Fig. 3: Early SFV neuroinvasion in C57BL/6J mice occurs through choroid plexus epithelial cells.

a Kaplan–Meier analysis of mice infected intravenously (IV) with 1 × 10⁶ PFU SFV4 or SFV4(A774st). Statistical analysis done with log-rank test. Data from two independent experiments. b Representative immunostaining for SFV proteins in mouse brain at end point (day 5) after SFV4(A774st) injection. Magnified regions are shown from hippocampus and cerebellum. c Analysis of virus in different brain regions (as indicated), blood and CSF with plaque titration (PFU/ml). Samples from 5 mice collected at d2, 3 and 4 after 1 × 10⁶ PFU (blue circles) IV injection of SFV4(A774st). Additional CSF samples analyzed at d3 after 1 × 10⁷ PFU injection (gray dots). ND: not detected. Limit of detection: 50 PFU/ml. Each data point represents the result from an individual mouse. d Representative immunostaining of choroid plexus 2 days after 1 × 10⁶ PFU IV SFV4(A774st) injection. SFV protein staining can be seen in the outer surface of VLDLR-positive epithelial cells (indicated with arrows). e Representative immunostaining of SFV protein in ventricle wall 2 days after 1 × 10⁶ PFU IV SFV4(A774st) injection. f Representative immunostaining for SFV proteins (green) in WT mouse brain at day 3 after 1 × 10⁶ PFU IV SFV4(A774st) injection show expression of SFV proteins in ventral regions. Top right corner shows schematic picture of CSF fluid flow in the mouse brain. Created in BioRender. Martikainen, M. (2024) https://BioRender.com/o42e737. All experiments are done with 7–9-week-old female C57BL/6J mice. Source data for (a, c) is provided as a Source Data file.