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. 2020 Nov 30;11:6106. doi: 10.1038/s41467-020-19826-2

Fig. 1. Screening for mammalian neuro-invasive pathogens in a brain explant set-up identifies Group B Streptococcus as able to cross the Drosophila blood–brain barrier.

Fig. 1

a Schematic representation of Drosophila third instar larva showing the brain suspended in the haemolymph. Top and orthogonal views of the brain covered by the BBB (dark orange). A, anterior. P, posterior. D, dorsal. V, ventral. a’ Schematic representations of the composite Drosophila and mammalian BBBs, which include a layer of extracellular matrix (ECM in grey), a regulatory layer (perineurial glia (PG) and pericytes (PC) in light orange) and a barrier layer (subperineurial glia (SPG) and endothelial cells (EC), dark orange) harbouring strong cell junctions (septate junctions and tight junctions, yellow). Neurons (N), one major type of brain cell populations, are illustrated in blue. b Confocal images of the Drosophila BBB (top view and 3D orthogonal view) labelled for the ECM in grey (vkg::GFP), the PG in light orange (NP6293-GAL4>mCD8-GFP) and the SPG in red (mdr65-mtd-tomato). c Septate junctions in green (Lachesin::GFP). d Ex vivo protocol. Step 1 depicts the dissection method used to expose the brain while minimising damages. Step 2 illustrates the culture and infection protocols. Step 3 depicts confocal images of the brains (top and orthogonal views) stained with phalloidin (white). Bacteria (L. plantarum and S. agalactiae [GBS]) are stained in green. Orange arrows show GBS inside the brain. e Screening mammalian neurotropic pathogens for their ability to cross the Drosophila BBB. S. agalactiae (GBS), S. pneumoniae, N. meningitidis, L. monocytogenes and C. glabrata were able to cross the Drosophila BBB. C. albicans exists in a filamentous, hyphal form linked to pathogenicity, which destroyed the brain, and in yeast, non-hyphal form (C. albicans Δfilamentous) which entered the brain. L. innocua rarely crossed the BBB, while non-pathogenic E. coli, L. plantarum, S. cerevisiae and C. neoformans were not able to invade the brain. Results are presented as box and whisker plots. Whiskers mark the minimum and maximum, the box includes the 25th–75th percentile, and the line in the box is the median. Numbers above the boxes represent the number of larvae analysed. Source data are provided as a Source Data file for e.