A tandem-repeat galectin-4 from Nile tilapia (Oreochromis niloticus) is involved in immune response to bacterial infection via mediating pathogen recognition and opsonization.

ABSTRACT

Galectins are the family of carbohydrate-binding proteins that participate in host-pathogen interaction. In this study, a galectin-4 homolog (OnGal-4) from Nile tilapia (Oreochromis niloticus) was characterized. The open reading frame of OnGal-4 was 1194 bp, encoding a peptide of 397 amino including two CRD regions and two carbohydrate recognition sites. OnGal-4 mRNA was expressed in all examined tissues with the highest level in spleen. After Streptococcus agalactiae (S.agalactiae) challenge, the OnGal-4 expression was up-regulated in the spleen, head kidney, brain, and monocytes/macrophages (Mo/MΦ). The in vitro experiments showed that recombinant OnGal-4 (rOnGal-4) protein could bind and agglutinate S.agalactiae and A.hydrophila. Also, rOnGal-4 could induce cytokines expressions and increased bactericidal activity of Mo/MΦ. Further in vivo analysis indicated that OnGal-4 overexpression could protect O.niloticus from S.agalactiae infection through modulating inflammation response. Our study suggested that OnGal-4 could improve immune response against bacterial infection by mediating pathogen recognition and opsonization.