Katz, M. A. | bioRxiv Science

bioRxiv2026

Viral Microglia Reprogramming Clears Oligomeric Neurotoxic Debris

Owing to pivotal roles in CNS debris clearance and homeostasis, microglia are central targets for the therapy of neurodegenerative diseases. Intricate proximity to neurons, the inherent danger of neuroimmune toxicity, and intrinsically high plasticity and adaptability, impose high hurdles on microglia modulation. Attenuated viruses are being tested extensively against CNS malignancies (i.e., cancer virotherapy); yet, aside from viral vector-mediated payload delivery, virotherapy for non-neoplastic CNS disease remains unexplored. Here we report disseminated targeting of microglia with the highly attenuated polio:rhinovirus chimera, PVSRIPO, that culminated in profound, durable microglia reprogramming. This phenotype, rooted in extended cytoplasmic viral (v)RNA replication, was non-cytopathogenic and did not yield virus progeny or dissemination. vRNA replication in microglia triggered selective interferon (IFN) regulatory factor (IRF) 3/IRF7 transcriptional programs in the relative absence of NF{kappa}B-driven proinflammatory cytokine responses and elicited robust phagocytosis of both tumor cells and amyloid-beta. Targeting of microglia with PVSRIPO mediated immunotherapy in a mouse glioma model and the clearance of oligomeric amyloid-beta deposits in an injectable model of neurotoxic amyloid accumulation. This work identifies attenuated virotherapy as an approach to safely and effectively invigorate microglia function in immune surveillance and neurotoxic debris clearance.

neuroscience↗

bioRxiv2023

Diverse viral cas genes antagonize CRISPR immunity

Prokaryotic CRISPR-Cas immunity is subverted via anti-CRISPRs (Acrs), small proteins that inhibit Cas protein activities when expressed during the phage lytic cycle or from resident prophages or plasmids. CRISPR-Cas defenses are classified into 6 types and 33 subtypes, which employ a diverse suite of Cas effectors and differ in their mechanisms of interference. As Acrs often work via binding to a cognate Cas protein, inhibition is almost always limited to a single CRISPR type. Furthermore, while acr genes are frequently organized together in phage-associated gene clusters, how such inhibitors initially evolve has remained unclear. Here we have investigated the Acr content and inhibition specificity of a collection of Listeria isolates, which naturally harbor four diverse CRISPR-Cas systems (types I-B, II-A, II-C, and VI-A). We observed widespread antagonism of CRISPR, which we traced to 12 novel and 4 known Acr gene families encoded on endogenous mobile genetic elements. Among these were two Acrs that possess sequence homology to type I-B Cas proteins and assemble into a defective interference complex. Surprisingly, an additional type I-B Cas homolog did not affect type I immunity, but instead inhibited the RNA-targeting type VI CRISPR system through sequestration of crRNA. By probing the IMGVR database of viral genomes, we detected abundant orphan cas genes located within putative anti-defense gene clusters. We experimentally verified the Acr activity of one viral cas gene, a particularly broad-spectrum cas3 homolog that inhibits type I-B, II-A, and VI-A CRISPR immunity. Our observations provide direct evidence of Acr evolution via cas gene co-option, and new genes with potential for broad-spectrum control of genome editing technologies.

microbiology↗