Background: Little data has been made on HLA-C restricted, HIV-1 specific CTL responses. HLA Cw1 is found approximately 1/5^th of our cohort (11/60). Our previous study has found a common (37%, 7/19) and new candidate HLA-Cw1 restricted CTL gag epitope, NKIVRMYSPVSILDIKQGPK (20 aa), of HIV-1 subtype A/E in HIV-1 infected Thai patients (pts). Further study has identified the 10 aa peptide “MYSPVSILDI” as the candidate HLA Cw1 restricted CTL epitope. This study has characterized the epitope.

Method: PBMCs from 7 pts (HLA Cw1⁺), who has CTL response to MYSPVSILDI gag A/E peptide, were tested with 4 truncated shorter peptides (8–9 aa in length) using IFN-γ ELISpot assay. CD4⁺ and CD8⁺ depletion were used to confirm whether it was CD8⁺ T-cell dependent activity. Both IFN-γ ELISpot and Cr51 release assays were used to perform the peptide titration analysis (10^-4–10^-15 M peptide). The positive peptide was re-confirmed of HLA-Cw1-restriction using Cr-51 release assay.

Results: All pts recognized a 9 aa “YSPVSILDI” HIV-1 A/E gag peptide and showed HLA-Cw1-restriction. Peptide titration assays found that YSPVSILDI could sensitize targets for 50% of maximal recognition by CD8⁺ T-cells at 10^-8 M.

Figures 1 and 2 showed the results of one subject.     

 

Conclusions: A new HLA Cw1 restricted subtype A/E gag epitope of 9 aa YSPVSILDI was identified. The significant of this novel epitope in HIV infection and its role in AIDS vaccine development required further investigation. This study also confirmed that IFN-γ ELISpot assay could be used for a fine epitope mapping and peptide titration study.