Li Meixia, Liu Bo, Gu Changqin, Zhang Wanpo, Yang Jun, Cheng Guofu, Liu Cuiping, Hu Xueying
College of Veterinary Medicine, Huazhong Agricultural University, Wuhan 430070, China.
Avian Dis. 2017 Mar;61(1):115-122. doi: 10.1637/11449-061216-Reg.
A previous study demonstrated that a highly virulent strain of Streptococcus gallolyticus subsp. pasteurianus, designated as the AL101002 strain, induced high mortality in ducklings with splenic lesions. In this study, 42 ducklings were subcutaneously inoculated with the AL101002 strain to study changes in splenic lesions over time. The spleens from these ducklings were significantly enlarged by congestion and edema, and/or showed multiple marbled areas 14 days postinoculation (dpi). The AL101002 strain was reisolated from the spleens and blood and confirmed by immunohistochemistry (IHC) with the use of anti-AL101002 antibody. Histopathologically, the main lesion was macrophage necrosis in the spleens from 1 to 7 dpi. Terminal dUTP nick-end labeling assay, transmission electron microscopy, and IHC by anti-macrosialin antibody (CD68) demonstrated that macrophage necrosis was necroptosis, which was further confirmed by quantitative (real-time) reverse-transcriptase PCR analysis. Two major factors of apoptosis, caspase 3 and caspase 8, did not significantly change during the AL101002 infection, suggesting that apoptosis signals were not activated. However, the key factor mixed lineage kinase like was increased significantly (P < 0.05) from Day 1 to Day 14 dpi. Inflammatory cytokine interleukin-1β and interleukin-6 had significantly (P < 0.01) upregulated expression in the spleens on Day 1 dpi. Tumor necrosis factor α was downregulated from Day 1 to Day 5 dpi, but increased from Day 7 to Day 14. Our results demonstrated that AL101002 strain mainly infects macrophages and resulted in macrophage necroptosis and suggested that macrophage necroptosis in spleens is involved in the pathogenesis of S. gallolyticus subsp. pasteurianus infection in ducklings.
先前的一项研究表明，一种高毒力的解没食子酸链球菌巴氏亚种菌株，命名为AL101002菌株，可在脾脏出现病变的雏鸭中引起高死亡率。在本研究中，42只雏鸭经皮下接种AL101002菌株，以研究脾脏病变随时间的变化。接种后14天（dpi），这些雏鸭的脾脏因充血和水肿而显著肿大，和/或出现多个大理石样区域。从脾脏和血液中重新分离出AL101002菌株，并使用抗AL101002抗体通过免疫组织化学（IHC）进行确认。组织病理学上，接种后1至7天，脾脏的主要病变是巨噬细胞坏死。末端脱氧核苷酸转移酶介导的缺口末端标记法、透射电子显微镜以及抗巨噬细胞唾液酸蛋白抗体（CD68）免疫组织化学表明，巨噬细胞坏死是坏死性凋亡，定量（实时）逆转录酶PCR分析进一步证实了这一点。凋亡的两个主要因子，半胱天冬酶3和半胱天冬酶8，在AL101002感染期间没有显著变化，这表明凋亡信号未被激活。然而，关键因子混合谱系激酶样蛋白从第1天到第14天显著增加（P<0.05）。炎性细胞因子白细胞介素-1β和白细胞介素-6在接种后第1天脾脏中的表达显著上调（P<0.01）。肿瘤坏死因子α在第1天到第5天下调，但从第7天到第14天增加。我们的结果表明，AL101002菌株主要感染巨噬细胞并导致巨噬细胞坏死性凋亡，提示脾脏中的巨噬细胞坏死性凋亡参与了解没食子酸链球菌巴氏亚种感染雏鸭的发病机制。
