碩士 / 國立臺灣大學 / 動物學研究所 / 88 / To evaluate the effect of viral infection on the cellular immune responses in the Pacific white shrimp (Litopenaeus vannamei), we intramuscularly injected shrimp with Taura syndrome virus (TSV). Hemolymph obtained from TSV-infected, mock-infected and untreated shrimps were measured for the total and differential hemocyte counts (THC and DHC). The separated hemocytes were further analyzed quantitatively for the intrahemocytic superoxide anion and the enzyme activities of transglutaminase (TGase）and phenoloxidase（PO）.
High mortality was observed in the TSV-infected shrimps. It reached up to 83.3% on the third day and 100% on the fourth day post infection. Shrimps showed a pale reddish coloration on the out-looking, lethargic and soft shell on the second day post infection. Withdrawn hemolymph showed a red coloration and coagulated poorly in some infected shrimps.
Hematological analysis showed that the THC decreased significantly (p<0.001) from 1.6~2.2´107 cells/ml in the untreated or mock-infected shrimps to 0.3´107 cells/ml in TSV-infected shrimps. In other words a 79 to 84% decrease. Although there is no difference observed in the ratios of differential hemocytes among the untreated, mock-infected and TSV-infected shrimps, the hyalinocytes decreased from 1.3~1.9 to 0.3´107 cells/ml (a 76 to 84% decrease) and granulocytes decreased from 0.13~0.31 to 0.022´107 cells/ml (a 83 to 93% decrease). These indicates an almost completely breakdown of hemocytes in an acute phase infection. The TGase activity in hemocyte lysate was found to decrease significantly from 21~32 to 12 units/mg. It suggests that an acute infection hampered the blood coagulation dramatically.
A significant increase of intrahemocytic superoxide anion was generated in TSV-infected shrimps using a nitroblue tetrazolium staining. However, the ratio of superoxide anion generation decreased in these hemocytes further stimulated with β-glucan, which is well-known an shrimp immunostimulant . This result suggests that a viral infection did enhance the phagocytic activity of hemocytes. Nevertheless, a poor response would occur in hemocytes on a further stimulation since they had been in an exhaused state. Plasma PO activity was found to increase significantly (p<0.05) from 0.04~0.14 to 0.29 units. This suggests that intrahemocytic PO was activated by a TSV-infection and then released into plasma.
Since TSV infection hampered blood coagulation, it would benefit the virus to disseminate through the shrimp body. Invaded viral particles may induce hemolysis or decrease the proliferation activity of hematopoietic tissue.
In the other hands, the circulating hemocytes may infiltrate into and play their functions in the infected foci. Increased intrahemocytic superoxide generation and PO activity via hemocyte degranulation or cytolysis, shrimps would strengthen their disease resistant and struggle against the viral infection.
During the process of host-virus interacton some hemolymph parameters were found to vary significantly. We, therefore, suggest they might be useful in the disease diagnostics.
| Identifer | oai:union.ndltd.org:TW/088NTU00312023 |
| Date | January 2000 |
| Creators | TzuWen Lien, 連姿雯 |
| Contributors | YenLing Song, 宋延齡 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 39 |
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