Production of anti-horse antibodies induced by IgG, F(ab')2 and Fab applied repeatedly to rabbits. Effect on antivenom pharmacokinetics

Abstract We separated whole IgG, Fab and F(ab') 2 fragments from horse plasma. We previously studied the pharmacokinetics of these immunoglobulins and fragments in rabbits and shown that Fab and F(ab') 2 pharmacokinetics were well described by a three-exponential kinetics, while IgG and IgG(T) pharmacokinetics, however, deviated from the three-exponential kinetics 120 h after injecting a bolus of the immunotherapeutics; this departure was shown to be due to a surge of anti-horse antibodies occurring after 120 h, peaking at ≈260 h and decaying slowly afterward (Vazquez et al., 2010). We now describe antivenom pharmacokinetics and anti-horse IgG production in rabbits receiving three boluses (300 μg/kg, I.V.) of Fab, F(ab') 2 or IgG separated by 21 days.