Geographic variation in the frequency of HIV-1C Tat CC variants. A. Frequency of HIV-1 Tat sequences with CC and CS from HIV-1-infected populations from Lusaka (Zambia), Cape Town (South Africa), Bangalore (India), and Dhaka (Bangladesh). B. Frequency of CC and CS variants in the sequence database among HIV-1 Tat sequences in countries where HIV-1C predominates. Sequences were downloaded from the Los Alamos database and aligned using Clustal-W software. Frequency of sequences with CC and CS at positions 30, 31 were calculated and plotted as stacked graphs. The numbers below the bars (n) are the total independent sequences analyzed in each case.