Teleost-specific TLR23 in Takifugu rubripes recruits MyD88 to trigger ERK pathway and promotes antibacterial defense.

Takifugu rubripes is a highly valued cultured fish in Asia, while pathogen infections can result in severe diseases and lead to substantial economic losses. Toll-like receptors (TLRs), as pattern recognition receptors, play a crucial role on recognition pathogens and initiation innate immune response. However, the immunological properties of teleost-specific TLR23 remain largely unknown.

IL8 of Takifugu rubripes is a chemokine that interacts with peripheral blood leukocytes and promotes antibacterial defense.

Interleukin 8 (IL8) is a CXC chemokine that plays a crucial role on promoting inflammatory response and immune regulation. In teleost, IL8 can induce the migration and activation of immune cells. However, the biological functions of IL8 are still unknown in Takifugu rubripes.

A novel C1qDC (PoC1qDC) with a collagen domain in Paralichthys olivaceus mediates complement activation and against bacterial infection.

Complement C1q domain containing protein (C1qDC) is a vital recognition molecule and has an important effect on immunity. The C1qDCs exhibit opsonic activity in fish, while the mechanisms of C1qDCs in activation complement still remain unclear. This study explored immunological characteristics of a C1qDC from Japanese flounder (Paralichthys olivaceus) (PoC1qDC).

An overview of complement systems in teleosts.

Complement plays an important role in the innate immune system, and it comprises about 35 individual proteins. In mammals, complement is activated via three different pathways, the classical pathway, the alternative pathway, and the lectin pathway. All three activation pathways produce C3-convertase in different forms.

Complement C3 and Activated Fragment C3a Are Involved in Complement Activation and Anti-Bacterial Immunity.

In the complement system, C3 is a central component in complement activation, immune defense and immune regulation. In all pathways of complement activation, the pivotal step is conversion of the component C3 to C3b and C3a, which is responsible to eliminate the pathogen and opsonization. In this study, we examined the immunological properties of C3 and its activated fragment C3a from Japanese flounder () (PoC3 and PoC3a), a teleost species with important economic value.

A deep-sea pathogenic Bacillus subtilis isolate employs different strategies to escape the killing of teleost and murine complements.

Bacillus subtilis subsp. subtilis G7 was isolated from a deep-sea hydrothermal vent and is pathogenic to pathogenic to fish (Japanese flounder) and mice. G7 is able to survive in host sera and phagocytes.

The Translocation and Assembly Module (TAM) of Is Essential for Stress Resistance and Host Infection.

Translocation and assembly module (TAM) is a protein channel known to mediate the secretion of virulence factors during pathogen infection. is a Gram-negative bacterium that is pathogenic to a wide range of farmed fish and other hosts including humans. In this study, we examined the function of the two components of the TAM, TamA and TamB, of (named and , respectively).

The trypsin-like serine protease domain of Paralichthys olivaceus complement factor I regulates complement activation and inhibits bacterial growth.

In mammals, complement factor I (CFI) is a serine protease in serum and plays a pivotal role in the regulation of complement activation. In the presence of cofactor, CFI cleaves C3b to iC3b, and further degrades iC3b to C3c and C3d. In teleost, the function of CFI is poorly understood.

Sip2: A Serum-Induced Protein That Is Essential to Serum Survival, Acid Resistance, Intracellular Replication, and Host Infection.

is a broad-host pathogen that can infect mammals, reptiles, and fish. exhibits a remarkable ability to survive in host serum and replicate in host phagocytes, but the underlining mechanism is unclear. In this study, in order to identify proteins involved in serum resistance, iTRAQ proteomic analysis was performed to examine the whole-cell protein profiles of TX01, a pathogenic isolate, in response to serum treatment.

A teleost CD46 is involved in the regulation of complement activation and pathogen infection.

In mammals, CD46 is involved in the inactivation of complement by factor I (FI). In teleost, study on the function of CD46 is very limited. In this study, we examined the immunological property of a CD46 molecule (CsCD46) from tongue sole, a teleost species with important economic value.

Characterization of a teleost membrane-associated protein that is involved in the regulation of complement activation and bacterial infection.

In mammals, membrane-associated complement regulatory proteins (MCRP) can protect host cells from the damaging of the activated complement. In teleost, few studies on the function of MCRP have been documented. In the present report, we identified a MCRP (named CsMCRP) from the teleost fish tongue sole Cynoglossus semilaevis and examined its immune function.

CsMAP34, a teleost MAP with dual role: A promoter of MASP-assisted complement activation and a regulator of immune cell activity.

In teleost fish, the immune functions of mannan-binding lectin (MBL) associated protein (MAP) and MBL associated serine protease (MASP) are scarcely investigated. In the present study, we examined the biological properties both MAP (CsMAP34) and MASP (CsMASP1) molecules from tongue sole (Cynoglossus semilaevis). We found that CsMAP34 and CsMASP1 expressions occurred in nine different tissues and were upregulated by bacterial challenge.

Tongue sole (Cynoglossus semilaevis) CD59: A complement inhibitor that binds bacterial cells and promotes bacterial escape from the killing of fish serum.

CD59 is a complement regulatory protein that inhibits the formation of membrane attack complex of complement. In this study, we examined the expression and activity of tongue sole (Cynoglossus semilaevis) CD59 (CsCD59). CsCD59 possesses the conserved structural features of CD59 and shares 33%-46% sequence identities with other fish CD59.

C5a of Cynoglossus semilaevis has anaphylatoxin-like properties and promotes antibacterial and antiviral defense.

Activation of the complement system leads to the cleavage of component factor C5 into C5a and C5b. C5a can induce chemotaxis and inflammatory responses in mammals. The function of C5a in fish is poorly understood.

CsTNF1, a teleost tumor necrosis factor that promotes antibacterial and antiviral immune defense in a manner that depends on the conserved receptor binding site.

Tumor necrosis factor (TNF) is one of the most important cytokines involved in inflammation, apoptosis, cell proliferation, and stimulation of the immune system. The TNF gene has been cloned in teleost fish; however, the in vivo function of fish TNF is essentially unknown. In this study, we report the identification of a TNF homologue, CsTNF1, from tongue sole (Cynoglossus semilaevis) and analysis of its expression and biological effect.

Molecular characterization and expression analysis of nine CC chemokines in half-smooth tongue sole, Cynoglossus semilaevis.

Chemokines are a large, diverse group of small cytokines that can be classified into several families, including the CC chemokine family, which plays a pivotal role in host defense by inducing leukocyte chemotaxis under physiological and inflammatory conditions. Here we studied 9 CC chemokines from half-smooth tongue sole (Cynoglossus semilaevis). Phylogenetic analysis divided these chemokines into four groups.

A CCL21 chemokine of tongue sole (Cynoglossus semilaevis) promotes host resistance against bacterial infection.

Chemokines are a large family of chemotactic cytokines. Based on the arrangement of the first two cysteine residues, chemokines are divided into four groups, one of which is the CC chemokine group. In this study, we characterized a CC chemokine, CsCCL21, from half-smooth tongue sole (Cynoglossus semilaevis), and analyzed its activity.

ORF75 of megalocytivirus RBIV-C1: A global transcription regulator and an effective vaccine candidate.

Megalocytivirus, a DNA virus belonging to the Iridoviridae family, is a severe pathogen to a wide range of marine and freshwater fish. In this study, using turbot (Scophthalmus maximus) as a host model, we examined the immunoprotective property of one megalocytivirus gene, ORF75, in the form of DNA vaccine (named pORF75). Immunofluorescence microscopy and RT-PCR analysis showed that P444, the protein encoded by ORF75, was naturally produced in the tissues of turbot during megalocytivirus infection, and that the vaccine gene in pORF75 was expressed in fish cells transfected with pORF75 and in the tissues of turbot immunized with pORF75.

CD83 is required for the induction of protective immunity by a DNA vaccine in a teleost model.

In mammals, CD83 is a surface marker on mature dendritic cells and vital to lymphocyte activation. In teleost, studies on the function of CD83 are very limited. In this study, we examined the potential involvement of turbot (Scophthalmus maximus) CD83, SmCD83, in vaccine-induced immunity.

Edwardsiella tarda evades serum killing by preventing complement activation via the alternative pathway.

Edwardsiella tarda is a Gram-negative bacterium with a broad host range that includes a wide variety of farmed fish as well as humans. E. tarda has long been known to be able to survive in host serum, but the relevant mechanism is unclear.

Edwardsiella tarda MliC, a lysozyme inhibitor that participates in pathogenesis in a manner that parallels Ivy.

Edwardsiella tarda, a bacterial pathogen to farmed fish as well as humans, possesses the genes of two lysozyme inhibitors, ivy and mliC (ivy(Et) and mliC(Et)). We recently studied IvyEt and found it to be implicated in E. tarda virulence.

NKLP27: a teleost NK-lysin peptide that modulates immune response, induces degradation of bacterial DNA, and inhibits bacterial and viral infection.

NK-lysin is an antimicrobial protein produced by cytotoxic T lymphocytes and natural killer cells. In this study, we examined the biological property of a peptide, NKLP27, derived from tongue sole (Cynoglossus semilaevis) NK-lysin. NKLP27 is composed of 27 amino acids and shares little sequence identity with known NK-lysin peptides.

Sil: a Streptococcus iniae bacteriocin with dual role as an antimicrobial and an immunomodulator that inhibits innate immune response and promotes S. iniae infection.

Streptococcus iniae is a Gram-positive bacterium and a severe pathogen to a wide range of economically important fish species. In addition, S. iniae is also a zoonotic pathogen and can cause serious infections in humans.

Turbot (Scophthalmus maximus) hepcidin-1 and hepcidin-2 possess antimicrobial activity and promote resistance against bacterial and viral infection.

Hepcidin is an antimicrobial peptide and a regulator of iron homeostasis. In turbot (Scophthalmus maximus), two types of hepcidins have been identified, which share approximately 50% sequence identity. In this study, we examined the antimicrobial potentials of the two hepcidins in the form of synthesized peptides, SmHep1P and SmHep2P.