FIG. 7.

Absorption and removal of anti-SARS-CoV-specific neutralization antibodies of New Zealand White rabbits (A), BALB/c mice (B), and monkeys (C) by an ACE2 receptor-binding region and human Fc fusion protein (RBR-Fc). For rabbit and mouse sera, the neutralization antibody-RBR-Fc complex was removed by agarose beads that were precoated with specific anti-human Fc antibodies. The anti-human Fc antibodies do not cross-react with rabbit or mouse immunoglobulin but do cross-react with monkey samples. Therefore, for monkey sera, neutralization antibodies were removed by beads directly conjugated with RBR-Fc. In each experiment, the corresponding beads controls did not affect the activity of neutralization antibodies, as presented in groups of RBR-Fc(−). The experiment was carried out in triplicates, and the average values are presented. The error bars stand for the standard deviation.