Imperial College Parturition Research Group, Department of Metabolism, Digestion and Reproduction, Imperial College London, London, United Kingdom.
Department of Obstetrics and Gynaecology, Faculty of Medicine, University of Malaya, Kuala Lumpur, Malaysia.
Front Immunol. 2020 Aug 25;11:1899. doi: 10.3389/fimmu.2020.01899. eCollection 2020.
Infection/inflammation is an important causal factor in spontaneous preterm birth (sPTB). Most mechanistic studies have concentrated on the role of bacteria, with limited focus on the role of viruses in sPTB. Murine studies support a potential multi-pathogen aetiology in which a double or sequential hit of both viral and bacterial pathogens leads to a higher risk preterm labour. This study aimed to determine the effect of viral priming on bacterial induced inflammation in human models of ascending and haematogenous infection. Vaginal epithelial cells, and primary amnion epithelial cells and myocytes were used to represent cell targets of ascending infection while interactions between peripheral blood mononuclear cells (PBMCs) and placental explants were used to model systemic infection. To model the effect of viral priming upon the subsequent response to bacterial stimuli, each cell type was stimulated first with a TLR3 viral agonist, and then with either a TLR2 or TLR2/6 agonist, and responses compared to those of each agonist alone. Immunoblotting was used to detect cellular NF-κB, AP-1, and IRF-3 activation. Cellular TLR3, TLR2, and TLR6 mRNA was quantified by RT-qPCR. Immunoassays were used to measure supernatant cytokine, chemokine and PGE2 concentrations. TLR3 ("viral") priming prior to TLR2/6 agonist ("bacterial") exposure augmented the pro-inflammatory, pro-labour response in VECs, AECs, myocytes and PBMCs when compared to the effects of agonists alone. In contrast, enhanced anti-inflammatory cytokine production (IL-10) was observed in placental explants. Culturing placental explants in conditioned media derived from PBMCs primed with a TLR3 agonist enhanced TLR2/6 agonist stimulated production of IL-6 and IL-8, suggesting a differential response by the placenta to systemic inflammation compared to direct infection as a result of haematogenous spread. TLR3 agonism generally caused increased mRNA expression of TLR3 and TLR2 but not TLR6. This study provides human evidence that viral infection may increase the susceptibility of women to bacterial-induced sPTB. Improved understanding of interactions between viral and bacterial components of the maternal microbiome and host immune response may offer new therapeutic options, such as antivirals for the prevention of PTB.
感染/炎症是自发性早产 (sPTB) 的一个重要病因。大多数机制研究都集中在细菌的作用上，而对病毒在 sPTB 中的作用关注有限。鼠类研究支持一种潜在的多病原体病因，即病毒和细菌病原体的双重或序贯打击会导致更高的早产风险。本研究旨在确定病毒引发对人类上行和血源性感染模型中细菌诱导炎症的影响。阴道上皮细胞、原代羊膜上皮细胞和肌细胞用于代表上行感染的细胞靶标，而外周血单核细胞 (PBMC) 与胎盘组织块之间的相互作用用于模拟全身感染。为了模拟病毒引发对随后对细菌刺激的反应的影响，每种细胞类型首先用 TLR3 病毒激动剂刺激，然后用 TLR2 或 TLR2/6 激动剂刺激，并将反应与每种激动剂单独刺激的反应进行比较。免疫印迹用于检测细胞 NF-κB、AP-1 和 IRF-3 激活。通过 RT-qPCR 定量检测细胞 TLR3、TLR2 和 TLR6 mRNA。免疫测定用于测量上清液细胞因子、趋化因子和 PGE2 浓度。TLR3（“病毒”）引发剂在 TLR2/6 激动剂（“细菌”）暴露之前，与单独激动剂相比，增强了 VECs、AECs、肌细胞和 PBMCs 的促炎、促早产反应。相比之下，在胎盘组织块中观察到增强的抗炎细胞因子（IL-10）产生。在由 TLR3 激动剂引发的 PBMC 衍生的条件培养基中培养胎盘组织块增强了 TLR2/6 激动剂刺激的 IL-6 和 IL-8 的产生，这表明由于血液传播，胎盘对全身炎症的反应与直接感染不同。TLR3 激动剂通常导致 TLR3 和 TLR2 的 mRNA 表达增加，但 TLR6 没有增加。本研究为人类提供了证据，表明病毒感染可能增加女性对细菌诱导的 sPTB 的易感性。更好地理解母体微生物组中病毒和细菌成分以及宿主免疫反应之间的相互作用，可能为预防 PTB 提供新的治疗选择，例如抗病毒药物。
