Figure 2.

Titers of antibodies to HO-PEG, mPEG, and interferon-α were determined by direct ELISAs of sera prepared from each of three monthly bleeds of rabbits immunized with either mPEG₁-IFN-α (A) or HO-PEG₁-IFN-α (B). (A) Anti-PEG antibodies were measured on assay plates coated with 2 μg/well of superoxide dismutase (SOD) coupled to either 10 kDa HO-PEG (red symbols) or 10 kDa mPEG (black symbols). Anti-IFN-α antibodies were measured on assay plates coated with 1 μg/well of recombinant human IFN-α (blue symbols). Mean values in sera from Bleeds 1, 2, and 3 were calculated from results obtained with HO-PEG-SOD (red dashed line), mPEG-SOD (black solid line), or IFN-α (blue solid line) as the antigen. Black arrows indicate the ratios of titers detected against the various antigens. (B) Sera from Bleeds 1, 2, and 3 of a rabbit immunized with HO-PEG₁-IFN-α were analyzed in the same way as described for (A).