Introduction of exogenous antigens into the MHC class I processing and presentation pathway by Drosophila antennapedia homeodomain primes cytotoxic T cells in vivo.

The epitope sequence corresponds to residues 194-203 of Swiss Prot ID P04222. A CTL clone (CAS 20) that recognizes the H-2Kd-restricted 170-179 HLA-Cw3 epitope was used in a CTL assay with target cells that had been preincubated with fusion peptides (AntpHD R3 or AntpHD R4) composed of the 170-179 HLA-C3w epitope fused to the homeodomain of the Antennapedia molecule (AntpHD) from Drosophila. The CAS 20 clone killed three different cell lines (P815, D2.1 and LKd) after the cell lines had been incubated with the fusion peptide. The response was blocked by anti-H-2-Kd antibodies. The response was inhibited by brefeldin A but not by chloroquine, suggesting that membrane trafficking is required, but endosomal proteolysis is not required, for presentation of the epitope from the fusion peptide. Presentation of the 170-179 HLA-Cw3 epitope was influenced by its flanking sequences within the fusion peptide, because removal of a c-myc tag located N-terminal to the epitope (in fusion protein AntpHD R2) abolished CTL recognition and killing. .