SURVIVAL OF VI-CAPSULATED AND VI-DELETED SALMONELLA-TYPHI STRAINS IN CULTURED MACROPHAGE EXPRESSING DIFFERENT LEVELS OF CD14 ANTIGEN

We examined the intracellular survival of Vi-capsulated (lipopolysacch aride; (LPS)-masked) and Vi-deleted (LPS-exposed) Salmonella typhi str ains inside macrophage cell lines. Growth of LPS-exposed S. typhi was inhibited in both mouse and human macrophage cell lines. However, the LPS-exposed strain survived in a CD14-deficient mouse macrophage cell lines. Wild-type S. typhi strain, which expressed the Vi antigen and m asked LPS, survived in the resting human macrophage cell line. When th e Vi-capsulated S. typhi entered the cells, the production of tumor ne crosis factor-alpha (TNF-alpha) was suppressed. In contrast, S. typhim urium and LPS-exposed S. typhi stimulated the macrophages to produce a high level of TNF-alpha.