EPITOPES RECOGNIZED BY HIV-SF2 NEF-SPECIFIC CD4-CELL CLONES GENERATEDFROM HIV-1-UNINFECTED DONORS( T)

Human T-cell clones with specificity to the HIV-1 nef protein were gen erated by the in vitro stimulation of peripheral blood mononuclear cel ls (PBMCs) from HIV-1-seronegative donors with purified nef from the H IV-SF2 isolate produced in genetically engineered yeast. Here the char acterization is described of a total of seven discrete clones derived from five different donors. Each clone was CD3+CD4+CD8- as determined by FACS analysis. The epitopes recognized by these clones were identif ied using synthetic overlapping peptides spanning the entire length of nef. Six discrete helper T-cell epitopes located in five distinct reg ions of nef were identified by this approach. Three of these epitopes are more than 80% conserved among all HIV-1 nef proteins for which seq uence data are available. The remaining epitopes are in regions of nef that vary among isolates. Many of the epitopes recognized by our clon es overlap T-cell epitopes identified by others examining T-cell respo nses to nef in HIV-1-infected patients and immunized animals. Using pa rtially class II-matched EBV-transformed B-cell lines, we were able to identify five different HLA class II alleles which encode restricting elements for the in vitro nef-specific proliferative response of thes e clones (DR1, DRw15(2), DRw6, DQw7, DP5).