Comparable NP-specific antibody responses were induced in both the rNP- and RVJ1175NP-immunized mice. BALB/c mice were immunized i.m. with 10, 30, or 90 μg of rNP or PBS alone, three times, two weeks apart. Mice immunized with RVJ1175NP (2×107 PFU) twice, four weeks apart, were used as positive controls. Serum samples were collected ten days after priming and boost immunization. NP-specific IgG responses were measured by ELISA as described. All data are shown as the log10 geometric mean titer ± standard deviation of four mice from each group.