Isolation of MHC class I-restricted tumor antigen peptide and its precursors associated with heat shock proteins hsp70, hsp90, and gp96

We have previously demonstrated that vaccination with heat shock proteins h sp70, hsp90, and gp96 elicits specific immunity against the tumor from whic h the hsps were purified. Although the association of tumor Ag peptides wit h these hsps have been suggested, the identification of the peptides or the ir precursors stripped from the hsps remained to be resolved. We show in th is report that an L-d-restricted cytotoxic T lymphocyte epitope of a mouse leukemia RL male 1 and its precursors are associated with the chaperones hs p90 and hsp70 in the cytosol and gp96 in the lumen of the endoplasmic retic ulum, Hsp70 was associated,vith only final sized octamer, while hsp90 was f ound to associate with the octamer and two distinct precursor peptides, The gp96,vas associated with the octamer and one of the two precursors. Thus, each of the hsps bound a distinct set of peptides, Our results have demonst rated for the first time that the hsps associate not only with final sized tumor Ag peptide but also with its precursors. The implication of this evid ence is also discussed in terms of the roles of hsps in MHC class I Ag proc essing/presentation.