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 immediate-early 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 in vitro 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.