VIRAL HEMAGGLUTININ AUGMENTS PEPTIDE-SPECIFIC CYTOTOXIC T-CELL RESPONSES

In attempt to increase the induction of peptide-specific cytolytic T c ells (CTL) we investigated the effect of the Newcastle disease virus ( NDV) hemagglutinin-neuraminidase (HN) gene product on the activation o f peptide-specific CTL. Spleen cells of CH3 mice immunized against the influenza nucleoprotein peptide 50-63 (NP 50-63) were restimulated in vitro (i) with peptide-pulsed syngeneic fibroblast cells (Ltk-) as an tigen-presenting cells, which were in addition (ii) infected with NDV or (iii) stably transfected with the HN cDNA of NDV. A greater than si xfold increase in peptide-specific CTL responses was observed in cultu res restimulated with peptide-pulsed Ltk- cells which coexpressed vira l hemagglutinin due to either infection or transfection. A similar aug mentation was seen in CTL responses against other types of antigen (ma jor histocompatibility complex alloantigens, minor histocompatibility antigens of tumor antigens) when suboptimal cultures were stimulated w ith the respective antigen-presenting cells modified by NDV infection. These findings suggest that NDV or viral HN expressed on antigen-pres ent in cells or tumor cells can exert a T cell co-stimulatory function .