Selected gene sets (sGS) were downregulated in rag1^−/− egg embryos but were similar in early hatched larvae and both showed high mortalities when infected by spring viremia carp virus (SVCV). (A) Expression folds in embryo eggs 1 day after fertilization (n = 60). Reverse transcriptase and quantitative polymerase chain reaction data were first normalized by the formula, expression of each gene/expression of ef1a. Differential folds were then calculated by the formula, normalized expression of each rag1^−/− gene/normalized expression of each rag1^+/+ gene. Tbk1 fold was lower than 2⁻⁶ (not shown). Tnfa and nklysin were not done. Red dashed line, onefold boundary. *Statistically different from onefold with p < 0.05 by the t-test. (B) Expression folds in hatched larvae 3 days after fertilization (n = 45) calculated as in (A). (C) Kaplan–Meier survival curves of naïve rag1^−/− (n = 90) and rag^+/+ (n = 90) recently hatched larvae after bath infection in 10⁴ pfu of SVCV per ml (n = 2) at 22°C (optimal replication for SVCV). Differences between rag1^−/− and rag^+/+ survival curves of SVCV-infected larvae as determined by the Gehan–Breslow–Wilcoxon test were significant with p < 0.05 (*). Solid lines, rag1^−/− larvae. Dashed lines, rag^+/+ larvae.

Naïve adult rag1^−/− zebra fish are more resistant to lethal spring viremia carp virus (SVCV) infection than rag1^+/+ zebra fish. (A) Kaplan–Meier survival curves of naïve rag1^−/− (n = 84) and rag^+/+ (n = 100) adult zebra fish after exposure to a lethal dose of 10⁴ pfu/ml of SVCV under the same challenge conditions as in panel (A). *Statistically significant differences between survival curves between rag1^−/− and rag^+/+ as determined by the Gehan–Breslow–Wilcoxon test with p < 0.05 (n = 2). Solid lines, rag1^−/− zebra fish larvae. Dashed lines, rag^+/+ zebra fish larvae. (B) SVCV titers from pooled whole zebra fish (n = 4 zebra fish per genotype) 3 days after SVCV infection as determined by plaque forming unit (pfu) assays.

Differential expression in skin/fins of adult zebra fish before and after spring viremia carp virus (SVCV) infection. The transcript differential expression folds of rag1^−/−/rag1^+/+ adult zebra fish in skin/fins were calculated as in Figure 1: (A) before infection and (B) 3 days after SVCV infection. Means and SDs were represented (n = 4–6 zebra fish). Red dashed line, onefold boundary. *Statistically different from onefold with p < 0.05 by the t-test.

Active CASPASE-3 staining in different tissues from uninfected and spring viremia carp virus (SVCV)-infected rag1^−/− and rag1^+/+ adult zebra fish. Tissue sections from (A) uninfected and (B) SVCV-infected rag1^−/− and rag1^+/+ adult zebra fish were stained by anti-human active CASPASE-3 antibody. Dark-stained areas in all rag1^−/− tissues indicate the presence of active CASPASE-3. Images are representative of at least two independent experiments. Horizontal red line, 30 μm.

Leukocyte infiltration in muscle and skin tissues in rag1^−/− and rag1^+/+ adult zebra fish. Histological sections from muscle and skin tissues of rag1^−/− and rag1^+/+ were stained with an antibody anti-l-plastin, a pan-leukocyte marker (dark-stained areas). Red arrows, examples of l-plastin stained cells. Images are representative of at least two independent experiments. Horizontal red line, 30 μm.