FIG. 2.

Purified complement proteins C1q, C2, C3, and C4 added to the indicated complement-depleted serum can restore HCV binding to erythrocytes. (A-E) Three milliliters of medium containing HCV1a virus (1 to 3 × 10⁷ genomic copies total) were treated with 100 μL of the indicated complement-depleted serum sample, complement-depleted serum sample plus the indicated purified complement protein, or purified complement protein only. After 30 minutes incubation at 25°C, 2 mL of erythrocytes (5 × 10⁸ cells total) in complete RPMI medium were added to the reaction mixture and incubated further at 25°C for 15 minutes. After adding EDTA to a final concentration of 20 mM, the erythrocytes were collected by centrifugation and washed three times with 1× PBS, pH7.4. Total RNA isolation from erythrocytes and quantification of HCV RNA were performed as described in Methods section. Each value represents the mean ± standard deviation of six determinations. The data are representative of two independent experiments using erythrocytes from at least two different healthy donors. Dpl, depleted.