Signature sequence analysis. Amino acid positions at which the peripheral-blood mononuclear cell (PBMC) and serum clonal distributions are significantly different at a threshold of 70% are underlined. “S30A” and “P30A” indicate, for example, a serum sample and a PBMC sample, respectively, from patient 30 at time point A. Nos. in parentheses indicate the no. of amino acid signatures present in PBMCs at that time point. Shown are the consensus amino acids at each position. In several instances, a given amino acid may appear to be identical between the 2 compartments; however, the frequency distribution of the 10 viral variants that make up that consensus is different between the 2 compartments. The bar highlights the 27 amino acids of HVR1.