TDP-43 promotes efficient HSV-1 replication in human DRG-derived neurons

TAR DNA-binding protein 43 (TDP-43) is a versatile nuclear RNA-binding protein that performs important functions in RNA localization, processing, and stability. In the neurodegenerative disease amyotrophic lateral sclerosis (ALS) TDP-43 forms toxic, insoluble cytoplasmic aggregates that ultimately lead to neuronal loss. Although TDP-43 is expressed in every cell type, its function and subcellular localization are particularly important for neuronal homeostasis. However, it is unknown if TDP-43 has a role during herpesvirus infection. Herpes simplex virus type-1 (HSV-1), a ubiquitous neurotropic pathogen, is considered a contributing factor to neurodegenerative disorders. In this study, we tested the requirement for TDP-43 during HSV-1 infection in neuronal and non-neuronal cells. HSV-1 infection of epithelial cells and primary fibroblasts did not change overall TDP-43 abundance, nor did TDP-43 depletion detectably alter HSV-1 productive replication in a multicycle growth experiment. By contrast, when TDP-43 was depleted in neuronally-derived, differentiated HD10.6 cells, HSV-1 infectious virus production was significantly reduced in both single- and multicycle growth experiments. Notably, TDP-43 depletion restricts viral lytic gene expression at the <i>immediate-early</i> phase. Through nanopore direct RNA-sequencing, we uncovered enhanced intron retention in two essential viral genes-ICP0 and UL15-upon TDP-43 depletion. Thus, while depletion of TDP-43 does not detectably affect HSV-1 reproduction in epithelial cells and fibroblasts, TDP-43 is required for efficient replication in HD10.6 cells through modifying the abundance and splicing of viral mRNAs.IMPORTANCEHerpes simplex virus type-1 is a widespread neurotropic pathogen that can cause life-threatening infections of the brain and is increasingly linked to neurodegenerative disease. However, due to the lack of scalable <i>in vitro</i> human neuronal models or small animal models that recapitulate disease, little is known about virus-host interactions in neurons specifically. Using human epithelial cells, primary fibroblasts and a human neuron-derived cell line, we uncovered a cell type specific TDP-43 requirement for efficient HSV-1 virus replication. TDP-43 is a critical neuronal disease factor gene, and we showed it promotes HSV-1 gene expression and splicing of viral mRNAs in neuron-derived cells. This raises the possibility that targeting of TDP-43 could reveal a new antiviral strategy for severe HSV-1 infections. This work further provides valuable insights into the possible etiology of neurodegenerative disease and highlights the importance of studying virus-host interactions in relevant cell types.