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CMV Infection of Polarized Cells

Our studies of viral replication in the epithelium used polarized retinal pigment epithelial cells, a target of viral infection in immunosuppressed patients. We showed that CMV virions penetrate cells and egress across apical membranes [J Gen Virol 77:61-74] through the action of gB, a conserved virion envelope glycoprotein [Virology 197:143-58; Infect Agents Dis 3:9-28]. Using site-specific mutagenesis, we showed that CMV gB contains signals for vectorial sorting, endocytosis and recycling to the apical membrane of polarized epithelial cells [J Virol 70:8029-40; J Virol 72:7374-86; J Virol 73:8677-88]. We found that the spread of infection in these cells requires a pathogenesis factor, glycoprotein US9 [J Virol 70:8402-10; J Virol 72:5717-27]. Currently, we are studying endothelial cell-tropic genes expressed by clinical strains that infect uterine endothelium and immune cells [Virology 304:53-69].

Model for CMV glycoprotein transport, virion envelopment and egress pathways in infected polarized epithelial cells.

Biology of CMV Infection at the Uterine-Placental Interface

Congenital CMV infection affects 1 to 3% of infants in the United States annually and remains an important public health problem causing significant morbidity and mortality. Early studies suggest that placental infection precedes virus transmission to the fetus. Our work indicates that CMV infection in the placenta is linked to the unusual interactions of specialized placental cells (cytotrophoblasts) with the pregnant uterus [J Virol 74:6808-20]. Using a model for virus spread, we showed that CMV could be transmitted from uterine endothelial cells to differentiating/invading cytotrophoblasts [Virology 304:53-69]. We are evaluating specific cell surface molecules used for infection of cytotrophoblast progenitors and differentiating/invading cells.

We are particularly intrigued by the unusual biology of CMV infection at the uterine-placental interface in the context of healthy pregnancies and complications associated with viral and bacterial pathogens [J Virol 77:13301-14; J Infect Dis 190:826-34]. By examining patterns of viral protein expression in biopsy specimens from the decidua and adjacent placenta, we found that CMV infection correlates inversely with the level of maternal neutralizing antibodies. We are interested in understanding how CMV exploits immune hyporesponsiveness in the pregnant uterus and the role of bacterial co-infections, inflammation and immune responses that suppress pathogen replication during gestation.

Schematic that illustrates and summarizes the pattern of CMV protein expression in the decidua that was associated with transmission of infection to the placenta. CMV-infected cells (red) and gB-containing vesicles (red) in macrophages and dendritic cells at the placental-decidual interface.

CMV Infection Impairs Endothelial Cell Migration and Cytotrophoblast Differentiation/Invasion

We found that CMV-infected cytotrophoblasts downregulate key adhesion and immune molecules and impair differentiation/invasion [J Virol 74:6808-20]. We are interested in identifying and elucidating the role of viral pathogenesis genes that alter cellular gene expression, in particular integrins and cell-cell adhesion molecules and other differentiation molecules. Using an in vitro invasion model, we found that cytotrophoblasts infected with a clinical CMV strain reduce metalloproteinase-9 production and activity by an immune mechanism that involves expression of the viral interleukin 10 [J Virol 78:2831-40]. Our current studies focus on CMV misregulation of upstream differentiation pathways and downstream differentiation molecules that control cell-ligand and cell-cell interactions.

Impaired cell motility in functional assays of endothelial cell wound healing in vitro. Human Fibroblasts (top) and HUVEC (bottom) were infected with VR1814 and treated with hIL-10 or cmvIL-10 (100 ng/ml). The horizontal line indicates the original width of a wounded cell sheet.