Cubated for 3 h. The supernatant was removed and 200 ml of complete medium was added to each well. The plates were incubated for 48 h and the levels of secreted alkaline phosphate 
(SEAP) were estimated at 48 h using a colorimetric assay (Toyobo). As a control, 96-well plates were coated with 100 ml of full-length Tat protein (5 mg/ml in carbonate buffer (pH 9.6) or protein G to deplete the buy RE640 Tat-specific antibody or IgG fraction of the plasma. Then the depleted plasma were used for the inhibition assay. As a 1676428 positive control for Tat neutralization, we used an IgG1 monoclonal antibody, which was raised in-house ZK-36374 against B-Tat; this antibody recognizes the N-terminal 20 amino acid residues of Tat and blocks extracellular-Tat with high efficiency.Statistical analysesStatistical analyses were performed using SPSS 17.0 and SAS 9.3. All experiments were performed three times, and the values obtained from three replicate samples were averaged for each experiment. Data 15481974 are presented as the median and quartiles. Statistical significance was tested using Nemenyi or Wilcoxon nonparametric test. Differences between measurements were considered to be significant at p-values of less than 0.05. The correlation was assessed by Spearman correlation coefficient.Figure 2. Characterization of antibody responses to full-length Tat and seven Tat peptides. (a) A comparison of the antibody reactivity against Tat of the seven analytic Tat peptides and gp41 in Chinese individual infected with HIV-1. Recombinant subtype B full-length Tat protein and six Tat peptides were used in the assays. The gp41 commercial kit used a pool of peptides representing the immunodominant epitopes in the ectodomain of gp41. The boxes represent the interquartile range, the line inside each box represents the median of the samples and the whiskers represent the range of the data. Statistical significance was tested using Wilcoxon non-parametric test. (b) Characterization of antibody responses to various antigens. The positive rate of antibody response was plotted on the y-axis with the seven antigens on the x-axis. The positive rate corresponding to the N antigens represented the total positive rate of antibody responses detected by Tat(1?1), Tat(1?8) and Tat(1?6) in the 42 anti-Tat-seropositive samples (details were showed in Fig. 3a). The positive rate corresponding to the C antigens represented the total positive rate of antibody responses detected by Tat(38?1), Tat(22?00), Tat(38?00) and Tat(41?1C) in the 42 anti-Tat-seropositive samples. The positive rate (39/ 42) corresponding to N+C represented the total positive rate of antibody responses detected by the N antigens (25/42) and specific antibody responses only detected by the C antigens (14/42). doi:10.1371/journal.pone.0060825.gTat Antibody Responses to HIV-1 InfectionTat Antibody Responses to HIV-1 InfectionFigure 3. Characteristics of anti-Tat antibody and Tat-neutralizing potential. (a) Characteristics of reactivity with various analytic antigens and the Tat-neutralizing potential of plasma samples of six profiles. The reactivity of each plasma sample with the peptides as assayed by ELISA is presented according to the OD value, as determined by duplicate measurements. Individual values are shown in color, as indicated in the top right corner, with red representing the strongest reaction. The OD values of twelve HIV-1-seropositive and anti-Tat-seronegative plasma samples and 18 plasma samples from healthy blood donors were incl.Cubated for 3 h. The supernatant was removed and 200 ml of complete medium was added to each well. The plates were incubated for 48 h and the levels of secreted alkaline phosphate (SEAP) were estimated at 48 h using a colorimetric assay (Toyobo). As a control, 96-well plates were coated with 100 ml of full-length Tat protein (5 mg/ml in carbonate buffer (pH 9.6) or protein G to deplete the Tat-specific antibody or IgG fraction of the plasma. Then the depleted plasma were used for the inhibition assay. As a 1676428 positive control for Tat neutralization, we used an IgG1 monoclonal antibody, which was raised in-house against B-Tat; this antibody recognizes the N-terminal 20 amino acid residues of Tat and blocks extracellular-Tat with high efficiency.Statistical analysesStatistical analyses were performed using SPSS 17.0 and SAS 9.3. All experiments were performed three times, and the values obtained from three replicate samples were averaged for each experiment. Data 15481974 are presented as the median and quartiles. Statistical significance was tested using Nemenyi or Wilcoxon nonparametric test. Differences between measurements were considered to be significant at p-values of less than 0.05. The correlation was assessed by Spearman correlation coefficient.Figure 2. Characterization of antibody responses to full-length Tat and seven Tat peptides. (a) A comparison of the antibody reactivity against Tat of the seven analytic Tat peptides and gp41 in Chinese individual infected with HIV-1. Recombinant subtype B full-length Tat protein and six Tat peptides were used in the assays. The gp41 commercial kit used a pool of peptides representing the immunodominant epitopes in the ectodomain of gp41. The boxes represent the interquartile range, the line inside each box represents the median of the samples and the whiskers represent the range of the data. Statistical significance was tested using Wilcoxon non-parametric test. (b) Characterization of antibody responses to various antigens. The positive rate of antibody response was plotted on the y-axis with the seven antigens on the x-axis. The positive rate corresponding to the N antigens represented the total positive rate of antibody responses detected by Tat(1?1), Tat(1?8) and Tat(1?6) in the 42 anti-Tat-seropositive samples (details were showed in Fig. 3a). The positive rate corresponding to the C antigens represented the total positive rate of antibody responses detected by Tat(38?1), Tat(22?00), 
Tat(38?00) and Tat(41?1C) in the 42 anti-Tat-seropositive samples. The positive rate (39/ 42) corresponding to N+C represented the total positive rate of antibody responses detected by the N antigens (25/42) and specific antibody responses only detected by the C antigens (14/42). doi:10.1371/journal.pone.0060825.gTat Antibody Responses to HIV-1 InfectionTat Antibody Responses to HIV-1 InfectionFigure 3. Characteristics of anti-Tat antibody and Tat-neutralizing potential. (a) Characteristics of reactivity with various analytic antigens and the Tat-neutralizing potential of plasma samples of six profiles. The reactivity of each plasma sample with the peptides as assayed by ELISA is presented according to the OD value, as determined by duplicate measurements. Individual values are shown in color, as indicated in the top right corner, with red representing the strongest reaction. The OD values of twelve HIV-1-seropositive and anti-Tat-seronegative plasma samples and 18 plasma samples from healthy blood donors were incl.
