HCMV virus produced in different cell types induces different transcriptional responses

Human cytomegalovirus infects multiple cell types, including fi- broblasts and epithelial cells. It penetrates fibroblasts by fusion at the cell surface but is endocytosed into epithelial cells. In this report, we demonstrate by electron microscopy that the virus uses two different routes to enter retinal pigmented epithelial cells, depending on the cell type in which the infecting virus was produced. Virus produced in epithelial cells preferentially fuses with the plasma membrane, whereas fibroblast-derived virus mostly enters by receptor-mediated endocytosis. Treatment of epithelial cells with agents that block endosome acidification inhibited infection by virus produced in fibroblasts but had only a modest effect on infection by virus from epithelial cells. Epithelial cell-generated virions had higher intrinsic ‘‘fusion-from-without’’ activity than fibroblast-generated particles, and the two virus preparations triggered different cellular signaling responses, as evidenced by markedly different transcriptional profiles. We propose that the cell type in which a human cytomegalovirus particle is produced likely influences its subsequent spread and its contribution to pathogenesis. Keywords: cell type comparison, viral infection, cell tropism, viral entry A single strain of Human Cytomegalovirus (HCMV), termed BADrUL131, was used to prepare viral stocks from either fibroblast cells or from endothelial cells. These viral preparations (fibroBADrUL131 and epiBADrUL131) were used to infect ARP-19 cells (Human retinal pigmented epithelial cells) for either 6 hours or 10 hours. Total RNA was collected, labeled and used to hybridize to Agilent whole genome oligo microarrays and were normalized to a control reference RNA pool.