Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China.
Dev Comp Immunol. 2011 Apr;35(4):441-51. doi: 10.1016/j.dci.2010.11.011. Epub 2010 Nov 30.
Chinese soft-shelled turtle (Trionyx sinensis) is an important culture reptile. However, little is known about its acute phase response (APR) caused by bacteria. Serum amyloid A (SAA) is a major acute phase protein (APP). In this study, a turtle SAA homologue was identified and described in reptiles. The full-length cDNA of turtle SAA was 554 bp and contained a 381 bp open reading frame (ORF) coding for a protein of 127 aa. Similar to other known SAA genes, the turtle SAA gene contained three exons and two introns. The promoter region of turtle SAA gene contained the consensus binding sites for nuclear factor (NF)-κB and c-Rel. The turtle SAA amino acid sequence shared the highest identity to avian SAA sequences. Meantime, we present the first systematic study with expression levels of five genes encoding APPs in immune response caused by Aeromonas hydrophila infection. After infection, turtle SAA mRNA was induced in liver at 8h, then increased more than 1200-fold at 2d; in spleen and kidney, the SAA mRNAs were also induced during 8h-7d, but the level was far lower than that in the liver. The complement 3 (C3), fibrinogen-gamma chain (Fb-G) and cathepsin L (CathL) mRNAs were increased in liver at 2d, whereas the albumin (ALB) mRNA was significantly decreased during 8h-7d. Our studies suggest that the APR in turtle with A. hydrophila infection is similar to that in mammals, and SAA is a major indicator of bacterial infection, especially at early stage, in reptiles. Additionally, the different expression patterns of five APP genes observed in present studies could provide clues for understanding the innate immune mechanisms in the APR of reptiles.
中华鳖（Trionyx sinensis）是一种重要的养殖爬行动物。然而，人们对其由细菌引起的急性期反应（APR）知之甚少。血清淀粉样蛋白 A（SAA）是主要的急性期蛋白（APP）之一。在本研究中，鉴定并描述了一种爬行动物 SAA 同源物。中华鳖 SAA 的全长 cDNA 为 554bp，包含一个编码 127 个氨基酸的 381bp 开放阅读框（ORF）。与其他已知的 SAA 基因相似，中华鳖 SAA 基因包含三个外显子和两个内含子。中华鳖 SAA 基因启动子区域含有核因子（NF）-κB 和 c-Rel 的结合位点。中华鳖 SAA 氨基酸序列与禽类 SAA 序列具有最高的同源性。同时，我们首次系统研究了在嗜水气单胞菌感染引起的免疫反应中，五种编码 APPs 的基因的表达水平。感染后，中华鳖 SAA mRNA 在肝脏中于 8h 时被诱导，然后在 2d 时增加了 1200 多倍；在脾脏和肾脏中，SAA mRNA 也在 8h-7d 时被诱导，但水平远低于肝脏。补体 3（C3）、纤维蛋白原-γ 链（Fb-G）和组织蛋白酶 L（CathL）mRNA 在肝脏中于 2d 时增加，而白蛋白（ALB）mRNA 在 8h-7d 时显著降低。我们的研究表明，中华鳖在感染嗜水气单胞菌后的 APR 与哺乳动物相似，SAA 是细菌感染的主要标志物，尤其是在早期阶段。此外，本研究中观察到的五种 APP 基因的不同表达模式为理解爬行动物 APR 中的先天免疫机制提供了线索。
