RESUMO
Leukocyte cell-derived chemotaxin 2 (LECT2) is a multifunctional cytokine that especially plays an important role in innate immune. However, the roles of LECT2 in the immune response of the economically important fish Nile tilapia (Oreochromis niloticus) against bacterial infection remains unclear. In this study, a lect2 gene from Nile tilapia (On-lect2) was identified, and its roles in the fish's immune response against bacterial infection were determined and characterised. On-lect2 contains an open reading frame of 456 bp that encodes a peptide of 151 amino acids, as well as the conservative peptidase M23 domain. On-LECT2 is 62%-84% identical to other fish species and about 50% identical to mammals. The highest transcriptional level of On-lect2 was detected in the liver, whereas the lowest levels were detected in the other tissues. Moreover, the On-LECT2 protein is located mainly in the brain and head kidney. The transcriptional levels of On-lect2 substantially increased in the head kidney, brain, liver and spleen after Streptococcus agalactiae infection. Knockdown On-lect2 led to higher mortality due to liver necrosis or haemorrhage and splenomegaly. In vitro analysis indicated that the recombinant protein of On-LECT2 improved phagocytic activity of head kidney-derived macrophages. In vivo challenge experiments revealed several functions of On-LECT2 in the immune response of Nile tilapia against bacterial infection, including promotion of inflammation, reduction of tissue damages and improvement of survival rate.
Assuntos
Ciclídeos/microbiologia , Doenças dos Peixes/prevenção & controle , Proteínas de Peixes/metabolismo , Imunidade Inata , Peptídeos e Proteínas de Sinalização Intercelular/metabolismo , Macrófagos/microbiologia , Infecções Estreptocócicas/veterinária , Streptococcus agalactiae/patogenicidade , Animais , Ciclídeos/genética , Ciclídeos/imunologia , Ciclídeos/metabolismo , Doenças dos Peixes/imunologia , Doenças dos Peixes/metabolismo , Doenças dos Peixes/microbiologia , Proteínas de Peixes/genética , Interações Hospedeiro-Patógeno , Peptídeos e Proteínas de Sinalização Intercelular/genética , Macrófagos/imunologia , Macrófagos/metabolismo , Infecções Estreptocócicas/metabolismo , Infecções Estreptocócicas/microbiologia , Infecções Estreptocócicas/prevenção & controle , Streptococcus agalactiae/imunologia , Transcrição GênicaRESUMO
Galectin-related protein is a kind of lectin without canonical activity that regulates cell adhesion and cell growth. In this study, a novel galectin-related protein B (OnGRPB) was identified from Nile tilapia (Oreochromis niloticus). The open reading frame of OnGRPB was 438 bp and encoded a peptide of 145 amino acids. The deduced protein sequence of OnGRPB possessed a conserved carbohydrate recognition domain (CRD) with partial sugar binding sites (N-R, V-N and W-E) and shared high identities with other fish GRPB proteins. The qRT-PCR analysis found that OnGRPB was widely distributed in various tissues and monocyte/macrophages (Mo/MΦ) of healthy tilapia. After Streptococcus agalactiae infection, OnGRPB transcripts were significantly up-regulated in liver, spleen, head kidney and Mo/MΦ. The recombinant OnGRPB protein (rOnGRPB) had the binding activity and agglutination ability to bacteria. Also, rOnGRPB could modulate antibacterial activity and inflammatory factor expression of Mo/MΦ. These data collectively indicate that OnGRPB plays roles in the immune response of Nile tilapia against bacterial infection.
Assuntos
Ciclídeos/imunologia , Doenças dos Peixes/imunologia , Galectinas/imunologia , Infecções Estreptocócicas/veterinária , Sequência de Aminoácidos , Animais , Ciclídeos/genética , Proteínas de Peixes/química , Proteínas de Peixes/genética , Proteínas de Peixes/imunologia , Galectinas/química , Galectinas/genética , Regulação da Expressão Gênica , Infecções Estreptocócicas/imunologia , Infecções Estreptocócicas/microbiologia , Streptococcus agalactiae/fisiologiaRESUMO
Galectin-3 is a kind of ß-galactoside-binding lectin involved in host defense against pathogen infection. However, the immune functions of fish galectin-3 remain poorly understood. In this study, the roles of a fish galectin-3 (OnGal-3) from Nile tilapia (Oreochromis niloticus) on the binding activity on bacterial pathogens or PAMPs, the agglutinating activity on bacterial pathogens and the regulatory effects on monocytes/macrophages activity were investigated. After in vitro challenge of Streptococcus agalactiae and Aeromonas hydrophila, OnGal-3 expressions were significantly up-regulated in monocytes/macrophages. In addition, recombinant OnGal-3(rOnGal-3) protein showed strong binding activity on bacterial pathogens or PAMPs. Also, rOnGal-3 agglutinated Gram-positive and Gram-negative bacteria. Moreover, rOnGal-3 could induce the inflammatory factors expressions in monocytes/macrophages and enhance phagocytosis and respiratory burst activity of monocytes/macrophages. These results suggest that fish galectin-3 participates in anti-bacterial immune response through recognizing pathogens and modulating monocytes/macrophages activity.
