A recombinant Salmonella typhimurium vaccine strain is taken up and survives within murine Peyer's patch dendritic cells

Abstract

The attenuated Salmonella typhimurium PhoP(c) strain is avirulent but immunogenic via the oral route in mice and is attenuated in survival in macrophage cell lines. In this study, the fate of PhoP(c) bacteria expressing green fluorescent protein was investigated in murine Peyer's patches. The survival of PhoP(c) was monitored after orogastric inoculation of BALB/c mice. Bacteria persisted for several weeks in the Peyer's patches and were also recovered from the mesenteric lymph nodes and spleen. Confocal microscopy analysis identified dendritic cells as the Peyer's patch cell type that internalized PhoP(c) expressing green fluorescent protein at early time points. In addition, live PhoP(c) were found in Peyer's patch dendritic cells and not in B cells 3 days after orogastric inoculation. Taken together, these results provide strong evidence that PhoP(c) is internalized and survives within Peyer's patch dendritic cells. As these cells are potent antigen- presenting cells, these data could explain the immunogenicity of S. typhimurium vaccine strains in vivo.