Comparative proteomic analysis of hepatic mechanisms of Megalobrama amblycephala infected by Aeromonas hydrophila

Advances and Challenges in Aeromonas hydrophila Vaccine Development: Immunological Insights and Future Perspectives

Aeromonas hydrophila presents a significant threat to global aquaculture due to its ability to infect freshwater and marine fish species, leading to substantial economic losses. Effective mitigation methods are essential to address these challenges. Vaccination has emerged as a promising strategy to reduce A. hydrophila infections; however, it faces several obstacles, including variability in immune responses, pathogen diversity, and environmental factors affecting vaccine efficacy. To enhance vaccine performance, researchers focus on adjuvants to boost immune responses and develop multivalent vaccines targeting multiple A. hydrophila strains. Tailoring vaccines to specific environmental conditions and optimizing vaccination schedules can further address the challenges posed by pathogen diversity and variable immune responses. This review provides an in-depth analysis of the immunological hurdles associated with A. hydrophila vaccine development. Current vaccine types-live attenuated, inactivated, subunit, recombinant, and DNA-exhibit diverse mechanisms for stimulating innate and adaptive immunity, with varying levels of success. Key focus areas include the potential of advanced adjuvants and nanoparticle delivery systems to overcome existing barriers. The review also highlights the importance of understanding host-pathogen interactions in guiding the development of more targeted and effective immune responses in fish. Complementary approaches, such as immunostimulants, probiotics, and plant-based extracts, are explored as adjuncts to vaccination in aquaculture health management. Despite notable progress, challenges remain in translating laboratory innovations into scalable, cost-effective solutions for aquaculture. Future directions emphasize the integration of advanced genomic and proteomic tools to identify novel antigen candidates and the need for industry-wide collaborations to standardize vaccine production and delivery. Addressing these challenges can unlock the potential of innovative vaccine technologies to safeguard fish health and promote sustainable aquaculture practices globally.

Full-length transcriptome assembly of black amur bream (Megalobrama terminalis) as a reference resource

BACKGROUND

The genus Megalobrama holds significant economic value in China, with M. terminalis (Black Amur bream) ranking second in production within this group. However, lacking comprehensive genomic and transcriptomic data has impeded research progress. This study aims to fill this gap through an extensive transcriptomic analysis of M. terminalis.

METHODS AND RESULTS

We utilized PacBio Isoform Sequencing to generate 558,998 subreads, totaling 45.52 Gb, which yielded 22,141 transcripts after rigorous filtering and clustering. Complementary Illumina short-read sequencing corrected 967,114 errors across these transcripts. Our analysis identified 12,426 non-redundant isoforms, with 11,872 annotated in various databases. Functional annotation indicated 11,841 isoforms matched entries in the NCBI non-redundant protein sequences database. Gene Ontology analysis categorized 10,593 isoforms, revealing strong associations with cellular processes and binding functions. Additionally, 8203 isoforms were mapped to pathways in the Kyoto Encyclopedia of Genes and Genomes, highlighting significant involvement in immune system processes and complement cascades. We notably identified key immune molecules such as alpha-2-macroglobulin and complement component 3, each with multiple isoforms, underscoring their potential roles in the immune response. Our analysis also uncovered 853 alternative splicing events, predominantly involving retained introns, along with 672 transcription factors and 426 long non-coding RNAs.

CONCLUSIONS

The high-quality reference transcriptome generated in this study provides a valuable resource for comparative genomic studies within the Megalobrama genus, supporting future research to enhance aquaculture stocks.

Proteomic analysis of liver tissue reveals Aeromonas hydrophila infection mediated modulation of host metabolic pathways in Labeo rohita

Aeromonas hydrophila (Ah) is a Gram-negative bacterium and a serious global pathogen causing Motile Aeromonas Septicaemia (MAS) in fish leading to global loss in aquaculture. Investigation of the molecular alterations of host tissues such as liver could be a powerful approach to identify mechanistic and diagnostic immune signatures of disease pathogenesis. We performed a proteomic analysis of Labeo rohita liver tissue to examine the protein dynamics in the host cells during Ah infection. The proteomic data was acquired using two strategies; discovery and targeted proteomics. Label-free quantification was performed between Control and challenged group (AH) to identify the differentially expressed proteins (DEPs). A total of 2525 proteins were identified and 157 were DEPs. DEPs include metabolic enzymes (CS, SUCLG2), antioxidative proteins, cytoskeletal proteins and immune related proteins (TLR3, CLEC4E). Pathways like lysosome pathway, apoptosis, metabolism of xenobiotics by cytochrome P450 were enriched by downregulated proteins. However, upregulated proteins majorly mapped to innate immune system, signaling of B cell receptor, proteosome pathway, ribosome, carbon metabolism and protein processing in ER. Our study would help in exploring the role of Toll-like receptors, C-type lectins and, metabolic intermediates like citrate and succinate in Ah pathogenesis to understand the Ah infection in fish. SIGNIFICANCE: Bacterial diseases such as motile aeromonas septicaemia (MAS) are among the most serious problems in aquaculture industry. Small molecules that target the metabolism of the host have recently emerged as potential treatment possibilities in infectious diseases. However, the ability to develop new therapies is hampered due to lack of knowledge about pathogenesis mechanisms and host-pathogen interactions. We examined alterations in the host proteome during MAS caused by Aeromonas hydrophila (Ah) infection, in Labeo rohita liver tissue to find cellular proteins and processes affected by Ah infection. Upregulated proteins belong to innate immune system, signaling of B cell receptor, proteosome pathway, ribosome, carbon metabolism and protein processing. Our work is an important step towards leveraging host metabolism in targeting the disease by providing a bigger picture on proteome pathology correlation during Ah infection.

Fish infections associated with the genus Aeromonas: a review of the effects on oxidative status

The aim of this review was to summarize the current knowledge regarding the effects of aeromonosis on fish oxidative status. The bibliographic survey was carried out on the research platforms: Scopus and Science Direct. The keywords 'Aeromonas', 'fish' and 'oxidative status' (or 'oxidative stress', 'oxidative damage' and similar terms) were used. Scientific papers and short communications were considered. Studies involving fish aeromonosis and enzymatic or non-enzymatic markers of oxidative status were selected. The results of antioxidant enzymes activities/expressions after infection lack consistency, suggesting that these findings should be interpreted with caution. Most of the analysed studies pointed to an increase in reactive oxygen species, malondialdehyde and protein carbonylation levels, indicating possible oxidative damage caused by the infection. Thus, these three biomarkers are excellent indicators of oxidative stress during infection. Regarding respiratory burst activity, several studies have indicated increased activity, but other studies have indicated unchanged activity after infection. Nitric oxide levels also increased after infection in most studies. Therefore, it is suggested that the fish's immune system tries to fight a bacterial infection by releasing reactive oxygen and nitrogen species.

Differentially expressed proteins in the intestine of Cynoglossus semilaevis Günther following a Shewanella algae challenge

Fish intestine is an important constituent of the mucosal immune system. The gut and gut-associated lymphoid tissue construct a local immune environment. A Shewanella algae strain was previously reported to be a pathogen causing ascitic disease accompanied with intestinal inflammation in Cynoglossus semilaevis. This study aimed to investigate the intestine immune response in C. semilaevis to S. algae infection at the protein level. Two-dimensional electrophoresis coupled with mass spectrometry proteomics was utilized to compare protein expression in the intestines from normal and S. algae-infected C. semilaevis. A total of 70 differentially expressed proteins (DEPs), consisting of 16 upregulated and 54 downregulated proteins, were identified in the intestine tissue of C. Semilaevis. These protein expression changes were further validated using western blot analysis and quantitative real-time PCR. Gene ontology enrichment analysis showed that these 70 DEPs could be assigned across three categories: "cellular components", "molecular function", and "biological process". Forty-one DEPs (six up-regulated and 35 down-regulated proteins) related to metabolic processes were identified. In addition, 20 DEPs (eight up-regulated and 12 down-regulated proteins) related to stress and immune responses were identified. A protein-protein interaction network generated by the STRING (Search Tool for the Retrieval of Interacting Genes/protein) revealed that 30 DEPs interacted with one another to form an integrated network. Among them, 29 DEPs were related to stress, immune, and metabolism processes. In the network, some of the immune related proteins (C9, FGB, KNG1, apolipoprotein A-IV-like, and PDIA3) were up-regulated and most DEPs involved in metabolism processes were down-regulated. These results indicate that the immune defense response of the intestine was activated and the intestinal function associated with metabolism processes was disturbed. This study provides valuable information for further research into the functions of these DEPs in fish.

An iTRAQ-Based Comparative Proteomics Analysis of the Biofilm and Planktonic States of Aeromonas veronii TH0426

Aeromonas veronii is a virulent fish pathogen that causes extensive economic losses in the aquaculture industry worldwide. In this study, a virulent strain of A. veronii TH0426 was used to establish an in vitro biofilm model. The results show that the biofilm-forming abilities of A. veronii TH0426 were similar in different media, peaking under conditions of 20 °C and pH 6. Further, isobaric tags for relative and absolute quantitation (iTRAQ)-based quantitative proteomics methods were used to compare the differential expression of A. veronii between the biofilm and planktonic cells. The results show alterations in 277 proteins, with 130 being upregulated and 147 downregulated. Pathway analysis and GO (Gene Ontology) annotations indicated that these proteins are mainly involved in metabolic pathways and the biosynthesis of secondary metabolites and antibiotics. These proteins are the main factors affecting the adaptability of A. veronii to its external environment. MRM (multiple reaction 27 monitoring) and qPCR (qPCR) were used to verify the differential proteins of the selected A. veronii. This is the first report on the biofilm and planktonic cells of A. veronii, thus contributing to studying the infection and pathogenesis of A. veronii.

Proteomic characterization of the hepatopancreas in the Pacific white shrimp Litopenaeus vannamei under cold stress: Revealing the organism homeostasis mechanism

To understand the homeostasis mechanism of crustacean hepatopancreas to cold stress, iTRAQ proteomics based on the genome database of Litopenaeus vannamei (L. vannamei) was applied to investigate proteins changes and variety of the hepatopancreas during cold stress stage in this study. A total of 4062 distinct proteins were identified, 137 differentially expressed proteins (DEPs) including 62 differentially up-regulated proteins (DUPs) and 75 differentially down-regulated proteins (DDPs) were identified in G1 (18 °C) compared with CK (28 °C), 359 DEPs including 131 DUPs and 228 DDPs were identified in G2 (13 °C for 24 h) compared with CK. Based on bioinformatics analysis, the cold tolerance of L. vannamei might be related to energy metabolism such as amino acid, carbohydrate, lipid, and oxidative phosphorylation. Moreover, shrimp immunity was declined during cold stress stage. However, L. vannamei could cope with cold stress by enhancing the production of ATP and UFA. Notably, arginine kinase, heat shock proteins, and histones may act as positive regulators in L. vannamei under cold stress. Ten randomly selected proteins were used for validation using qRT-PCR and the expressions on the transcription level for most of the genes were similar to the results of iTRAQ. These results indicated that L. vannamei can maintain the organism homeostasis by a series of orderly regulatory process during cold stress. Furthermore, the results can provide guidance for shrimp farming.