GENERATION OF MHC CLASS I-RESTRICTED CYTOTOXIC T-LYMPHOCYTES BY EXPRESSION OF A VIRAL PROTEIN IN MUSCLE-CELLS - ANTIGEN PRESENTATION BY NONMUSCLE CELLS

Expression of reporter genes in muscle cells has been achieved by intr amuscular (i.m.) injection of plasmid DNA expression vectors. We previ ously demonstrated that this technique is an effective means of immuni zation to elicit both antibodies capable of conferring homologous prot ection and cell-mediated immunity leading to cross-strain protection a gainst influenza virus challenge in mice. These results suggested that expression of viral proteins by muscle cells can result in the genera tion of cellular immune responses, including cytotoxic T lymphocytes ( CTL). However, because DNA has the potential to be internalized and ex pressed by other cell types, we sought to determine whether or not ind uction of CTL required synthesis of antigen in non-muscle cells and, i f not, whether transfer of antigen to antigen-presenting cells from mu scle cells may be involved. In the present study, we demonstrate that transplantation of nucleoprotein (NP)-transfected myoblasts into synge neic mice led to the generation of NP-specific antibodies and CTL, and cross-strain protective immunity against a lethal challenge with infl uenza virus. Furthermore, transplantation of NP-expressing myoblasts ( H-2(k)) intraperitoneally into F1 hybrid mice (H-2(d) x H-2(k)) elicit ed NP CTL restricted by the MHC haplotype of both parental strains. Th ese results indicate that NP expression by muscle cells after transpla ntation was sufficient to generate protective cell-mediated immunity, and that induction of the CTL response was mediated, at least in part, by transfer of antigen from the transplanted muscle cells to a host c ell.