Purification of antigenic peptide from murine hepatoma cells recognized byclass-I major histocompatibility complex molecule-restricted cytotoxic T-lymphocytes induced with B7-1-gene-transfected hepatoma cells

Background/Aim: It has been reported that expression of costimulatory molec ules, such as B7, on tumors is essential for priming tumor-specific cytotox ic T-lymphocytes (CTLs), Here, we have attempted to: induce murine hepatoma -specific CTLs by immunizing with the B7-1-gene-expressing hepatoma cells, and to identify the epitope(s) presented on the hepatoma cells, Methods: The B7-1-gene encoding plasmid was transferred into the murine hep atoma cell lie, Hepal-6, Syngeneic C57BL/6 mice were immunized with the B7- 1-transfected cells via various routes to prime CTLs, The mild acid elution method was used to isolate antigenic fractions from the class-1 major hist ocompatibility complex (MHC) molecules on the Hepal-6 cells, Cytotoxicity w as measured by standard Cr-51-releasing assay. The effect of the CTLs on he patoma growth was evaluated in hepatoma-bearing SCID mice to which the cell s were preadministered, Results: A clone, termed L1, highly expressing the B7-1-gene, has been esta blished. Killer cells generated from mice immunized intraperitoneally with L1 cells eliminated both L1 and Hepal-6 cells, and also another syngeneic h epatoma cell line, Hepa1-clc7. The killer cells were CD8(+) and the class-1 MHC molecule-restricted CTLs which might recognize hepatoma-specific antig enic peptide(s) in association with the D(b)class-I MHC molecules, A functi onal peptide fraction was obtained from eluted fluid of the Hepal-6 cells, In addition, intravenous preadministration of the CTLs inhibited the hepato ma growth in SCID mice, Conclusions: The hepatoma epitope-specific CTLs which suppressed hepatoma g rowth in vivo could be generated with the B7-1-gene-transfected hepatoma ce lls. These results will be useful in establishing inmunotherapy against hep atocellular carcinoma.