New strategy for the design, production and pre-purification of chimeric peptide with immunomodulatory activity in Salmosalar

Design and functional characterization of Salmo salar TLR5 agonist peptides derived from high mobility group B1 acidic tail

Toll-like receptor 5 (TLR5) responds to the monomeric form of flagellin and induces the MyD88-depending signaling pathway, activating proinflammatory transcription factors such as NF-κB and the consequent induction of cytokines. On the other hand, HMGB1 is a highly conserved non-histone chromosomal protein shown to interact with and activate TLR5. The present work aimed to design and characterize TLR5 agonist peptides derived from the acidic tail of Salmo salar HMGB1 based on the structural knowledge of the TLR5 surface using global molecular docking platforms. Peptide binding poses complexed on TLR5 ectodomain model from each algorithm were filtrated based on docking scoring functions and predicted theoretical binding affinity of the complex. Circular dichroism spectra were recorded for each peptide selected for synthesis. Only intrinsically disordered peptides (6W, 11W, and SsOri) were selected for experimental functional assay. The functional characterization of the peptides was performed by NF-κB activation assays, RT-qPCR gene expression assays, and Piscirickettsia salmonis challenge in SHK-1 cells. The 6W and 11W peptides increased the nuclear translation of p65 and phosphorylation. In addition, the peptides induced the expression of genes related to the TLR5 pathway activation, pro- and anti-inflammatory response, and differentiation and activation of T lymphocytes towards phenotypes such as TH1, TH17, and TH2. Finally, it was shown that the 11W peptide protects immune cells against infection with P. salmonis bacteria. Overall, the results indicate the usefulness of novel peptides as potential immunostimulants in salmonids.

Immunomodulatory role of vasoactive intestinal peptide and ghrelin in Oncorhynchus mykiss

Neuropeptides are a group of peptides derived from precursor proteins synthesized in neuronal and nonneuronal cells. The classical functions of neuropeptides have been extensively studied in mammals, including neuromodulation in the central nervous system, molecular signaling in the peripheral nervous system, and immunomodulation associated mainly with anti-inflammatory activity. In contrast, in teleosts, studies of the immunomodulatory function of these neuropeptides are limited. In Oncorhynchus mykiss, vasoactive intestinal peptide (VIP) mRNA sequences have not been cloned, and the role of VIP in modulating the immune system has not been studied. Furthermore, in relation to other neuropeptides with possible immunomodulatory function, such as ghrelin, there are also few studies. Therefore, in this work, we performed molecular cloning, identification, and phylogenetic analysis of three VIP precursor sequences (prepro-VIP1, VIP2 and VIP3) in rainbow trout. In addition, the immunomodulatory function of both neuropeptides was evaluated in an in vitro model using the VIP1 sequence identified in this work and a ghrelin sequence already studied in O. mykiss. The results suggest that the prepro-VIP2 sequence has the lowest percentage of identity with respect to the other homologous sequences and is more closely related to mammalian orthologous sequences. VIP1 induces significant expression of both pro-inflammatory (IFN-γ, IL-1β) and anti-inflammatory (IL-10 and TGF-β) cytokines, whereas ghrelin only induces significant expression of proinflammatory cytokines such as IL-6 and TNF-α.

Chitosan Microparticles Enhance the Intestinal Release and Immune Response of an Immune Stimulant Peptide in Oncorhynchus mykiss

The aquaculture industry is constantly increasing its fish production to provide enough products to maintain fish consumption worldwide. However, the increased production generates susceptibility to infectious diseases that cause losses of millions of dollars to the industry. Conventional treatments are based on antibiotics and antivirals to reduce the incidence of pathogens, but they have disadvantages, such as antibiotic resistance generation, antibiotic residues in fish, and environmental damage. Instead, functional foods with active compounds, especially antimicrobial peptides that allow the generation of prophylaxis against infections, provide an interesting alternative, but protection against gastric degradation is challenging. In this study, we evaluated a new immunomodulatory recombinant peptide, CATH-FLA, which is encapsulated in chitosan microparticles to avoid gastric degradation. The microparticles were prepared using a spray drying method. The peptide release from the microparticles was evaluated at gastric and intestinal pH, both in vitro and in vivo. Finally, the biological activity of the formulation was evaluated by measuring the expression of il-1β, il-8, ifn-γ, Ifn-α, and mx1 in the head kidney and intestinal tissues of rainbow trout (Oncorhynchus mykiss). The results showed that the chitosan microparticles protect the CATH-FLA recombinant peptide from gastric degradation, allowing its release in the intestinal portion of rainbow trout. The microparticle-protected CATH-FLA recombinant peptide increased the expression of il-1β, il-8, ifn-γ, ifn-α, and mx1 in the head kidney and intestine and improved the antiprotease activity in rainbow trout. These results suggest that the chitosan microparticle/CATH-FLA recombinant peptide could be a potential prophylactic alternative to conventional antibiotics for the treatment of infectious diseases in aquaculture.