CD4 and infection: Consistent with the increase in sequence length over time, there were significant correlations between the number of amino acids in the V2 region and the duration of the infection (n = 213, r = 0.60, p < 0.001) as well as between CD4+ T cell count and the number of amino acids in the V2 region in 75 patients (n = 213, r = −0.17, p < 0.05).