Fig. 5

Caspr1(203–355) peptides attenuates bacterial penetration through the BBB leading to reduced E. coli meningitis in neonatal rats. a Recombinant His-tagged IbeA proteins were added to the plate coated with GST-tagged Caspr1(203–355) protein, with GST coated plate as control. The binding was assessed by in vitro binding assay by measuring the absorbance at 370 nm. Values are mean ± SD from three independent experiments. **P < 0.01; ***P < 0.001, one-way ANOVA. b E. coli were pre-incubated with indicated concentrations of Caspr1(203–355) recombinant protein for 30 min and then bacterial invasion assays were performed. Values are mean ± SD from five independent experiments. *P < 0.05, **P < 0.01, one-way ANOVA. c Half-life of Caspr1(203–355) recombinant protein in rat blood (30 μg/rat). Values are mean ± SD from three independent experiments. d, e The neonatal rats were subcutaneously inoculated with 1 × 10⁵ CFUs of E44 pre-treated with GST-Caspr1(203–355) peptide (30 μg/rat), with GST protein as control. After 18 h, d the blood samples were collected for bacteremia measurement. The CSF were collected and cultured for bacteria. e The brains were harvested and sectioned for HE staining, and the representative images were provided. The bottom panels are a higher magnification of the boxed regions in the top panels. Arrows indicate neutrophils. Scale, 100 μm. The rate of meningitis occurrence was calculated by dividing the number of rats with both positive CSF and meningeal inflammation by the total number of rats. *P < 0.05, Chi-square test. f Neonatal rats were subcutaneously injected with 4 × 10² CFUs of E44 strain together with GST-Caspr1(203–355) peptide (30 μg/rat), with GST protein as control. The daily mortality was recorded and survival curves were plotted. n = 14 (each group). P < 0.05, Log-rank (Mantel–Cox) test