Brucella, the bacterial agent of common zoonotic brucellosis, primarily infects specific animal species. The Brucella outer membrane proteins (Omps) are particularly attractive for developing vaccine and improving diagnostic tests and are associated with the virulence of smooth Brucella strains. Omp16 is a homologue to peptidoglycan-associated lipoproteins (Pals), and an omp16 mutant has not been generated in any Brucella strain until now. Very little is known about the functions and pathogenic mechanisms of Omp16 in Brucella. Here, we confirmed that Omp16 has a conserved Pal domain and is highly conserved in Brucella. We attempted to delete omp16 in Brucella suis vaccine strain 2 (B. suis S2) without success, which shows that Omp16 is vital for Brucella survival. We acquired a B. suis S2 Omp16 mutant via conditional complementation. Omp16 deficiency impaired Brucella outer membrane integrity and activity in vitro. Moreover, inactivation of Omp16 decreased bacterial intracellular survival in macrophage RAW 264.7 cells. B. suis S2 and its derivatives induced marked expression of IL-1β, IL-6, and TNF-a mRNA in Raw 264.7 cells. Whereas inactivation of Omp16 in Brucella enhanced IL-1β and IL-6 expression in Raw 264.7 cells. Altogether, these findings show that the Brucella Omp16 mutant was obtained via conditional complementation and confirmed that Omp16 can maintain outer membrane integrity and be involved in bacterial virulence in Brucella in vitro and in vivo. These results will be important in uncovering the pathogenic mechanisms of Brucella.

中文翻译：

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Omp16是一种与肽聚糖相关的保守脂蛋白，在体外与布鲁氏菌毒力有关。

布鲁氏菌是常见的人畜共患布鲁氏菌病的细菌，主要感染特定的动物物种。在布鲁氏菌外膜蛋白（外膜蛋白）是用于开发疫苗和改进的诊断测试特别有吸引力的，并与光滑的毒力相关的布鲁氏菌菌株。Omp16是肽聚糖相关脂蛋白（Pals）的同源物，到目前为止，在任何布鲁氏菌属菌株中均未产生omp16突变体。关于布鲁氏菌中的Omp16的功能和致病机理知之甚少。在这里，我们确认Omp16具有保守的Pal结构域，并且在布鲁切拉（Brucella）中高度保守。我们试图删除omp16在猪布鲁氏菌疫苗株2（B.猪S2）没有成功，这表明Omp16是至关重要的布鲁氏菌存活。我们通过条件互补获得了猪双歧杆菌S2 Omp16突变体。Omp16缺乏会损害布鲁氏菌体外膜的完整性和活性。此外，Omp16的失活降低了巨噬细胞RAW 264.7细胞中细菌的细胞内存活。猪双歧杆菌S2及其衍生物在Raw 264.7细胞中诱导IL-1β，IL-6和TNF-a mRNA的明显表达。布鲁氏菌中Omp16的失活增强了Raw 264.7细胞中IL-1β和IL-6的表达。总而言之，这些发现表明通过条件互补获得布鲁氏菌Omp16突变体，并证实了Omp16可以维持体外和体内布鲁氏菌的外膜完整性并参与细菌的致病性。这些结果对揭示布鲁氏菌的致病机制具有重要意义。