The Indian cobra reference genome and transcriptome enables comprehensive identification of venom toxins

Snakebite envenoming is a serious and neglected tropical disease that kills ~100,000 people annually. High-quality, genome-enabled comprehensive characterization of toxin genes will facilitate development of effective humanized recombinant antivenom. We report a de novo near-chromosomal genome assembly of Naja naja, the Indian cobra, a highly venomous, medically important snake. Our assembly has a scaffold N50 of 223.35 Mb, with 19 scaffolds containing 95% of the genome. Of the 23,248 predicted protein-coding genes, 12,346 venom-gland-expressed genes constitute the \u27venom-ome\u27 and this included 139 genes from 33 toxin families. Among the 139 toxin genes were 19 \u27venom-ome-specific toxins\u27 (VSTs) that showed venom-gland-specific expression, and these probably encode the minimal core venom effector proteins. Synthetic venom reconstituted through recombinant VST expression will aid in the rapid development of safe and effective synthetic antivenom. Additionally, our genome could serve as a reference for snake genomes, support evolutionary studies and enable venom-driven drug discovery

Insights into complement convertase formation based on the structure of the factor B-cobra venom factor complex

Immune protection by the complement system critically depends on assembly of C3 convertases on the surface of pathogens and altered host cells. These short-lived protease complexes are formed through pro-convertases, which for the alternative pathway consist of the complement component C3b and the pro-enzyme factor B (FB). Here, we present the crystal structure at 2.2-Å resolution, small-angle X-ray scattering and electron microscopy (EM) data of the pro-convertase formed by human FB and cobra venom factor (CVF), a potent homologue of C3b that generates more stable convertases. FB is loaded onto CVF through its pro-peptide Ba segment by specific contacts, which explain the specificity for the homologous C3b over the native C3 and inactive products iC3b and C3c. The protease segment Bb binds the carboxy terminus of CVF through the metal-ion dependent adhesion site of the Von Willebrand factor A-type domain. A possible dynamic equilibrium between a ‘loading' and ‘activation' state of the pro-convertase may explain the observed difference between the crystal structure of CVFB and the EM structure of C3bB. These insights into formation of convertases provide a basis for further development of complement therapeutics

Cytokine storm in a mouse model of IgG-mediated hemolytic transfusion reactions

Cytokines are hypothesized to play a central role in the pathophysiology of IgG-mediated hemolytic transfusion reactions (HTRs), and deeper understanding is required for improving therapy for these events. After establishing well-defined mouse models of HTRs, we tested whether cytokines were involved. Red blood cells (RBCs) from human glycophorin A transgenic (hGPA-Tg) or wild-type (WT) mice were transfused into non-Tg recipients passively immunized with monoclonal antibodies (Mabs). Only transfusions of incompatible RBCs induced IgG-mediated HTRs, exemplified by rapid clearance and hemoglobinuria. Very high plasma levels of monocyte chemoattractant protein-1 (MCP-1) and interleukin-6 (IL-6), and lower levels of tumor necrosis factor-α (TNF-α), were induced after incompatible transfusion. No significant changes in IL-10, IL-12, or interferon-γ (IFN-γ) levels were observed. The proinflammatory cytokines elaborated in this in vivo mouse model are also implicated in the systemic inflammatory response syndrome (SIRS) and confirm the hypothesis that cytokine storm occurs as a result of HTRs