節肢動物專一性免疫起始反應可達到超過兩個星期之專一性病原體抵抗能力，然而從中之作用機制未明。近年來研究發現，具有高變異度之唐氏綜合症細胞黏附分子(Dscam) ，可能參與在上述反應過程之特定病原體識別機制。在本研究中發現，澳洲淡水螯蝦(Cherax quadricarinatus)在感染白點症病毒(WSSV)後，其Dscam (CqDscam)並不像典型先天免疫因子在數小時內具有立即性反應，反而在2-5天後，其mRNA和蛋白質層次才有提升現象。這第一波Dscam反應雖在大約2個星期內消退，但大約在1個月後又再次開始另一個Dscam表現波峰期。除此之外，在WSSV存活兩個月者血漿中，CqDscam對WSSV具有較高的結合親和力。為測試此種結合是否具有減緩WSSV致病性，我們進行了試管內Dscam-WSSV中和反應，研究結果顯示在感染後1~2個月存活者血漿中，病毒所誘導的CqDscam具有中和WSSV致病性的能力。此外， 在WSSV存活者血漿中，我們發現這些螯蝦的免疫作用機制，從廣泛免疫分子作用依賴性轉換為Dscam作用依賴性，顯示病毒感染後，螯蝦嘗試改變其免疫火力平衡已達到存活目標。

One of the major gaps in our understanding of arthropod specific immune priming concerns the mechanism[s] by which the observed long-term (>2 weeks) protective effects might be mediated. Hypervariable Dscam (Down syndrome cell adhesion molecule) might support arthropod innate immunity with specificity for more extended periods. We show here that, in the relatively long-lived arthropod Cherax quadricarinatus, CqDscam does not behave like a typical, immediately-acting, short-lived innate immune factor: CqDscam was not induced within hours after challenge with a lethal virus, but instead was only up-regulated after 2-5 days. This initial response faded within ~2 weeks, but another maximum was reached ~1 month later. At around 2 months after the initial challenge, the virus-induced CqDscam bound to the virus virion and acted to neutralize the virus However, although CqDscam helped crayfish to survive during persistent infection, it nevertheless failed to provide any enhanced protection against a subsequent WSSV challenge. Thus, CqDscam is capable of supporting extended anti-virus immune memory in arthropods, even though the precise mechanism remains unclear. Also, during a persistent virus infection, the balance of “immune firepower” in crayfish appears to be altered such that the general immune factors become depleted while CqDscam becomes relatively predominant.

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