Effect of vaccines on the level of serum specific anti-P. salmonis IgM and gene expression of cell response immunity markers. A The fish were intraperitoneally immunized with two formulations (vaccine 1 or vaccine 2) or a control (injected intraperitoneally with 100 µL of sterile saline). Piscirickettsia salmonis specific IgM were measured by ELISA. The data are mean ± SD of 5 fish per treatment at each sampling point (pre-vaccination, first immunization, second immunization). ANOVA and subsequent Tukey’s multiple comparisons test. Different capital letters indicate significant differences (p ≤ 0.05) between sampling points and lowercase letter indicate significant differences (p ≤ 0.05) within the sampling point. B Expression of cellular immune response markers analyzed by qPCR. Tumor necrosis factor alpha (tnfα), interferon gamma (ifnγ), major histocompatibility complex I (mhc1), cluster of differentiation 8a (cd8α), T cell receptor beta 1 (trb-I). The results are the mean ± SEM of 5 individuals, Kruskal–Wallis test followed by a Dunn’s post-test. Different lowercase letters indicate significant differences (p ≤ 0.05).