Introduction of protein or DNA delivered via recombinant Salmonella typhimurium into the major histocompatibility complex class I presentation pathway of macrophages

Recombinant (r) Salmonella typhimurium aroA strains which display the hen egg ovalbumin OVA 257-264 peptide SIINFEKL in secreted form were constructed. In addition, attenuated r S. typhimurium pcDNA-OVA constructs harbouring a eukaryotic expression plasmid encoding complete OVA were used to introduce the immunodominant OVA 257-264 epitope into the major histocompatibility complex (MHC) class I presentation pathway. Both modes of antigen delivery (DNA and protein) by Salmonella vaccine carriers stimulated OVA 257-264-specific CD8 T-cell hybridomas. An in vitro infection system was established that allowed both r Salmonella carrier devices to facilitate MHC class I delivery of OVA 257-264 by coexpression of listeriolysin (Hly) or by coinfection with r S. typhimurium Hlys (Hess J., Gentschev I., Miko D., Welzel M., Ladel C., Goebel W., Kaufmann S.H.E., Proc. Natl. Acad. Sci. USA 93 (1996) 1458-1463). Coexpression of Hly and coinfection with r S. typhimurium Hlys slightly improved MHC class I processing of OVA. Our data provide further evidence for the feasibility of attenuated, Hly-expressing r S. typhimurium carriers secreting heterologous antigens or harbouring heterologous DNA as effective vaccines for stimulating CD8 T cells in addition to CD4 T cells.