Fig. 4.

N-specific lymphocyte proliferation assay. Pooled splenocytes were obtained from mice (5 mice per group) on day 10 after the final immunization. Mice immunized with the DNA vaccine intramuscularly (i.m.), by electroporation (i.e.), orally using live-attenuated Salmonella typhimurium (oral). Splenocytes were stimulated in vitro with N protein (test groups), Con A (positive controls), and BSA (irrelevant antigen controls). Splenocytes from the control groups (CS022, pcDNA3.1, or PBS) were stimulated with N protein, and served as negative controls and sham controls. The stimulation index (SI) was calculated using the following formula: SI = (mean OD of Con A- or antigen-stimulated proliferation)/(mean OD of non-stimulated proliferation). Each bar represents the mean SI ± S.D. of 5 mice.