The interleukin-17 (IL-17) family of cytokines is critical for host defense responses and mediates different pro- or anti-inflammatory mediators through different signaling pathways. However, the function of the related family member, IL-17B, in teleosts is poorly understood. In the present study, an IL-17B homolog (CcIL-17B) in common carp (Cyprinus carpio) was identified, and sequence analysis showed that CcIL-17B had eight conserved cysteine residues, four of which could form two pairs of disulfide bonds, which in turn formed a ring structure composed of nine amino acids (aa). The deduced aa sequences of CcIL-17B shared 35.79-92.93% identify with known homologs. The expression patterns were characterized in healthy and bacteria-infected carp. In healthy carp, IL-17B mRNA was highly expressed in the spleen, whereas Aeromonas veronii effectively induced CcIL-17B expression in the liver, head, kidney, gills, and intestine. The recombinant protein rCcIL-17B could regulate the expression levels of inflammatory cytokines (such as IL-1β, IL-6, TNF-α, and IFN-γ) in primary cultured head kidney leukocytes in vitro. As an adjuvant for the formalin-killed A. veronii (FKA) vaccine, rCcIL-17B induced the production of specific antibodies more rapidly and effectively than Freund\'s complete adjuvant (FCA). The results of the challenge experiments showed that the relative percent survival (RPS) after vaccination with rCcIL-17B was 78.13%. This percentage was significantly elevated compared to that observed in the alternative experimental groups (62.5% and 37.5%, respectively). Additionally, the bacterial loads in the spleen of the rCcIL-17B + FKA group were significantly lower than those in the control group from 12 h to 48 h after bacterial infection. Furthermore, histological analysis showed that the epithelial cells were largely intact, and the striated border structure was complete in the intestine of rCcIL-17B+FKA group. Collectively, our results demonstrate that CcIL-17B plays a crucial role in eliciting immune responses and evokes a higher RPS against A. veronii challenge compared to the traditional adjuvant FCA, indicating that rCcIL-17B is a promising vaccine adjuvant for controlling A. veronii infection.

Common carp (Cyprinus carpio) is one of the most consumed fish in the world and can be exposed to various forms of pollution, such as potential toxic elements (PTEs). Several studies have been conducted on the concentration of PTEs in common carp fish. The aims of the current study were to meta-analyze the concentration of PTEs in common carp fish and estimate human health risks in consumers. A search was conducted in international databases, including Scopus, PubMed, Science Direct, Web of Science, and Embase to retrieve papers up to January 20, 2024. The non-carcinogenic risk due to PTEs in fish fillets was calculated via the target hazard quotient (THQ), and the carcinogenic risk due to iAs in fish fillets was calculated via cancer risk (CR). The highest concentrations of Cu, methyl-Hg, and Ni were observed in the fillets of common carp fish. The non-carcinogenic risk was lower than 1 in all countries; hence, consuming common carp fish does not pose a non-carcinogenic risk. Adult consumers in Iraq were exposed to an unacceptable carcinogenic due to iAs in common carp fish. Hence, it is recommended that plans be conducted to reduce the concentration of PTEs in common carp fish in Iraq.

This study aimed to assess the toxicity effects of chlorpyrifos and imidacloprid, alone and in combination, on oxidative biomarkers and blood biochemistry of Cyprinus carpio. A total of 324 common carp (Cyprinus carpio) were distributed among 27 tanks and exposed to concentrations of 0.0, 100, and 200 μg L-1 of chlorpyrifos and 0.0, 10.0, and 20.0 μg L-1 of imidacloprid for 28 days. Changes in enzyme activities in the plasma of fish exposed to chlorpyrifos depended on the dose. In contrast, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), lactate dehydrogenase (LDH), creatine phosphokinase (CPK), gamma-glutamyl transferase (GGT) activities were significantly increased in fish exposed to imidacloprid, alone and in combination with chlorpyrifos. However, the activity of butyrylcholinesterase (BChE) was significantly decreased. Exposure to imidacloprid and chlorpyrifos, alone and in combination, increased glucose, urea, cholesterol, triglycerides, and creatinine levels, whereas total protein and albumin levels were significantly decreased. The activity of superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and catalase (CAT) was significantly increased, while glutathione reductase (GR) was significantly decreased. Additionally, although the total antioxidant capacity (TAN) was significantly decreased, malondialdehyde (MDA) levels increased after exposure to imidacloprid and chlorpyrifos, alone and in combination. In conclusion, exposure to imidacloprid and chlorpyrifos, alone and in combination, induced oxidative stress and altered blood biochemistry in carp fish. Moreover, imidacloprid and chlorpyrifos had synergistic effects on some oxidative and biochemical biomarkers.

Prostaglandin-endoperoxide synthase 2 (PTGS2), a common biological macromolecule, is pivotal for innate immunity and pathogen recognition. In this study, we identified and characterized a CcPTGS2a-like gene in the common carp (Cyprinus carpio) with an open reading frame (ORF) of 1821 bp and epidermal growth factor and peroxidase domains. Our multiple sequence analysis revealed high homology between the amino acid sequence of CcPTGS2a-like and those of its homologs in other fish. CcPTGS2a-like mRNA and protein expressions were significantly upregulated in the spleen, head kidney, liver, and gill tissues upon exposure to Aeromonas hydrophila stimulation. CcPTGS2a-like protein recognized the conserved bacterial surface components and exhibited detectable bacterial binding activity. CcPTGS2a-like overexpression before exposure to A. hydrophila notably enhanced the survival rate of common carp, concomitant with decreased bacterial burden. The NF-κB/ERK signaling pathway initiated the immune response in common carp upon infection with A. hydrophila. CcPTGS2a-like overexpression or interference in the head kidney and Epithelioma papulosum cyprinid cells could modulate the p-NF-κB (p-p-65), p-IκBα, and p-ERK1/2 levels as well as the IL-1β and IL-6 mRNA expression. These results indicated potential CcPTGS2a-like involvement in the immune response of the common carp to bacterial infections through the NF-κB/ERK signaling pathway.

The immune system of bony fish closely resembles that of mammals, comprising both specific (adaptive) and non-specific (innate) components. Notably, the mucosa-associated lymphoid tissue (MALT) serves as the first line of defense within the non-specific immune system, playing a critical role in protecting these aquatic organisms against invading pathogens. MALT encompasses a network of immune cells strategically distributed throughout the gills and intestines, forming an integral part of the mucosal barrier that interfaces directly with the surrounding aquatic environment. Spring Viremia of Carp Virus（SVCV）, a highly pathogenic agent causing substantial harm to common carp populations, has been designated as a Class 2 animal disease by the Ministry of Agriculture and Rural Affairs of China. Utilizing a comprehensive array of research techniques, including Hematoxylin and Eosin (HE)、Alcian Blue Periodic Acid-Schiff (AB-PAS)、transcriptome analysis for global gene expression profiling and Reverse Transcription-Polymerase Chain Reaction (RT-qPCR), this study uncovered several key findings: SVCV is capable of compromising the mucosal architecture in the gill and intestinal tissues of carp, and stimulate the proliferation of mucous cells both in gill and intestinal tissues. Critically, the study revealed that SVCV\'s invasion elicits a robust response from the carp\'s mucosal immune system, demonstrating the organism\'s capacity to resist SVCV invasion despite the challenges posed by the pathogen.

Sequestosome 1 (SQSTM1/p62) is a selective autophagy adapter protein that participates in antiviral and bacterial immune responses and plays an important regulatory role in clearing the proteins to be degraded and maintaining intracellular protein homeostasis. In this study, two p62 genes were cloned from common carp (Cyprinus carpio), namely Ccp62-1 and Ccp62-2, and conducted bioinformatics analysis on them. The results showed that Ccp62s had the same structural domain (Phox and Bem1 domain, ZZ-type zinc finger domain, and ubiquitin-associated domain) as p62 from other species. Ccp62s were widely expressed in various tissues of fish, and highly expressed in immune organs such as gills, spleen, head kidney, etc. Subcellular localization study showed that they were mainly distributed in punctate aggregates in the cytoplasm. After stimulation with Aeromonas hydrophila and spring viraemia of carp virus (SVCV), the expression level of Ccp62s was generally up-regulated. Overexpression of Ccp62s in EPC cells could inhibit SVCV replication. Upon A. hydrophila challenge, the bacterial load in Ccp62s-overexpressing group was significantly reduced, the expression levels of pro-inflammatory cytokines and interferon factors were increased, and the survival rate of the fish was improved. These results indicated that Ccp62s were involved in the immune response of common carp to bacterial and viral infections.

This study investigates the impact of including sorghum in the diet of the common carp (Cyprinus carpio) on its growth, blood parameters, meat composition, intestinal microbiota, and oxidative stress. Experimental diets with varying sorghum content (0%-V0 or control, 10%-V1, 20%-V2, and 30%-V3) were administered to carp weighing 43 g initially. Notably, in the 30% variant, sorghum entirely replaced corn and barley in the diet. Chemical analysis of sorghum unveiled a protein content of 14% and a fat content of 3.9%. Sorghum inclusion led to a decline in final body weight and weight gain, particularly notable in the V3 group with 30% sorghum. However, other physiological parameters, such as feed conversion ratio, specific growth rate, and organ indices, remained unaffected. Protein and salt content in carp flesh increased with higher sorghum inclusion levels, while hematological parameters showed minimal variations. Analysis of the intestinal microbiota revealed increases in both aerobic and anaerobic bacterial populations with sorghum inclusion. Furthermore, sorghum concentration inversely correlated with glutathione levels and positively correlated with malondialdehyde content, indicating a disruption of antioxidant defense mechanisms and elevated oxidative stress.

Ohmic heating (OH) at different conditions (voltage: 15, 20, 25 V; frequency: 1, 5, 10 kHz) and one-step water bath (WB) were used to heat wash and unwash surimi prepared from fresh pre-rigor common carp. The optimal heating conditions were established through assessments of gel strength, Texture Profile Analysis (TPA), water-holding capacity (WHC), whiteness, and sensory evaluation. Then, the impact of heating modes on gelation properties of unwashed surimi based on the optimal heating conditions was investigated. The study findings indicated a significant enhancement in gel properties compared to WB. Unwashed surimi gel properties showed improvement when derived from freshly caught raw fish and subjected to OH treatment. Moreover, variations in frequencies and voltages were observed to influence the heating rate. Optimal gel quality was achieved at 10 kHz 20 V (10 V/cm), facilitating swift progression through the gel deterioration stage, inhibition of protein hydrolyzing enzymes activity, and establishment of a stable gel network. Continuing to increase the heating rate would disrupt its network structure, resulting in diminished gel strength and WHC. The best quality of unwashed surimi gel was achieved by heating to 40°C for 30 min, followed by heating to 90°C for another 30 min (40°C 30 min + 90°C 30 min) under 10 kHz 20 V. The gel strength increased when held for 1 h at 40°C. For optimal heating efficiency, the heating mode of 40°C 30 min + 90°C 30 min is recommended to prepare unwashed surimi gel. PRACTICAL APPLICATION: Ohmic heating, as a rapid food heat treatment method, can both increase the heating rate and improve the gelation properties of freshwater surimi. There is a wide range of potential applications for the heat treatment of the surimi.

Triclosan (TCS), an antimicrobial additive in various personal and health care products, has been widely detected in aquatic environment around the world. The present study investigated the impacts of TCS in the gills of the fish, Cyprinus carpio employing histopathological, biochemical, molecular docking and simulation analysis. The 96 h LC50 value of TCS in C. carpio was found to be 0.968 mg/L. Fish were exposed to 1/1000th (1 µg/L), 1/100th (10 µg/L), and 1/10th (100 µg/L) of 96 h LC50 value for a period of 28 days. The histopathological alterations observed in the gills were hypertrophy, hyperplasia, edematous swellings, and fusion of secondary lamellae in TCS exposed groups. The severity of these alterations increased with both the concentration as well as the duration of exposure. The present study revealed that the activity of antioxidant enzymes such as superoxide dismutase, catalase, glutathione-S-transferase, glutathione reductase, glutathione peroxidase, and reduced glutathione content decreased significantly (p < 0.05) in both concentration and duration dependent manner. However, a significant (p < 0.05) increase in the activity of the metabolic enzymes such as acid phosphatase and alkaline phosphatase was observed in all three exposure concentrations of TCS from 7 to 28 days. The activity of acetylcholinesterase declined significantly (p < 0.05) from 7 to 28 days whereas the content of acetylcholine increased significantly at the end of 28 day. The experimental results were further confirmed by molecular docking and simulation analysis that showed strong binding of TCS with acetylcholinesterase enzyme. The study revealed that long-term exposure to sublethal concentrations of TCS can lead to severe physiological and histopathological alterations in the fish.

A feeding trial spanning two months was conducted to evaluate the effects of Chlamydomonas sp. on growth performance, water quality, survival, proximate composition and biochemical profile of common carp (Cyprinus carpio) where fishmeal was partially replaced using Chlamydomonas sp. in the diet. Twenty uniform-sized common carp fries were distributed into triplicate groups and placed in 40-liter rectangular glass tanks. Chlamydomonas sp. was added at different levels in the diet: 0 % (control), 5 % (C5), 10 % (C10), 15 % (C15) along with the commercial feed (CMF). After the experiment, random sampling of fish was performed to conduct all the analyses. Significant variations (p < 0.05) were found in the chemical water quality parameters. The highest survival rate was recorded from C15 (81.67 %) followed by C10 (71.67 %), CMF (63.33 %) and C5 (58.33 %) respectively compared with the control (43.2 %). There were significant differences (p < 0.05) observed among all the treatments in terms of Average Daily Gains (ADG), Specific Growth Rate (SGR) and length increments. Protein content ranged the highest and the lowest in C15 (35.6 %) and control (24.8 %) respectively. The C15 group showed the highest lipid content (15.7 %) and the control group showed the lowest lipid (8.4 %). The inclusion of Chlamydomonas sp. in the diet had a significant positive impact on the fatty acid and amino acid profile of whole common carp. Present data revealed that substituting a portion of fishmeal with Chlamydomonas sp. powder could provide higher growth performance, offering both nutritional benefits and higher survival rate in common carp (Cyprinus carpio).