AUTHOR=Niu Jinzhong , Huang Yu , Liu Xinchao , Wu Fenglei , Tang Jufen , Wang Bei , Lu Yishan , Cai Jia , Jian Jichang 

TITLE=Fish Galectin8-Like Exerts Positive Regulation on Immune Response Against Bacterial Infection

JOURNAL=Frontiers in Immunology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2020.01140

DOI=10.3389/fimmu.2020.01140

ISSN=1664-3224

ABSTRACT=<p>Galectin-8 is a member of the galectin family that is involved in immune response against pathogens. However, the roles of fish galectin-8 during pathogen infection require comprehensive studies. In this study, a galectin-8 homolog (OnGal8-like, OnGal8-L) was characterized from Nile tilapia (<italic>Oreochromis niloticus</italic>), and its roles in response to bacterial infection were analyzed. The <italic>OnGal8-L</italic> contains an open reading frame of 891 bp, encoding a peptide of 296 amino acids with two CRD regions of tandem-repeat galectin and two carbohydrate recognition sites. The <italic>OnGal8-L</italic> protein shares 46.42% identities with reported <italic>Oreochromis niloticus</italic> galectin-8 protein. Transcriptional expression analysis revealed that OnGal8-L was constitutively expressed in all examined tissues and was highly expressed in spleen. The transcript levels of OnGal8-L were up-regulated in the spleen, head kidney, and brain, following <italic>Streptococcus agalactiae</italic> (<italic>S. agalactiae</italic>) challenge. Further <italic>in vitro</italic> analysis indicated that the recombinant protein of OnGal8-L (rOnGal8L) could agglutinate erythrocyte, <italic>S. agalactiae</italic>, and <italic>A. hydrophila</italic> and bind <italic>S. agalactiae, A. hydrophila</italic>, and various PAMPs (lipopolysaccharides, lipoteichoic acid, poly I:C, peptidoglycan, galactose, mannose, and maltose). Also, rOnGal8L could regulate inflammatory-related gene expression, phagocytosis, and a respiratory burst of monocytes/macrophages. Moreover, <italic>in vivo</italic> analysis showed that OnGal8-L overexpression could protect <italic>O. niloticus</italic> from <italic>S. agalactiae</italic> infection through modulating serum antibacterial activity (AKP, ACP, and LZM), antioxidant capacity (CAT, POD, and SOD), and monocyte/macrophage proliferation and cytokine expression, as well as reducing bacterial burden and decreasing tissue damage. Our results collectively indicate that OnGal8-L plays important regulatory roles in immune response against bacterial infection.</p>