Correlation between total and antigen-specific IgG responses and development of broadly neutralizing antibody responses.

Correlations were assessed by Spearman analyses: p-values and r-values are indicated; (ns) not significant. Linear, semi-Log or Log-log regressions are also shown as dotted lines. Neutralization score corresponds to a participant’s best neutralization score on the 6-virus panel across all tested time points. (A,C) IgG binding activity to recombinant MN gp41 (Subtype B), BG505 gp120 (subtype A) and IAVIC22 gp120 (Subtype B) was assessed, by ELISA, in plasma samples of Protocol C participants (N = 61) from the M48+ subset, at visits matching development of bnAb responses (M24-72, mean = 36.6 mpi). (B) Avidity index for IAVIC22-gp120 IgG titers were calculated from high salt (1.5M or 3M NaSCN) ELISA experiments. (C) Total IgG titers were assessed by ELISA. (D) Total IgG titers in pre-infection (N = 27), ~4mpi (N = 56, M00, mean = 4.0 mpi) and ~36mpi (N = 61) M24-72) samples. (E) Total IgG titers in ~36mpi samples (M24-72). (F) ELISA binding ID50 and neutralization score from (A) were standardized to a reference concentration of 20mg/mL of total plasma IgG.