Figure 2. Inhibition of P. falciparum 7G8 invasion by sCR1 and antibodies against CR1.

(A) sCR1 blocked invasion of neuraminidase-treated erythrocytes in a dose-dependent manner while bovine serum albumin (BSA) and α-2-macroglobulin had no effect. (B) No protein had an effect on the invasion of untreated erythrocytes. (C) Chicken anti-human CR1 Fab blocked invasion of neuraminidase-treated erythrocytes in a dose-dependent manner while purified chicken IgY Fab control had no effect. (D) No antibody had effect on the inhibition of intact red cells. (C–D) The concentration of antibody stocks was 80 µg/ml. Summary of three experiments. (E) Inhibition of P. falciparum 7G8 invasion using anti-CR1 monoclonal antibodies. Numbers above bars are P values for the comparison with the no antibody (No Ab) control using Dunnett's pairwise multiple comparison t-test, taking into account matching by experiment date. An IgG₁ irrelevant monoclonal (R&D Systems, Minneapolis, MN, USA) and anti-CD55 monoclonal (clone NaM16-4D3) (4D3) (Santa Cruz Biotechnology, Inc.) were used as negative controls. E11, To5, J3D3, and J3B11 are anti-CR1 monoclonal antibodies. All monoclonal antibodies were used at 1 µg/ml except in two experiments where every monoclonal was used at 15 µg/ml. Bars represent means ± standard deviations. Invasion rates in untreated controls (no antibody) ranged from 2% to 14%.