A Novel Trichinella spiralis Galectin Strengthens the Macrophage ADCC Killing of Larvae via Driving M1 Polarization

Galectin recognizes β-galactosides through its carbohydrate recognition domains (CRDs). This study aimed to determine the biological features of a novel <i>Trichinella spiralis</i> galectin (galactoside-binding lectin family protein, TsGLFP) and its role in driving macrophage M1 polarization and enhancing ADCC killing of larvae. TsGLFP belongs to the galectin family and has two CRDs. The complete TsGLFP cDNA sequence was cloned and then expressed in <i>Escherichia coli</i> BL21. The results of qPCR, Western blot, and indirect immunofluorescence tests (IIFTs) revealed that TsGLFP was expressed in various stages of <i>T. spiralis</i> worms and principally localized at the cuticle and around the female embryos of the nematode. rTsGLFP had the function of agglutinating mouse erythrocytes, and this agglutination activity could be inhibited by lactose. After the mouse macrophage RAW264.7 was incubated with rTsGLFP, the expression level of the M1 genes (iNOS, IL-6, and TNF-α) and NO production were obviously increased. After incubating macrophages with rTsGLFP, there was a noticeable rise in the expression levels of p-IκB-α and p-NF-κB p65. Additionally, rTsGLFP enhanced the macrophage's ability to kill newborn larvae by ADCC cytotoxicity. When the macrophages were pretreated with the specific p-NF-κB p65 inhibitor PDTC, and then stimulated with rTsGLFP, the expression levels of iNOS, NO, and p-NF-κB p65 and the macrophages' ADCC cytotoxicity were distinctly decreased. These findings indicated that rTsGLFP enhanced the macrophage ADCC killing of larvae by driving M1 polarization through activating the NF-κB pathway.