Humoral response of mice inoculated with Zera® separately. Four mice per group were immunized with 100 μg DNA vaccine or 50 μg protein and blood was taken post-immunization (day of splenectomy). Direct ELISA was performed against both Zera® and 16E7 protein using anti-Zera and anti-16E7 IgGs. Data gives the mean ± SEM of duplicates of the indicated group (n = 4). One representative of the two experiments is shown. pTH-ZERA-16E7SH DNA compared to pTH-16E7SH (p < 0.005), 16E7SH protein compared to 16E7SH protein plus Zera® PBs (p < 0.005).