GYPA and HIV-1 infection: While CCR5 co-expression had no impact on the potency of CD4-GpA-RBCs, co-expression of CCR5 lowered the neutralization activity of CD4-CCR5-RBCs by almost 3-fold in comparison to CD4-RBCs (Figure 3B; Table 1), implying that HIV-1 infection of RBC viral traps was not required for potent neutralization.