Biology Reference
In-Depth Information
αVβ3 was found as cytotrophoblasts differentiated and invaded. Moreover, caveolin-1
was expressed, as reported for syncytiotrophoblasts and villous cytotrophoblasts
where CMV virion gB was localized (Maidji et al. 2006). Function-blocking
antibody to EGFR blocked 63% of infectivity, whereas antibody to integrin β1
blocked 80% and antibody to integrin αV blocked 43%. Function-blocking antibody
to integrin α5 and isotype controls failed to reduce viral replication. When CMV
virions were pretreated with soluble forms of integrins before infection, α1β1
blocked 100% of virion infectivity. Pretreatment with soluble integrin αVβ3 reduced
infectivity by approximately 37%, and pretreatment with soluble integrin α3β1
reduced infectivity by 13%. Together the results of function-perturbing experiments
confirmed that EGFR and integrins α1β1 and αVβ3 - developmentally regulated
molecules - function as CMV receptors as cytotrophoblasts progress along the
differentiation pathway.
Infection Impairs Cell Functions Through Diverse Membrane
Proximal Events
CMV replication in early gestation differentiating/invading cytotrophoblasts radi-
cally impacts cell function and development. Infected cytotrophoblasts dysregulate
expression of stage-specific adhesion molecules, HLA-G and MMP-9 activity
(Fisher et al. 2000; Yamamoto-Tabata et al. 2004; Tabata et al. 2007). Importantly,
cytotrophoblasts' central function, invasiveness, is significantly impaired through
membrane-proximal defects. This includes downregulation of integrins α1β1 and
α9 and VE-cadherin (Fisher et al. 2000; Tabata et al. 2007), stage-specific proteins
that mediate cell-matrix and cell-cell adhesion and invasion. In contrast, integrin
α5, which counterbalances invasion, was not affected. Activated MMP-9 is required
for cytotrophoblast invasion, whereas pro-MMP-9, the uncleaved precursor, is
associated with noninvasive cells and preeclampsia (Librach et al. 1991). Using
zymography, we examined MMP-9 protein and gelatinase activity of cytotrophob-
lasts infected with the pathogenic strain VR1814 and observed reduced MMP-9
protein and activity (Yamamoto-Tabata et al. 2004).
Functional assays of the cells' invasiveness showed significant impairment.
Human IL-10, a pleiotropic cytokine, downregulates MMP-9 activity and impairs
cytotrophoblast invasiveness (Roth et al. 1996; Roth and Fisher 1999). cmvIL-10
(Kotenko et al. 2000) has comparable immunosuppressive activity (Spencer et al.
2002) and impairs immune cell functions in vitro (Chang et al. 2004). Examination
of MMP-9 production and activity in differentiating cytotrophoblasts treated with
recombinant proteins showed that cmvIL-10-treated cytotrophoblasts contain less
MMP-9 protein and activity and upregulate human IL-10 (Yamamoto-Tabata et al.
2004). The impact of viral infection on cytotrophoblast invasiveness was evaluated
using a functional assay that tests the ability of differentiating cells plated on the
upper surfaces of Matrigel-coated filters to penetrate the surface, pass through
pores in the underlying filter and emerge on the lower surface of the membrane
