Fig. 2

a The relative prevalence of PTAP insertion in HIV-1 subtypes. Full-length gag sequences belonging to the various genetic subtypes of HIV-1 were downloaded from the LANL HIV sequence database. The subtype identity, total number of gag sequences used in the present analysis and the number of viral isolates containing the PTAP motif duplication are shown. The percent prevalence of the PTAP motif duplication under each genetic subtype is depicted. Subtype A represents subtypes A, A1, and A2 and subtype F represents subtypes F, F1, and F2. BC includes 7 different BC recombinants (CRF_07: 8/98, CRF_08: 7/83, CRF_31: 1/3, CRF_60: 0/3, CRF_61: 0/4, CRF_62: 0/3 and CRF_64: 0/6) with PTAP duplication. Inset: The number and percentage of viral sequences containing insertions of 3 aa or shorter and 12 amino acids or longer are depicted for subtypes B and C. b The relative prevalence of double-PTAP strains in HIV-1 subtype B and C over the past 30 years. Only those sequences that contained the core PTAP motif (four amino acids or more) were included in the analysis. Subsets of the full-length gag sequences belonging to HIV-1 subtype B (3,647 sequences) and C (1,787 sequences) were used in the analysis. Only one sequence per subject was included in the analysis. Sequences were categorized into 5-year periods starting from 1979 (subtype B) or 1986 (subtype C) to 2015. The subtype identity, total number of gag sequences used in the analysis and the number of viral isolates containing the PTAP motif duplication are shown. The percent prevalence of the PTAP motif duplication under each genetic subtype is depicted. The increasing trend of PTAP duplication in subtype C was found to be statistically significant (p < 0.05) using the regression analysis