【摘要】 多杀性巴氏杆菌（Pasteurella multocida,Pm）是一种重要的人畜共患致病菌，其中牛源A型Pm（PmA）主要引起牛肺炎等呼吸系统疾病，给我国养牛业造成了重大的经济损失。目前，临床上缺乏针对PmA的有效疫苗。本研究利用同源重组的方法，成功构建了基因缺失菌株PmCQ6△007170。通过与野生菌株PmCQ6（天然弱毒株）比较，PmCQ6△007170的生长速度及生物膜含量显著增加，而荚膜含量及血清敏感性显著下调；此外，PmCQ6△007170在小鼠组织（肺脏、肝脏和脾脏）中的定殖量及肺组织炎性损伤显著性降低，毒力显著性下调(PmCQ6△007170:LD₅₀=2.29×10¹¹ CFU);PmCQ6△007170制备的弱毒疫苗，对感染PmA（PmCQ2:强毒株）、PmB和PmF的小鼠分别有100%、70%和50%的保护效力。本研究为研制具有交叉免疫保护作用的PmA弱毒疫苗提供了重要的试验依据。更多还原

【Abstract】 Pasteurella multocida（Pm） is an important zoonotic pathogen,among them,bovine type A Pm（PmA） mainly causes respiratory diseases such as bovine pneumonia and leads to significant economic losses to the cattle industry in China.Currently,there are few effective vaccines against PmA in clinical practice.Hence,this study describes the successful construction of a gene deletion strain,PmCQ6△007170,via homologous recombination.Compared with the wild strain PmCQ6（a naturally attenuated strain）,the growth rate and biofilm content of PmCQ6△007170significantly increased,while the capsule content and serum sensitivity were significantly reduced.Moreover,the virulence of PmCQ6△007170 was significantly downregulated(PmCQ6△007170:LD50=2.29×10¹¹ CFU),as evidenced by markedly reduction of bacterial loads as well as inflammatory factors in murine tissues,including lungs,liver,and spleen.Significantly,the attenuated vaccine derived from PmCQ6△007170 provided 100 %,70% and 50% protective efficacy against PmA（PmCQ2:virulent strain）,PmB and PmF infections in mice,respectively.These findings provide a critical theoretical basis for the development of a PmA attenuated vaccine possessing crossimmune protection.更多还原