An inquiry into the effects of the producer cell type on Herpes simplex virus type-1 infectivity and the virion-associated proteome

Abstract

Viruses inherently rely upon the host cell to produce infectious virions, and many viruses can infect several cell types. The type of cell used to produce a virus, i.e. the producer cell type, has been shown to alter the macromolecular composition of the virions that are produced. These alterations can change the capacity of virions to infect cells, spread within the host, and interact with the immune system. Herpes Simplex Virus Type-1 (HSV-1) is a ubiquitous human pathogen that can elicit disease outcomes ranging from the development of orofacial lesions to blindness or encephalitis. This range of disease is possible because HSV-1 replicates in multiple cell types. To study HSV-1 replication and disease, researchers must propagate virus that is subsequently used to establish infection in cell culture or animal models. Currently, there is no standard cell line used for the propagation of HSV-1 in research, although the vero cell is among the most used cell types for this purpose. We hypothesize that the producer cell type of HSV-1 alters the macromolecular composition and infectivity of the virions that are produced. To test this hypothesis, we propagated HSV-1 from African green monkey kidney cells (vero), immortalized human keratinocytes (HaCaT), and primary human foreskin fibroblasts (HFF-1). The capacity for virions to replicate was measured by quantifying viral gene expression, protein production, and the output of infectious virions from infected target cells. We also used liquid chromatography-mass spectrometry (LC-MS/MS) to quantify proteins that are incorporated into virions derived from each cell type. We found that HSV-1 derived from HaCaTs produce more viral protein and infectious virions from infected cells relative to HSV-1 derived from vero or HFF-1 cells. We also identified many viral and cellular proteins that are differentially incorporated into HSV-1 virions in a producer cell-dependent manner. This data suggests that the producer cell type of HSV-1 alters virion infectivity and protein composition, which may have implications for how the virus spreads in humans. In addition, these results allude to the possibility that the producer cell type may influence experimental outcomes in studies that investigate HSV-1 replication and pathogenesis.