321 HIV-1 Regulatory Protein (nef, tat, rev, vif, vpu, vpr)-CTL Responses and Epitope Mapping in Subtype A/E-Infected Thais with CD4 >300 cells/mm3 S. Buranapraditkun*1, K. Ruxrungtham1, S. Sirivichayakul1, S. Kosonsiriluk1, S. Kerdsanti1, P. Hansasuta1, S. Rowland-Jones2, P. Phanuphak1 1Bangkok, Thailand and 2Oxford, UK
Background: There is no data on CTL responses against subtype A/E HIV-1 regulatory proteins. In addition, the HLA polymorphism among Thais is also remarkably different from the western cohorts.
Method: CTL responses and epitope mapping and HLA restriction were performed by IFN-gamma ELISpot assay. HIV-1 subtype A/E truncated peptides of nef, tat, rev, vif, vpu, vpr (15-21 a.a in length, with 10-a.a overlaps between sequential peptides) were used for the CTL screening (16 pools of peptides, 5 peptides/pool) and epitope mapping. HLA class I and HIV-1 subtype was analyzed by DNA sequencing analysis. The positive cut-off of ELISpot was 100 SFU/106 PBMCs and 2 folds higher than the background.
Results: Twenty-eight (28) Clade A/E infected and treatment naive patients (pts) were included. Mean CD4 count 533 cells/mm3 (range 303-968). Median plasma HIV-1 RNA 7,526 (range 102-53,684). HLA typing showed: A11 (50%), A24 (28%), A2 (31%); B40, B58, B15 (25%), B27, B46 (19%); and Cw7 (50%), Cw3, Cw1 (13%) and Cw6 (25%). All pts showed IFN-gamma ELISpot positive against at least 1 pool of the peptides. The proportion of positive responses to nef, vpr, tat, vif, rev, vpu was 93, 46, 46, 39, 36, and 21%, respectively. CTL epitope mapping was performed in 15 pts. Thirty-five (35) epitopes were identified (10 in nef, 7 in vif, 6 in rev, 5 in each of tat, vpr, and 2 in vpu). Interestingly, 25 possible novel epitopes are identified.
Conclusion: IFN-gamma ELISpot-based CTL responses to HIV-1 regulatory proteins are common among subtype A/E HIV-1 infected Thais (93% nef and 46% vpr and tat). The results support the potential role of HIV-1 regulatory proteins to be included in an AIDS vaccine candidate. Further characterization of those possible novel epitopes is under way.
