa:MUC1-ED complexes were detected in the supernatants of alveolar epithelia exposed to wild-type Pa, but not to the flagellin-deficient Pa strain. Finally, human recombinant MUC1-ED dose-dependently disrupted multiple flagellin-driven processes, including Pa motility, Pa biofilm formation, and Pa adhesion to human alveolar epithelia, while enhancing human neutrophil-mediated Pa phagocytosis. Therefore, shed desialylated MUC1-ED functions as a novel flagellin-targeting, Pa-responsive decoy receptor that participates in the host response to Pa at the airway epithelial surface.

Persistent Control of SIV Infection in Rhesus Macaques By Expressing a Highly Potent SIV Decoy Receptor after In Vivo HSC Transduction

Despite the success achieved by antiretroviral HIV-1 therapies, long-term and repeated drug administration is associated with toxicity, virus evasion and high cost. We aim to develop a gene therapy approach for persistent control against HIV-1 infection by delivering the transgene expressing a decoy receptor (eCD4-Ig) to hematopoietic stem cells (HSCs) by in vivo transduction. In this approach, HSCs are mobilized from the bone marrow into the peripheral blood stream and transduced with intravenously injected virus vectors. We use an integrating, helper-dependent adenovirus (HDAd5/35++) vector system that targets human CD46, a receptor that is abundantly expressed on primitive HSCs. Transgene integration is achieved by a hyperactive Sleeping Beauty transposase and transgene marking in peripheral blood cells can be increased by in vivo selection. The efficacy and safety of our in vivo HSC transduction/selection strategy has been previously demonstrated for the treatment of b-hemoglobinopathies, hemophilia A, and cancer in murine disease models. In non-human primates, we showed efficient transgene (g-globin) expression in peripheral red blood cells using this strategy. eCD4-Ig functions like a neutralizing antibody and shows broad neutralization spectrum against HIV-1, HIV-2 and SIV isolates. We have designed and produced an HDAd5/35++ vector expressing rhesus eCD4-Ig (rh-eCD4-Ig) from a constitutive and highly active EF1a promoter. In CD46-transgenic mice, over 50µg/mL eCD4-Ig in serum was measured after in vivo transduction and selection, with no obvious adverse events observed. Neutralization assay with serum samples showed that the produced eCD4-Ig effectively inhibited HIV-1 and SIV infection. We then performed studies in a rhesus macaque. After in vivo HSC transduction/selection of a rhesus macaque, eCD4-Ig serum levels were stable at 20-30 mg/ml. In vitro SIVmac239 neutralization assays using week 13 serum and recombinant eCD4-Ig protein determined that the IC50 of eCD4-Ig in rhesus serum is 1.0 mg/ml. This implies that the serum eCD4-Ig concentration at the time of SIVmac239 challenge was ~25-fold higher than the IC50. High-level eCD4-Ig expression had no clinical or hematological side effects. The first SIVmac239 challenge (20pg) was given on June 22 nd. Increasing rechallenge doses are currently injected monthly. So far, the viral load measured by quantitative RT-PCR is below detection limit. The animal is without symptoms and has normal lymphocyte/subset counts. Our study demonstrates an in vivo HSC transduction approach for potential long-term control of HIV-1 infection. Disclosures Kiem: VOR Biopharma: Consultancy; Ensoma Inc.: Consultancy, Current holder of individual stocks in a privately-held company; Homology Medicines: Consultancy. Lieber: Ensoma: Research Funding.

Characterization of SARS-CoV-2 variants B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.618 on cell entry, host range, and sensitivity to convalescent plasma and ACE2 decoy receptor

ABSTRACTRecently, highly transmissible SARS-CoV-2 variants B.1.617.1 (Kappa), B.1.617.2 (Delta) and B.1.618 were identified in India with mutations within the spike proteins. The spike protein of Kappa contains four mutations E154K, L452R, E484Q and P681R, and Delta contains L452R, T478K and P681R, while B.1.618 spike harbors mutations Δ145-146 and E484K. However, it remains unknown whether these variants have altered in their entry efficiency, host tropism, and sensitivity to neutralizing antibodies as well as entry inhibitors. In this study, we found that Kappa, Delta or B.1.618 spike uses human ACE2 with no or slightly increased efficiency, while gains a significantly increased binding affinity with mouse, marmoset and koala ACE2 orthologs, which exhibits limited binding with WT spike. Furthermore, the P618R mutation leads to enhanced spike cleavage, which could facilitate viral entry. In addition, Kappa, Delta and B.1.618 exhibits a reduced sensitivity to neutralization by convalescent sera owning to the mutation of E484Q, T478K, Δ145-146 or E484K, but remains sensitive to entry inhibitors-ACE2-lg decoy receptor. Collectively, our study revealed that enhanced human and mouse ACE2 receptor engagement, increased spike cleavage and reduced sensitivity to neutralization antibodies of Kappa, Delta and B.1.618 may contribute to the rapid spread of these variants and expanded host range. Furthermore, our result also highlighted that ACE2-lg could be developed as broad-spectrum antiviral strategy against SARS-CoV-2 variants.

Structure-guided glyco-engineering of ACE2 for improved potency as soluble SARS-CoV-2 decoy receptor

Infection and viral entry of SARS-CoV-2 crucially depends on the binding of its Spike protein to angiotensin converting enzyme 2 (ACE2) presented on host cells. Glycosylation of both proteins is critical for this interaction. Recombinant soluble human ACE2 can neutralize SARS-CoV-2 and is currently undergoing clinical tests for the treatment of COVID-19. We used 3D structural models and molecular dynamics simulations to define the ACE2 N-glycans that critically influence Spike-ACE2 complex formation. Engineering of ACE2 N-glycosylation by site-directed mutagenesis or glycosidase treatment resulted in enhanced binding affinities and improved virus neutralization without notable deleterious effects on the structural stability and catalytic activity of the protein. Importantly, simultaneous removal of all accessible N-glycans from recombinant soluble human ACE2 yields a superior SARS-CoV-2 decoy receptor with promise as effective treatment for COVID-19 patients.

Gene Editing of the Decoy Receptor LeEIX1 Increases Host Receptivity to Trichoderma Bio-Control

Fungal and bacterial pathogens generate devastating diseases and cause significant tomato crop losses worldwide. Due to chemical pesticides harming the environment and human health, alternative disease control strategies, including microorganismal bio-control agents (BCAs), are increasingly sought-after in agriculture. Bio-control microorganisms such as Trichoderma spp. have been shown to activate induced systemic resistance (ISR) in the host. However, examples of highly active bio-control microorganisms in agricultural settings are still lacking, due primarily to inconsistency in bio-control efficacy, often leading to widespread disease prior to the required ISR induction in the host. As part of its plant colonization strategy, Trichoderma spp. can secrete various compounds and molecules, which can effect host priming/ISR. One of these molecules synthesized and secreted from several species of Trichoderma is the family 11 xylanase enzyme known as ethylene inducing xylanase, EIX. EIX acts as an ISR elicitor in specific plant species and varieties. The response to EIX in tobacco and tomato cultivars is controlled by a single dominant locus, termed LeEIX, which contains two receptors, LeEIX1 and LeEIX2, both belonging to a class of leucine-rich repeat cell-surface glycoproteins. Both receptors are able to bind EIX, however, while LeEIX2 mediates plant defense responses, LeEIX1 acts as a decoy receptor and attenuates EIX induced immune signaling of the LeEIX2 receptor. By mutating LeEIX1 using CRISPR/Cas9, here, we report an enhancement of receptivity to T. harzianum mediated ISR and disease bio-control in tomato.