That no AIDS events were observed in persistently anti-Tat-seropositive subjects[13,14,15,16,17]. These results strongly suggest that Tat is a promising target for the development of both preventive and therapeutic vaccines [18,19]. However, several contrary results were also reported[20,21,22], and the detailed host anti-Tat antibody responses remains unclear. In this study, we performed anti-Tat immunoprofile analysis in 326 Chinese individuals infected with HIV-1 and defined six immunological profiles of anti-Tat antibodies responses. Our findings provide a novel source of information with respect to anti-Tat responses and Tat-neutralizing potential that should be very important for understanding the role of this response in the prevention of HIV pathogenesis and vaccine design.Materials and Methods Ethics statementAll aspects of the study were approved by the Ethics Committee of Beijing You An Hospital,Capital Medical University, China. Written informed consent was obtained from all participants in the study.Tat Antibody Responses to HIV-1 InfectionVectors, bacterial strain and reagentsThe prokaryotic expression plasmid pPEPTIDE2, as well as the two E. coli host strains BL21(DE3) and DH5a, were purchased from Novagen (Germany). A mouse monoclonal antibody that recognizes the N-terminus of native and recombinant HIV-1 Tat (strain HXB2) was purchased from United States Biological. HRPLD5 consists of HRP conjugated to LD5, which is a novel evolved immunoglobulin-binding 25837696 molecule (NEIBM) with a characteristic structure of consisting of alternating Finegoldia magna protein L B3 and staphylococcal protein A D domains; this structure creates synergistic double binding sites for the VH3 and Vk regions of Fab as well as to IgG Fc [23]. HRP-LD5 shows high binding affinity for IgM, IgG and IgA [24].KS-176 custom synthesis Clinical samplesClinical AKT inhibitor 2 chemical information samples for this study were collected from the AIDS high-risk Cohort at YouAn Hospital in Beijing, China. Informed consent was obtained from each of the participants prior to blood collection. Clinical information for each of the 326 samples was also recorded (Table S1). The cohort contained of 252 males (mean age = 33.6, SD = 8.5) and 74 females (mean age = 38.4, SD = 6.8). Mean CD4 counts/ml for the males and females were 437.4 (SD = 150.9) and 340 (SD = 283), respectively. The seropositive status of the participants was confirmed using ELISA (Diagnostic Kit for 
Antibody to HIV (ELISA), Shanghai Kehua Bio-Engineering Co., LTD., China) and Western blotting (HIV Blot 2.2 WB, MP Biomedicals Asia Pacific Pte. Ltd., Singapore). Control samples were obtained from 100 healthy blood donors who were confirmed to be HIV seronegative. All samples were stored at 280uC in 1.5 ml aliquots.Synthesis of the Tat N terminusThe peptide HIV-1 HXB2 Tat 1?1 aa (sTat1?1) was produced using solid-phase synthesis by Temple University (Philadelphia, USA).Figure 1. Design, expression and purification of Tat peptides. (a) Design of the seven analytic Tat peptides. (b) Expression and purification of recombinant full-length Tat protein and the six analytic Tat peptides. Recombinant full-length Tat and six analytic Tat peptides were induced by IPTG, and the relative molecular weight (MW) of the expressed products were as follows: 34,540 for Tat, 28,710 for Tat(1?8), 32,890 for Tat(1?6), 32,230 for Tat(22?00), 30,470 for Tat(38?00), 20,670 for Tat(38?1) and 36,850 for Tat(41?1C). The seven expressed products were purified by Ni-NTA column affinity chrom.That no AIDS events were observed in persistently anti-Tat-seropositive subjects[13,14,15,16,17]. These results strongly suggest that Tat is a promising target for the development of both preventive and therapeutic vaccines [18,19]. However, several contrary results were also reported[20,21,22], and the detailed host anti-Tat antibody responses remains unclear. In this study, we performed anti-Tat immunoprofile analysis in 326 Chinese individuals infected with HIV-1 and defined six immunological profiles of anti-Tat antibodies responses. Our findings provide a novel source of information with respect to anti-Tat responses and Tat-neutralizing potential that should be very important for understanding the role of this response in the prevention of HIV pathogenesis and vaccine design.Materials and Methods Ethics statementAll aspects of the study were approved by the Ethics Committee of Beijing You An Hospital,Capital Medical University, China. Written informed consent was obtained from all participants in the study.Tat Antibody Responses to HIV-1 InfectionVectors, bacterial strain and reagentsThe prokaryotic expression plasmid pPEPTIDE2, as well as the two E. coli host strains BL21(DE3) and DH5a, were purchased from Novagen (Germany). A mouse monoclonal antibody that recognizes the N-terminus of native and recombinant HIV-1 Tat (strain HXB2) was purchased from United States Biological. HRPLD5 consists of HRP conjugated to LD5, which is a novel evolved immunoglobulin-binding 25837696 molecule (NEIBM) with a characteristic structure of consisting of alternating Finegoldia magna protein L B3 and staphylococcal protein A D domains; this structure creates synergistic double binding sites for the VH3 and Vk regions of Fab as well as to IgG Fc [23]. HRP-LD5 shows high binding affinity for IgM, IgG and IgA [24].Clinical samplesClinical samples for this study were collected from the AIDS high-risk Cohort at YouAn Hospital in Beijing, China. Informed consent was obtained from each of the participants prior to blood collection. Clinical information for each of the 326 samples was also recorded (Table S1). The cohort contained of 252 males (mean age = 33.6, SD = 8.5) and 74 females (mean age = 38.4, SD = 6.8). Mean CD4 counts/ml for the males and females were 437.4 (SD = 150.9) and 340 (SD = 283), respectively. The seropositive status of the participants was confirmed using ELISA (Diagnostic Kit for Antibody to HIV (ELISA), Shanghai Kehua Bio-Engineering Co., LTD., China) and Western blotting (HIV Blot 2.2 WB, MP Biomedicals Asia Pacific Pte. Ltd., Singapore). Control samples were obtained from 100 healthy blood donors who were confirmed to be HIV seronegative. All samples were stored at 280uC in 1.5 ml aliquots.Synthesis of the Tat N terminusThe peptide HIV-1 HXB2 Tat 1?1 aa (sTat1?1) was produced using solid-phase synthesis by Temple University (Philadelphia, USA).Figure 1. Design, expression and purification of Tat peptides. (a) Design of the seven analytic Tat peptides. (b) Expression and purification of recombinant full-length Tat protein and the six analytic Tat peptides. Recombinant full-length Tat and six analytic Tat peptides were induced by IPTG, and the relative molecular weight (MW) of the expressed products were as follows: 34,540 
for Tat, 28,710 for Tat(1?8), 32,890 for Tat(1?6), 32,230 for Tat(22?00), 30,470 for Tat(38?00), 20,670 for Tat(38?1) and 36,850 for Tat(41?1C). The seven expressed products were purified by Ni-NTA column affinity chrom.