Fish-egg lectins (FELs) have been identified in several teleost species and have been proved to play important roles in innate immune system against pathogen infection. In this study a novel fish-egg lectin (OppFEL) was identified from spotted knifejaw (Oplegnathus punctatus), and the expression patterns against bacterial infection was characterized. The amino acid sequence is highly homologous to other teleost FELs, containing five repeats of the conserved TECPR domain. Expression of OppFEL was widely observed in examined tissues, with the most abundant transcripts observed in gill, showing a pattern of tissue specific expression. The OppFEL expression was significantly up-regulated following a Gram-negative bacterium (Vibrio anguillarum) challenge in vivo, suggesting participation in host antibacterial immune responses. Recombinant OppFEL protein (rOppFEL) possessed calcium dependent binding capacities and agglutination to four Gram-negative bacterium and two Gram-positive bacterium. Sugar binding assay revealed that rOppFEL specifically bound to insoluble lipopolysaccharide and peptidoglycan. In addition, rOppFEL was also proved to have hemagglutinating activity against erythrocytes from Mus musculus, O. punctatus, Sebastes schlegelii and Paralichthys olivaceus. Dual-luciferase analysis showed that overexpression of OppFEL could suppress the activity of NF-κB in a dose dependent manner. Taken together, these results suggest that OppFEL is a unique fish-egg lectin that possesses apparent immunomodulating property and is involved in host defense against pathogens invasion.

鱼卵凝集素 (FELs) 已在几种硬骨鱼物种中得到鉴定，并已被证明在先天免疫系统对抗病原体感染中发挥重要作用。在这项研究中，从斑点刀颚 ( Oplegnathus punctatus ) 中鉴定出一种新型鱼卵凝集素 ( Opp FEL )，并表征了抗细菌感染的表达模式。氨基酸序列与其他硬骨鱼 FEL 高度同源，包含五个重复的保守 TECPR 结构域。在检查的组织中广泛观察到Opp FEL 的表达，在鳃中观察到最丰富的转录物，显示出组织特异性表达的模式。所述奥普FEL表达显著上调下列一种革兰氏阴性细菌（Vibrio anguillarum )体内挑战，表明参与宿主抗菌免疫反应。重组Opp FEL 蛋白 (r Opp FEL) 具有钙依赖性结合能力和对四种革兰氏阴性细菌和两种革兰氏阳性细菌的凝集能力。糖结合测定表明 r Opp FEL 与不溶性脂多糖和肽聚糖特异性结合。此外，r Opp FEL 还被证明对来自Mus musculus、O. punctatus、Sebastes schlegelii和Paralichthys olivaceus 的红细胞具有血凝活性. 双荧光素酶分析表明，Opp FEL 的过表达可以以剂量依赖性方式抑制 NF-κB 的活性。总之，这些结果表明Opp FEL 是一种独特的鱼卵凝集素，具有明显的免疫调节特性，并参与宿主防御病原体入侵。