Viral Single Stranded RNA Induces a Trophoblast Pro-Inflammatory and Antiviral Response in a TLR8-Dependent and -Independent Manner1

Abstract

Interest is growing in the role of viral infections and their association with adverse pregnancy outcomes. The trophoblast is permissive to viruses, but little is known about their impact on the placenta. We previously established that viral single stranded RNA (ssRNA), a Toll-like receptor 8 (TLR8) agonist, induces a restricted trophoblast pro-inflammatory cytokine/chemokine response by upregulating the secretion of interleukin (IL)-6 and IL-8. In parallel, the type I interferon, IFNbeta, is produced and acts back on the cell in an autocrine/paracrine manner to trigger caspase-3-dependent apoptosis. In this study, we sought to extend these findings by determining the mechanisms involved, examining whether viral ssRNA could induce a trophoblast antiviral response, and evaluating the influence of viral ssRNA on pregnancy outcome using a mouse model. Viral ssRNA induced human first-trimester trophoblast inflammation, type I interferon production, an antiviral response, and apoptosis in both a TLR8/MyD88-dependent and -independent manner. Furthermore, administration of viral ssRNA to pregnant mice induced placental caspase-3 activation, a pro-inflammatory cytokine/chemokine, type I interferon, and antiviral response as well as immune cell infiltration. Thus, ssRNA viral infections may compromise pregnancy by altering placental trophoblast survival and function through both TLR8 and non-TLR8 signaling pathways, leading to immune changes at the maternal-fetal interface.

Viral Infection Sensitizes Human Fetal Membranes to Bacterial Lipopolysaccharide by MERTK Inhibition and Inflammasome Activation

“…Human and mouse FMs were homogenized and total RNA extracted as previously described (6, 40). Quantitative real-time RT-PCR was performed using the KAPA SYBR Fast qPCR kit (Kapa Biosystems, Woburn, MA), and PCR amplification performed on the BioRad CFX Connect Real-time System (BioRad).…”

Placental origins of adverse pregnancy outcomes: potential molecular targets: an Executive Workshop Summary of the Eunice Kennedy Shriver National Institute of Child Health and Human Development

“…82 This placental ssRNA-induced response is mirrored in vivo without triggering preterm birth. 82 In contrast, viral dsRNA induces preterm birth through TLR3 79,83 while other groups have reported preeclampsia-like symptoms in viral dsRNA-treated mice. 84 …”

“…80,81,82 Furthermore, independent of TLR8, viral ssRNA also induces trophoblast expression of IL-1β, anti-viral factors, as well as inducing apoptosis. 82 This placental ssRNA-induced response is mirrored in vivo without triggering preterm birth.…”

“…80,81,82 Furthermore, independent of TLR8, viral ssRNA also induces trophoblast expression of IL-1β, anti-viral factors, as well as inducing apoptosis. 82 This placental ssRNA-induced response is mirrored in vivo without triggering preterm birth. 82 In contrast, viral dsRNA induces preterm birth through TLR3 79,83 while other groups have reported preeclampsia-like symptoms in viral dsRNA-treated mice.…”

Outcomes of Congenital Zika Disease Depend on Timing of Infection and Maternal-Fetal Interferon Action

“…However, a strong IFN-I response is often followed by the recruitment of neutrophils, inflammatory monocytes, NK and T lymphocytes, leading to tissue damage and immunopathology (Iwasaki and Pillai, 2014). During pregnancy, viral single-stranded RNA and bacteria induce an antiviral response, IFN-I, cytokine and chemokine production, immune cell infiltration and placental caspase-3 activation in mice (Potter et al, 2015; Racicot et al, 2016). Elevated IFN-α can also dysregulate angiogenesis in the placenta, which correlates with risks for preeclampsia in patients (Andrade et al, 2015).…”