TARGETING A POLYEPITOPE PROTEIN INCORPORATING MULTIPLE CLASS II-RESTRICTED VIRAL EPITOPES TO THE SECRETORY ENDOCYTIC PATHWAY FACILITATES IMMUNE RECOGNITION BY CD4(+) CYTOTOXIC T-LYMPHOCYTES - A NOVEL-APPROACH TO VACCINE DESIGN/

The role of CD4(+) and CD8(+) cells in the generation of an effective immune response against viral infections is well established, Moreover , there is an increasing realization that subunit vaccines which inclu de both CD4+- and CD8(+)-T-cell epitopes are highly effective in contr olling viral infections, as opposed to those which are designed to act ivate a CD8(+)- or CD4(+)-T-cell response alone, One of the major limi tations of epitope-based vaccines designed to stimulate virus-specific CD4(+) T cells is that endogenously expressed class Ii-restricted min imal cytotoxic-T-lymphocyte (CTL) epitopes are poorly recognized by CD 4(+) CTLs, In the present study we attempted to enhance the efficiency of class II-restricted endogenous presentation of minimal class II-re stricted CTL epitopes by specifically targeting a polyepitope protein to class II processing compartments through the endosomal and/or lysos omal pathway, A significantly enhanced stimulation of virus-specific C D4(+)-T-cell clones by antigen-presenting cells (APC) expressing the r ecombinant polyepitope protein targeted to the endocytic/secretory pat hway was readily demonstrated in cytoxicity assays, In addition, in vi tro activation of Epstein-Barr virus-and influenza virus specific CD4( +) memory CTLs by the recombinant constructs encoding the polyepitope protein, specifically targeted to the lysosomal compartment, was also demonstrated, The enhanced stimulatory capacity of APC expressing a ly sosome-targeted polyepitope protein has important implications for vac cine design.