2005 Fiscal Year Final Research Report Summary
Immunoprotection Mechanism in Flounder Streptococcosis
| Project/Area Number |
15580166
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
General fisheries
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| Research Institution | Nagasaki University |
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Principal Investigator |
KANAI Kinya Nagasaki University, Fac.Fisheries, Prof., 水産学部, 教授 (40145222)
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| Project Period (FY) |
2003 – 2005
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| Keywords | Paralichthys olivaceus / Streptococcosis / Streptococcus iniae / Immunoprotection / Macrophage / Antibody / Vaccine |
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| Research Abstract |
Japanese flounder Paralichthys olivaceus is protected from streptococcosis by immunizing with formalin-killed cells (FKC) of Streptococcus iniae, the causative agent of the disease. It is known that the serum of immunized flounder taken two days after challenging with S.iniae (immunized and challenged serum ; IC serum) has an activity that activates the defense system of flounder. The aim of this study is to identify the defense system-activating factor in the IC serum and to clarify the mechanism how to protect from S.iniae infection.
Chromatographic fractionation of IC serum revealed that agglutinative antibody fraction had no protective effect on artificial infection with S.iniae Antibody fraction separated from IC serum by affinity chromatography using mouse anti-flounder antibody monoclonal antibody as a ligand also had no protective effect against artificial infection or no effect on phagocytic activity (phagocytic index and production of reactive oxygen intermediate) of the peritoneal macrophage. These results indicate that the antibody plays no central role in immunoprotection against S.iniae infection. On the other hand, several chromatographic fractions other than antibody fraction had the protective activities, in particular, a fraction of high molecular weight (〜1,000kDa). IC serum had a macrophage-activating effect as well as opsonizing effect. Collectively, it is suggested that upon infecting with S.iniae immunized flounder produce defense system-activating factors, other than antibody, that activate the phagocytic activity of macrophage and that they protect themselves from lethal S.iniae infection.
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