Recombinant variant of Fasciola hepatica fatty acid binding protein impairs the NF-κB activation in response to toll-like receptors agonists

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Abstract In recent years, it has been demonstrated that a strong Th2 immune response is able to suppress the inflammatory type or Th1 response; this Th1 response is linked to septic shock and some autoimmune diseases. Fasciola hepatica promotes a Th2 response during chronic infections, hence the production of anti-inflammatory cytokines. Our research group published that fatty acid binding protein (FABP) purified in native form (Fh12) from F. hepatica adult worm impairs the inflammatory cytokines storm typically induced by exposure to Lipopolysaccharides (LPS). Our work aimed to determine whether a recombinant variant of FABP could have a similar effect. We optimized the expression in E. Coli of an isoform of FABP named Fh15 and performed western blot analysis to confirm an immunological similarity between Fh12 and Fh15. Human monocytes THP1-CD14 cells were treated with Fh15, then stimulated separately with specific activation ligands for TLR 2, 4, 5 and 8 in order to determine the capacity to inhibit the NF-κB activation; we used Quanti-Blue medium to quantify the inhibition. Our results showed that both proteins are immunologically similar. Also, Fh15 was able to block the NF-κB activation induced by specific TLR ligands up to 95%, showing similar capacity as Fh12. The use of bacterial expression lead us to conclude that the glycosylation sites described for Fh12 are not required for the effect. We can anticipate that Fh15 has the potential to exhibit an inflammatory cytokines suppression effect. Fh15 impairs the NF-κB activation induced by different TLR-ligands suggesting a broad spectrum of action. We are working to elucidate the mechanisms for this effect and examine the potential of Fh12 and Fh15 as anti-inflammatory molecules in animal models.