EFFICIENT LOADING OF IDENTICAL VIRAL PEPTIDE ONTO CLASS-II MOLECULES BY ANTIGENIZED IMMUNOGLOBULIN AND INFLUENZA-VIRUS

Several prior reports have identified peptides that are naturally asso ciated with major histocompatibility complex (MHC) class II molecules on presenting cells. We have examined the delivery of a peptide from e xogenous sources to MHC class II molecules. The peptide derives from t he influenza virus hemagglutinin (HA) and activates a CD4+ T cell hybr idoma. In functional assays of antigen presentation, this epitope is d elivered effectively to T cells either in the context of influenza vir us or chimeric immunoglobulin (Ig) molecules (Ig-HA) in which the pept ide has replaced the CDR3 loop of the heavy chain. We find that the id entical 11-mer peptide can be isolated from mouse MHC class II antigen s whether the exogenous source of peptide is free HA peptide, the Ig-H A chimera, or ultraviolet-inactivated PR8 influenza virus. The Ig-HA c himera proves to be the most efficient vehicle for charging class II m olecules via the exogenous route. Given the fact that self Igs represe nt natural long-lived carriers, we suggest that antigenized Igs have c onsiderable potential for peptide delivery to MHC molecules in situ.