Thermoregulation of Meningococcal fHbp, an Important Virulence Factor and Vaccine Antigen, Is Mediated by Anti-ribosomal Binding Site Sequences in the Open Reading Frame

During colonisation of the upper respiratory tract, bacteria are exposed to gradients of temperatures. Neisseria meningitidis is often present in the nasopharynx of healthy individuals, yet can occasionally cause severe disseminated disease. The meningococcus can evade the human complement system using a range of strategies that include recruitment of the negative complement regulator, factor H (CFH) via factor H binding protein (fHbp). We have shown previously that fHbp levels are influenced by the ambient temperature, with more fHbp produced at higher temperatures (i.e. at 37°C compared with 30°C). Here we further characterise the mechanisms underlying thermoregulation of fHbp, which occurs gradually over a physiologically relevant range of temperatures. We show that fHbp thermoregulation is not dependent on the promoters governing transcription of the bi- or mono-cistronic fHbp mRNA, or on meningococcal specific transcription factors. Instead, fHbp thermoregulation requires sequences located in the translated region of the mono-cistronic fHbp mRNA. Site-directed mutagenesis demonstrated that two anti-ribosomal binding sequences within the coding region of the fHbp transcript are involved in fHbp thermoregulation. Our results shed further light on mechanisms underlying the control of the production of this important virulence factor and vaccine antigen.

细菌在上呼吸道定植过程中，会暴露于温度梯度环境中。脑膜炎奈瑟菌（Neisseria meningitidis）常定植于健康个体的鼻咽部，但偶尔也可引发重症播散性疾病。脑膜炎球菌可通过多种策略逃逸人类补体系统，其中包括通过因子H结合蛋白（fHbp）募集补体负调控因子H（CFH）。我们先前的研究已证实，fHbp的表达水平受环境温度影响，在较高温度（如37℃）下的fHbp产量高于30℃。本研究进一步解析了fHbp温度调控的潜在机制，该调控过程在生理相关的温度范围内逐步发生。研究发现，fHbp的温度调控并不依赖于调控双顺反子或单顺反子fHbp mRNA转录的启动子，也不依赖于脑膜炎球菌特异性转录因子。相反，该调控过程需要单顺反子fHbp mRNA的翻译区序列。定点突变实验证实，fHbp转录本编码区内的两个抗核糖体结合序列参与了fHbp的温度调控。本研究结果进一步阐明了这一重要毒力因子与疫苗抗原的表达调控机制。