Serum sensitivity of HIV-1 propagated in PBMCs from ABO-defined donors. (A) Serum sensitivity of SF162 grown in PBMCs from ABO-secreting donors in the presence of autologous serum. Virus (200 FFU) was incubated for 1 hour at 37°C with varying concentrations of donor serum diluted against a constant background of matched heat-inactivated serum so that total serum concentration was 10%. The viruses were then plated onto target NP2CD4CCR5 cells, and virus infection was scored by in situ p24 staining 72 hours later. The results are expressed as the percentage of viral infection compared with the matched HI control. Diamonds (♦), squares (▪), and triangles (▴) represent viral infections in the presence of O, A, or B sera, respectively. Error bars represent ± SEM. (B) HIV-1 89.6, 2028, or SF-2 from ABO-defined PBMCs were treated as in panel A. Results represent the percentage infection of these viruses in 10% O (▪), A(□), and B (▦) serum compared with a matched HI control.