Targeting the BspC-vimentin interaction to develop anti-virulence therapies during Group B streptococcal meningitis

Abstract

Bacterial infections are a major cause of morbidity and mortality worldwide and the rise of antibiotic resistance necessitates development of alternative treatments. Pathogen adhesins that bind to host cells initiate disease pathogenesis and represent potential therapeutic targets. We have shown previously that the BspC adhesin in Group B Streptococcus (GBS), the leading cause of bacterial neonatal meningitis, interacts with host vimentin to promote attachment to brain endothelium and disease development. Here we determined that the BspC variable (V-) domain contains the vimentin binding site and promotes GBS adherence to brain endothelium. Site directed mutagenesis identified a binding pocket necessary for GBS host cell interaction and development of meningitis. Using a virtual structure-based drug screen we identified compounds that targeted the V-domain binding pocket, which blocked GBS adherence and entry into the brain in vivo. These data indicate the utility of targeting the pathogen-host interface to develop anti-virulence therapeutics.

The Group B Streptococcal Adhesin BspC Interacts with Host Cytokeratin 19 To Promote Colonization of the Female Reproductive Tract

“…We have previously shown that BspC is necessary and sufficient to induce neutrophil chemokine signaling in brain endothelial cells and during the progression of meningitis in vivo ( 15 , 16 ). As neutrophil influx is associated with chorioamnionitis and preterm labor after bacterial ascending infection ( 8 , 26 to 28 ), we sought to investigate the proinflammatory potential of BspC within this niche.…”

“…We recently determined that the BspC V-domain binding pocket was critical for BspC-dependent interaction with brain endothelial cells and vimentin ( 15 ). We hypothesized that the V-domain may similarly contribute to BspC-mediated adherence to FRT cells, auto-aggregation, and K19 interaction.…”

“…After confirming the importance of the V-domain in these interactions, we aimed to investigate a ligand-binding pocket contained within the V-domain. Previously, we used site-directed mutagenesis to create three multipoint mutants that alter key residues that form the ligand-binding pocket: left pocket mutant (LPM; F267A, F269A, and H271A), right pocket mutant (RPM; F379A, K380E, H382A, and W384A), and gating loop mutant (GLM; A250P/A259P) ( 15 ). The locations of the specific residues mutated in each of these strains are shown in Fig.…”

“…Strains within the majority of Streptococcus species possess genes encoding AgI/II proteins, which have been implicated in promotion of adherence to various surfaces, including teeth, lung epithelium, and the blood-brain barrier (BBB) endothelium ( 13 , 14 ). The GBS Bsp genes have 4 known homologs, BspA–BspD, which have been identified in ~27% of GBS genomes, with 55% of these being BspC ( 15 ). We recently showed that BspC adherence to the BBB contributes to the pathogenesis of GBS meningitis ( 16 ).…”

“…BspC interacts directly with the type-III intermediate filament protein known as vimentin, which is highly expressed in BBB endothelial cells ( 17 , 18 ). The BspC-vimentin interaction is mediated by a ligand-binding pocket guarded by a gating loop contained in the BspC variable (V-) domain ( 15 ). Bsp proteins have also been shown to be necessary for optimal GBS adherence to vaginal epithelial cells ( 19 ).…”