Immune Response Nile tilapia (Oreochromis niloticus) vaccinated against Streptococcus agalactiae

Abstract

ABSTRACTThe infection caused by Streptococcus agalactiae causes great losses in intensive farming of tilapia in Brazil and one of the solutions to minimize these losses is the use of vaccines. Thus, this study aims to evaluate the cellular and humoral immune response of a vaccine against Streptococcus agalactiae. For this, we used 142 Nile tilapia, Oreochromis niloticus, weighing 200 ± 25 g. The standardization of the vaccine inoculum of S. agalactiae be performed by determining the lethal bacterial concentration to 50.0% of the fish (LC50) to be used in a previous study to assess which of the portions (soluble or insoluble) obtained from the antigen resulting from the sonication S. agalactiae, shall be greater relative percentage survival (PRS). Will be used for both groups (n = 15), where the first group (G1) injected with PBS, group 2 (G2) immunized with the soluble portion and group 3 (G3) immunized with the insoluble portion. After 21 days of immunization the fish will be challenged with an inoculum of S. agalactiae (CL50). Later a vaccine will be prepared containing the largest portion with PRS. To evaluate the cellular immune response are divided into four groups (n = 21), and G1 unimmunized injected with 0.65% saline, G2 not immunized and inoculated with S. agalactiae (LC50), G3 immunized and injected with saline 0.65% and G4 immunized and inoculated with S. agalactiae (LC50). All injections and inoculations are performed in the swim bladder. Sampling and analysis of the exudates will be performed on days 12, 24 and 48 hours after stimulation, to count and differential of cells accumulated in the bladder. On the same occasions blood samples will be collected from the tail vein for assessment of hematological profile. To evaluate the humoral immune response will be divided into four groups (n = 7), G5 is not immunized injected with PBS 0.65% and G6 not immunized and inoculated with S. agalactiae (LC50) and G7 immunized and injected with PBS and G8 immunized and inoculated with S. agalactiae (LC50). The stimuli are caused by intra-coelomic (ic). In all groups will be collected blood before immunization and sequential samples after immunization in times of 7, 14, 21, 28 and 35 days for evaluation of immune response by direct agglutination plate. The results are compared using analysis of variance (ANOVA) at 5% probability level and the difference between the average is compared by the Tukey test.Keyword: tilapia, inflammation, estreptococose