Department of Veterinary Pathobiology, University of Missouri, Columbia, Missouri, USA.
Department of Population Heath, College of Veterinary Medicine, University of Georgia, Athens, Georgia, USA.
FASEB J. 2022 Mar;36(3):e22197. doi: 10.1096/fj.202101485R.
Neonatal meningitis-associated Escherichia coli (NMEC) is among the leading causes of bacterial meningitis and sepsis in newborn infants. Several virulence factors have been identified as common among NMEC, and have been shown to play an important role in the development of bacteremia and/or meningitis. However, there is significant variability in virulence factor expression between NMEC isolates, and relatively little research has been done to assess the impact of variable virulence factor expression on immune cell activation and the outcome of infection. Here, we investigated the role of NMEC strain-dependent P2X receptor (P2XR) signaling on the outcome of infection in neonatal mice. We found that alpha-hemolysin (HlyA)-expressing NMEC (HlyA ) induced robust P2XR-dependent macrophage cell death in vitro, while HlyA NMEC did not. P2XR-dependent cell death was inflammasome independent, suggesting an uncoupling of P2XR and inflammasome activation in the context of NMEC infection. In vivo inhibition of P2XRs was associated with increased mortality in neonatal mice infected with HlyA NMEC, but had no effect on the survival of neonatal mice infected with HlyA NMEC. Furthermore, we found that P2XR-dependent protection against HlyA NMEC in vivo required macrophages, but not neutrophils or NLRP3. Taken together, these data suggest that HlyA NMEC activates P2XRs which in turn confers macrophage-dependent protection against infection in neonates. In addition, our findings indicate that strain-dependent virulence factor expression should be taken into account when studying the immune response to NMEC.
新生儿脑膜炎相关大肠杆菌(NMEC)是导致新生儿细菌性脑膜炎和败血症的主要原因之一。已经确定了几种毒力因子在 NMEC 中较为常见,并且这些因子在菌血症和/或脑膜炎的发展中发挥了重要作用。然而,NMEC 分离株之间的毒力因子表达存在显著差异,并且相对较少的研究评估了可变毒力因子表达对免疫细胞激活和感染结果的影响。在这里,我们研究了 NMEC 菌株依赖性 P2X 受体(P2XR)信号在新生小鼠感染中的作用。我们发现,表达α-溶血素(HlyA)的 NMEC(HlyA)在体外诱导强烈的 P2XR 依赖性巨噬细胞死亡,而 HlyA NMEC 则不会。P2XR 依赖性细胞死亡与炎症小体无关,这表明在 NMEC 感染的情况下,P2XR 与炎症小体激活之间存在解偶联。体内抑制 P2XR 与感染 HlyA NMEC 的新生小鼠死亡率增加相关,但对感染 HlyA NMEC 的新生小鼠的存活没有影响。此外,我们发现体内 P2XR 依赖性对 HlyA NMEC 的保护作用需要巨噬细胞,但不需要中性粒细胞或 NLRP3。总之,这些数据表明,HlyA NMEC 激活 P2XR,进而赋予巨噬细胞依赖的抗感染保护作用。此外,我们的研究结果表明,在研究 NMEC 免疫反应时,应考虑菌株依赖性毒力因子表达。