ABSTRACT
Effects of ß-glucan on innate immune responses and survival were studied in pacu experimentally infected with Aeromonas hydrophila. Fish fed diets containing 0, 0.1% and 1% ß-glucan were injected with A. hydrophila. ß-glucan enhanced fish survival in both treated groups (26.7% and 21.2% of the control, respectively). Leukocyte respiratory burst and alternative complement pathway activities were elevated after bacterial challenge regardless the ß-glucan concentration. Lysozyme activity was higher after infection and showed a gradual increase as ß-glucan concentration increased. A significant elevation in WBC count was observed either after bacterial challenge or by influence of ß-glucan separately. The same response was observed in the number of thrombocytes, lymphocytes, eosinophils, LG-PAS positive cell and monocytes. It can be concluded that feeding pacu with ß-glucan can increase protection against A. hydrophila, due to changes in non-specific immune responses.
Subject(s)
Aeromonas hydrophila , Animal Feed , Disease Resistance/immunology , Fish Diseases/immunology , Gram-Negative Bacterial Infections/veterinary , beta-Glucans/administration & dosage , Animals , Disease Resistance/drug effects , Gram-Negative Bacterial Infections/immunology , Survival AnalysisABSTRACT
Antibody can be assessed by agglutinating antibody titer which is a quantitative measure of circulating antibodies in serum from fish previously immunized. The antibody evaluation has been performed with different fish species, and is considered a reliable method that can be applied to confirm several hypothesis regarding acquired immunity, even in conjunction with precise methods to describe immune mechanisms. In order to provide appropriate analytical methods for future studies on the specific immune system of native fish, the present study standardized on assay to measure the serum agglutinating antibody titer produced after immunization with inactivated A. hydrophila and levamisole administration in pacu. It was possible to determine the agglutinating antibodies titer in a satisfactorily way in pacu immunized with inactive A. hydrophila, and the highest titers were observed on fish fed with levamisole.
Subject(s)
Adaptive Immunity/immunology , Aeromonas hydrophila/immunology , Characidae/immunology , Fish Diseases/prevention & control , Adjuvants, Immunologic/administration & dosage , Agglutination Tests/veterinary , Animals , Antibodies, Bacterial/blood , Characidae/classification , Fish Diseases/immunology , Levamisole/administration & dosageABSTRACT
The immune system of teleost fish has mechanisms responsible for the defense against bacteria through protective proteins in several tissues. The protein action can be evaluated by serum bactericidal activity and this is an important tool to analyze the immune system. Pacu, Piaractus mesopotamicus, is one of the most important fish in national aquaculture. However there is a lack of studies on its immune responses. In order to standardize and assess the accuracy of the serum bactericidal activity assay, fish were briefly challenged with Aeromonas hydrophila and sampled one week after the challenge. The bacterial infection increased the concentration of protective proteins, resulting in a decrease of colony-forming unit values expressed as well as an enhanced serum bactericidal activity. The protocol showed a reliable assay, appropriate to determine the serum bactericidal activity of pacu in the present experimental conditions.
O sistema imune de peixes teleósteos tem mecanismos responsáveis pela defesa contra bactérias e atua através de proteínas presentes em diversos tecidos. A ação destas proteínas pode ser avaliada pela atividade bactericida do soro, sendo esta uma importante ferramenta para analisar o sistema imune. O pacu, Piaractus mesopotamicus, é um peixe nativo muito importante para aquicultura nacional, entretanto há pouco conhecimento sobre o funcionamento de seu sistema imune. Assim foi realizado experimento para padronizar e avaliar a eficiência do ensaio de atividade bactericida. Resumidamente, peixes foram desafiados por Aeromonas hydrophila e amostradas uma semana após o desafio. A infecção bacteriana promoveu um aumento na concentração de proteínas protetoras, resultando em diminuição dos valores de unidades formadoras de colônias ou expressos também como aumento da atividade bactericida do soro. O protocolo se mostrou confiável, sendo apropriado para determinar a atividade bactericida do soro de pacu nas condições experimentais.
Subject(s)
Animals , Anti-Bacterial Agents , Immunity, Humoral/immunology , Immune System/physiology , Fishes/classificationABSTRACT
The present study evaluated the assay to quantify the respiratory burst activity of blood leukocytes of pacu as an indicator of the innate immune system, using the reduction of nitroblue tetrazolium (NBT) to formazan as a measure of the production of reactive oxygen species (ROS). In order to assess the accuracy of the assay, fish were challenged by Aeromonas hydrophila and sampled one week after challenge. The A. hydrophila infection increased the leukocyte respiratory burst activity. The protocol showed a reliable and easy assay, appropriate to determine the respiratory burst activity of blood leukocytes of pacu, a neotropical fish, in the present experimental conditions.
