DENDRITIC CELLS PROCESS EXOGENOUS VIRAL-PROTEINS AND VIRUS-LIKE PARTICLES FOR CLASS-I PRESENTATION TO CD8(-LYMPHOCYTES() CYTOTOXIC T)

Previous reports have indicated that both dendritic cells and macropha ges have the ability to induce cytotoxic T lymphocyte (CTL) and T help er (Th) cell responses in vivo. Dendritic cells process exogenous anti gens conventionally for presentation on major histocompatibility compl ex (MHC) class II molecules. However, unconventional processing of exo genous antigens in vitro for presentation on MHC class I molecules is still an open question. In this study, we report that a cloned dendrit ic cell line (D2SC/1) is able to present cell debris-associated exogen ous viral proteins to MHC class I-restricted CTL in vitro. The dendrit ic cell line was very efficient in processing recombinant lymphocytic choriomeningitis virus nucleoprotein (LCMV NP) and presenting the clas s I-restricted epitope to Cm primed in vivo. Peritoneal macrophages co uld also process the recombinant LCMV NP for subsequent MHC class I pr esentation, but were less efficient compared to the dendritic cells. F urthermore, recombinant yeast-derived virus-like particles carrying th e HIV-1 V3 loop (V3-VLP), which are protenaceous and do not contain an y lipid, were also found to be efficiently processed by the dendritic cell line for presentation of the class I-restricted epitope. These re sults clearly indicate that viral proteins, in particulate form or ass ociated with cell debris, are processed by dendritic cells for CTL ind uction.