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The immune efficacy of a Streptococcus agalactiae immersion vaccine for different sizes of young tilapia

2021; Elsevier BV; Volume: 534; Linguagem: Inglês

10.1016/j.aquaculture.2020.736289

1873-5622

Xiaoli Ke, Zhigang Liu, S. Chen, Zhiting Chen, Defeng Zhang, Fengying Gao, Maixin Lu,

Immune Response and Inflammation

In order to explore the immune efficacy of a Streptococcus agalactiae immersion vaccine for young tilapia, three sizes of tilapia were selected and immunized a single time with an S. agalactiae immersion vaccine. The results that showed the whole cell antigen was crushed into nanoparticles and positive signals of antigen uptake were found in different sizes of tilapia and were mainly distributed in the gill, oropharynx, kidney, liver, spleen, intestine, and fish skin. The relative peak expression values for IgM, IgT, CD8+, and C3 from 1 g tilapia were significantly higher than those in 0.1 g and 0.5 g groups (P < 0.05). The differential expression of IgT was most significant, and the peak expression of C3 was maintained the longest time. The antibody level peak values appeared in 0.5 g and 1 g groups at the second week post-vaccination; both were significantly higher than that in 0.1 g tilapia (P < 0.05), and the higher antibody level in 1 g tilapia lasted longer than in the other two sizes. During the three months post-vaccination, the peak RPS in three different sizes of tilapia were all higher than 60% and the effective protection period in 1 g tilapia was longer than those of the 0.1 g and 0.5 g groups (P < 0.05). These results suggested that the immersion vaccine employed in the present study was effective against S. agalactiae infection for young tilapia (0.1–1 g) through one-time bath. In addition, the RPS and effective protection period in 1 g tilapia was higher and longer than those of the 0.1 g and 0.5 g groups.