用於治療廣泛抗藥性鮑氏不動桿菌的候選疫苗

Abstract

細菌的多重抗藥性一直是全球性的公衛問題。根據台灣院內感染監視系統，鮑氏不動桿菌對具碳青黴烯類抗生素有抗藥性的比率，由2002年的3.4%提高到2016的72.6%。因為具碳青黴烯類抗生素是對抗這類革蘭氏陰性細菌的最後一道防線，所以發展新的治療策略來對抗多重抗藥性的鮑氏不動桿菌迫在眉梢。 莢膜多醣是鮑氏不動桿菌的一個致病因子。先前的實驗，用莢膜多醣產生的多株抗體在動物實驗可以提供55%的被動保護力。而且鮑氏不動桿菌被報導具有分歧生合成途徑，即表面的多醣的生合成可以用來修飾一些膜蛋白聚醣基化和用來生合成莢膜多醣。因此帶有莢膜多醣的膜蛋白可能可以作為自然的醣複合疫苗，來有效的活化免疫防禦系統。在本實驗當中，我們利用莢膜多糖產生的抗體作為探針，篩選出外膜蛋白38可能可以做為候選疫苗物，以及其帶有莢膜多醣的位置。結合莢膜多糖特異性抗體和質譜分析法，經抗體純化後的膜蛋白在脫去反應後利用麥可加成法加上二硫蘇糖醇後，從而在外膜蛋白38上發現六個高可能性的醣基化位置(306S, 307T, 90S, 166S, 338S, 334T)。這些發現提供了更廣的視野，來開發針對廣泛抗藥性鮑氏不動桿菌的新一類候選疫苗物。

Multidrug resistance in bacteria is always a global health problem. According to the Taiwan Nosocomial Infections Surveillance System, the ratio of carbapenem-resistant Acinetobacter baumannii increased from 3.4% in 2002 to 72.6% in 2016. Since carbapenems are the last line of antibiotics used for the treatment of gram-negative bacteria, developing new therapeutic strategies against multidrug-resistant A. baumannii is urgent. Capsular polysaccharide (CPS) is a virulence factor of A. baumannii. In our previous study, the CPS-induced antibody provided 55% protection in the animal model. A. baumannii was reported to have a bifurcated pathway for both O-glycosylation in some outer membrane proteins and capsule biosynthesis. Therefore, CPS-anchored outer membrane proteins might serve as natural glycoconjugate vaccines to effectively activate adaptive immunity. In this study, we identified Omp38 as a virulence-relevant vaccine candidate along with its CPS-anchoring position. Together with the CPS-specific antibody and mass-based strategy, the antibody-enriched glycoproteins were subjected to perform a mild -elimination followed by Michael addition of dithiothreitol (BEMAD). These thereby led to the discovery of six highly potential glycosylation sites, 306S, 307T, 90S, 166S, 338S, 334T, on Omp38. As a summary, this study has provided a better insight into the development of the new class of vaccine candidate against extensively drug-resistant (XDR) A. baumannii.