Zuza Adriano Lara, Barros Heber Leão Silva, de Mattos Silva Oliveira Thelma Fátima, Chávez-Pavoni Juliana Helena, Zanon Renata Graciele
Institute of Bioscience, Federal University of Uberlandia, Para 1720, Uberlandia, Minas Gerais CEP 38400-902, Brazil.
School of Medicine, Federal University of Mato Grosso, MT 270 St., Km 06, Rondonopolis, Mato Grosso, Brazil.
Virus Res. 2016 Jun 2;217:92-100. doi: 10.1016/j.virusres.2016.03.005. Epub 2016 Mar 11.
St. Louis encephalitis virus (SLEV), a flavivirus transmitted to humans by Culex mosquitoes, causes clinical symptoms ranging from acute febrile disorder to encephalitis. To reach the central nervous system (CNS) from circulating blood, the pathogen must cross the blood-brain barrier formed by endothelial cells and astrocytes. Because astrocytes play an essential role in CNS homeostasis, in this study these cells were infected with SLEV and investigated for astrogliosis, major histocompatibility complex (MHC)-I-dependent immune response, and apoptosis by caspase-3 activation. Cultures of Vero cells were used as a positive control for the viral infection. Cytopathic effects were observed in both types of cell cultures, and the cytotoxicity levels of the two were compared. Astrocytes infected with a dilution of 1E-01 (7.7E+08 PFU/mL) had a reduced mortality rate of more than 50% compared to the Vero cells. In addition, the astrocytes responded to the flavivirus infection with increased MHC-I expression and astrogliosis, characterized by intense glial fibrillary acidic protein expression and an increase in the number and length of cytoplasmic processes. When the astrocytes were exposed to higher viral concentrations, a proportional increase in caspase-3 expression was observed, as well as nuclear membrane destruction. SLEV immunostaining revealed a perinuclear location of the virus during the replication process. Together, these results suggest that mechanisms other than SLEV infection in astrocytes must be associated with the development of the neuroinvasive form of the disease.
圣路易斯脑炎病毒（SLEV）是一种由库蚊传播给人类的黄病毒，可引起从急性发热性疾病到脑炎的一系列临床症状。病原体要从循环血液进入中枢神经系统（CNS），必须穿过由内皮细胞和星形胶质细胞形成的血脑屏障。由于星形胶质细胞在中枢神经系统稳态中起重要作用，在本研究中，这些细胞被SLEV感染，并对其进行星形胶质细胞增生、主要组织相容性复合体（MHC）-I依赖性免疫反应以及通过半胱天冬酶-3激活诱导的凋亡研究。将Vero细胞培养物用作病毒感染的阳性对照。在两种类型的细胞培养物中均观察到细胞病变效应，并比较了两者的细胞毒性水平。与Vero细胞相比，感染稀释度为1E-01（7.7E+08 PFU/mL）的星形胶质细胞死亡率降低了50%以上。此外，星形胶质细胞对黄病毒感染的反应是MHC-I表达增加和星形胶质细胞增生，其特征是胶质纤维酸性蛋白强烈表达以及细胞质突起的数量和长度增加。当星形胶质细胞暴露于更高的病毒浓度时，观察到半胱天冬酶-3表达成比例增加以及核膜破坏。SLEV免疫染色显示病毒在复制过程中位于核周。这些结果共同表明，星形胶质细胞中除SLEV感染之外的机制必定与该疾病神经侵袭形式的发展有关。
