Herpes simplex virus type I (HSV-1) infection is a potential risk factor involved in the Amyloid β (Aβ) associated neuropathology. However, further understanding of the neuropathological effects of the HSV-1 infection is hampered by the limitations of existing infection models due to the distinct differences between human brains and other mammalians’ brains. Here we generated cerebral organoid models derived from pluripotent stem cells to investigate the HSV-induced Aβ associated neuropathology and the role of antiviral drugs in the phenotypic rescue. Our results identified that the HSV-1-infected cerebral organoids recapitulated Aβ associated neuropathology including the multicellular Aβ deposition, dysregulated endogenous AD mediators, reactive gliosis, neuroinflammation, and neural loss, indicating that cerebral organoids offer an opportunity for modeling the interaction of HSV-1 with the complex phenotypes across the genetic, cellular, and tissue levels of the human Alzheimer’s disease (AD). Furthermore, we identified that two antiviral drugs, namely Ribavirin (RBV) and Valacyclovir (VCV), inhibited HSV-1 replication and rescued the neuropathological phenotypes associated with AD in the HSV-1-infected cerebral organoids, implying their therapeutic potential to slow down the progression of AD. Our study provides a high-fidelity human-relevant in-vitro HSV-1 infection model to reconstitute the multiscale neuropathological features associated with AD and discover therapeutic drug candidates relevant to the AD viral hypothesis.

Background and Purpose: Follistatin-like protein 1 (Fstl1) is a secreted glycoprotein with context-dependent inflammatory activity. We investigated whether Fstl1 is a reproducible feature of traumatic spinal cord injury (SCI) and whether it regulates macrophage activation through interferon regulatory factor 5 (IRF5). Methods: A target-blind analysis integrated four public SCI bulk transcriptomic cohorts with single-cell and spatial datasets. Findings were tested in wild-type and Fstl1+/− mice after SCI using spinal cord RNA sequencing, molecular and histological assays, behavioral testing, and bone marrow-derived macrophages with IRF5 gain- and loss-of-function. Adult-induced Postn-CreER-mediated Fstl1 deletion was evaluated in fibroblast–macrophage non-contact co-cultures. Results: The public-data screen reduced 440 cross-cohort candidates to four non-structural extracellular genes, including Fstl1. Fstl1 was consistently upregulated across SCI cohorts, correlated with myeloid signatures, and was predominantly associated with non-myeloid cell sources in single-cell data. Experimental SCI increased spinal Fstl1 and inflammatory cytokines, whereas partial Fstl1 depletion reduced tissue damage and improved locomotor recovery. Fibroblast Fstl1 deletion reduced macrophage iNOS, Il6, and Tnf and increased Arg-1 and Il10 in co-culture. Spinal cord RNA sequencing showed broad remodeling of immune and tissue-related programs after Fstl1 depletion. Computational perturbation and experimental validation identified IRF5 as a downstream mediator. Recombinant Fstl1 increased IRF5, iNOS, and CD80 while reducing Arg-1 and CD163; IRF5 silencing reversed these changes. Conclusions: Fstl1 is a reproducible SCI-associated extracellular candidate that supports IRF5-dependent inflammatory macrophage activation. Targeting the Fstl1-IRF5 axis may help limit secondary neuroinflammation after SCI.