MOLECULAR ANALYSIS OF THE SPECIFICITY OF ANTI-FRIEND VIRUS CYTOTOXIC T LYMPHOCYTES

Abstract

Anti-tumor cytotoxic T lymphocytes (CTL) are generated by immunization of H-2('b) mice with Friend erythroleukemia virus complex (FV) or with syngeneic FV-induced tumor cells. These effector cells can recognize and lyse only those cells expressing cell-surface antigens of both FV and a class I major histocompatibility complex molecule of the H-2('b) haplotype (H-2 restriction). Previous studies indicated that only the H-2D('b) and not the H-2K('b) molecule can participate in the formation of the structure(s) recognized by these CTL, but the viral molecule(s) involved remain to be identified.;In a study of these viral specificities, Fisher rat embryo (FRE) fibroblasts infected with one or both of the two components of FV, helper Friend murine leukemia virus (F-MuLV) and defective spleen focus-forming virus (SFFV), have been used to create "synthetic" target cells by transfection with the molecularly cloned genes for either the D('b) or the K('b) class I molecules. These genes are stably expressed in transfected FRE clones and are recognized by allospecific CTL; in addition, the transfected D('b) molecule can serve as an H-2 restricting element for anti-viral CTL. The results indicate that both F-MuLV- and SFFV-encoded specificities are involved in recognition of FV-infected cells. An unexpected finding was that anti-F-MuLV CTL, but not anti-FV complex CTL, were also able to lyse FRE clones that expressed the K('b) molecule in either the presence or absence of FV.;To identify the specific viral molecule(s) involved in target complex formation, DNA vectors for the expression of the individual genes of the two viruses have been constructed. Transfection of the F-MuLV-derived vectors into FRE cells led to the stable expression of cell-surface proteins encoded by either the viral env or gag genes. Several definitive experiments have demonstrated that either of these molecules, in association with contransfected D('b), can be recognized by anti-Friend virus cytotoxic T lymphocytes.