Fig 3.

TRIM21 levels determine neutralization efficiency. (A) IFN-α was added to HeLa cells (circles) or HeLa cells transduced with TRIM21 shRNA (squares), and TRIM21 mRNA levels were quantified by RT-qPCR. (B) TRIM21 protein levels were quantified by immunoblotting and normalized to β-actin levels. (C) Relative TRIM21 mRNA and protein levels are closely correlated (P < 0.001 by Pearson's product-moment correlation; R² = 0.83). (D) Virus neutralization assays were performed on these cells, which display an initial gradient of neutralization that varies with TRIM21 levels. (E) The number of antibody molecules per virus at each concentration of 9C12 was calculated by using binding parameters obtained as described above (Fig. 2F). Linear regression was used in order to calculate the number of molecules of 9C12 bound at 1/e neutralization (λ). λ was found to decrease exponentially with the TRIM21 concentration, reaching a plateau at 4.2 antibody molecules per virus (dashed line). For panels D and E, circles indicate HeLa cells, and squares indicate HeLa cells expressing TRIM21-directed shRNA. Points for panels A and C to E are shaded white to black according to IFN levels.