Leucocyte integrins, but neither caspases nor NLR inflammasome are associated with lipopolysaccharide recognition and response in barramundi (Lates calcarifer)

Functional and expression analysis reveals the involvement of integrin αvβ3 in antiviral immunity of grass carp (Ctenopharyngodon idella)

Integrins are α-β heterodimeric cell receptors that can bind the protein components of pathogens, and play crucial roles in mammalian immune responses, but the immune functions mediated by integrins remains largely unknown in teleost fish. In this study, an integrin αvβ3 (GCαvβ3) originally assembled by αv (GCαv) and β3 (GCβ3) subunits, was identified from a teleost fish grass carp Ctenopharyngodon idella. The pairwise alignment analyses showed that the amino acid sequences of GCαv and GCβ3 shared high similarity (75.2-95.1%) and identity (58.6-90.7%) with their homologs from other vertebrates. Both GCαv and GCβ3 harbored the conserved protein domains and motifs, and were clustered in fish branch of the phylogenetic tree containing the counterparts from various vertebrates. Co-immunoprecipitation displayed that GCβ3 could interact with the grass carp reovirus (GCRV) outer capsid protein VP5. Two incubation experiments revealed that the interaction of GCRV or VP5 proteins with GCβ3 could induce the expressions of type I interferons (IFNs) including IFN2 and IFN3 in grass carp ovary cell line. The functional analysis demonstrated that GCαvβ3 served as a receptor of viral protein components to be involved in antiviral immunity as human integrin αvβ3 did. In addition, both GCαv and GCβ3 were significantly upregulated in various tissues of grass carp after GCRV infection. This study might provide fundamental basis for understanding the molecular characteristics and immune functions of GCαvβ3, and offer a new insight into the antiviral immune mechanism specific to the integrins in grass carp.

Black Soldier Fly, Hermetia illucens as an Alternative to Fishmeal Protein and Fish Oil: Impact on Growth, Immune Response, Mucosal Barrier Status, and Flesh Quality of Juvenile Barramundi, Lates calcarifer (Bloch, 1790)

Simple Summary

Fishmeal and fish oil being recognized as nutritionally balanced and preferred protein and lipid sources in aquafeeds for finfish farming. However, the limited supply, soaring prices, and depletion of wild capture fisheries have prompted the aquaculture industry to look for widely available and less expensive alternatives for fishmeal and fish oil to ensure the sustainability of aquaculture production. As an alternative to fishmeal protein and oil, black soldier fly (BSF) larvae is considered a promising candidate for its high protein, lipid and minerals content, as well as for its bioactive potential with anti-microbial, anti-fungal, and anti-viral functions. This study investigated the effects of partial substitution of fishmeal protein and fish oil with partially defatted BSF larvae protein and oil on growth performance, non-specific immunity, mucosal barrier status and muscle fatty acids composition in barramundi. The findings of the study confirmed that BSF could substitute 30% fishmeal and fish oil successfully without compromising the growth of barramundi. Further, partial replacement of fishmeal and fish oil with BSF diets improved bactericidal activity, immune-related cytokine expression, and mucin cells in both gut and skin which are an indication of improved immunity of barramundi.

Abstract

A feeding trial was conducted to test the effects of partial replacement of fishmeal (FM) protein and fish oil (FO) with partially defatted black soldier fly, Hermetia illucens insect protein, and oil, respectively, on growth performance, immune response, gut and skin barrier status, and flesh quality in juvenile barramundi. Four isonitrogenous and isocaloric diets used in the study were a control diet based on FM, 30% FM replaced with H. illucens protein (HiP), 30% FO replaced with H. illucens oil (HiO), and both 30% FM and 30% FO replaced with H. illucens protein and oil (HiPO). Diets were fed twice a day to satiety in triplicated groups of barramundi with an initial body weight of 1.74 ± 0.15 g per fish. At the end of the trial, growth and feed utilization indices were found insignificant (p > 0.05) between the test diets and control. A significant increase in bactericidal activity was observed in fish fed the HiP diet while serum lysozyme activity was unchanged. Stress-related heat shock proteins (HSP70 and HSP90) did not differ significantly among the test diets while immune-relevant genes (IL-1β and IL-10) were significantly upregulated in HiP and HiOP groups. The number of mucin cells were increased in the gut and skin of HiP and HiOP fed fish when compared to the control diet. The total fatty acid compositions (∑SFA, ∑MUFA, ∑PUFA, ∑n-3, and ∑n-6) in the muscles of barramundi were not significantly influenced with H. illucens protein and oil diets when compared to the control.

Impact of varied combinatorial mixture of non-fishmeal ingredients on growth, metabolism, immunity and gut microbiota of Lates calcarifer (Bloch, 1790) fry

The search for suitable fish meal replacements in aqua-diets is a salient agenda in the constant effort of making aquaculture practices more sustainable. In this study, we tested four customised diets composed by systematic inclusion of pre-selected fish meal substitutes, lupin kernel meal, BSF meal, TH and PBM on growth, metabolism, cytokine profile, gut morphology and microbiota of juvenile Lates calcarifer. Five isoproteic and isoenergetic diets were prepared viz. FM100 as a control (without fish meal substitute), while FM75, FM50, FM25 and FM0 indicates replacement of fish meal (FM) at 25%, 50%, 75%, and 100%, respectively by a mixture of four different pre-selected non-fish meal (NFM) ingredients. Fish fed FM100, FM75, FM50, FM25 exhibited consistent growth and haematological response, while the fish fed no fishmeal (FM0) showed significant decline in final body weight (FBW) and specific growth rate (SGR). The poor growth performance was correlated with a decrease in villous width, microvilli height and goblet cells density. A significant shift in abundance profile of Psychrobacter in the gut microbial profile of fish fed FM50 was noticed compared to fish fed FM100. The results of qRT-PCR showed up-regulated expression of innate immune responsive genes in the FM50 group. The adverse impacts on growth performance and gut health of fish fed FM0 suggest that the complete substitution of fishmeal is not advisable and the inclusion range of these alternatives should be decided for a species only after examining their effect on maximal physiological performance.

Influence of fish protein hydrolysate produced from industrial residues on antioxidant activity, cytokine expression and gut microbial communities in juvenile barramundi Lates calcarifer

The present study investigated the supplemental effects of tuna hydrolysate (TH) in poultry by-product meal (PBM) and dietary fishmeal (FM) diets on antioxidant enzymatic activities, gut microbial communities and expression of cytokine genes in the distal intestine of juvenile barramundi, Lates calcarifer. Fish were fed with fermented (FPBM + TH) as well as non-fermented PBM (PBM + TH) and FM (FMBD + TH) diets with 10% TH supplementation for 10 weeks. A basal diet prepared without TH supplementation served as control. The results showed that the activity of glutathione peroxidase was significantly higher in FPBM + TH than the control, while the malondialdehyde and catalase activities were unchanged. FPBM + TH diet significantly (P < 0.05) upregulated the pro-inflammatory cytokines including IL-1β and TNF-α while considerable downregulation (P < 0.05) was observed in the mRNA expression levels of anti-inflammatory cytokine, IL-10 in the distal intestine of fish. The 16SrRNA analysis using V3-V4 region evidenced the ability of FPBM + TH to modulate the distal intestinal gut microbiome, augmenting the richness of Firmicutes and Fusobacteriaat at phylum level and Bacillus, Lactococcus and Cetobacterium at genus level. All these results have shown that fermented PBM with TH supplementation could improve the antioxidant capacity and inflammatory responses of juvenile barramundi while influencing the microbial communities at both phylum and genera levels.