Antigen-specific antibody titer against recombinant HlFER1 (rHlFER1) (A) and recombinant HlFER2 (rHlFER2) (B). Rabbit sera were collected for serum ELISA at days 0, 7, 21, and 35. Antibody titers reflect the mean absorbance at OD450 of sera (104 dilution) for each vaccinated group from two separate trials (n = 3). The times of immunizations are indicated by arrows. Control, rabbits injected with adjuvant only; rHlFER1, rabbits injected with rHlFER1; rHlFER2, rabbits injected with rHlFER2. Bars represent standard deviation.