Duration of Protection and Humoral Immune Response in Nile Tilapia ( Oreochromis niloticus L.) Vaccinated against Streptococcus agalactiae

• Published in: Animals (Basel) 2024-06, Vol.14 (12), p.1744
• Main Authors: Queiróz, Guilherme Alves de, Silva, Tarcísio Martins França E, Leal, Carlos Augusto Gomes
• Format: Article
• Language: English
• Subjects: Animals; Antibiotics; Antibodies; antibody; Aquaculture industry; Drug resistance; Efficiency; ELISA; Enzyme-linked immunosorbent assay; Feeds; immune response; Infectious diseases; International economic relations; Mortality; Pathogens; Serology; streptococcosis; Tilapia; Vaccination; Vaccines; Viral antibodies; Water temperature
• ISSN: 2076-2615; 2076-2615
• DOI: 10.3390/ani14121744

Streptococcosis caused by ( is a major bacterial disease affecting the production of Nile tilapia ( L.), causing significant economic losses due to mortality in the growing phase. Vaccination is the most effective method for preventing streptococcosis on Nile tilapia farms. In Brazil, the major tilapia-producing regions have long production cycles (6-10 months) and harvest tilapias weighing over 900 g for fillet production. Thus, data on the duration of the humoral immune response and protection in farmed tilapia have not been reported or are poorly described. Furthermore, the efficiency of serological testing for the long-term monitoring of immune responses induced by vaccination against has never been addressed. This study evaluated the duration of protection and humoral immune response induced in Nile tilapia vaccinated against until 300 days post-vaccination (dpv). The immunization trial was composed of two groups: vaccinated (Vac), vaccinated intraperitoneally with a commercial vaccine, and unvaccinated (NonVac) group, injected fish with sterile saline solution. At 15, 30, 150, 180, 210, and 300 dpv, blood sampling was conducted to detect anti- IgM antibodies using indirect Enzyme-Linked Immunosorbent Assay (ELISA), and the fish were challenged with pathogenic to determine the duration of vaccine protection through relative percentage survival (RPS). Spearman's rank correlation was performed between the ELISA optical density (OD) of vaccinated tilapia and the duration of vaccine protection (RPS). The mean cumulative mortality in NonVac and Vac groups ranged from 65 to 90% and less than 35%, respectively. The average RPS was 71, 93, 94, 70, 86, and 67% at 15, 30, 150, 180, 210, and 300 dpv, respectively. RPS revealed that the vaccine provided protection from 15 to 300 dpv. The specific anti- IgM antibody levels were significantly higher in the Vac group than that non-Vac group up to 180 dpv. The vaccinated fish exhibited significant protection for up to 10 months after vaccination. There was a positive correlation between the antibody response and RPS. This study revealed that a single dose of commercial vaccine administered to Nile tilapia can confer long-term protection against and that indirect ELISA can monitor the duration of the humoral immune response for up to six months following vaccination. Finally, vaccine protection over six months can be associated with other components of the fish immune system beyond the humoral immune response by IgM a