Fig. 7

IFN-I signal in tissue-resident cells plays a crucial role in inducing CNS neuroinflammation through the peripheral restriction of viral dissemination. BM cells from wild-type C57BL/6 (BL/6) or IFNAR1 KO (KO) mice were grafted into lethally irradiated BL/6 or IFNAR1 KO recipient mice, which were infected with JEV (5 × 10⁶ ffu) via footpad route 5 weeks later. a Requirement of IFN-I signaling in tissue-resident cells for inducing CNS neuroinflammation. The proportion of surviving mice in each group was monitored daily for 20 days (left graph). Ratio of mice showing neurological disorder in inoculated recipients was recorded daily during JE progression (right graph). b Viral burden in the peripheral and CNS tissues of BM chimeric hosts. Viral burdens were assessed by real-time qRT-PCR using total RNA extracted from the peripheral and CNS tissues including popliteal LNs (pLN), spleen, liver, intestine, and brain 48 h pi. The viral RNA load was expressed by viral RNA copy number per microgram of total RNA (n = 4). Each symbol represents the level of an individual mouse; the horizontal line indicates the mean ± SEM of each group. c IFN-I signal deficiency in tissue-resident cells is required for high induction of inflammatory cytokine mRNA. The mRNA levels of the indicated cytokines and chemokines were determined by real-time qRT-PCR 48 h pi. Radar charts summarize the mean mRNA expression levels of the indicated cytokines in the indicated tissue with a log₁₀ scale normalized to β-actin expression. d Indispensable role of IFN-I signal in tissue-resident cells in inducing “cytokine storm”. Serum levels of cytokines and CC chemokines were determined by cytokine ELISA (IL-6 and TNF-a) and cytokine bead array (CC chemokines) using sera collected from inoculated recipients 48 h pi. Radar chart shows the mean levels of the indicated cytokines with a log₁₀ scale of cytokine level (pg/ml). e Complete blood count (CBC) data of BM chimeric hosts following JEV infection. The levels of white blood cells (WBC), red blood cells (RBC), hemoglobin (Hgb), hematocrit (Hct), and platelets (PLT) were determined using an automated hematology analyzer 48 h pi. Data are expressed by the change percentage compared to mock-infected recipients. f Liver and kidney functions of BM chimeric hosts following JEV infection. The injury of liver and kidney function was evaluated by the levels of ALT and AST for liver, and the levels of BUN, creatinine, and glucose for kidney using a clinical chemistry analyzer. g The amount of extravasated Evans blue dye in the intestine of JEV-infected BM chimeras. The amount of extravasated Evans blue dye was quantified by measuring the absorbance (620 nm) after homogenization and TCA-precipitation of the intestine tissue. Data in the graphs denote the mean ± SEM. Results are representative of one out of at least two individual experiments with four to five mice per group. Statistical significance *p < 0.05; **p < 0.01; ***p < 0.001 was assessed by an unpaired two-tailed Student’s t test