FIG. 4.

Spot-forming unit (SFU) counts, determined by subtracting background values, for samples isolated at all postvaccination time points and assessed for responses to HIV peptide pools during an HIV vaccine trial. Freshly isolated PBMC were used in Nairobi, and responses (y axes) were correlated to those of thawed frozen PBMC in the assay performed at the IAVI Core in London (x axes). Spearman's correlation coefficient is also shown and is statistically significant for all peptide pools (P is <0.05 for all except Pol B1, for which P is 0.0562). Regression lines were calculated only for positive responses (i.e., a response of >0 SFU after the subtraction of background values).