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Calreticulin (CRT) is a multifunctional ubiquitous protein that is widely presented in all cells in eukaryotes except erythrocytes. CRT is well known for diverse cellular functions such as endoplasmic reticulum (ER)-specialized protein quality control during protein synthesis and folding, in-vivo Ca2+ homeostasis, antigen presentation, phagocytosis, wound-healing, proliferation, adhesion, and migration of cells. In the current study, we identified CRT from Hippocampus abdominalis (HaCRT) and analyzed expression profiles and functional properties. The cDNA sequence of HaCRT was identified with an open reading frame of 1226 bp. The molecular weight of HaCRT was estimated as 49 kDa. The in-silico study revealed conserved sequence arrangements such as two CRT signature motifs (5′-KHEQSIDCGGGYVKVF-3′ and 5′-LMFGPDICG-3′), triplicate repeats (5′-IKDPEAKKPEDWD-3′, 5′-IPDPDDTKPEDWD-3′, 5′-IPDPDAKKPDDWD-3′), signal peptide and an ER-targeting 5′-KDEL-3′ sequence of HaCRT. Close sequence similarity of HaCRT was observed with Hippocampus comes from phylogenetic analysis and pairwise sequence comparison. From quantitative polymerase chain reaction (qPCR) results, HaCRT was ubiquitously distributed in all tested tissues and expression levels of HaCRT were significantly modulated in blood, liver and gill tissues after stimulation with Streptococcus iniae , Edwardsiella tarda , polyinosinic:polycytidylic acid, and lipopolysaccharides. Bacterial- and pathogen-associated molecular patterns-binding activities were observed with recombinant HaCRT (rHaCRT). The treatment of murine macrophages with rHaCRT induced the expression of immune genes, such as tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), inducible nitric oxide synthase (iNOS), and interleukin-1β (IL-1β). Furthermore, rHaCRT exhibited wound-healing ability. Based on the results from the above study, we suggest that HaCRT play an indispensable role in the immunity of big-belly seahorses by recognition and elimination of pathogens as well as the tissue repairing process. • Calreticulin was identified and characterized from Big-belly seahorse (HaCRT). • Bacterial- and PAMPs-binding activity of recombinant HaCRT (rHaCRT) was identified in-vitro. • The rHaCRT was able to activate macrophages by inducing the production of cytokines and interleukins. • The rHaCRT demonstrated the detectable wound-healing ability. • HaCRT was ubiquitously expressed in all tested tissues and the expression was modulated upon immune challenge. [ABSTRACT FROM AUTHOR]

We analyzed the effects of levamisole on stress and the innate immune responses of pacu ( Piaractus mesopotamicus ). A total of 300 fish (180 ± 1.27 g) were fed a diet containing levamisole hydrochloride (LHC) for 15 days, then distributed into the following groups: T0 (control group); T1 (100), T2 (150), T3 (300) and T4 (500) mg kg −1 LHC (15 fish per group and four replicates per treatment). After this, fish (n = 8 per treatment) were exposed to air for three minutes to simulate stress conditions and were then challenged with the bacterium Aeromonas hydrophila to stimulate the immune system. Fish were sampled at 1, 3 and 24 h after bacterial inoculation to measure plasma cortisol and glucose concentrations, the leukocyte respiratory burst (LRB), hemolytic activity of the complement system (HAC 50 ) and serum lysozyme activity (SLA). LHC attenuated the increase in plasma cortisol at 1 h (500 mg kg −1 ) and 3 h (300 mg kg −1 ) after air exposure and bacterial inoculation compared to control fish. The highest glucose concentrations were observed at 1 and 3 h after stress, which then returned to initial levels after 24 h, without any effect of LHC. The LHC 100 mg kg −1 dose increased LRB 1 h after inoculation and activated the HAC 50 3 h later. At 24 h, all LHC concentrations increased the HAC 50 . SLA was reduced after inoculation, throughout the experimental period, without an effect of levamisole. Our results indicate that the oral administration of levamisole for 15 days modulated circulating cortisol levels during the stress response and improved the innate immune response against A. hydrophila infection in pacu. [ABSTRACT FROM AUTHOR]