Molecular cloning and functional analyses of C-C motif chemokine ligand 3 (CCL3) in mandarin fish Siniperca chuatsi.

Chemokines are critical molecules involved in immune reaction and immune system homeostasis, and some chemokines play a role in antiviral immunity. It is not known if the C-C motif chemokine ligand 3 (CCL3), a member of the CC chemokine family, possesses antiviral properties in fish. In this study, a ccl3 was cloned from the mandarin fish (Siniperca chuatsi), and it has an open reading frame (ORF) of 276 base pairs, which are predicted to encode a 91-amino acid peptide. Mandarin fish CCL3 revealed conserved sequence features with four cysteine residues and closely relationships with the CCL3s from other vertebrates based on the sequence alignment and phylogenetic analysis. The transcripts of ccl3 were notably enriched in immune-related organs, such as spleen and gills in healthy mandarin fish, and the ccl3 was induced in the isolated mandarin fish brain (MFB) cells following infection with infectious spleen and kidney necrosis virus (ISKNV). Moreover, in MFB cells, overexpression of CCL3 induced immune factors, such as IL1ß, TNFα, MX, IRF1 and IFNh, and exhibited antiviral activity against ISKNV. This study sheds light on the immune role of CCL3 in immune response of mandarin fish, and its antiviral defense mechanism is of interest for further investigation.

Risk assessment of wild fish as environmental sources of red sea bream iridovirus (RSIV) outbreaks in aquaculture.

Red sea bream iridovirus (RSIV) causes substantial economic damage to aquaculture. In the present study, RSIV in wild fish near aquaculture installations was surveyed to evaluate the risk of wild fish being an infection source for RSIV outbreaks in cultured fish. In total, 1102 wild fish, consisting of 44 species, were captured from 2 aquaculture areas in western Japan using fishing, gill nets, and fishing baskets between 2019 and 2022. Eleven fish from 7 species were confirmed to harbor the RSIV genome using a probe-based real-time PCR assay. The mean viral load of the RSIV-positive wild fish was 101.1 ± 0.4 copies mg-1 DNA, which was significantly lower than that of seemingly healthy red sea bream Pagrus major in a net pen during an RSIV outbreak (103.3 ± 1.5 copies mg-1 DNA) that occurred in 2021. Sequencing analysis of a partial region of the major capsid protein gene demonstrated that the RSIV genome detected in the wild fish was identical to that of the diseased fish in a fish farm located in the same area in which the wild fish were captured. Based on the diagnostic records of RSIV in the sampled area, the RSIV-infected wild fish appeared during or after the RSIV outbreak in cultured fish, suggesting that RSIV detected in wild fish was derived from the RSIV outbreak in cultured fish. Therefore, wild fish populations near aquaculture installations may not be a significant risk factor for RSIV outbreaks in cultured fish.

Integrated multi-omics analysis reveals liver metabolic reprogramming by fish iridovirus and antiviral function of alpha-linolenic acid.

Iridovirus poses a substantial threat to global aquaculture due to its high mortality rate; however, the molecular mechanisms underpinning its pathogenesis are not well elucidated. Here, a multi-omics approach was applied to groupers infected with Singapore grouper iridovirus (SGIV), focusing on the roles of key metabolites. Results showed that SGIV induced obvious histopathological damage and changes in metabolic enzymes within the liver. Furthermore, SGIV significantly reduced the contents of lipid droplets, triglycerides, cholesterol, and lipoproteins. Metabolomic analysis indicated that the altered metabolites were enriched in 19 pathways, with a notable down-regulation of lipid metabolites such as glycerophosphates and alpha-linolenic acid (ALA), consistent with disturbed lipid homeostasis in the liver. Integration of transcriptomic and metabolomic data revealed that the top enriched pathways were related to cell growth and death and nucleotide, carbohydrate, amino acid, and lipid metabolism, supporting the conclusion that SGIV infection induced liver metabolic reprogramming. Further integrative transcriptomic and proteomic analysis indicated that SGIV infection activated crucial molecular events in a phagosome-immune depression-metabolism dysregulation-necrosis signaling cascade. Of note, integrative multi-omics analysis demonstrated the consumption of ALA and linoleic acid (LA) metabolites, and the accumulation of L-glutamic acid (GA), accompanied by alterations in immune, inflammation, and cell death-related genes. Further experimental data showed that ALA, but not GA, suppressed SGIV replication by activating antioxidant and anti-inflammatory responses in the host. Collectively, these findings provide a comprehensive resource for understanding host response dynamics during fish iridovirus infection and highlight the antiviral potential of ALA in the prevention and treatment of iridoviral diseases.

Fish ELOVL7a is involved in virus replication via lipid metabolic reprogramming.

The elongation of very long chain fatty acids (ELOVL) proteins are key rate-limiting enzymes that catalyze fatty acid synthesis to form long chain fatty acids. ELOVLs also play regulatory roles in the lipid metabolic reprogramming induced by mammalian viruses. However, little is known about the roles of fish ELOVLs during virus infection. Here, a homolog of ELOVL7 was cloned from Epinephelus coioides (EcELOVL7a), and its roles in red-spotted grouper nervous necrosis virus (RGNNV) and Singapore grouper iridovirus (SGIV) infection were investigated. The transcription level of EcELOVL7a was significantly increased upon RGNNV and SGIV infection or other pathogen-associated molecular patterns stimulation in grouper spleen (GS) cells. Subcellular localization analysis showed that EcELOVL7a encoded an endoplasmic reticulum (ER) related protein. Overexpression of EcELOVL7a promoted the viral production and virus release during SGIV and RGNNV infection. Furthermore, the lipidome profiling showed that EcELOVL7a overexpression reprogrammed cellular lipid components in vitro, evidenced by the increase of glycerophospholipids, sphingolipids and glycerides components. In addition, VLCFAs including FFA (20:2), FFA (20:4), FFA (22:4), FFA (22:5) and FFA (24:0), were enriched in EcELOVL7a overexpressed cells. Consistently, EcELOVL7a overexpression upregulated the transcription level of the key lipid metabolic enzymes, including fatty acid synthase (FASN), phospholipase A 2α (PLA 2α), and cyclooxygenases -2 (COX-2), LPIN1, and diacylglycerol acyltransferase 1α (DGAT1α). Together, our results firstly provided the evidence that fish ELOVL7a played an essential role in SGIV and RGNNV replication by reprogramming lipid metabolism.

Study of the antivirus function mediated by STING in Micropterus salmoides.

Stimulator of interferon genes (STING) has been demonstrated as a critical mediator in the innate immune response to cytosolic DNA and RNA derived from different pathogens. While the role of Micropterus salmoides STING (MsSTING) in largemouth bass virus is still unknown. In this study, RT-qPCR assay and Western-blot assay showed that the expression levels of MsSTING and its downstream genes were up-regulated after LMBV infection. Pull down experiment proved that a small peptide called Fusion peptide (FP) that previously reported to target to marine and human STING as a selective inhibitor also interacted with MsSTING in vitro. Comparing with the RNA-seq of Largemouth bass infected with LMBV singly, 326 genes were significantly up-regulated and 379 genes were significantly down-regulated in the FP plus LMBV group in which Largemouth bass was treatment with FP before LMBV-challenged. KEGG analysis indicated that the differentially expressed genes (DEGs) were mainly related to signaling transduction, infectious disease viral, immune system and endocrine system. Besides, the survival rate of LMBV-infected largemouth bass was highly decreased following FP treatment. Taken together, our study showed that MsSTING played an important role in immune response against LMBV infection.

Berberine inhibits SGIV replication by suppressing inflammatory response and oxidative stress.

Singapore grouper iridovirus (SGIV) is one of the major infectious diseases responsible for high mortality and huge economic losses in the grouper aquaculture industry. Berberine (BBR), a naturally occurring plant alkaloid, is a phytochemical having a variety of biological properties, such as antiviral, antioxidant, and anti-inflammatory effects. In this work, we used an in vitro model based on Western blot, ROS fluorescence probe, and real-time quantitative PCR (qRT-PCR) to examine the antiviral qualities of BBR against SGIV. The outcomes demonstrated that varying BBR concentrations could significantly inhibit the replication of SGIV. In addition, BBR greatly inhibited the production of genes associated with pro-inflammatory cytokines in SGIV-infected or SGIV-uninfected GS cells based on qRT-PCR data. Subsequent investigations demonstrated that BBR suppressed the expression of the promoter activity of NF-κB and NF-κB-p65 protein. Additionally, BBR reduced the phosphorylation of ERK 1/2, JNK, and p38. Furthermore, BBR also inhibits SGIV-induced ROS production by upregulating the expression of antioxidant-related genes. In conclusion, BBR is a viable therapy option for SGIV infection due to its antiviral properties.

Hypermethylated genome of a fish vertebrate iridovirus ISKNV plays important roles in viral infection.

Iridoviruses are nucleocytoplasmic large dsDNA viruses that infect invertebrates and ectothermic vertebrates. The hypermethylated genome of vertebrate iridoviruses is unique among animal viruses. However, the map and function of iridovirus genomic methylation remain unknown. Herein, the methylated genome of Infectious spleen and kidney necrosis virus (ISKNV, a fish iridovirus), and its role in viral infection, are investigated. The methylation level of ISKNV is 23.44%. The hypermethylated genome is essential for ISKNV amplification, but there is no correlation between hypermethylation and viral gene expression. The hypomethylated ISKNV (obtained via 5-Azacytidine) activates a strong immunoreaction in vitro and reduces its pathogenicity in vivo. The unmethylated viral DNA can induce a stronger immunoreaction in vitro, whereas inactivated hypomethylated ISKNV can induce a stronger immunoreaction in vivo, suggesting ISKNV may evade from immune system by increasing its genome methylation level. Our work provides new insights into the role of genome methylation in viral infection.

Rapid and sensitive detection of large yellow croaker iridovirus by real-time RPA and RPA-LFD.

Large yellow croaker (Larimichthys crocea) is a vital marine-cultured species in China. Large yellow croaker iridovirus (LYCIV) can cause a high mortality rate in L. crocea. Rapid and convenient detection of LYCIV is an urgent demand for diagnosis. In this study, rapid and simple recombinase polymerase amplification (RPA), real-time RPA and RPA combined with lateral flow dipstick (RPA-LFD) methods were developed for the detection of LYCIV based on the conserved sequence of the LYCIV major capsid protein (MCP) gene. With these optimized RPA analyses, LYCIV detection could be completed within 20 min at 40°C. Both RPA and real-time RPA could detect viral DNA as low as 102 copies/µL, while the detection limit of RPA-LFD was 101 copies/µL, and there was no cross-reaction with other aquatic pathogens (KHV, CyHV-2, GCRV-JX01, SVCV, LCDV and LMBV). In practical evaluation of RPA, real-time RPA and RPA-LFD methods, the results showed consistency with the general PCR detection. In short, the developed RPA, real-time RPA and RPA-LFD analyses could be simple, rapid, sensitive and reliable methods for field diagnosis of LYCIV infection and have significant potential in the protection of LYCIV infection.

Characterization and functional analysis of SOCS9 from orange-spotted grouper (Epinephelus coioides) during virus infection.

The suppressor of cytokine signaling (SOCS) proteins family have twelve members including eight known mammalian SOCS members (CISH, SOCS1-7) and four new discovery members (SOCS3b, SOCS5b, SOCS8 and SOCS9) that is regarded as a classic feedback inhibitor of cytokine signaling. Although the function of the mammalian SOCS proteins have been well studied, little is known about the roles of SOCS in fish during viral infection. In this study, the molecular characteristics of SOCS9 from orange-spotted grouper (Epinephelus coioides, EcSOCS9) is investigated. The EcSOCS9 protein encoded 543 amino acids with typical SH2 (389-475aa) and SOCS_box (491-527aa), sharing high identities with reported fish SOCS9. EcSOCS9 was expressed in all detected tissues and highly expressed in kidney. After red-spotted grouper nervous necrosis virus (RGNNV) infection, the expression of EcSOCS9 was significantly induced in vitro. Furthermore, EcSOCS9 overexpression enhanced RGNNV replication, promoted virus-induced mitophagy that evidenced by the increased level of LC3-Ⅱ, BCL2, PGAM5 and decreased level of BNIP3 and FUNDC1. Besides, EcSOCS9 overexpression suppressed the expression levels of ATP6, CYB, ND4, ATP level and induced ROS level. The expression levels of interferon (IFN) related factors (IRF1, IRF3, IRF7, P53), inflammatory factors (IL1-ß, IL8, TLR2, TNF-α) and IFN-3, ISRE, NF-κB, AP1 activities were also reduced by overexpressing EcSOCS9. These date suggests that EcSOCS9 impacts RGNNV infection through modulating mitophagy, regulating the expression levels of IFN- related and inflammatory factors, which will expand our understanding of fish immune responses during viral infection.

Torque teno sus virus k2a (TTSuVk2a) in wild boars from northeastern Patagonia, Argentina.

Torque teno sus virus k2a (TTSuVk2a) is a member of the family Anelloviridae that can establish persistent infections in both domestic pigs and wild boars. Its association with diseases has not been precisely elucidated, and it is often considered only as a commensal virus. This infectious agent has been reported in herds throughout the world. In this study, we investigated the detection rate and diversity of TTSuVk2a in free-living wild boars from northeastern Patagonia, Argentina. Total DNA was extracted from tonsil samples of 50 animals, nested PCR assays were carried out, and infection was verified in 60% of the cases. Sequence analysis of the viral non-coding region revealed distinct phylogenetic groups. These clusters showed contrasting patterns of spatial distribution, which presented statistically significant differences when evaluating spatial aggregation. In turn, the sequences were compared with those available in the database to find that the clusters were distinguished by having similarity with TTSuVk2a variants of different geographic origin. The results suggested that Patagonian wild boar populations are bearers of diverse viral strains of Asian, European, and South American provenance.

Development and immune evaluation of LAMP1 chimeric DNA vaccine against Singapore grouper iridovirus in orange-spotted grouper, Epinephelus coioides.

Grouper is one of the most important and valuable mariculture fish in China, with a high economic value. As the production of grouper has increased, massive outbreaks of epidemic diseases have limited the development of the industry. Singapore grouper iridovirus (SGIV) is one of the most serious infectious viral pathogens and has caused huge economic losses to grouper farming worldwide due to its rapid spread and high lethality. To find new strategies for the effective prevention and control of SGIV, we constructed two chimeric DNA vaccines using Lysosome-associated membrane protein 1 (LAMP1) fused with major capsid proteins (MCP) against SGIV. In addition, we evaluated the immune protective effects of vaccines including pcDNA3.1-3HA, pcDNA3.1-MCP, pcDNA3.1-LAMP1, chimeric DNA vaccine pcDNA3.1-MLAMP and pcDNA3.1-LAMCP by intramuscular injection. Our results showed that compared with groups injected with PBS, pcDNA3.1-3HA, pcDNA3.1-LAMP1 or pcDNA3.1-MCP, the antibody titer significantly increased in the chimeric vaccine groups. Moreover, the mRNA levels of immune-related factors in groupers, including IRF3, MHC-I, TNF-α, and CD8, showed the same trend. However, MHC-II and CD4 were significantly increased only in the chimeric vaccine groups. After 28 days of vaccination, groupers were challenged with SGIV, and mortality was documented for each group within 14 days. The data showed that two chimeric DNA vaccines provided 87 % and 91 % immune protection for groupers which were significantly higher than the 52 % protection rate of pcDNA3.1-MCP group, indicating that both forms of LAMP1 chimeric vaccines possessed higher immune protection against SGIV, providing the theoretical foundation for the creation of novel DNA vaccines for fish.

Ranavirus (Frog Virus 3) Infection in Free-Living Three-Toed Box Turtles (Terrapene mexicana triunguis) in Missouri, USA.

Frog virus 3 (FV3) and related ranaviruses are emerging infectious disease threats to ectothermic vertebrate species globally. Although the impact of these viruses on amphibian health is relatively well studied, less is understood about their effects on reptile health. We report two cases of FV3 infection, 11 mo apart, in three-toed box turtles (Terrapene mexicana triunguis) from a wildlife rehabilitation center. Case 1 had upper respiratory signs upon intake but had no clinical signs at the time of euthanasia 1 mo later. Case 2 presented for vehicular trauma, had ulcerative pharyngitis and glossitis, and died overnight. In case 1, we detected FV3 nucleic acid with qPCR in oral swabs, kidney, liver, spleen, and tongue. In case 2, we detected FV3 in an oral swab, an oral plaque, heart, kidney, lung, liver, spleen, and tongue. We also detected FV3 nucleic acid with in situ hybridization for case 2. For both cases, FV3 was isolated in cell culture and identified with DNA sequencing. Histopathologic examination of postmortem tissue from case 1 was unremarkable, whereas acute hemorrhagic pneumonia and splenic necrosis were noted in case 2. The difference in clinical signs between the two cases may have been due to differences in the temporal course of FV3 disease at the time of necropsy. Failure to detect this infection previously in Missouri reptiles may be due to lack of surveillance, although cases may also represent a novel spillover to box turtles in Missouri. Our findings reiterate previous suggestions that the range of FV3 infection may be greater than previously documented and that infection may occur in host species yet to be tested.

Abnormalities in red blood cell production and pathogenesis of anemia in the progression of rock bream iridovirus (RBIV).

Rock bream iridovirus (RBIV), belonging to Megalocytivirus, causes severe mortality in rock bream. Almost all deaths associated with RBIV are accompanied by splenic enlargement and anemia. Although red blood cells (RBCs) are involved in the immune response against viral infections, their involvement in rock bream has not yet been studied in terms of the immune response against RBIV. In this study, the viral replication patterns, blood characteristics and anemia-related factors were evaluated in rock bream post RBIV infection. The virus-infected RBCs of rock bream demonstrated similarities in the expression levels of hemoglobins (HGB) (α and ß), cytokine-dependent hematopoietic cell linker (CLNK) and hematopoietic transcription factor GATA (GATA), with significantly decreasing levels from 4 days post infection (dpi) to 17 (dpi), when the viral replication was at its peak. This suggests that the expression of blood-related genes is inadequate for HGB synthesis and RBC production, thereby causing anemia leading to death. Moreover, the levels of complete blood cell count (CBC) indicators, such as RBCs, HGB and hematocrit (HCT), significantly decreased from 10 to 17 dpi. This phenomenon suggests that blood-related gene expression and/or RBC-, HGB- and HCT-related levels are critical factors in RBIV-induced anemia and disease progression. These results highlight the significance of blood-mediated immune responses against RBIV infection in rock bream. Understanding blood-related gene levels to identify blood-related immune response interactions in rock bream will be useful for development of future strategies in controlling RBIV diseases in rock bream.

Vitamin D3 can effectively and rapidly clear largemouth bass ranavirus by immunoregulation.

Largemouth bass ranavirus (LMBV) is a highly destructive pathogen that causes significant mortality rates among largemouth bass populations. Unfortunately, there is a dearth of drug development efforts specifically aimed at treating LMBV. To address this, our study sought to investigate the potential effectiveness of incorporating varying doses of VD3 into the diet as a treatment for LMBV. Through qRT-PCR and semi-qPCR, we observed significant suppression and clearance of LMBV pathogens in largemouth bass fed with 15000 IU/Kg and 20000 IU/Kg of VD3 within 14 days. In addition, VD3 treatment significantly increased the expression levels of key immune-related genes such as IL-1ß, IFN-γ, Mx, and IgM. Encouragingly, we observed that VD3 significantly increased antioxidant and immune activities such as TSOD, TAOC and C3 in serum and maintained total protein levels. Additionally, tissue pathology sections highlighted a dose-dependent relationship between VD3 supplementation and tissue damage, with the 15000 IU and 20000 IU groups exhibiting minimal damage. In conclusion, a reasonable concentration of VD3 effectively reduced LMBV replication and tissue damages, while improved immune-related genes expression and serum biochemical indices. These findings declare the considerable therapeutic potential of VD3 supplementation for combating LMBV disease and provide an alternative treatment option for fish farming.

Antiviral Effect and Mechanism of Edaravone against Grouper Iridovirus Infection.

Singapore grouper iridovirus (SGIV) is a virus with high fatality rate in the grouper culture industry. The outbreak of SGIV is often accompanied by a large number of grouper deaths, which has a great impact on the economy. Therefore, it is of great significance to find effective drugs against SGIV. It has been reported that edaravone is a broad-spectrum antiviral drug, most widely used clinically in recent years, but no report has been found exploring the effect of edaravone on SGIV infections. In this study, we evaluated the antiviral effect of edaravone against SGIV, and the anti-SGIV mechanism of edaravone was also explored. It was found that the safe concentration of edaravone on grouper spleen (GS) cells was 50 µg/mL, and it possessed antiviral activity against SGIV infection in a dose-dependent manner. Furthermore, edaravone could significantly disrupt SGIV particles and interference with SGIV binding to host cells, as well as SGIV replication in host cells. However, edaravone was not effective during the SGIV invasion into host cells. This study was the first time that it was determined that edaravone could exert antiviral effects in response to SGIV infection by directly interfering with the processes of SGIV infecting cells, aiming to provide a theoretical basis for the control of grouper virus disease.

Transcriptome analysis reveals molecular mechanisms of lymphocystis formation caused by lymphocystis disease virus infection in flounder (Paralichthys olivaceus).

Lymphocystis disease is frequently prevalent and transmissible in various teleost species worldwide due to lymphocystis disease virus (LCDV) infection, causing unsightly growths of benign lymphocystis nodules in fish and resulting in huge economic losses to aquaculture industry. However, the molecular mechanism of lymphocystis formation is unclear. In this study, LCDV was firstly detected in naturally infected flounder (Paralichthys olivaceus) by PCR, histopathological, and immunological techniques. To further understand lymphocystis formation, transcriptome sequencing of skin nodule tissue was performed by using healthy flounder skin as a control. In total, RNA-seq produced 99.36%-99.71% clean reads of raw reads, of which 91.11%-92.89% reads were successfully matched to the flounder genome. The transcriptome data showed good reproducibility between samples, with 3781 up-regulated and 2280 down-regulated differentially expressed genes. GSEA analysis revealed activation of Wnt signaling pathway, Hedgehog signaling pathway, Cell cycle, and Basal cell carcinoma associated with nodule formation. These pathways were analyzed to interact with multiple viral infection and tumor formation pathways. Heat map and protein interaction analysis revealed that these pathways regulated the expression of cell cycle-related genes such as ccnd1 and ccnd2 through key genes including ctnnb1, lef1, tcf3, gli2, and gli3 to promote cell proliferation. Additionally, cGMP-PKG signaling pathway, Calcium signaling pathway, ECM-receptor interaction, and Cytokine-cytokine receptor interaction associated with nodule formation were significantly down-regulated. Among these pathways, tnfsf12, tnfrsf1a, and tnfrsf19, associated with pro-apoptosis, and vdac2, which promotes viral replication by inhibiting apoptosis, were significantly up-regulated. Visual analysis revealed significant down-regulation of cytc, which expresses the pro-apoptotic protein cytochrome C, as well as phb and phb2, which have anti-tumor activity, however, casp3 was significantly up-regulated. Moreover, bcl9, bcl11a, and bcl-xl, which promote cell proliferation and inhibit apoptosis, were significantly upregulated, as were fgfr1, fgfr2, and fgfr3, which are related to tumor formation. Furthermore, RNA-seq data were validated by qRT-PCR, and LCDV copy numbers and expression patterns of focused genes in various tissues were also investigated. These results clarified the pathways and differentially expressed genes associated with lymphocystis nodule development caused by LCDV infection in flounder for the first time, providing a new breakthrough in molecular mechanisms of lymphocystis formation in fish.

Red sea bream iridovirus infection downregulates inflammation-related genes in the spleen of rock bream (Oplegnathus fasciatus).

This study investigated the kinetics of red sea bream iridovirus and host gene expression during infection in rock bream (Oplegnathus fasciatus), a species highly sensitive to the virus. After intraperitoneal injection of the viral solution at 104 TCID50/fish, the viral genome copy number in the spleen was 104.7 ± 0.2 and 105.9 ± 0.4 copies/µg DNA at 3 and 5 days post-injection (dpi), respectively. Using transcriptomic analyses via MiSeq, viral gene transcripts were detected at 3 and 5 dpi. Six genes including RING-finger domain-containing protein and laminin-type epidermal growth factor-like domain genes were significantly expressed at 5 dpi. Further, 334 host genes were differentially expressed compared with those before infection. Genes were clustered into four groups based on their expression profiles. Interferon-stimulated genes were more prevalent in groups showing upregulation at 5 dpi and 3 and 5 dpi. In contrast, the group showing downregulation at 3 dpi included inflammation-related genes, such as granzyme and eosinophil peroxidase genes. Downregulation of certain inflammation-related genes may contribute to the susceptibility of this fish to the virus.

Isolation and identification of a megalocytivirus strain (SKIV-TJ) from cultured spotted knifejaw (Oplegnathus punctatus) in China and its pathogenicity analysis.

The spotted knifejaw (Oplegnathus punctatus) has recently emerged as a highly economically significant farmed fish in China. However, due to increasing environmental pollution and breeding density, a range of infectious diseases, including the iridovirus pathogen, have begun to spread widely. In this study, we isolated and identified a strain of Megalocytivirus, SKIV-TJ, from cultured spotted knifejaw in Tianjin, China. We observed significant cytopathic effects (CPE) in SKIV-TJ-infected spotted knifejaw brain (SKB) cells, and electron microscopy showed numerous virus particles in the cytoplasm of SKB cells 6 days post-infection. The annotated complete genome of SKIV-TJ (GenBank accession number ON075463) contained 112,489 bp and 132 open reading frames. Based on the multigene association evolutionary tree using 26 iridovirus core genes, SKIV-TJ was found to be most closely related to Rock bream iridovirus (RBIV). Cumulative mortality of spotted knifejaw infected with SKIV-TJ reached 100% by day 9. A transcriptomic analysis were conducted and a total of 5517 differentially expressed genes were identified, including 2757 upregulated genes and 2760 downregulated genes. The upregulated genes were associated with viral infection and immune signaling pathways. Our findings provide a valuable genetic resource and a deeper understanding of the immune response to SKIV infection in spotted knifejaw.

Detection of porcine circovirus 2, porcine parvovirus 1, and torque teno sus virus k2a in wild boars from northeastern Patagonia, Argentina.

Wild boars can act as a reservoir of pathogenic viruses that affect the pig industry. Here, we assessed the presence of porcine circovirus 2, porcine parvovirus 1, and torque teno sus virus k2a in wild boars in northeastern Patagonia (Argentina). Total DNA was extracted from the tonsils of 27 animals (collected between early 2016 and mid-2019) and used to prepare sample pools, which were subjected to viral detection through two-round PCR assays. Sequencing of the amplification products and phylogenetic analysis confirmed the occurrence of all of the aforementioned infectious agents.