Virus neutralization assays carried out with Ig fractions from 5 LTNP sera displaying anti-CCR5 Abs. A neutralizing anti-CD4 mAb (SIM4) and a neutralizing serum from a patient with AIDS (tested at the same dilutions of the LTNP sera) were used as positive control. As negative control, a pool of sera from 5 HCs was also used. The data are expressed as the percentage of infectivity reduction and are representative of 3 experiments. (A) Mediated antibody infectivity reduction obtained with subtype B isolate HIV-36. (B) Mediated antibody infectivity reduction obtained with subtype B isolate HIV-40.