Fig. 1: GBS localizes within tissue-resident macrophages and expresses cadD at high levels within macrophages.

A–C Immunofluorescence microscopy examination of the placenta of either uninfected (A) or GBS-infected (B) mice reveals macrophages within the tissue as determined by staining with a monoclonal antibody to F4/80 (red). Tissues were also stained with a polyclonal antibody to GBS (green), and counter-stained with 4′,6-diamidino-2-phenylindole (DAPI; blue) to visualize cell nuclei. Merged images reveal co-localization of GBS and macrophages (yellow), magnification bar indicates 50 μm. C Enlargement of inset panel of the merged image in B indicates GBS cells associated with tissue macrophages within the placenta (yellow arrows). Micrographs are shown which are representative of images collected from 3 separate dams from each experimental group (uninfected or GBS-infected, n = 3). D, E GBS cultured within THP-1 macrophages in vitro were subjected to transcriptional analyses. D RNAseq analysis revealed that cadD was upregulated after 24 h of culture within macrophages, a result that was confirmed by quantitative real-time PCR (E), bars indicate mean and error bars indicate +/− SEM. *P = 0.0083, two-tailed, paired Student’s t test, n = 3 separate biological replicates. F Gene sequencing indicates that cadD is organized within a short operon and is highly conserved across numerous Streptococcus spp. including oral streptococci. The maximum likelihood phylogeny was constructed with 500 bootstrap replications; bootstrap support values are indicated at each node, scale bar indicates number of substitutions per site.