Animal Reproduction and Biotechnology Laboratory, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO, USA.
School of Veterinary Science, The University of Queensland - Gatton Campus, Gatton, QLD, Australia.
Biol Reprod. 2020 Aug 21;103(3):560-571. doi: 10.1093/biolre/ioaa088.
Bovine viral diarrhea virus continues to cost the cattle industry millions of dollars each year despite control measures. The primary reservoirs for bovine viral diarrhea virus are persistently infected animals, which are infected in utero and shed the virus throughout their lifetime. The difficulty in controlling the virus stems from a limited understanding of transplacental transmission and fetal development of immunotolerance. In this study, pregnant bovine viral diarrhea virus naïve heifers were inoculated with bovine viral diarrhea virus on day 75 of gestation and fetal spleens were collected on gestational days 82, 97, 190, and 245. Microarray analysis on splenic RNA from days 82 and 97 revealed an increase in signaling for the innate immune system and antigen presentation to T cells in day 97 persistently infected fetuses compared to controls. Reverse transcription quantitative polymerase chain reaction on select targets validated the microarray revealing a downregulation of type I interferons and lymphocyte markers in day 190 persistently infected fetuses compared to controls. Protein was visualized using western blot and tissue sections were analyzed with hematoxylin and eosin staining and immunohistochemistry. Data collected indicate that fetal immunotolerance to bovine viral diarrhea virus developed between days 97 and 190, with mass attenuation of the immune system on day 190 of gestation. Furthermore, lymphocyte transcripts were initially unchanged then downregulated, suggesting that immunotolerance to the virus stems from a blockage in lymphocyte activation and hence an inability to clear the virus. The identification of lymphocyte derived immunotolerance will aid in the development of preventative and viral control measures to implement before or during pregnancy.
尽管采取了控制措施，但牛病毒性腹泻病毒每年仍使奶牛业损失数百万美元。牛病毒性腹泻病毒的主要储存宿主是持续感染的动物，这些动物在子宫内感染，并在其一生中持续排出病毒。该病毒难以控制的原因在于对胎盘传播和胎儿免疫耐受形成的了解有限。在这项研究中，妊娠 75 天的无牛病毒性腹泻病毒感染的奶牛病毒感染病毒，并在妊娠第 82、97、190 和 245 天采集胎儿脾脏。第 82 和 97 天的脾脏 RNA 微阵列分析显示，与对照组相比，第 97 天持续感染胎儿的先天免疫系统信号和抗原呈递给 T 细胞的信号增加。对选定靶标的逆转录定量聚合酶链反应验证了微阵列的结果，显示第 190 天持续感染胎儿的 I 型干扰素和淋巴细胞标志物下调。使用 Western blot 检测蛋白质，使用苏木精和伊红染色和免疫组织化学分析组织切片。收集的数据表明，胎儿对牛病毒性腹泻病毒的免疫耐受在第 97 天至 190 天之间形成，妊娠第 190 天免疫系统大量衰减。此外，淋巴细胞转录物最初不变，随后下调，表明对病毒的免疫耐受源于淋巴细胞激活受阻，因此无法清除病毒。鉴定淋巴细胞来源的免疫耐受将有助于制定预防和病毒控制措施，以便在妊娠前或妊娠期间实施。
