Microglia activation was highly increased by infection in OPN KO mice, as revealed by a decreased Iba-1 staining on day 5 pi compared to uninfected and to WT animals (Figures 8(m), 8(n), 8(o), and 8(p)), in parallel with TUNEL and caspase 3, suggesting that microglial activation is associated with more cell death. This evidence concerns the gene SPP1 and infection.