In the present study, two C-type lectins (designated as VpClec-3 and VpClec-4) were identified and characterized from the manila clam Venerupis philippinarum. Multiple alignment and phylogenetic relationship analysis strongly suggested that VpClec-3 and VpClec-4 belong to the C-type lectin family. In nonstimulated clams, the VpClec-3 transcript was dominantly expressed in the hepatopancreas, while the VpClec-4 transcript was mainly expressed in gill tissues. Both VpClec-3 and VpClec-4 mRNA expression was significantly upregulated following Vibrio anguillarum challenge. Recombinant VpClec-4 (rVpClec-4) was shown to bind lipopolysaccharide (LPS) and glucan in vitro, whereas recombinant VpClec-3 (rVpClec-3) only bound to glucan. In addition, rVpClec-3 and rVpClec-4 displayed broad agglutination activities towards Vibrio harveyi, Vibrio splendidus and V. anguillarum, while no agglutination activities towards Enterobacter cloacae or Aeromonas hydrophila were observed in rVpClec-3. Moreover, hemocyte phagocytosis was significantly enhanced by rVpClec-3 and rVpClec-4. All the results showed that VpClecs function as pattern recognition receptors (PRRs) with distinct recognition spectra and are potentially involved in the innate immune responses of V. philippinarum.

在本研究中，从菲律宾马尼拉蛤仔中鉴定出两种C型凝集素（分别称为VpClec-3和VpClec-4）。多重比对和系统发育关系分析强烈表明，VpClec-3和VpClec-4属于C型凝集素家族。在未经刺激的蛤中，VpClec-3转录本主要在肝胰腺中表达，而VpClec-4转录本主要在g组织中表达。鳗弧菌攻击后，VpClec-3和VpClec-4 mRNA表达均显着上调。重组VpClec-4（rVpClec-4）已显示在体外结合脂多糖（LPS）和葡聚糖，而重组VpClec-3（rVpClec-3）仅与葡聚糖结合。此外，rVpClec-3和rVpClec-4对哈维弧菌，锦绣弧菌和鳗弧菌显示出广泛的凝集活性，而在rVpClec-3中未观察到对阴沟肠杆菌或嗜水气单胞菌的凝集活性。此外，rVpClec-3和rVpClec-4显着增强了血细胞吞噬作用。所有结果表明，VpClecs用作模式识别受体（PRR），具有不同的识别光谱，并可能参与菲律宾飞蛾的先天免疫应答。