In the present study, we have shown that the non-AMA1 IgGs from Malian children interfere with the growth-inhibitory activity of anti-AMA1 antibodies obtained from malaria naïve U.S. volunteers vaccinated with AMA1 (US-total IgG). Interestingly, the interference effect of non-AMA1 IgG from total IgG pools with higher titers of AMA1 was higher than those from total IgG pools with lower titers. However, while the non-AMA1 IgGs showed this interference in GIA, they did not block binding of anti-AMA1 antibodies in US-total IgG to AMA1 protein in a competition ELISA.