Human Cytomegalovirus-Induces Cytokine Changes in the Placenta with Implications for Adverse Pregnancy Outcomes

Stuart T Hamilton,Zin Naing,Nicole Graf,Gillian Scott,Maria E Craig,Jenna Iwasenko,Beverley Hall,Susan Arbuckle,William D Rawlinson,Lynette Kay Rogers

doi:10.1371/journal.pone.0052899

Stuart T Hamilton, Zin Naing + Show 8 more

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https://doi.org/10.1371/journal.pone.0052899

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Abstract

Human cytomegalovirus (CMV) infection of the developing fetus can result in adverse pregnancy outcomes including death in utero. Fetal injury results from direct viral cytopathic damage to the CMV-infected fetus, although evidence suggests CMV placental infection may indirectly cause injury to the fetus, possibly via immune dysregulation with placental dysfunction. This study investigated the effects of CMV infection on expression of the chemokine MCP-1 (CCL2) and cytokine TNF-α in placentae from naturally infected stillborn babies, and compared these changes with those found in placental villous explant histocultures acutely infected with CMV ex vivo. Tissue cytokine protein levels were assessed using quantitative immunohistochemistry. CMV-infected placentae from stillborn babies had significantly elevated MCP-1 and TNF-α levels compared with uninfected placentae (p = 0.001 and p = 0.007), which was not observed in placentae infected with other microorganisms (p = 0.62 and p = 0.71) (n = 7 per group). Modelling acute clinical infection using ex vivo placental explant histocultures showed infection with CMV laboratory strain AD169 (0.2 pfu/ml) caused significantly elevated expression of MCP-1 and TNF-α compared with uninfected explants (p = 0.0003 and p<0.0001) (n = 25 per group). Explant infection with wild-type Merlin at a tenfold lower multiplicity of infection (0.02 pfu/ml), caused a significant positive correlation between increased explant infection and upregulation of MCP-1 and TNF-α expression (p = 0.0001 and p = 0.017). Cytokine dysregulation has been associated with adverse outcomes of pregnancy, and can negatively affect placental development and function. These novel findings demonstrate CMV infection modulates the placental immune environment in vivo and in a multicellular ex vivo model, suggesting CMV-induced cytokine modulation as a potential initiator and/or exacerbator of placental and fetal injury.

Highlights

Human cytomegalovirus (CMV) is the leading infectious cause of congenital malformation in developed countries, with a mean global incidence of 0.64% [1]
MCP-1 and TNF-a were elevated in CMV-infected placentae delivered from infected women, compared with placentae infected with other microorganisms and uninfected placentae (Figure 1)
MCP-1 and TNF-a protein localised in syncytiotrophoblast, cytotrophoblast, mesenchymal and endothelial cells of chorionic villi in CMV-infected placentae, placentae infected with other microorganisms and uninfected placentae from stillborn babies (Figure 1B)

Summary

Introduction

Human cytomegalovirus (CMV) is the leading infectious cause of congenital malformation in developed countries, with a mean global incidence of 0.64% [1]. Congenital CMV may result in the development of serious clinical sequelae [2,3,4], or at the most severe, fetal and neonatal death [5,6,7]. Reactivation of latent CMV results in at least as many adverse outcomes as primary infections [8]. With transplacental movement of CMV across the materno-fetal interface, is a pre-requisite for infection of the fetus [9,10]. Infection can be restricted to the placenta [6,12], and there is increasing evidence that indirect effects of CMV through placental infection contribute to adverse pregnancy outcomes [6,13]

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