Andexanet alfa effectively reverses edoxaban anticoagulation effects and associated bleeding in a rabbit acute hemorrhage model.

INTRODUCTION: Increasing use of factor Xa (FXa) inhibitors necessitates effective reversal agents to manage bleeding. Andexanet alfa, a novel modified recombinant human FXa, rapidly reverses the anticoagulation effects of direct and indirect FXa inhibitors. OBJECTIVE: To evaluate the ability of andexanet to reverse anticoagulation in vitro and reduce bleeding in rabbits administered edoxaban. MATERIALS AND METHODS: In vitro studies characterized the interaction of andexanet with edoxaban and its ability to reverse edoxaban-mediated anti-FXa activity. In a rabbit model of surgically induced, acute hemorrhage, animals received edoxaban vehicle+andexanet vehicle (control), edoxaban (1 mg/kg)+andexanet vehicle, edoxaban+andexanet (75 mg, 5-minute infusion, 20 minutes after edoxaban), or edoxaban vehicle+andexanet prior to injury. RESULTS: Andexanet bound edoxaban with high affinity similar to FXa. Andexanet rapidly and dose-dependently reversed the effects of edoxaban on FXa activity and coagulation pharmacodynamic parameters in vitro. In edoxaban-anticoagulated rabbits, andexanet reduced anti-FXa activity by 82% (from 548±87 to 100±41 ng/ml; P<0.0001), mean unbound edoxaban plasma concentration by ~80% (from 100±10 to 21±6 ng/ml; P<0.0001), and blood loss by 80% vs. vehicle (adjusted for control, 2.6 vs. 12.9 g; P = 0.003). The reduction in blood loss correlated with the decrease in anti-FXa activity (r = 0.6993, P<0.0001) and unbound edoxaban (r = 0.5951, P = 0.0035). CONCLUSION: These data demonstrate that andexanet rapidly reversed the anticoagulant effects of edoxaban, suggesting it could be clinically valuable for the management of acute and surgery-related bleeding. Correlation of blood loss with anti-FXa activity supports the use of anti-FXa activity as a biomarker for assessing anticoagulation reversal in clinical trials.

Defensins enable macrophages to inhibit the intracellular proliferation of Listeria monocytogenes.

Listeria monocytogenes is a facultative intracellular pathogen that infects a large diversity of host cells, including macrophages. To avoid the phagosome microbicidal environment, L. monocytogenes secretes a pore-forming toxin (listeriolysin O, LLO) that releases the bacterium into the cytoplasm. We hypothesized that the α-defensins (HNPs) and/or humanized θ-defensin (RC-1) peptides produced by human and non-human primate neutrophils, respectively, cooperate with macrophages to control L. monocytogenes infection. Our results establish that HNP-1 and RC-1 enable macrophages to control L. monocytogenes intracellular growth by inhibiting phagosomal escape, as a consequence, bacteria remain trapped in a LAMP-1-positive phagosome. Importantly, HNP-1 interaction with macrophages and RC-1 interaction with bacteria are required to prevent macrophage infection. In accordance with these results, RC-1 is a more potent anti-listerial peptide than HNP-1 and HNP-1 is acquired by macrophages and trafficked to the phagocytosed bacteria. Finally, HNP-1 and RC-1 antimicrobial activity is complemented by their ability to prevent LLO function through two mechanisms, blocking LLO-dependent perforation of macrophage membranes and the release of LLO from the bacteria. In conclusion, at the site of infection the cooperation between antimicrobial peptides, such as HNP-1, and macrophages likely plays a critical role in the innate immune defence against L. monocytogenes.

Grifonin-1: a small HIV-1 entry inhibitor derived from the algal lectin, Griffithsin.

BACKGROUND: Griffithsin, a 121-residue protein isolated from a red algal Griffithsia sp., binds high mannose N-linked glycans of virus surface glycoproteins with extremely high affinity, a property that allows it to prevent the entry of primary isolates and laboratory strains of T- and M-tropic HIV-1. We used the sequence of a portion of griffithsin's sequence as a design template to create smaller peptides with antiviral and carbohydrate-binding properties. METHODOLOGY/RESULTS: The new peptides derived from a trio of homologous ß-sheet repeats that comprise the motifs responsible for its biological activity. Our most active antiviral peptide, grifonin-1 (GRFN-1), had an EC50 of 190.8±11.0 nM in in vitro TZM-bl assays and an EC(50) of 546.6±66.1 nM in p24gag antigen release assays. GRFN-1 showed considerable structural plasticity, assuming different conformations in solvents that differed in polarity and hydrophobicity. Higher concentrations of GRFN-1 formed oligomers, based on intermolecular ß-sheet interactions. Like its parent protein, GRFN-1 bound viral glycoproteins gp41 and gp120 via the N-linked glycans on their surface. CONCLUSION: Its substantial antiviral activity and low toxicity in vitro suggest that GRFN-1 and/or its derivatives may have therapeutic potential as topical and/or systemic agents directed against HIV-1.