Oral feed-based administration of phage cocktail protects rohu fish (Labeo rohita) against Aeromonas hydrophila infection.

Aeromonas hydrophila is one of the major freshwater fish pathogens. In the current study, a cocktail of D6 and CF7 phages was given orally to Labeo rohita to assess phage survival in fish organs as well as to determine the therapeutic efficacy of phage treatment against fish mortality caused by A. hydrophila. In the phage-coated feed, prepared by simple spraying method, phage counts were quite stable for up to 2 months with a decline of ≤ 0.23 log10 and ≤ 1.66 log10 PFU/g feed during 4 oC and room temperature storage. Throughout the experimental period of 7 days, both phages could be detected in the gut of fish fed with phage-coated feed. Besides, both CF7 and D6 phages were also detected in fish kidneys indicating the ability of both the phage to cross the intestinal barrier. During challenge studies with LD50 dose of A. hydrophila, phage cocktail doses of 1 × 106 - 1 × 108 PFU/g feed prevented the mortality in L. rohita with relative percentage survival (RPS) of 8.7-65.2. When challenged with LD90 dose of A. hydrophila, an RPS value of 28.6 was obtained at a phage cocktail dose of 1 × 108 PFU/g feed. The RPS data showed that orally-fed phage cocktail protected the fish against the mortality caused by A. hydrophila in a dose-dependent manner. Simple practical approaches for phage cocktail development, medicated feed preparation and oral administration along with phage survival and protection data make the current study useful for farmer-level application.

Infection of guppies (Poecilia reticulata) with the Asian fish tapeworm Schyzocotyle acheilognathi in an urban stream in Brazil.

Schyzocotyle acheilognathi is a fish tapeworm native to Asia but has been reported as an alien species on practically all other continents. Its invasive potential is due to its low host specificity and high adaptability to different environments, and its spread to new areas can result in economic and ecological impacts. Studies reporting this species in South America are still scarce, indicating the need to monitor its dispersion to new areas. Herein, tapeworms found in guppies, Poecilia reticulata, from an urban stream located in Belo Horizonte, Minas Gerais, Brazil, in April 2021 were subjected to morphological and molecular characterization. As a result, 5/13 (38.5%) of the P. reticulata specimens evaluated were infected with intestinal tapeworms. It was verified a mean intensity of infection of 7.8 (1-25) and a mean abundance of infection of 3 (0-25). The morphology of the cestodes obtained was compatible with that of S. acheilognathi. Moreover, genetic analysis based on cytochrome c oxidase subunit 1 gene (Cox-1) revealed 97.89-99.77% similarity to isolates of this species from different localities. The possibility that S. acheilognathi is expanding to new regions of South America is discussed.

Redox profile of silver catfish challenged with Aeromonas hydrophila and treated with hexane extract of Hesperozygis ringens (Benth.) Epling through immersion bath.

The growing increase in the fish farming sector has favored the establishment of bacterial outbreaks caused by Aeromonas hydrophila in several species. The hexane extract of Hesperozygis ringens (HEHR) (Lamiaceae) leaves increased the survival rate of silver catfish (Rhamdia quelen) experimentally infected by A. hydrophila. However, it is noteworthy that no reports have been found on the possible mechanisms of action of this extract in infected fish. This study aimed to evaluate the effect of the HEHR, administered through single immersion bath, on lipid peroxidation and antioxidant defenses in muscle and liver tissue of silver catfish challenged with A. hydrophila. The results showed that the oxidative status of silver catfish was altered, although oxidative stress was not triggered during the experiment. HEHR at 30 mg/L (HEHR30) was not characterized as a pro-oxidant agent in the presence of infection, unlike florfenicol and HEHR at 15 mg/L treatments in some cases. In short, HEHR30 provided an important increase in hepatic catalase activity, characterizing one of the possible mechanisms involved in the greater survival of fish experimentally infected by A. hydrophila. Additionally, HEHR30 did not induce lipid peroxidation, nor reduced antioxidant defenses of silver catfish infected or not by A. hydrophila.

Biocontrol of multidrug resistant pathogens isolated from fish farms using silver nanoparticles combined with hydrogen peroxide insight to its modulatory effect.

This study was divided into two parts. The first part involved the isolation, and detection of the prevalence and antimicrobial resistance profile of Aeromonas hydrophila, Pseudomonas aeruginosa, and Vibrio species from Nile tilapia fish and marine aquatic water. One hundred freshly dead Nile tilapia fish were collected from freshwater aquaculture fish farms located in Al-Abbassah district, Sharkia Governorate, and 100 samples of marine aquatic water were collected from fish farms in Port Said. The second part of the study focused on determining the in vitro inhibitory effect of dual-combination of AgNPs-H2O2 on bacterial growth and its down regulatory effect on crucial virulence factors using RT-PCR. The highest levels of A. hydrophila and P. aeruginosa were detected in 43%, and 34% of Nile tilapia fish samples, respectively. Meanwhile, the highest level of Vibrio species was found in 37% of marine water samples. Additionally, most of the isolated A. hydrophila, P. aeruginosa and Vibrio species exhibited a multi-drug resistance profile. The MIC and MBC results indicated a bactericidal effect of AgNPs-H2O2. Furthermore, a transcriptional modulation effect of AgNPs-H2O2 on the virulence-associated genes resulted in a significant down-regulation of aerA, exoU, and trh genes in A. hydrophila, P. aeruginosa, and Vibrio spp., respectively. The findings of this study suggest the effectiveness of AgNPs-H2O2 against drug resistant pathogens related to aquaculture.

[Investigation of Anisakis infections in coastal marine fishes and awareness of anisakiasis control knowledge among residents in Yantai City in 2021].

OBJECTIVE: To investigate the prevalence of Anisakis infections in coastal marine fishes and awareness of anisakiasis control knowledge among local residents in Yantai City, Shandong Province in 2021, so as to provide insights into formulation of anisakiasis control interventions. METHODS: Marine fishes were purchased from Shunxin Port, Yantai City, Shandong Province in November 2021, and the presence of Anisakis was detected in different species of fishes and different fish sites. The correlations between body length and weight of marine fish and intensity of Anisakis infections were examined using Spearman's rank correlation analysis, and the dietary habits and anisakiasis control knowledge were investigated using questionnaire surveys among local residents. RESULTS: A total of 201 marine fishes belonging to 20 species were dissected, and Anisakis was detected in 77 marine fishes (38.31%) belonging to 11 species (55.00%), with a mean infection intensity of 45.04 parasites per fish (3 468/77). Spearman's rank correlation analysis revealed that the body length (rs = 0.74, P < 0.05) and weight (rs = 0.79, P < 0.01) of the monkfish correlated positively with the intensity of Anisakis infections, and the body length (rs = 0.68, P < 0.05) of the flatfish correlated positively with the intensity of Anisakis infections, while no correlations were examined between the body length or weight of other marine fishes and the intensity of Anisakis infections. Of all respondents, 53.38% men and 56.67% women did not know anisakiasis control knowledge at all, and there was a significant difference in the proportion of respondents using separate chopping boards for raw and cooked food from different villages (χ2 = 17.89, P < 0.01), while there was an age-specific proportion of respondents with habitats of eating raw or semi-raw seafood (χ2 = 28.27, P < 0.01). CONCLUSIONS: The prevalence and intensity of Anisakis infections were high in coastal marine fishes in Yantai City in 2021, and the awareness of anisakiasis control knowledge was low among local residents. Intensified health education pertaining to anisakiasis control knowledge is recommended to reduce the risk of Anisakis infections.

Stressing out-carp edema virus induces stress and modulates immune response in common carp.

Introduction: Carp edema virus (CEV) is a fish poxvirus that primarily infects the gills of common carp. CEV causes koi sleepy disease (KSD), which is highly contagious and can result in mortality of up to 100%. Methods: In the present study, we analyzed the stress and immune responses during KSD in two strains of common carp with different resistance to CEV: susceptible koi and resistant Amur sazan. Experiments were performed at two temperatures: 12°C and 18°C. In the case of koi carp, we also analyzed the effect of supplementation of 0.6% NaCl into tank water, which prevents mortality of the CEV-infected fish (salt rescue model). Results: We found that CEV-infected koi kept at 18°C had the highest viral load, which correlated with the most severe histopathological changes in the gills. CEV infection resulted in the activation of stress response reflected by the upregulated expression of genes involved in stress response in the stress axis organs and increased levels of cortisol and glucose in the blood plasma. These changes were the most pronounced in CEV-infected koi kept at 18°C. At both temperatures, the activation of antiviral immune response was observed in koi kept under freshwater and NaCl conditions upon CEV infection. Interestingly, a clear downregulation of the expression of adaptive immune genes was observed in CEV-infected koi kept under freshwater at 18°C. Conclusion: CEV induces a stress response and modulates adaptive immune response in koi, and this is correlated with the level of viral load and disease development.

Pseudomonas putida infection induces immune-antioxidant, hepato-renal, ethological, and histopathological/immunohistochemical disruptions in Oreochromis niloticus: the palliative role of titanium dioxide nanogel.

BACKGROUND: Pseudomonas putida is a pathogenic bacterium that induces great losses in fishes, including Nile tilapia (Oreochromis niloticus). Currently, the application of nanomaterials in aquaculture practices has gained more success as it endows promising results in therapies compared to traditional protocols. OBJECTIVE: Therefore, the current perspective is considered the first report to assess the anti-bacterial efficacy of titanium dioxide nanogel (TDNG) against Pseudomonas putida (P. putida) in Nile tilapia. METHODS: The fish (n = 200; average body weight: 47.50±1.32 g) were allocated into four random groups (control, TDNG, P. putida, and TDNG + P. putida), where 0.9 mg/L of TDNG was applied as bath treatment for ten days. RESULTS: Outcomes revealed that P. putida infection caused ethological alterations (surfacing, abnormal movement, and aggression) and depression of immune-antioxidant variables (complement 3, lysozyme activity, total antioxidant capacity, superoxide dismutase, and reduced glutathione content). Additionally, a substantial elevation in hepatorenal biomarkers (aspartate and alanine aminotransferases and creatinine) with clear histopathological changes and immuno-histochemical alterations (very weak BCL-2 and potent caspase-3 immuno-expressions) were seen. Surprisingly, treating P. putida-infected fish with TDNG improved these variables and obvious restoration of the tissue architectures. CONCLUSION: Overall, this report encompasses the key role of TDNG as an anti-bacterial agent for controlling P. putida infection and improving the health status of Nile tilapia.

Parasites (Monogenea) of tilapias Oreochromis niloticus and Coptodon rendalli (Cichlidae) in a river spring in Brazil.

In the present study, we examined 30 individuals of introduced African cichlids, Oreochromis niloticus and Coptodon rendalli, collected in a river spring of the Pardo River, Paranapanema River basin, southeastern Brazil. Based on morphological and molecular analyses of the partial LSU rDNA gene, we identified four species of monogeneans, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei, and Scutogyrus longicornis on the gills of O. niloticus, whereas individuals of C. rendalli were infested only with C. papernastrema. This is the first record of C. mbirizei and C. papernastrema in tilapias from Brazil. The ecological consequences of the introduction of exotic species of tilapia such as O. niloticus and C. rendalli along with their monogenean parasites in a wild environment represented by a river spring are discussed. Our new molecular data on Cichlidogyrus and Scutogyrus contribute to the investigation of the phylogenetic interrelationships of these widely distributed genera of monogeneans since their species composition is still unsettled.

Title: Parasites (Monogenea) des tilapias Oreochromis niloticus et Coptodon rendalli (Cichlidae) dans une source au Brésil. Abstract: Dans la présente étude, nous avons examiné 30 individus de cichlidés africains introduits, Oreochromis niloticus et Coptodon rendalli, collectés dans une source fluviale du fleuve Pardo, bassin du fleuve Paranapanema, dans le sud-est du Brésil. Sur la base d'analyses morphologiques et moléculaires du gène partiel de l'ADNr LSU, nous avons identifié quatre espèces de monogènes, Cichlidogyrus tilapiae, C. thurstonae, C. mbirizei et Scutogyrus longicornis sur les branchies d'O. niloticus, alors que les individus de C. rendalli étaient infestés uniquement par C. papernastrema. Il s'agit du premier signalement de C. mbirizei et C. papernastrema chez des tilapias du Brésil. Les conséquences écologiques de l'introduction d'espèces exotiques de tilapia telles que O. niloticus et C. rendalli ainsi que leurs monogènes parasites dans un environnement sauvage représenté par une source fluviale sont discutées. Nos nouvelles données moléculaires sur Cichlidogyrus et Scutogyrus contribuent à l'étude des interrelations phylogénétiques de ces genres de monogènes largement distribués puisque leur composition spécifique est encore incertaine.

Consistent Negative Correlations between Parasite Infection and Host Body Condition Across Seasons Suggest Potential Harmful Impacts of Salmincola markewitschi on Wild White-Spotted Charr, Salvelinus leucomaenis.

Assessing the impacts of parasites on wild fish populations is a fundamental and challenging aspect of the study of host-parasite relationships. Salmincola, a genus of ectoparasitic copepods, mainly infects salmonid species. This genus, which is notorious in aquaculture, damages host fishes, but its impacts under natural conditions remain largely unknown or are often considered negligible. In this study, we investigated the potential impacts of mouth-attaching Salmincola markewitschi on white-spotted charr (Salvelinus leucomaenis) through intensive field surveys across four seasons using host body condition as an indicator of harmful effects. The prevalence and parasite abundance were highest in winter and gradually decreased in summer and autumn, which might be due to host breeding and/or wintering aggregations that help parasite transmissions. Despite seasonal differences in prevalence and parasite abundance, consistent negative correlations between parasite abundance and host body condition were observed across all seasons, indicating that the mouth-attaching copepods could reduce the body condition of the host fish. This provides field evidence suggesting that S. markewitschi has a potential negative impact on wild white-spotted charr.

Some trematodes including three new species from freshwater fishes of Venezuela.

The present paper comprises a systematic survey of trematodes found in 13 species of freshwater fishes in Venezuela collected in 1992, 1996 and 2001. The following 15 trematode species were recorded: Adults: Genarchella venezuelaensis sp. n., Thometrema dissimilis sp. n., Megacoelium spinicavum Thatcher et Varella, 1981, Doradamphistoma bacuense Thatcher, 1999, Crassicutis cichlasomae Manter, 1936, Parspina carapo Ostrowski de Núñez, Arredonto et Gil de Pertierra, 2011, Phyllodistomoides hoplerythrini sp. n. Larvae (metacercariae): Clinostomatopsis sorbens (Braun, 1899), Clinostomum marginatum (Rudolphi, 1819), C. detruncatum Braun, 1899, Ithyoclinostomum dimorphum (Diesing, 1850), Odhneriotrema microcephala (Travassos, 1922), Tylodelphys sp., Posthodiplostomum sp., Sphincterodiplostomum sp. All these parasites are reported from Venezuela for the first time and many of these findings represent new host records. The new species G. venezuelaensis sp. n., T. dissimilis sp. n. and P. hoplerythrini sp. n. were collected from the accessory respiratory organ of Loricariichthys brunneus (Hancock) (Loricariidae), from the stomach of Hoplerythrinus unitaeniatus (Spix et Agassiz) (Erythrinidae) and from the intestine of H. unitaeniatus, respectively. All parasites are briefly described and illustrated and problems concerning their morphology, taxonomy, hosts and geographical distribution are discussed. Megacoelium spinispecum Thatcher et Varella, 1981 is considered a junior synonym of M. spinicavum Thatcher et Varella, 1981, and Crassicutis opisthoseminis Bravo-Hollis et Arroyo, 1962 as a junior synonym of C. cichlasomae Manter, 1936.

Modulation of infectious Salmon Anaemia virus infection by clathrin-mediated endocytosis and macropinocytosis inhibitors.

Infectious salmon anaemia virus (ISAV) is a pathogen that causes disease and large mortality in farm-raised Salmo salar L., being considered as a major problem in the salmon industry. However, despite its relevance, there are still numerous knowledge gaps on virus entry and early stages of infection. Previous studies suggested that virus entry into cells occurs via endocytosis, with no description of specific mechanisms. However, it remains unknown if the endocytosis induced by ISAV is a clathrin-dependent or clathrin-independent process. This study aimed to identify cellular mechanisms allowing ISAV entry into Atlantic Salmon head kidney (ASK) cells. Our results showed that ISAV can be found in coated pits and membrane ruffles, the latter being induced by a rearrangement of actin filaments promoted by ISAV infection. Additionally, it was determined that ISAV stimulate the uptake of extracellular fluid in a multiplicity of infection (MOI)-dependent manner. When the clathrin-mediated endocytic pathway was pharmacologically inhibited, ISAV infection was significantly reduced but not entirely inhibited. Similarly, when the Na+/H+ exchanger (NHE), a key component of macropinocytosis, was inhibited, ISAV infection was negatively affected. Our results suggest that ISAV enters cells via both clathrin-mediated endocytosis and most likely macropinocytosis.

Two new species of Diaphorocleidus and new data on D. affinis (Monogenoidea: Dactylogyridae) parasitizing Bryconops cf. affinis (Characiformes: Iguanodectidae) from the Munim River basin, State of Maranho, northeastern Brazil.

During a study conducted on the helminth fauna of fishes in the middle Munim River basin, State of Maranho, northeastern Brazil, three species (two new) of Diaphorocleidus Jogunoori, Kritsky & Venkatanarasaiah, 2004 are reported from the gills of the piaba Bryconops cf. affinis (Iguanodectidae): Diaphorocleidus affinis (Mizelle, Kritsky & Crane, 1968), D. forcipiformis n. sp. and D. munimensis n. sp. New morphological data, drawings, and geographic distribution were provided for D. affinis. Diaphorocleidus forcipiformis n. sp. is characterized by a male copulatory organ with 2 rings counterclockwise and base forming a small tube with two circular flanges and accessory piece bifurcated, claw-shaped, with parts similar in shape and size, one of them distally bifid. Diaphorocleidus munimensis n. sp. is differentiated by the accessory piece, which is composed of two large pieces, united in their proximal part, claw-shaped, and distally hooked. The findings of this initial survey on the helminth parasites of fishes in this area emphasize the importance of carrying out comparable surveys on other fish species. Such surveys may lead to the identification of unknown species or new occurrences.

New species of Echinobothrium van Beneden, 1849 (Cestoda: Diphyllidea) from Indo-Pacific maskrays (Neotrygon Castelnau) off Australia and Borneo.

Four new diphyllidean species of the genus Echinobothrium van Beneden, 1849 are described from Indo-Pacific maskrays (Neotrygon Castelnau, Dasyatidae). Echinobothrium giraffaeous sp. n. from Neotrygon leylandi (Last) off northern Australia, Echinobothrium ivanovae sp. n. from Neotrygon orientalis Last, White et Serét off Borneo, and Echinobothrium bethae sp. n. from Neotrygon varidens (Garman) off Borneo are distinguished from all but one of the 33 valid species of the genus by the possession of the outermost A hooks with an extended base into which the bases of the three outermost B hooks are inserted. Echinobothrium rhynchobati (Khalil et Abdul-Salam, 1989) is the only known species with this unique feature, but its rostellum has a system of interlocking knobs and sockets that articulate bases of the A and B type hooks with one another, which is not present in any of the newly described species. Echinobothrium tyleri sp. n. from Neotrygon australiae Last, White et Serét off northern Australia is distinguished from all known species of Echinobothrium by its unique rostellar hook formula {2-3 18/17 2-3}. With the present addition of four new species, the central Indo-Pacific realm becomes the major hotspot for Echinobothrium, from which 13 species have been reported.

Correlation of skin color and plasma carotenoid-related metabolites of ornamental koi carp under temperature fluctuations.

The skin color of koi carp (Cyprinus carpio L.) is one of the traits that most influence their ornamental and economic values. The present study suggested the effects of temperature fluctuation on koi carp in terms of skin color and plasma carotenoids and related-metabolites. The main results were as follows. (1) The vulnerability of koi skin color to acute temperature stress was in the order of white koi> black koi> yellow koi. Both high- (25°C-30°C-25°C) and low-temperature (25°C-20°C-25°C) fluctuations tended to decrease the saturation of white koi. The temperature fluctuation had little effects on the skin color of black and yellow koi. (2) Targeted metabolomics analysis indicated that the effects of cooling stress on oxycarotenoids of all five koi varieties were reversible. The plasma oxycarotenoids in mirror koi with all colors were insensitive to acute heat stress. However, the cooling process from a high temperature (30°C-25°C) still made contributions to the increase of oxycarotenoids. (3) The principal component analysis confirmed the deviation of carotenoid-related metabolites after high temperature fluctuation and the reversibility after low temperature fluctuation. Finally, the correlation analysis revealed that koi skin brightness was negatively correlated with the plasma guanine content and that temperature fluctuations might change koi skin brightness via the L(-)-epinephrine-guanine pathway. The red hue and yellow hue were negatively correlated with the oxycarotenoids in plasma, suggesting that oxycarotenoids were favorable for enhancing koi skin color saturation. Overall, this study revealed the direct action of temperature fluctuations on the skin color and carotenoid-related metabolites of koi.

Inhibition mechanism of crude lipopeptide from Bacillus subtilis against Aeromonas veronii growth, biofilm formation, and spoilage of channel catfish flesh.

Aeromonas veronii is associated with food spoilage and some human diseases, such as diarrhea, gastroenteritis, hemorrhagic septicemia or asymptomatic and even death. This research investigated the mechanism of the growth, biofilm formation, virulence, stress resistance, and spoilage potential of Bacillus subtilis lipopeptide against Aeromonas veronii. Lipopeptides suppressed the transmembrane transport of Aeromonas veronii by changing the cell membrane's permeability, the structure of membrane proteins, and Na+/K+-ATPase. Lipopeptide significantly reduced the activities of succinate dehydrogenase (SDH) and malate dehydrogenase (MDH) by 86.03% and 56.12%, respectively, ultimately slowing Aeromonas veronii growth. Lipopeptides also restrained biofilm formation by inhibiting Aeromonas veronii motivation and extracellular polysaccharide secretion. Lipopeptides downregulated gene transcriptional levels related to the virulence and stress tolerance of Aeromonas veronii. Furthermore, lipopeptides treatment resulted in a considerable decrease in the extracellular protease activity of Aeromonas veronii, which restrained the decomposing of channel catfish flesh. This research provides new insights into lipopeptides for controlling Aeromonas veronii and improving food safety.

New record of Philometra species from the marine edible fish Terapon jarbua collected from the Sindh, Arabian Sea, Pakistan.

Diseases in fish due to helminth parasites, especially Philometra species, are the primary worry in aquaculture. Philometra are responsible for health problem in fishes they directly affect fish growth and population parameters. A comprehensive survey was conducted involving the examination of the marine fish species Terapon jarbua, gathered from the coastal waters of Sindh, Pakistan In this research different Philometra species from marine fish Terapon jarbua during 2021 and 2022. Philometra nematodes, belonging to the family Philometridae, are common parasitic organisms inhabiting both marine and freshwater environments. Their prevalence, particularly when existing in high numbers within host organisms, can lead to severe and potentially lethal consequences. Employing light microscopy techniques, diverse species of Philometra were identified, including Philometra teraponi, P. jarbuai, P. arabiai, P. karachii, and P. awarii, localized primarily within the ovaries of the host fish. A total of 140 fish samples were examined and 76 were infected. The intensity of infected fish was 54.28%. The identification process encompassed meticulous analysis of crucial parameters, such as body size, esophagus length, positioning of the nerve ring, dimensions of the ventriculus, and ligament size. Intriguingly, the parasites were found in varying contexts; while some were free within the ovaries, others were embedded within tissues, inducing severe muscular dystrophy. This research presents novel findings of Philometra nematodes in the marine waters of Pakistan, extending their host and geographical distribution records. Future studies are needed to better evaluate and describe the dynamics and the epidemiology of Philometra infection in wild and cultured fish species.

Mannose modified targeted immersion vaccine delivery system improves protective immunity against Infectious spleen and kidney necrosis virus in mandarin fish (Siniperca chuatsi).

Vaccination is an effective method to prevent viral diseases. However, the biological barrier prevents the immersion vaccine from achieving the best effect without adding adjuvants and carriers. Researches on the targeted presentation technology of vaccines with nanocarriers are helpful to develop immersion vaccines for fish that can break through biological barriers and play an effective role in fish defense. In our study, functionally modified single-walled carbon nanotubes (SWCNTs) were used as carriers to construct a targeted immersion vaccine (SWCNTs-M-MCP) with mannose modified major capsid protein (MCP) to target antigen-presenting cells (APCs), against iridovirus diseases. After bath immunization, our results showed that SWCNTs-M-MCP induced the presentation process and uptake of APCs, triggering a powerful immune response. Moreover, the highest relative percent survival (RPS) was 81.3% in SWCNTs-M-MCP group, which was only 41.5% in SWCNTs-MCP group. Altogether, this study indicates that the SWCNTs-based targeted immersion vaccine induces strong immune response and provided an effective protection against iridovirus diseases.

Identification of the C1qDC gene family in grass carp (Ctenopharyngodon idellus) and the response of C1qA, C1qB, and C1qC to GCRV infection in vivo and in vitro.

Proteins from the C1q domain-containing (C1qDC) family recognize self-, non-self-, and altered-self ligands and serves as an initiator molecule for the classical complement pathway as well as recognizing immune complexes. In this study, C1qDC gene family members were identified and analyzed in grass carp (Ctenopharyngodon idellus). Members of the C1q subfamily were cloned, and their response to infection with the grass carp virus was investigated. In the grass carp genome, 54 C1qDC genes and 67 isoforms have been identified. Most were located on chromosome 3, with 52 shared zebrafish homologies. Seven substantially differentially expressed C1qDC family genes were identified in the transcriptomes of cytokine-induced killer (CIK) cells infected with grass carp reovirus (GCRV), all of which exhibited sustained upregulation. The opening reading frames of grass carp C1qA, C1qB, and C1qC, belonging to the C1q subfamily, were determined to be 738, 732, and 735 base pairs, encoding 245, 243, and 244 amino acids with molecular weights of 25.81 kDa, 25.63 kDa and 26.16 kDa, respectively. Three genes were detected in the nine collected tissues, and their expression patterns were similar, with the highest expression levels observed in the spleen. In vivo after GCRV infection showed expression trends of C1qA, C1qB, and C1qC in the liver, spleen, and kidney. An N-type pattern in the liver and kidney was characterized by an initial increase followed by a decrease, with the highest expression occurring during the recovering period, and a V-type pattern in the spleen with the lowest expression levels during the death period. In vitro, after GCRV infection showed expression trends of C1qA, C1qB, and C1qC, and this gradually increased within the first 24 h, with a notable increase observed at the 24 h time point. After CIK cells incubation with purified recombinant proteins, rC1qA, rC1qB, and rC1qC for 3 h, followed by GCRV inoculation, the GCRV replication indicated that rC1qC exerted a substantial inhibitory effect on viral replication in CIK cells after 24 h of GCRV inoculation. These findings offer valuable insights into the structure, evolution, and function of the C1qDC family genes and provide a foundational understanding of the immune function of C1q in grass carp.

Exosomes derived from olive flounders infected with Streptococcus parauberis: Proteomic analysis, immunomodulation, and disease resistance capacity.

Multidrug-resistant Streptococcus parauberis causes high fish mortality in aquaculture, necessitating an urgent need for innovative control strategies. This study aimed to develop an immunizing agent against S. parauberis using exosomes isolated from the plasma of olive flounders infected experimentally with S. parauberis (Sp-Exo). Initially, we tested the in vitro immunomodulatory effect of Sp-Exo in murine macrophage RAW264.7 cells and compared it to that of exosomes isolated from naïve fish (PBS-Exo-treated). Notably, Sp-Exo treatment significantly (p < 0.05) upregulated pro-and anti-inflammatory cytokines (Il1ß, Tnfα, and Il10), antimicrobial peptide, defensin isoforms (Def-rs2 and Def-ps1), and antiviral (Ifnß1 and Isg15) genes. In vivo studies in larval and adult zebrafish revealed similar patterns of immunomodulation. Furthermore, larval and adult zebrafish exhibited significantly (p < 0.05) enhanced resistance to S. parauberis infection following treatment with Sp-Exo compared to that with PBS-Exo. Proteomic analysis using isobaric tags for relative and absolute quantitation (iTRAQ) approach revealed the presence of 77 upregulated and 94 downregulated differentially expressed proteins (DEPs) in Sp-Exo, with 22 and 37 significantly (p < 0.05) upregulated and downregulated DEPs, respectively. Gene Ontology, Kyoto Encyclopedia of Genes and Genomes, and Search Tool for the Retrieval of Interacting Genes/Proteins analyses revealed that these genes are associated with key pathways, such as innate immune responses, complement system, acute phase responses, phospholipid efflux, and chylomicron remodeling. In conclusion, Sp-Exo demonstrated superior immunomodulatory activity and significant resistance against S. parauberis infection relative to that on treatment with PBS-Exo. Proteomic analysis further verified that most DEPs in Sp-Exo were associated with immune induction or modulation. These findings highlight the potential of Sp-Exo as a promising vaccine candidate against S. parauberis and other bacterial infections in olive flounder.

The antiviral role of largemouth bass STING against iridovirus infection.

Stimulator of interferon gene (STING) plays a crucial role in the innate immune response against viral and bacterial pathogens. However, its function in largemouth bass iridovirus (LMBV) infection remains uncertain. Here, a STING homolog (MsSTING) from largemouth bass (Micropterus salmoides) was cloned and characterized. MsSTING encoded a 407-amino-acid polypeptide, which shared 84.08% and 41.45% identity with golden perch (Perca flavescens) and human (Homo sapiens) homologs, respectively. MsSTING contained four transmembrane domains and a conserved C-terminal domain. The mRNA level of MsSTING was significantly increased in response to LMBV infection in vitro. Subcellular localization observation indicated that MsSTING encoded a cytoplasmic protein, which co-localized predominantly with endoplasmic reticulum (ER) and partially with mitochondria. Moreover, its accurate localization was dependent on the N-terminal transmembrane motif (TM) domains. MsSTING was able to activate interferon (IFN) response, evidenced by the activation of IFN1, IFN3 and ISRE promoters by its overexpression in vitro. Mutant analysis showed that both the N-terminal and C-terminal domain of MsSTING were essential for its activation on IFN response. In addition, overexpression of MsSTING inhibited the transcription and protein levels of viral core genes, indicating that MsSTING exerted antiviral action against LMBV. Consistently, the inhibitory effects were significantly attenuated when the N-terminal or C-terminal domains of MsSTING was deleted. Furthermore, MsSTING overexpression upregulated the transcriptions of interferon-related genes and pro-inflammatory factors, including TANK-binding kinase 1(TBK1), interferon regulatory factor 3 (IRF3), interferon regulatory factor 7 (IRF7), interferon stimulated exonuclease gene 20 (ISG20), interferon-induced transmembrane protein 1(IFITM1), interferon γ (IFN-γ), tumor necrosis factor α (TNF-α), interleukin 1ß (IL-1ß), and interleukin 6 (IL-6). Together, MsSTING exerted antiviral action upon LMBV infection through positive regulation the innate immune response.