Harnessing Posap for Superior Antibacterial Immunity in Teleost Fish

Strategic Insights -

Researchers from Yantai University have unveiled new findings on the antibacterial immunity of Serum Amyloid P Component (SAP), a multifaceted protein involved in immune responses. The study, which was financially supported by the Development Plan of Youth Innovation Team in Colleges and Universities of Shandong Province and the Yantai University Doctoral Start-up Foundation, aimed to investigate the antibacterial immunity of SAP in Japanese Flounder (Paralichthys olivaceus). The research team discovered that SAP, also known as Posap, has a unique ability to bind to bacterial species and activate the classical complement pathway, leading to enhanced antibacterial effects. The study's findings provide valuable insights into the potential applications of Posap as a novel approach to combating bacterial infections in teleost fish.

Key Takeaways:

  • Posap, a Serum Amyloid P Component, plays a crucial role in immune responses and has been found to have antibacterial properties.
  • The recombinant Posap (rPoSAP) was able to bind to eight bacterial species, agglutinate S. aureus and P. fluorescens, and exhibit bacteriostatic activity against seven bacterial species.
  • RPoSAP demonstrated the ability to bind to peripheral blood leukocytes, activate their chemotaxis, proliferation, inflammatory gene expression, phagocytosis, and reactive oxygen species production, leading to leukocytemediated antibacterial effects.
  • Neutrophils stimulated with rPoSAP were able to extrude neutrophil extracellular traps, a mechanism that contributes to antibacterial effects.
  • In vivo, Posap expression was significantly regulated by bacterial infection, and rPoSAP enhanced antibacterial effects in flounder tissues.
  • The study's findings suggest that Posap may have potential applications in developing novel strategies to combat bacterial infections in aquatic animals.

Statistics:

  • 215 amino acids comprise the amino acid sequence of Posap.
  • 55.6-76.1% overall sequence identity with other fish species was observed.
  • In vitro, rPoSAP demonstrated differential binding ability to eight bacterial species, with the ability to agglutinate S. aureus and P. fluorescens.
  • RPoSAP was found to have bacteriostatic activity against seven bacterial species and bactericidal activity against E. tarda.
  • In serum, the addition of rPoSAP or blocking endogenous PoSAP significantly regulated hemolytic and bactericidal activity.

Sources:

  • Harnessing Posap, a Serum Amyloid P Component In Japanese Flounder (Paralichthys Olivaceus) for Superior Antibacterial Immunity In Teleost Fish. Aquaculture, 2025;609.
  • Yantai University. "Harnessing Posap, a Serum Amyloid P Component In Japanese Flounder (Paralichthys Olivaceus) for Superior Antibacterial Immunity In Teleost Fish". NewsRx. October 21, 2025.