2. Academic Validation
  3. Type I and II pili mediate Streptococcus pneumoniae invasion into human blood-brain barrier-derived cells through extracellular matrix protein receptors and different endocytosis pathways

Type I and II pili mediate Streptococcus pneumoniae invasion into human blood-brain barrier-derived cells through extracellular matrix protein receptors and different endocytosis pathways

  • Int Immunopharmacol. 2025 Jul 28:160:114918. doi: 10.1016/j.intimp.2025.114918.
Sui-Ning Chen 1,  Yu-Jin Wang 2,  Meng-Jie Li 3,  Yi-Qiong Xing 3,  Meng-Yi Guo 3,  Jie Yan 4,  Ai-Hua Sun 5
Affiliations

Affiliations

  • 1 School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, Zhejiang 310053, PR China; School of Public Health, Hangzhou Medical College, Hangzhou, Zhejiang 310053, PR China. Electronic address: 881012022162@hmc.edu.cn.
  • 2 School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, Zhejiang 310053, PR China. Electronic address: 130232023003@hmc.edu.cn.
  • 3 School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, Zhejiang 310053, PR China.
  • 4 Zhejiang Provincial Society for Microbiology, Hangzhou, Zhejiang 310058, PR China.
  • 5 School of Basic Medical Sciences and Forensic Medicine, Hangzhou Medical College, Hangzhou, Zhejiang 310053, PR China. Electronic address: sunaihua@hmc.edu.cn.
PMID: 40449266 DOI: 10.1016/j.intimp.2025.114918
Abstract

Backgroud: Streptococcus pneumoniae is the most common pathogen of Bacterial meningitis, but mechanisms of this pathogen invading blood-brain barrier (BBB) remain unknown.

Methods: Invasion of S. pneumoniae strains and microbeads coated with recombinant pilin, rRrgA-B or rPitB, into human BBB-derived brain microvascular endothelial cells (HBMECs), brain vascular pericytes (HBVPs), and astrocytes (HAs) by laser scanning confocal microscopy (LSCM). Fibronectin (FN), laminin (LN), and collagen-1/3/4 (COL-1/3/4) in the extracellular matrix (ECM) were detected by LSCM and flow cytometry. rRrgA-B and rPitB binding to the ECM proteins were identified using surface plasmon resonance. Pneumococcal endocytosis pathways, CA2+ level, microfilament (MF) and microtubule (MT) polymerization in the cells were determined by LSCM-based inhibition assay.

Results: Type I/II pili-positive S. pneumoniae SP007 displayed natably stronger invasiveness into the cells than pilus-free S. pneumoniae ATCC49619. rRrgA-B-/rPitB-coated microbeads also exhibited invasion ability. HBMECs express FN, LN, and COL1, while HBVPs and HAs express all the ECM proteins. rRrgA-B and rPitB displayed a rapid binding to all the ECM proteins with KD values ranging from 3.25 × 10-7 to 9.58 × 10-8 M. Intracellular free CA2+ increase and MF-dependent Cytoskeleton rearrangement occurred during invasion of the pneumococcal strains and rRrgA-B-/rPitB-coated microbeads. Invasion of the strains and rRrgA-B-/rPitB-coated microbeads into these cells involved Integrin (ITG), focal adhesion kinase (FAK), Rho-associated coiled-coil forming kinase (ROCK) or phosphatidylinositol-3-kinase (PI3K), clathrin (CLN)-, caveolae (CAV)- or macropinocytosis (MPC)-dependent endocytosis.

Conclusion: Type I and II pili play important roles to mediate S. pneumoniae invasion into BBB-direived cells through FN/LN/COL1-ITG-FAK/ROCK-Ca2+-MF-CLN/CAV/MPC- or FN/LN/COL1/3/4-ITG-FAK/PI3K-Ca2+-MF-CLN/CAV-dependent endocytosis pathways to cause meningitis.

Keywords

Bacterial meningitis / pathogenesis; Blood-brain barrier; Invasion / endocytosis; Pilus; Streptococcus pneumoniae.

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