Background:  Several lines of evidence have indicated that the development of an HIV-1-specific cytotoxic T lymphocyte (CTL) response plays a critical role in controlling HIV-1 infection. To develop a new modality to augment HIV-1-specific CTL responses in HIV-infected patients, we evaluated the capacity of lentiviral vectors encoding T-cell receptor (TCR) -a and -b chains derived from human HIV-1-specific CTL to generate human HIV-specific CTL after transduction of human CD8⁺ lymphocytes.

Methods:  The TCR-a and TCR-b chain cDNA from the human HIV-restricted, SL-9-specific A*0201-restricted CTL clone, 1803.D23.18 (1803), were cloned out, linked in a single transcript using a picornavirus-like “self-cleaving” 2A peptide, and expressed using a third-generation, 4-plasmid lentiviral vector system. CD8⁺ T cells isolated from A*0201⁺ human peripheral blood mononuclear cells (PBMC) (95% pure) were transduced with a lentiviral vector expressing the 1803 TCR.

Results:  CD8⁺ T cells transduced with the 1803 TCR-encoding lentiviral vector were between 10% and 30% of the CD8⁺ cells positive for staining with an HLA-A*0201-restricted SL9-specific PE-conjugated tetramer. ELISpot analysis showed the 1803 CTL clone itself generated >10-fold higher numbers of spot-forming cells [SFC]) to SL9 than to a control peptide (IV9) while the 1803-TCR-transduced human CD8⁺ cells displayed almost 4-fold higher levels of SFC in response to SL9 peptide than to a control peptide (IV9). One week after intrasplenically injecting SCID mice with HIV-infected human CD8-depleted PBMC and either the 1803 CTL clone, 1803-TCR-transduced human CD8⁺ cells or control vector-transduced human CD8⁺ cells, the number of HIV-infected PBMC in the spleens was quantified. While >3125 HIV-infected HLA-A*0201⁺ PBMC/10⁶ splenocytes were detected in SCID mice injected with control-vector-transduced CD8⁺ cells, no HIV-infected HLA-A*0201⁺ cells were detected in SCID mice injected with the 1803 CTL clone or the 1803-TCR-transduced human CD8⁺ cells. The suppression was HLA-specific as indicated by the significant difference (p <0.03) in the elimination of HLA-A*0201⁺ HIV-infected PBMC compared to HLA-A*0201^– HIV-infected PBMC.

Conclusions:  We demonstrated as a “proof-of-concept” that HLA-restricted HIV-specific CD8⁺ CTL can be generated by delivering genes encoding the α and β chain of TCR derived from a potent HIV-specific CTL into CD8⁺ T cells that displayed in vitro and in vivo HIV-specific function.