Fig. 6

In situ characterization of “in transition” microglia/microglia-like cells in HSV-1-infected VPLs. a Distribution of HSV-1 transcripts was analyzed to identify infected cell sub-clusters on two-dimensional UMAP (td-UMAP) visualization of aggregated data (three infected and two uninfected mice on day 6 p.i.). “In transition” microglia/microglia-like cell sub-cluster corresponds to HSV-1-infected microglia/microglial-like cells. b Feature plots show the distribution of Tmem119, Iba-I (Aif1), CD68, Nlrp3, and Il-1β genes with on td-UMAP of aggregated data. Available antibodies against the proteins encoded by canonical genes were used to identify “in transition” microglia/microglia-like cells. c (top, left) IBA-I⁺ cells expressing high levels of CD68 clustered (white circle) in highly infected thalamus. (top, right) TMEM119 and IBA-I immunostaining revealed ramified TMEM119⁺/IBA-I⁺ cells (white circle) near clusters of TMEM119⁻/IBA-I⁺ cells in infected thalamus on day 6 p.i. Inflammasome activity in “in transition” microglia/microglia-like cells was studied using NLRP3 (middle, left, and right) and IL-1β (bottom, left) immunostaining on HSV-1⁺ VPLs. Confocal microscopy images revealed TMEM119⁺/NLRP3⁺ and IBA-I⁺/IL-1β ⁺ microglia/microglia-like cell populations (white arrow) highlighting “in transition” microglia/microglia-like cells. (bottom, right) Immunohistochemical staining for HSV-1 showed that these ramified TMEM119⁺/IBA-I⁺ cells were HSV-1⁺ (white arrow) (scale, 20 μm)