E possibility that these subjects are genetically predisposed to the C-prone response needs to be evaluated in buy PS 1145 future studies. Very interesting, Tat(1?1) had previously been shown to be a dominant linear epitope. In addition to the Tat(1?1) domain, the Tat(1?8) antigen contains an additional cysteine-rich domain (CRD), which was recently identified as an immunodominant Bcell Peptide M epitope [27] and could account for the enhanced antigenicity of Tat(1-48). Unexpectedly, Tat(1-86), which contained at least one more 1676428 known epitope (the BD epitope) in addition to those in Tat(1?8), showed weaker antigenicity compared with Tat(1?8). This indicates that the 49?6 aa in Tat(1?6) does not provide additional reactive epitopes but does affect the conformation of the reactive epitopes found in the Tat(1?8) fragment, which provides new supportive evidence for the conformational nature of the Tat antigen [32]. Theoretically, Tat-neutralization potential, as opposed to antiTat reactivity, could represent well the anti-Tat protective role. Our study shows that strong Tat-neutralization potential is related to N-preferred reaction in combined response immunoprofiles which represent newly elicited complete anti-Tat antibody responses (Fig. 4b). Also, Tat-neutralization potential was showed to be significantly related to the reactivity of the specific antigens Tat(1?6), Tat(38?1), full-length Tat, Tat(1?8), Tat(1?1) and Tat(38?00). Among N antigens, the reactivity of Tat(1?8) and Tat(1?6) significantly related to Tat-neutralization potential. Considering that the reactivity of Tat(1?8) and Tat(1?6) ishighly correlated with that of 1317923 full-length Tat (Fig. 3b), and the previous findings that B-clade Tat(1?6) is the mostly wellcharacterized active form of Tat, it is reasonable to conclude that the principle protective epitopes of full-length Tat should be in the N-terminal 1-48 aa. Among four C antigens, only the reactivity of Tat(38?1) and Tat(38?00) significantly related to Tat-neutralization potential (Fig. 4b). It was intriguing to find that the reactivity of Tat(38-100) showed a highest correlation to that 
of Tat(38?1) with R value of 0.833 among all C antigens. Considering that all four of the C antigens contained the 38?1 aa domain, Tat(38?1) and Tat(38?00) carried 
no or the least additional amino acids which could affect the conformation of Tat(38?1), it is reasonable to hypothesize that Tat(38?1) contains an another important protective epitope. These findings are likely to be important for understanding of protective anti-Tat antibody responses as well as for future vaccine designs. In conclusion, in this study, we define for the first time six different immunoprofiles of anti-Tat responses in Chinese patients infected with HIV-1, which represent two types of anti-Tat antibody responses: the major complete response and the alternative C-prone response. Tat-neutralizing potential was demonstrated to be significantly related to specific immunoprofiles and to the reactivity of specific antigens. The findings presented here could significantly contribute to our understanding of antiTat responses in preventing Tat-mediated HIV pathogenesis and aid in future vaccine designs.Supporting InformationTable SBaseline characteristics of the study partici-pants. (DOC)Table S2 Primers for amplifying HIV-1 Tat peptides.(DOC)Table S3 Tat anti-sera reactivity to Tat peptides.(DOC)AcknowledgmentsWe thank Dr. Udaykumar Ranga at the Jawaharlal Nehru Centre for Advanced Scientifi.E possibility that these subjects are genetically predisposed to the C-prone response needs to be evaluated in future studies. Very interesting, Tat(1?1) had previously been shown to be a dominant linear epitope. In addition to the Tat(1?1) domain, the Tat(1?8) antigen contains an additional cysteine-rich domain (CRD), which was recently identified as an immunodominant Bcell epitope [27] and could account for the enhanced antigenicity of Tat(1-48). Unexpectedly, Tat(1-86), which contained at least one more 1676428 known epitope (the BD epitope) in addition to those in Tat(1?8), showed weaker antigenicity compared with Tat(1?8). This indicates that the 49?6 aa in Tat(1?6) does not provide additional reactive epitopes but does affect the conformation of the reactive epitopes found in the Tat(1?8) fragment, which provides new supportive evidence for the conformational nature of the Tat antigen [32]. Theoretically, Tat-neutralization potential, as opposed to antiTat reactivity, could represent well the anti-Tat protective role. Our study shows that strong Tat-neutralization potential is related to N-preferred reaction in combined response immunoprofiles which represent newly elicited complete anti-Tat antibody responses (Fig. 4b). Also, Tat-neutralization potential was showed to be significantly related to the reactivity of the specific antigens Tat(1?6), Tat(38?1), full-length Tat, Tat(1?8), Tat(1?1) and Tat(38?00). Among N antigens, the reactivity of Tat(1?8) and Tat(1?6) significantly related to Tat-neutralization potential. Considering that the reactivity of Tat(1?8) and Tat(1?6) ishighly correlated with that of 1317923 full-length Tat (Fig. 3b), and the previous findings that B-clade Tat(1?6) is the mostly wellcharacterized active form of Tat, it is reasonable to conclude that the principle protective epitopes of full-length Tat should be in the N-terminal 1-48 aa. Among four C antigens, only the reactivity of Tat(38?1) and Tat(38?00) significantly related to Tat-neutralization potential (Fig. 4b). It was intriguing to find that the reactivity of Tat(38-100) showed a highest correlation to that of Tat(38?1) with R value of 0.833 among all C antigens. Considering that all four of the C antigens contained the 38?1 aa domain, Tat(38?1) and Tat(38?00) carried no or the least additional amino acids which could affect the conformation of Tat(38?1), it is reasonable to hypothesize that Tat(38?1) contains an another important protective epitope. These findings are likely to be important for understanding of protective anti-Tat antibody responses as well as for future vaccine designs. In conclusion, in this study, we define for the first time six different immunoprofiles of anti-Tat responses in Chinese patients infected with HIV-1, which represent two types of anti-Tat antibody responses: the major complete response and the alternative C-prone response. Tat-neutralizing potential was demonstrated to be significantly related to specific immunoprofiles and to the reactivity of specific antigens. The findings presented here could significantly contribute to our understanding of antiTat responses in preventing Tat-mediated HIV pathogenesis and aid in future vaccine designs.Supporting InformationTable SBaseline characteristics of the study partici-pants. (DOC)Table S2 Primers for amplifying HIV-1 Tat peptides.(DOC)Table S3 Tat anti-sera reactivity to Tat peptides.(DOC)AcknowledgmentsWe thank Dr. Udaykumar Ranga at the Jawaharlal Nehru Centre for Advanced Scientifi.