Evaluation of the specificity and isotype of serum antibody responses by ELISA. The level of anti-NR21-specific IgG1, IgG2a, and IgG2b subclass antibody in the sera collected from sham-immunized mice, mice immunized with full-length P1, or the truncated protein lacking 2 putative T cell epitopes was evaluated by ELISA. All results are expressed as mean ± SEM and data are representative of at least three independent experiments. Statistically significant differences of the T-delete compared to CG14 were determined by two-way ANOVA. p≤0.05 (IgG1) , p≤0.0001 (IgG2a), p≤0.01 (IgG2b)