Molecular interaction between the peptide/MHC class I complexes (pMHCs) and T cell receptor (TCR) is fundamental to the effector function of cytotoxic T lymphocytes (CTLs). Monoclonal antibody against pMHC with TCR-like specificity is a possible research tool for the antigen presentation. However, it is notoriously difficult to isolate monoclonal antibodies against pMHCs by the conventional hybridoma technique. To isolate monoclonal antibodies against an immunodominant HIV-1-derived CTL epitope in the nef gene, we panned phage clones from a human scFv phage display library. Eight Nef138-10/HLA-A*24(A24)-specific scFv clones were isolated and two of them (scFv#3 and scFv#27) were selected for further analysis. The clones stained A24-positive cells pulsed with Nef138-10 peptides specifically. We reconstituted humanized immunoglobulin Gs (IgGs) using a baculovirus expression system. Reconstituted IgGs kept the original specificities of the parental scFvs. The dissociation constants were 23 microM and 20 microM by Biacore, respectively. This is the first report of a successful generation of monoclonal antibodies against an HIV-1 CTL epitope loaded on an MHC class I molecule.