Genomic Bioinformatics Laboratory, Department of Molecular Biology, Ariel University, Ariel, Israel; Adelson School of Medicine, Ariel University, Israel.
Department of Bacteriology, Kimron Veterinary Institute, Bet Dagan, Israel.
Int J Med Microbiol. 2020 Jan;310(1):151363. doi: 10.1016/j.ijmm.2019.151363. Epub 2019 Oct 21.
Brucella melitensis Rev.1 is the live attenuated Elberg-originated vaccine strain of the facultative intracellular Brucella species, and is widely used to control brucellosis in small ruminants. However, Rev.1 may cause abortions in small ruminants that have been vaccinated during the last trimester of gestation, it is pathogenic to humans, and it induces antibodies directed at the O-polysaccharide (O-PS) of the smooth lipopolysaccharide, thus making it difficult to distinguish between vaccinated and infected animals. Rough Brucella strains, which lack O-PS and are considered less pathogenic, have been introduced to address these drawbacks; however, as Rev.1 confers a much better immunity than the rough mutants, it is still considered the reference vaccine for the prophylaxis of brucellosis in small ruminants. Therefore, developing an improved vaccine strain, which lacks the Rev.1 drawbacks, is a highly evaluated task, which requires a better understanding of the molecular mechanisms underlying the virulence attenuation of Rev.1 smooth strains and of natural Rev.1 rough strains, which are currently only partly understood. As the acidification of the Brucella-containing vacuole during the initial stages of infection is crucial for their survival, identifying the genes that contribute to their survival in an acidic environment versus a normal environment will greatly assist our understanding of the molecular pathogenic mechanisms and the attenuated virulence of the Rev.1 strain. Here, we compared the transcriptomes of the smooth and natural rough Rev.1 strains, each grown under either normal or acidic conditions. We found 12 key genes that are significantly downregulated in the Rev.1 rough strains under normal pH, as compared with Rev.1 smooth strains, and six highly important genes that are significantly upregulated in the smooth strains under acidic conditions, as compared with Rev.1 rough strains. All 18 differentially expressed genes are associated with bacterial virulence and survival and may explain the attenuated virulence of the rough Rev.1 strains versus smooth Rev.1 strains, thus providing new insights into the virulence attenuation mechanisms of Brucella. These highly important candidate genes may facilitate the design of new and improved brucellosis vaccines.
布氏杆菌 melitensis Rev.1 是一种减毒活疫苗株，源自于 Elberg 的兼性细胞内布鲁氏菌属，广泛用于控制小反刍动物的布鲁氏菌病。然而，Rev.1 可能会导致在妊娠最后三个月接种疫苗的小反刍动物流产，对人类也具有致病性，并且它会诱导针对光滑脂多糖的 O-多糖（O-PS）的抗体，从而使人们难以区分接种疫苗和感染的动物。缺乏 O-PS 且被认为致病性较低的粗糙布鲁氏菌菌株已被引入以解决这些缺点；然而，由于 Rev.1 比粗糙突变体提供更好的免疫力，因此它仍被认为是预防小反刍动物布鲁氏菌病的参考疫苗。因此，开发一种缺乏 Rev.1 缺点的改良疫苗株是一项高度评价的任务，这需要更好地了解 Rev.1 光滑菌株毒力减弱的分子机制以及目前仅部分了解的天然 Rev.1 粗糙菌株的分子机制。由于在感染的初始阶段布鲁氏菌包含的空泡酸化对其存活至关重要，因此确定有助于它们在酸性环境而非正常环境中存活的基因将极大地帮助我们了解分子发病机制和 Rev.1 菌株的减弱毒力。在这里，我们比较了在正常或酸性条件下生长的光滑和天然粗糙 Rev.1 菌株的转录组。我们发现，与 Rev.1 光滑菌株相比，在正常 pH 下，Rev.1 粗糙菌株中有 12 个关键基因的表达显著下调，而在酸性条件下，与 Rev.1 粗糙菌株相比，有 6 个重要基因的表达显著上调。所有 18 个差异表达基因都与细菌的毒力和存活有关，可能解释了粗糙 Rev.1 菌株相对于光滑 Rev.1 菌株的毒力减弱，从而为布鲁氏菌的毒力减弱机制提供了新的见解。这些非常重要的候选基因可能有助于设计新的和改进的布鲁氏菌病疫苗。
