Sur J H, Doster A R, Osorio F A
Department of Veterinary and Biomedical Sciences, University of Nebraska, Lincoln, USA.
Vet Pathol. 1998 Nov;35(6):506-14. doi: 10.1177/030098589803500605.
We studied apoptosis caused by porcine reproductive and respiratory syndrome virus (PRRSV) in vivo, focusing on the tissues that constitute the main targets for infection: lung and lymphoid tissues. Previous investigators have shown that the PRRSV glycoprotein p25, encoded by PRRSV open reading frame 5, induces apoptosis when expressed in COS-1 cells. Results of studies conducted in our laboratory indicate the simultaneous occurrence of PRRSV-induced alterations of spermatogenesis and apoptotic death of germinal epithelial cells in the testicle. In this study, the goal was to determine whether virus-induced apoptosis is a direct mechanism of cell death caused by PRRSV in infected pigs. Eight 3-week-old pigs were intranasally inoculated with PRRSV 16244B, a highly virulent field strain. Lung, tonsil, bronchial lymph node, spleen, and heart were assessed histologically at 4 and 7 days postinfection. To characterize PRRSV-infected cells and apoptotic cell death, we used immunohistochemical methods for detection of viral antigen, DNA electrophoresis for detection of DNA fragmentation, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-fluorescein nick end labeling method for in situ detection of DNA strand breaks, and electron microscopy for ultrastructural morphologic studies. PRRSV infection resulted in widespread apoptosis in the lungs and lymphoid tissues of infected pigs. Virus infection-induced apoptotic cells were more abundant than PRRSV-infected cells in all tissues. DNA laddering was detected in lung and lymphoid tissues. However, double-labeling experiments demonstrated that the majority of apoptotic cells did not colocalize with PRRSV-infected cells. Our findings suggest the presence of an indirect mechanism in the induction of apoptosis for PRRSV.
我们研究了猪繁殖与呼吸综合征病毒（PRRSV）在体内引起的细胞凋亡，重点关注构成主要感染靶标的组织：肺和淋巴组织。先前的研究人员表明，PRRSV开放阅读框5编码的PRRSV糖蛋白p25在COS-1细胞中表达时可诱导细胞凋亡。我们实验室进行的研究结果表明，PRRSV感染可同时导致睾丸生精过程改变和生精上皮细胞凋亡性死亡。在本研究中，目标是确定病毒诱导的细胞凋亡是否是PRRSV感染猪后导致细胞死亡的直接机制。八只3周龄仔猪经鼻接种高致病性田间毒株PRRSV 16244B。在感染后第4天和第7天对肺、扁桃体、支气管淋巴结、脾脏和心脏进行组织学评估。为了鉴定PRRSV感染的细胞和凋亡性细胞死亡，我们使用免疫组化方法检测病毒抗原，用DNA电泳检测DNA片段化，用末端脱氧核苷酸转移酶介导的脱氧尿苷三磷酸荧光素缺口末端标记法原位检测DNA链断裂，并用电子显微镜进行超微结构形态学研究。PRRSV感染导致感染猪的肺和淋巴组织广泛凋亡。在所有组织中，病毒感染诱导的凋亡细胞比PRRSV感染的细胞更为丰富。在肺和淋巴组织中检测到DNA梯状条带。然而，双重标记实验表明，大多数凋亡细胞与PRRSV感染的细胞并不共定位。我们的研究结果提示，PRRSV诱导细胞凋亡存在间接机制。
