Cloning and characterization of apolipoprotein A-IV (ApoA-IV) from Oreochromis niloticus involved in immune defense functions

Apolipoprotein A-IV (ApoA-IV) is a multifunctional protein that participates in a broad spectrum of biological processes, including the modulation of immune function. Nevertheless, the specific roles of ApoA-IV in the immune response to acute bacterial infections in Nile tilapia (Oreochromis niloticus) are yet to be fully elucidated. In the present study, we identified ApoA-IV from O. niloticus (On-ApoA-IV) and examined its role in bacterial infections. The open reading frame of On-ApoA-IV spanned 768 bp and encoded a sequence of 255 amino acids. Its transcriptional abundance was the highest in the intestine, and On-ApoA-IV was induced in tilapia challenged with Streptococcus agalactiae. Additionally, experimental findings indicated that On-ApoA-IV can inhibit inflammatory processes and apoptosis, thereby enhancing tilapia survival during acute bacterial infection. The current data provide a theoretical foundation for further elucidation of the mechanisms by which ApoA-IV safeguard fish against pathogens.