Kinetics of anti-HTNV N and anti-HTNV GP IgG antibody responses. Mice were intramuscularly immunized with 100 μg of DNA constructs with or without CpG motifs on day 0, day 7 and day 4 and bled before each immunization. HTNV N and GP specific IgG antibody responses were evaluated by ELISA (A) and IFA (B) respectively. Antibody endpoint was reciprocal of the highest dilution of serum that conferred optical density above cutoff or positive fluorescence signal. *p < 0.05 between two groups denoted by the capped line.