TCR vaccines for active immunotherapy of T cell malignancies.

We have developed a TCR-based vaccine approach for the treatment of T cell malignancies. TCR genes were isolated from C6VL, a T cell tumor of C57BL/Ka origin. The transmembrane encoding domains of the TCR genes were replaced by sequences encoding for phosphatidylinositol-linked cell surface expression. A high expressing cell line was produced by transfection and amplification of the TCR genes. Large quantities of soluble native C6VL TCR-alphabeta protein was obtained by treating the high-expressing cells with a specific phospholipase and purifying the released TCR by affinity chromatography. Following vaccination with the TCR linked to keyhole limpet hemocyanin, specific anti-TCR humoral responses were induced. Both the carrier protein and an adjuvant were required for optimal responses. Hyperimmune serum from vaccinated mice reacted specifically with C6VL cells, and the immunizations did not affect the TCR repertoire, which suggested that the immune response was Id specific. The TCR-vaccinated mice were specifically protected from a lethal number of C6VL tumor cells. B cell-deficient mice were not protected by TCR vaccinations. Similarly, TCR-immunized mice depleted of CD8+ cells prior to tumor challenge were not protected. Thus, C6VL TCR vaccine effectively stimulated tumor protection, which depends on the presence of both B cells and CD8+ T cells.

Kinetics of the reaction of a myelin basic protein peptide with soluble IAu.

The kinetics of formation and dissociation of IAu-peptide complexes have been examined in the absence of detergent, using a glycosylphosphatidylinositol (GPI)-linked form of IAu. The GPI-linked form contains a lipid membrane anchor which can be specifically cleaved by phosphatidylinositol-specific phospholipase C to yield a water-soluble form of IAu. We find rapid binding of the myelin basic protein (MBP) peptide analogue Ac(1-14)A4C15 to IAu, as well as rapid dissociation of IAu-MBP peptide complexes at neutral pH in the absence of detergent. The reaction kinetics of the water-soluble and detergent-solubilized complexes are the same to within experiment error. In the presence of this MBP peptide, Ac(1-14)A4C15, cells transfected with native IAu as well as cells transfected with a GPI-linked form of IAu are functional in stimulating T-helper hybridoma cells.

Myelin basic protein peptide complexes with the class II MHC molecules I-Au and I-Ak form and dissociate rapidly at neutral pH.

The acetylated N-terminal peptide of myelin basic protein (MBP) is the immunodominant T cell epitope in the induction of experimental autoimmune encephalomyelitis in the I-Au- and I-Ak-expressing mouse strains. We used a direct binding assay to examine the kinetics of binding and dissociation of a series of MBP peptide analogues with the affinity-purified class II MHC molecules I-Au and I-Ak. We observe much faster in vitro rates of binding and dissociation than has been reported previously for other immunogenic peptides at neutral pH. The kinetics also reveal inactivation of the peptide-free class II MHC molecules. These results are consistent with previously proposed mechanisms for tolerance escape and autoimmune disease.

Multiple genetic mechanisms have contributed to the generation of the HLA-A2/A28 family of class I MHC molecules.

The genetic events that produce diversity in class I MHC genes and proteins has been investigated by using a family of closely related HLA-A alleles. Five genes coding for HLA-A2.2Y, HLA-A2.3, and HLA-Aw68.2 have been isolated. Exon sequences are compared with the known sequences for HLA-A2.1, HLA-A2.2F, HLA-A2.4, HLA-Aw68.1, and HLA-Aw69. Pairwise comparison of the eight unique sequences shows that point mutation, reciprocal recombination, and gene conversion have all contributed significantly to the diversification of this family of alleles. These results are compared with those of other studies that have emphasized the role of gene conversion. A predominance of coding substitutions in the alpha 1 and alpha 2 domains is found, consistent with positive selection for polymorphism being a major factor in the fixation of these alleles. In the three cases examined, genes for phenotypically identical proteins gave identical nucleotide sequences, indicating that most, if not all, of the class I polymorphism is detectable by immunological methods. The apparent stability of the sequences suggests that the events generating some of the alleles occurred before the origin of modern Homo sapiens.