Reactive oxygen species (ROS) are continuously produced and eliminated by living organisms normally maintaining ROS at certain steady-state levels Under some circumstances, the balance between ROS generation and elimination is disturbed leading to enhanced ROS level called "oxidative stress" The primary goal of this review is to characterize two principal mechanisms of protection against oxidative stress - regulation of membrane permeability and antioxidant potential The ancillary goals of this work are to describe up to date knowledge on the regulation of the previously mentioned mechanisms and to identify areas of prospective research and emerging directions in investigation of adaptation to oxidative stress The ubiquity for challenges leading to oxidative stress development calls for identification of common mechanisms They are cysteine residues and [Fe,S]-clusters of specific regulatory proteins The latter mechanism is realized via SoxR bacterial protein, whereas the former mechanism is involved in operation of bacterial OxyR regulon, yeast H(2)O(2)-stimulon, plant NPR1/TGA and Rap24a systems, and animal Keap1/Nrf2, NF-κB and AP-1, and others Although hundreds of studies have been carried out in the field with different taxa, the comparative analysis of adaptive response is quite incomplete and therefore, this work aims to cover a plethora of phylogenetic groups to delineate common mechanisms In addition, this article raises some questions to be elucidated and points out future directions of this research The comparative approach is used to shed light on fundamental principles and mechanisms of regulation of antioxidant systems The idea is to provide starting points from which we can develop novel tools and hypothesis to facilitate meaningful investigations in the physiology and biochemistry of organismic response to oxidative stress

Adaptive response to oxidative stress: Bacteria, fungi, plants and animals.

Receptors that recognize conserved pathogen molecules are the first line of cellular innate immunity defense. Toll-like receptors (TLRs) are the best understood of the innate immune receptors that detect infections in mammals. Key features of the fish TLRs and the factors involved in their signaling cascade have high structural similarity to the mammalian TLR system. However, the fish TLRs also exhibit very distinct features and large diversity which is likely derived from their diverse evolutionary history and the distinct environments that they occupy. Six non-mammalian TLRs were identified in fish. TLR14 shares sequence and structural similarity with TLR1 and 2, and the other five (TLR19, 20, 21, 22 and 23) form a cluster of novel TLRs. TLR4 was lost from the genomes of most fishes, and the TLR4 genes found in zebrafish do not recognize the mammalian agonist LPS and are likely paralogous and not orthologous to mammalian TLR4 genes. TLR6 and 10 are also absent from all fish genomes sequenced to date. Of the at least 16 TLR types identified in fish, direct evidence of ligand specificity has only been shown for TLR2, TLR3, TLR5M, TLR5S and TLR22. The common carp TLR2 was shown to recognize the synthetic triacylated lipopeptide Pam(3)CSK(4) and lipopeptides from gram positive bacteria. The membrane-bound TLR5 (TLR5M) signaling in response to flagellin in rainbow trout is amplified through interaction with the soluble form (TLR5S) in a positive loop feedback. In Fugu, TLR3 is localized to the endoplasmic reticulum (ER) and recognizes relatively short dsRNA, while TLR22 has a surveillance function like the human cell-surface TLR3. Genome and gene duplications have been major contributors to the teleost's rich evolutionary history and genomic diversity. Duplicate or multi-copy TLR genes were identified for TLR3 and 7 in common carp, TLR4b, 5, 8 and 20 in zebrafish, TLR8a in rainbow trout and TLR22 in rainbow trout and Atlantic salmon. The main task for current and near-future fish TLRs research is to develop specificity assays to identify the ligands of all fish TLRs, which will advance comparative immunology research and will contribute to our understanding of disease resistance mechanisms in fish and the development of new adjuvants and/or more effective vaccines and therapeutics.

Toll-like receptors in bony fish: from genomics to function.

Fish is considered to be an important model in comparative immunology studies because it is a representative population of lower vertebrates serving as an essential link to early vertebrate evolution. Fish immune-relevant genes have received considerable attention due to its role in improving understanding of both fish immunology and the evolution of immune systems. In this review, we discuss the current understanding of teleost immune-relevant genes for both innate and adaptive immunity, including pattern recognition receptors, antimicrobial peptides, complement molecules, lectins, interferons and signaling factors, inflammatory cytokines, chemokines, adaptive immunity relevant cytokines and negative regulators, major histocompatibility complexes, immunoglobulins, and costimulatory molecules. The implications of these factors on the evolutionary history of immune systems were discussed and a perspective outline of innate and adaptive immunity of teleost fish was described. This review may provide clues on the evolution of the essential defense system in vertebrates.

Advances in research of fish immune-relevant genes: a comparative overview of innate and adaptive immunity in teleosts.

Toll-like receptor signaling in bony fish.

Interferons (IFNs) are the hallmark of the vertebrate antiviral system. Two of the three IFN families identified in higher vertebrates are now known to be important for antiviral defence in teleost fish. Based on the cysteine patterns, the fish type I IFN family can be divided into two subfamilies, which possibly interact with distinct receptors for signalling. The fish type II IFN family consists of two members, IFN-γ with similar functions to mammalian IFN-γ and a teleost specific IFN-γ related (IFN-γrel) molecule whose functions are not fully elucidated. These two type II IFNs also appear to bind to distinct receptors to exert their functions. It has become clear that fish IFN responses are mediated by the host pattern recognition receptors and an array of transcription factors including the IFN regulatory factors, the Jak/Stat proteins and the suppressor of cytokine signalling (SOCS) molecules.

Teleost fish interferons and their role in immunity.

TLR22 occurs exclusively in aquatic animals and its role is unknown. Herein we show that the fugu (Takifugu rubripes) (fg)TLR3 and fgTLR22 link the IFN-inducing pathway via the fg Toll-IL-1R homology domain-containing adaptor protein 1(fgTICAM-1, or TRIF) adaptor in fish cells. fgTLR3 resides in endoplasmic reticulum and recognizes relatively short-sized dsRNA, whereas fgTLR22 recognizes long-sized dsRNA on the cell surface. On poly(I:C)-stimulated fish cells, both recruit fgTICAM-1, which in turn moves from the TLR to a cytoplasmic signalosome region. Thus, fgTICAM-1 acts as a shuttling platform for IFN signaling. When fish cells expressing fgTLR22 are exposed to dsRNA or aquatic dsRNA viruses, cells induce IFN responses to acquire resistance to virus infection. Thus, fish have a novel TICAM-1-coupling TLR that is distinct from the mammalian TLR3 in cellular localization, ligand selection, and tissue distribution. TLR22 may be a functional substitute of human cell-surface TLR3 and serve as a surveillant for infection with dsRNA virus to alert the immune system for antiviral protection in fish.

/pdf/teleost-tlr22-recognizes-rna-duplex-to-induce-ifn-and-xu020f0soe.pdf

Teleost TLR22 recognizes RNA duplex to induce IFN and protect cells from birnaviruses.

Current growth in aquaculture production is parallel with the increasing number of disease outbreaks, which negatively affect the production, profitability, and sustainability of the global aquaculture industry. Vibriosis is among the most common diseases leading to massive mortality of cultured shrimp, fish, and shellfish in Asia. High incidence of vibriosis can occur in hatchery and grow-out facilities, but juveniles are more susceptible to the disease. Various factors, particularly the source of fish, environmental factors (including water quality and farm management), and the virulence factors of Vibrio, influence the occurrence of the disease. Affected fish show weariness, with necrosis of skin and appendages, leading to body malformation, slow growth, internal organ liquefaction, blindness, muscle opacity, and mortality. A combination of control measures, particularly a disease-free source of fish, biosecurity of the farm, improved water quality, and other preventive measures (e.g., vaccination) might be able to control the infection. Although some control measures are expensive and less practical, vaccination is effective, relatively cheap, and easily implemented. In this review, the latest knowledge on the pathogenesis and control of vibriosis, including vaccination, is discussed.

/pdf/vibriosis-in-fish-a-review-on-disease-development-and-4notmr5m0l.pdf

Vibriosis in Fish: A Review on Disease Development and Prevention

The survivability of koi herpesvirus (KHV) in environmental water and sediment was evaluated using CCB cells. Samples were collected from Ibaraki prefecture, Kanagawa prefecture and Hakodate, Hokkaido. Significant reduction in the infectious titer of KHV was observed within 3 days in intact environmental water or sediment. However, KHV infectivity remained for more than 7 days in autoclaved or filtered (0.45 μm) water. In the autoclaved water containing sediment, KHV infectivity dropped below detectable limits within 7 days after inoculation. Ten of the 147 bac- terial strains from rivers in Kanagawa, and two of the 62 bacterial strains from water from, Hakodate showed anti-KHV properties. The results suggest that in the absence of hosts, KHV can be rapidly inactivated in environmental water.

/pdf/survival-of-koi-herpesvirus-khv-in-environmental-water-hrdfllc1jv.pdf

Survival of Koi Herpesvirus (KHV) in Environmental Water

Disinfection of water for aquaculture is critical for preventing the introduction and spread of infectious disease. A pathogen-free water source is essential for success in aquaculture. Typical treatment systems make use of high efficiency sand filters to clarify the water before treatment with ultraviolet (UV) light or ozonization. Fish pathogens are divided into two groups based on their sensitivity to UV and total residual oxidants (TROs) produced by ozonization of seawater. Hypochlorite produced by electrolysis of seawater (salt water) showed bactericidal and viricidal effects. This method can easily treat large volumes of water, and is suitable for disinfecting wastewater before discharging.

/pdf/disinfection-of-water-for-aquaculture-2ugo56htxj.pdf

Disinfection of water for aquaculture

The virucidal effects of ultraviolet (UV) irradiation, heat treatment and disinfectants against koi herpesvirus (KHV) were evaluated using KF-1 cells. KHV (KHV-I strain) was completely inactivated by UV irradiation at a dose of 4.0 ¥ 10 m Ws/cm or heating to temperatures above 50∞C for 1 min. KHV was completely inactivated by 200 mg/L iodophor, 60 mg/L benzalkonium chloride solution or 30% ethyl alcohol for 20 min. When chlorine concentration was measured after mixing with virus supernatant containing medium and fetal bovine serum, 97.5% and 98.5% reduction in infectivity was observed at 0.30 mg/L of chlorine for 30 s and 20 min, respectively. In practice, a tenfold concentration of chlorine (i.e. 3 mg/L) will be recommended to inactivate KHV completely.

https://www.jstage.jst.go.jp/article/jsfp1966/40/3/40_3_137/_pdf

Hisae Kasai

Papers

Teleost TLR22 recognizes RNA duplex to induce IFN and protect cells from birnaviruses.

Vibriosis in Fish: A Review on Disease Development and Prevention

Survival of Koi Herpesvirus (KHV) in Environmental Water

Disinfection of water for aquaculture

Virucidal Effects of Ultraviolet, Heat Treatment and Disinfectants against Koi Herpesvirus (KHV)