Aeromonas hydrophila induction method in adult zebrafish (Danio rerio) as animal infection models

Identification of a novel antimicrobial peptide from amphioxus ribosomal protein L27

Antimicrobial peptides (AMPs), derived from a variety of proteins such as ribosomal proteins, play a pivotal role in the innate immune system. However, information regarding ribosomal protein-derived AMPs is currently limited and their mechanisms of action remain poorly defined. Here we identified and characterized the antibacterial activity of amphioxus RPL27 (BjRPL27) and its core functional region located at residues 51-72 (termed BjRPL2751-72). We found that BjRPL27 expression was upregulated in the hepatic caecum following bacterial infection. Both the recombinant protein rBjRPL27 and the synthetic peptide BjRPL2751-72 effectively killed the Gram-positive bacterium Staphylococcus aureus and the Gram-negative bacterium Aeromonas hydrophila via a combined action of disrupting cell membrane integrity, inducing membrane depolarization, and increasing intracellular reactive oxygen species (ROS) production. Additionally, the sequence of BjRPL2751-72 was highly conserved among all eukaryotic RPL27s, implying an ancient origin for the antibacterial activity of the RPL27 family. In vivo assays showed that BjRPL2751-72 not only efficiently protected zebrafish from A. hydrophila infection, but also killed the bacterium S. aureus on the skin wound of rats. Furthermore, neither BjRPL27 nor BjRPL2751-72 exhibited hemolytic activity towards human red blood cells, making them promising lead molecules for designing novel AMPs. These findings highlight the potential of BjRPL2751-72 as a novel AMP with selective bactericidal properties.

A comprehensive review on probiotics and their use in aquaculture: Biological control, efficacy, and safety through the genomics and wet methods

Probiotics, defined as viable microorganisms that enhance host health when consumed through the diet, exert their effects through mechanisms such as strengthening the immune system, enhancing resistance to infectious diseases, and improving tolerance to stressful conditions. Driven by a growing market, research on probiotics in aquaculture is a burgeoning field. However, the identification of new probiotics presents a complex challenge, necessitating careful consideration of both the safety and efficacy of the microorganisms employed. This review aims to delineate the most utilized and effective methods for identifying probiotics. The most effective approach currently combines in silico analysis of genomic sequences with in vitro and in vivo experiments. Two main categories of genetic traits are analyzed using bioinformatic tools: those that could harm the host or humans (e.g., toxin production, antibiotic resistance) and those that offer benefits (e.g., production of helpful compounds, and enzymes). Similarly, in vitro experiments allow us to examine the safety of a probiotic but also its effectiveness (e.g., ability to adhere to epithelia). Finally, in vivo experiments allow us to study the effect of probiotics on fish growth and health, including the ability of the probiotic to manipulate the host's microbiota and the ability to mitigate the infections. This review comprehensively analyzes these diverse aspects, with a particular focus on the potential of studying the interaction between bacterial pathogens and probiotics through these integrated methods.

Hexane extract from black soldier fly prepupae: A novel immunomodulatory strategy against Aeromonas hydrophila infection in zebrafish

Background and Aim

Aeromonas hydrophila infections in fish result in significant financial losses within aquaculture. Previous research indicates black soldier fly (BSF) prepupae provide immunomodulatory benefits through their fatty acids, chitin, and proteins. The study evaluated the impact of hexane extract from black soldier fly prepupae (HEBP) on interleukin (IL)-4 and IL-10 cytokine expression in zebrafish, both infected and uninfected with A. hydrophila.

Materials and Methods

Adult zebrafish (aged 4-5 months) was assigned to a negative control group (fed commercial feed), a positive control group (commercial feed + A. hydrophila infection at 107 colony-forming unit/mL), and three treatment groups (T1, T2, T3) that received HEBP at doses of 1000; 2000 and 4000 mg/kg feed for 30 days, respectively. A. hydrophila infection was introduced on day 31 through immersion. Analysis of IL-4 and IL-10 expression in the head kidney trunk region (body without head and tail) through quantitative polymerase chain reaction was conducted on day 33.

Results

The HEBP modulated the immune response to A. hydrophila infection at a concentration of 1000 mg/kg feed, as evidenced by an increase in IL-4 and IL-10 expression in the groups not infected with the bacteria. However, these cytokines were decreased in the infected groups.

Conclusion

A feed concentration of 1000 mg/kg HEBP was identified as optimal for cytokine modulation. This discovery marks a significant advancement in the development and benefit of a natural extract-based immunomodulator in a zebrafish model, which is potentially immunotherapeutic against bacterial infections in fish for the aquaculture industry.

Effect of polar fractions of Marsilea crenata C. Presl. leaves in zebrafish locomotor activity

Neurodegenerative diseases (NDs) are pathological conditions initiated by the loss of neuronal cell structure and the progressive decline in function caused by prolonged neuroinflammation. Postmenopausal women are at a high risk of experiencing NDs due to estrogen deficiency in their bodies, necessitating the administration of phytoestrogens as a replacement for estrogen in the body. One alternative therapy is administering phytoestrogens, estrogen-like substances from plants, which can be obtained from Marsilea crenata C. Presl. leaves. The purpose of this study was to determine whether administration of the n-butanol fraction (BF) and water fraction (WF) of M. crenata leaves could increase locomotor activity in rotenone-induced zebrafish. Treatment was given to each group of zebrafish with BF and WF at doses of 2.5; 5; 10; and 20 ppm to determine the locomotor activity. Then an analysis was carried out by looking at each movement of the zebrafish swimming for 1 min at the time of observation on days 0, 7, 14, 21, and 28. The result showed that BF and WF significantly increased the locomotor activity of zebrafish at the optimum dose of 20 ppm for BF and 5 ppm for WF compared to the negative control. This concludes that the polar fraction of M. crenata leaves is proven to have the potential to prevent ND progressivity.

Proteomic analysis of crocodile white blood cells reveals insights into the mechanism of the innate immune system

Crocodiles have a particularly powerful innate immune system because their blood contains high levels of antimicrobial peptides. They can survive injuries that would be fatal to other animals, and they are rarely afflicted with diseases. To better understand the crocodile's innate immune response, proteomic analysis was performed on the white blood cells (WBC) of an Aeromonas hydrophila-infected crocodile. Levels of WBC and red blood cells (RBC) rapidly increased within 1 h. In WBC, there were 109 up-regulated differentially expressed proteins (DEP) that were up-regulated. Fifty-nine DEPs dramatically increased expression from 1 h after inoculation, whereas 50 up-regulated DEPs rose after 24 h. The most abundant DEPs mainly had two biological functions, 1) gene expression regulators, for example, zinc finger proteins and histone H1 family, and 2) cell mechanical forces such as actin cytoskeleton proteins and microtubule-binding proteins. This finding illustrates the characteristic effective innate immune response mechanism of crocodiles that might occur via boosted transcription machinery proteins to accelerate cytoskeletal protein production for induction of phagocytosis, along with the increment of trafficking proteins to transport essential molecules for combating pathogens. The findings of this study provide new insights into the mechanisms of the crocodile's innate immune system.