Zhou Hongzhuan, Lepp Dion, Pei Yanlong, Liu Mei, Yin Xianhua, Ma Rongcai, Prescott John F, Gong Joshua
Beijing Agro-Biotechnology Research Center, Beijing Academy of Agriculture and Forestry Sciences, Beijing, 100097 China.
Guelph Research and Development Centre, Agriculture and Agri-Food Canada, 93 Stone Road West, Guelph, ON N1G 5C9 Canada.
Gut Pathog. 2017 Jan 21;9:6. doi: 10.1186/s13099-016-0152-y. eCollection 2017.
Necrotic enteritis (NE) is an economically important disease of poultry caused by certain type A strains. The NetB toxin plays a critical role in the pathogenesis of NE. We previously demonstrated that is located within a 42 kb plasmid-encoded pathogenicity locus (NELoc-1), which also encodes 36 additional genes. Although NetB clearly plays a role in pathogenesis, the involvement of the other NELoc-1 genes has not yet been established. The current study was to provide experimental evidence to confirm the involvement of these genes in NE pathogenesis.
The present study has characterized a virulent strain (CP1) that has spontaneously lost the NELoc-1-encoding plasmid, pCP1netB. When assessed for cytotoxicity on Leghorn Male Hepatoma (LMH) cells, the culture supernatant of the pCP1netB-deficient CP1 variant (CP1ΔpCP1netB) demonstrated significantly reduced cytotoxicity compared to the wild-type. In addition, CP1ΔpCP1netB was unable to cause intestinal lesions in chickens in a NE disease model. When alone was introduced into CP1ΔpCP1netB, in vitro cytotoxicity was restored to the wild-type level; however, it did not completely restore virulence when used to challenge broiler chickens [mean lesion score of 0.71 compared to 3.23 in the wild type control group (n = 14)].
The results of this study suggest that other genes present in NELoc-1, in addition to , are required for full virulence in the chicken challenge model.
坏死性肠炎（NE）是由某些A型菌株引起的对家禽具有重要经济影响的疾病。NetB毒素在NE的发病机制中起关键作用。我们之前证明NetB位于一个42 kb质粒编码的致病位点（NELoc-1）内，该位点还编码另外36个基因。尽管NetB在发病机制中显然起作用，但其他NELoc-1基因的作用尚未确定。本研究旨在提供实验证据以证实这些基因参与NE的发病机制。
本研究鉴定了一种强毒株（CP1），其自发丢失了编码NELoc-1的质粒pCP1netB。当评估其对来航鸡雄性肝癌（LMH）细胞的细胞毒性时，pCP1netB缺陷型CP1变体（CP1ΔpCP1netB）的培养上清液与野生型相比，细胞毒性显著降低。此外，在NE疾病模型中，CP1ΔpCP1netB不能在鸡中引起肠道病变。当单独将NetB引入CP1ΔpCP1netB时，体外细胞毒性恢复到野生型水平；然而，用于攻击肉鸡时，它并未完全恢复毒力[平均病变评分为0.71，而野生型对照组为3.23（n = 14）]。
本研究结果表明，在鸡攻击模型中，除NetB外，NELoc-1中存在的其他基因对于完全毒力也是必需的。
