Temperature-dependent viral replication and antiviral apoptotic response in viral haemorrhagic septicaemia virus (VHSV)-infected olive flounder (Paralichthys olivaceus)

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• 作者：Satheesha Avunje^a ; Wi-Sik Kim^a ; Myung-Joo Oh^a ; Ilsu Choi^b ; Sung-Ju Jung^a ; ^{sungju@chonnam.ac.kr}
• 关键词：Viral haemorrhagic septicaemia virus (VHSV) ; Olive flounder (Paralichthys olivaceus) ; Apoptosis ; Caspase 3
• 刊名：Fish & Shellfish Immunology
• 出版年：2012
• 期刊代码：115_10504648
• 类别：abs
• 出版时间：June, 2012
• 卷：32
• 期：6
• 页码：1162-1170
• 文件大小：487 K

摘要

The olive flounder (Paralichthys olivaceus) shows a high rate of mortality to viral haemorrhagic septicaemia virus (VHSV) in the winter and spring but has zero mortality over 20聽掳C. In this experiment, we studied the effect of rearing temperature on viral replication, viral transcription and antiviral apoptotic immune response in VHSV-infected olive flounder by real-time polymerase chain reaction. Olive flounder were given intra-peritoneal injections of VHSV (10^7.8 TCID₅₀/ml) and were reared at 15聽掳C or 20聽掳C. Five fish were randomly sampled for head kidney at 3, 6 and 12聽h post-infection (hpi) and 1, 2, 4 and 7 days post-infection (dpi). Total RNA extracted from the tissue was reverse transcribed and used as template for real-time PCR. In the 15聽掳C group, the number of viral gRNA copies peaked after 2聽dpi and remained high through 7聽dpi, while in the 20聽掳C group, the copy number was at the highest at 1聽dpi but drastically declined at later stages. Viral mRNA levels in the 15聽掳C group gradually increased starting at 3聽hpi to reach their maximum value at 12聽hpi and remained high until 2聽dpi, whereas the other group showed much lower copy numbers that were undetectably low at 4 and 7聽dpi. Type II IFN expression increased as the viral copies increased and the 20聽掳C group showed quicker and stronger expression than the 15聽掳C group. The MHC class I and CD8 expression was high in both the groups at early stage of infection (3-6 hpi) but at later stages (2-7聽dpi) in 15聽掳C group expression reduced below control levels, while they expressed higher to control in 20聽掳C group. The expression of granzyme in 15聽掳C fish showed a single peak at 2聽dpi, but was consistently expressing in 20聽掳C fish. Individuals expressed very high levels of perforin expressed very high levels of caspase 3. In 15聽掳C fish, TNF伪, FasL and p53 expressed significantly higher than 20聽掳C only at initial stages of infection (3-6聽hpi). Caspase 3 expression found to be low in 15聽掳C fish whereas it was significantly elevated in 20聽掳C group. Interestingly individual fish with high caspase 3 expression contained very low viral RNA. Thus, from our experiment, we can conclude that an effective apoptotic immune response in VHSV-infected olive flounder plays a crucial role in the survival of the host at higher temperatures.