Stopping Marburg virus in its tracks
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Endosymbionts modulate virus effects on aphid-plant interactions
Vector-borne pathogens frequently modify traits of their primary hosts and vectors in ways that influence disease transmission. Such effects can themselves be altered by the presence of other microbial symbionts, yet we currently have limited understanding of these interactions. Here we show that effects of pea enation mosaic virus (PEMV) on interactions between host plants and aphid vectors are modulated by the presence of different aphid endosymbionts. In a series of laboratory assays, we found strong interactive effects of virus infection and endosymbionts on aphid metabolomic profiles, population growth, behavior, and virus transmission during aphid feeding. Furthermore, the strongest effects—and those predicted to favor virus transmission—were most apparent in aphid lines harboring particular endosymbionts. These findings show that virus effects on host-vector interactions can be strongly influenced by other microbial symbionts and suggest a potentially important role for such interactions in disease ecology and evolution.
Influenza A virus rapidly adapts particle shape to environmental pressures
Enveloped viruses such as influenza A virus (IAV) often produce a mixture of virion shapes, ranging from 100 nm spheres to micron-long filaments. Spherical virions use fewer resources, while filamentous virions resist cell-entry pressures such as antibodies. While shape changes are believed to require genetic adaptation, the mechanisms of how viral mutations alter shape remain unclear. Here we find that IAV dynamically adjusts its shape distribution in response to environmental pressures. We developed a quantitative flow virometry assay to measure the shape of viral particles under various infection conditions (such as multiplicity, replication inhibition and antibody treatment) while using different combinations of IAV strains and cell lines. We show that IAV rapidly tunes its shape distribution towards spheres under optimal conditions but favours filaments under attenuation. Our work demonstrates that this phenotypic flexibility allows IAV to rapidly respond to environmental pressures in a way that provides dynamic adaptation potential in changing surroundings.
Non-replicative herpes simplex virus genomic and amplicon vectors for gene therapy – an update
Two major types of defective vectors have been derived from herpes simplex virus type 1 (HSV-1), non-replicative genomic vectors (nrHSV-1), and amplicon vectors. This review recapitulates the main features of both vector types and summarizes recent improvements in our understanding of virus/vector biology, particularly with regard to the critical role played by the overpowering of antiviral cellular defenses and the epigenetic control of viral gene expression. Over the past years, significant breakthroughs in vector design, genetic engineering, and HSV-1 biology have accelerated the development of nrHSV-1 vectors. The low immunogenicity and enhanced safety profiles allowed the successful translation of these vectors into several clinical trials, with some being approved by the FDA. Regarding amplicons, despite their advantage in carrying very large or multiple transgenes, and their potential to avoid genome dilution in dividing cells, the absence of production procedures capable of generating large amounts of helper-free amplicons at reasonable cost with GMP compliance, still limits the translation of these outstanding vectors to clinical trials.
Neuronal guidance factor Sema3A inhibits neurite ingrowth and prevents chondrocyte hypertrophy in the degeneration of knee cartilage in mice, monkeys and humans
Osteoarthritis (OA) is a degenerative joint disease accompanied with the loss of cartilage and consequent nociceptive symptoms. Normal articular cartilage maintains at aneural state. Neuron guidance factor Semaphorin 3A (Sema3A) is a membrane-associated secreted protein with chemorepulsive properties for axons. However, the role of Sema3A in articular cartilage is still not clear. In the present studies, we investigated the functions of Sema3A in OA development in mice, non-human primates, and patients with OA. Sema3A has a protective effect on cartilage degradation, validated by the organoid culture in vitro and confirmed in chondrocyte-specific Sema3A conditional knockout mice. We demonstrated that Sema3A is a key molecule in maintaining cartilage homeostasis from chondrocyte hypertrophy via activating the PI3K pathway. The potential usage of Sema3A for OA treatment was validated in mouse and Rhesus macaque OA models through intra-articular injection of Sema3A, and also in patients by administering Sema3A containing platelet-rich plasma into the knee joints. Our studies demonstrated that Sema3A exerts a critical role in inhibiting neurite ingrowth and preventing chondrocyte hypertrophy in cartilage, and could be potentially used for OA treatment.
Apaf-1 is an evolutionarily conserved DNA sensor that switches the cell fate between apoptosis and inflammation
Apoptotic protease activating factor 1 (Apaf-1) was traditionally defined as a scaffold protein in mammalian cells for assembling a caspase activation platform known as the ‘apoptosome’ after its binding to cytochrome c. Although Apaf-1 structurally resembles animal NOD-like receptor (NLR) and plant resistance (R) proteins, whether it is directly involved in innate immunity is still largely unknown. Here, we found that Apaf-1-like molecules from lancelets, fruit flies, mice, and humans have conserved DNA sensing functionality. Mechanistically, mammalian Apaf-1 recruits receptor-interacting protein 2 (RIP2, also known as RIPK2) via its WD40 repeat domain and promotes RIP2 oligomerization to initiate NF-κB-driven inflammation upon cytoplasmic DNA recognition. Furthermore, DNA binding of Apaf-1 determines cell fate by switching the cellular processes between intrinsic stimuli-activated apoptosis and inflammation. These findings suggest that Apaf-1 is an evolutionarily conserved DNA sensor and may serve as a cell fate checkpoint, which determines whether cells initiate inflammation or undergo apoptosis by distinct ligand binding.
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