HUMAN IMMUNE-RESPONSE TO HIV-1-NEF .1. CD45RO(-) T-LYMPHOCYTES OF NONINFECTED DONORS CONTAIN CYTOTOXIC T-LYMPHOCYTE PRECURSORS AT HIGH-FREQUENCY

The immune response of peripheral blood lymphocytes (PBL) of non-expos ed human individuals to the Nef protein of HIV-1 was studied. Nef is a regulatory protein of HIV which is immediately expressed after infect ion and which seems to be important in the pathogenicity of HIV. Nef m ay therefore serve as a potential target for effective immunity agains t HIV infection. Epstein-Barr (EBV)-transformed lymphoblastoid a cell lines (LCL) were established from four healthy young seronegative adul ts and transfected with the Nef gene. These cells served as stimulator cells for autologous PBL in vitro and as target cells for CTL. CTL re sponses were readily generated against Nef-transfected LCL, consisting of Nef-specific and putative EBV-specific CTL. Nef-specific CTL were generated exclusively from CD8(+) cells and were MHC class I restricte d. Since a vigorous Nef-specific CTL response in non-infected individu als was unexpected, CTL precursor frequencies were determined by limit ing dilution analyses in non-fractionated PBL and in pal separated int o the CD45RO(-) (naive) and CD45RO(+) (memory) T cell populations. As expected, the putative EBV-specific CTL precursors were predominantly found in the CD45RO(+) subset at frequencies typical for memory T cell s. Nef-specific CTL precursors, in contrast, were found predominantly in the CD45RO(-) population, at even higher frequencies of -1/1000-1/3 000. Nef may thus display either an unusually high number of immunogen ic peptides or a limited number of peptides presented in a very effici ent way, so that many T cells including low affinity cells, would be t riggered.