Internalin B is essential for adhesion and mediates the invasion of Listeria monocytogenes into human endothelial cells

Abstract

SummaryListeria monocytogenes causes rhombencephalitis in humans and animals and also affects the fetus in utero, causing disseminated sepsis. In both instances, the infection occurs by the crossing of endothelial cells lining a physiological barrier, the blood-brain barrier or the transplacental barrier. In this study, the ability of L. monocytogenes wild-type EGD to invade human umbilical vein endothelial cells (HUVECs) was evaluated using wild-type bacteria and isogenic Listeria mutants. Here, we show that invasion of HUVECs by L. monocytogenes is dependent on the expression of the internalin B gene product. This was demonstrated in several ways. First, L. monocytogenes strains lacking the inl B gene did not invade HUVECs. Secondly, avid invasion was obtained when a strain deleted for inlAB was complemented with a plasmid harbouring inl B only, whereas strains expressing inlA did not enter HUVECs. Thirdly, entry of wild-type EGD could be blocked effectively with antibodies to InlB. Fourthly, cell binding assays and flow cytometry with HUVECs showed binding of purified InlB, but not InlA, suggesting a tropism of InlB for this cell type. Finally, physical association of purified native InlB with the surface of non-invasive mutants dramatically increased their ability to invade HUVECs. In laser-scanning confocal microscopy, binding of InlB was observed as focal and localized patches on the cell surface of HUVECs. Qualitative examination of the entry process by scanning electron microscopy revealed that both wild-type EGD and a recombinant strain overexpressing only InlB enter HUVECs in a similar fashion. The entry process was polarized, involved single bacteria and occurred over the entire surface of endothelial cells.

Repression of Inflammasome by Francisella tularensis during Early Stages of Infection

“…The region from amino acid residues 184 -200 showed homology to leucine-rich repeats of internalin B protein of Listeria monocytogenes. The leucine-rich repeats of internalin B has been shown to be required for inducing phagocytosis in non-phagocytic cells such as hepatocytes and endothelial and epithelial cells (46,47). We reported that FTL_0325 suppresses proinflammatory cytokines primarily by interfering with NF-B signaling (37).…”

Characterization of virulent and avirulent Listeria monocytogenes strains by PCR amplification of putative transcriptional regulator and internalin genes

“…Therefore, nucleotide-nucleotide BLAST searches were conducted to compare the gene sequences of L. monocytogenes transcriptional regulators against the genome sequence of L. innocua (Glaser et al, 2001); three genes (lmo2672, lmo1116 and lmo1134), which had the lowest nucleotide identity with any sequences from the L. innocua genome, were selected from the published L. monocytogenes EGD-e transcriptional regulator list. In addition, as internalins play important roles in listerial internalization and virulence (Gaillard et al, 1991;Lingnau et al, 1995;Parida et al, 1998), we selected two genes (lmo2470 and lmo2821) that encode internalin-like proteins from the L. monocytogenes EGD-e genome sequence, which do not have orthologues in the L. innocua genome (Glaser et al, 2001). (Erdenlig et al, 2000).…”

Listeria monocytogenesl‐forms respond to cell wall deficiency by modifying gene expression and the mode of division

“…Detection of InlA and InlB on parental and L-form cells was performed using polyclonal antibodies raised against InlA and InlB (Parida et al, 1998; kindly provided by Sabine Pilgrim, University of Wuerzburg, Germany). On a piece of parafilm (Pechiney Plastic Packaging Company, USA), a drop of the respective cell suspensions was covered with a round cover slip to let the cells adhere.…”