FIG. 1.

Amino acid variability in Gag p24 NTD. (A) Shannon entropy of p24 NTD amino acid sequences from 662 C-clade HIV-1 isolates. The three exposed tropism-determining loops are shown (gray bars). The shaded area represents entropy scores of ≥0.389 (entropy equal to or greater than that of position 219). Eight high-variability residues not statistically associated with any HLA class I allele are marked with an asterisk; six of these fall within the three loops. (B) Fourteen high-variability residues in p24 NTD (entropy score, ≥0.389). Top, six residues at which polymorphism is strongly associated with one or more HLA class I alleles. Bottom, eight residues at which polymorphism is not associated with HLA. HLA associations are previously described (25); for all associations, q was <0.05.