Immortalized Human Gallbladder Epithelial Cells-SV40

PltC Typhoid Toxin Promotes S. Typhi Pathogenicity In Vivo

Salmonella Typhi secretes two typhoid toxin forms using PltB and PltC subunits. While PltB tropism is established, PltC's cellular targets and functional consequences remain unknown. Kim et al. investigated PltC typhoid toxin tropism and its role in S. Typhi pathogenicity.

They identified PltC's hepatobiliary tropism through binding to sulfated glycans on liver sinusoidal endothelial and gallbladder epithelial cells, mediated by PltC R109 and carbohydrate sulfotransferases CHST2/4. PltC typhoid toxin reduced bile acids, promoting S. Typhi pathogenicity in infected mice. Then, they assessed whether bile acid levels affect S. Typhi infectivity into immortalized human gallbladder epithelial cells. WT Vi capsule S. Typhi strains were cultured in high-salt LB (0.3 M NaCl, SPI-1 inducing condition), showing equivalent growth with or without bile extract (Fig. 1K). For invasion assays, they osmolarity-balanced culture media to isolate bile acid effects (Fig. 1L), noting that unadjusted bile extract addition increases osmolarity and artificially enhances infectivity. Under these controlled conditions, bile acids inhibited S. Typhi invasion of human gallbladder epithelial cells (Fig. 1M), Henle 407 cells (Fig. 1N), and primary hepatocytes, with microscopy and CFU assays yielding consistent results (Fig. 1O). However, this inhibition was abolished in S. Typhi with hilD triple mutations (Fig. 1P), indicating that three residues in HilD's jellyroll motif are critical for bile acid-mediated suppression of cellular invasion.