碩士 / 國立臺灣大學 / 獸醫學研究所 / 89 / Abstract
Diseased groupers were collected from a net-cage farm at Hsiqu Liouchiou Island, near Dunggang, Taiwan. A virus was isolated from spleen tissue of diseased grouper Epinephelus awoara (Temminck & Schlegel), characterized as an iridovirus, and named grouper iridovirus (GIV). Cytopathic effect in the rounding, granular and refractile cells was induced in grouper kidney (GK) and grouper liver (GL) cells 3 days after inoculation with the filtrate from diseased grouper spleen. The virus titer in GK and GL cells was 108 and 106 TCID50 mL-1, respectively. Ultrastructure of the virus-infected cells showed an abundance of hexagonal virus particles inside the cytoplasm. The virus particles were 160-180 nm in diameter, containing the electron-dense cores (10010 nm) and the thin electron-lucent shell. The virus was purified to homogeneity by cesium chloride gradient centrifugation. The negatively stained virus particles were 17010 nm in diameter.
For classification, we cloned the major capsid protein (MCP) gene from GIV genome. The MCP gene contained an open reading frame of 1392 bp which encoded a polypeptide of 463 amino acids with a calculated molecular mass of 50272 Da. Compared with other known iridoviruses (FV3, LCDV, CIV, WIV, CzIV, TIV and IV22), the MCP of GIV was most homologous to the MCP from FV3 (73%), than that of LCDV (42%). Analysis of total RNA from infected GK cells indicated that 1.5 kb MCP gene transcript appeared at 10 hr, and maximally produced between 16-20 hr after infection. In SDS-PAGE the purified virus particles were separated into about 18 bands. The MCP may be located at the 45-50 kDa band which contained 40% of total viral proteins.
The healthy juvenile groupers were intraperitoneally injected with 107 and 104 TCID50 mL-1 of GIV. The cumulative mortality reached 100% at 11 and 25 days post infection, respectively. Large aggregation of virus particles were found in the cytoplasm of the spleen cells of these artificially infected groupers when they were examined under transmission electron microscopy. Juvenile groupers were vaccinated with formalin-inactivated GIV. After GIV challenging, the cumulative mortality reached 47% of control fish. However, 107 TCID50 mL-1 vaccinated group all survived. Even in low dosage of 104 TCID50 mL-1, the cumulative mortality was only 3.3%. These results showed that formalin-inactivated vaccine was useful for prevention of iridovirus infection.
| Identifer | oai:union.ndltd.org:TW/089NTU00541024 |
| Date | January 2001 |
| Creators | Min-Feng Wu, 吳明峰 |
| Contributors | Ing-Cherng Guo, Chi-Yao Chang, 郭應誠, 張繼堯 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 74 |
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