MCMV infection is lethal in acute GVHD. BALB/c (non-GVHD) and DBA/2 (GVHD) were transplanted with BALB/c BM (5 × 10⁶) and CD3⁺ T (2.5 × 10⁶) cells. Mice were infected with 5 × 10³ plaque-forming units (pfu) MCMV 4 weeks after transplantation. The impact of MCMV infection on (A) survival and (B) clinical scores was assessed. † indicates mice were sacrificed. (C-D) Organs were collected on day 6 PI to (C) grade GVHD pathology, as described.²¹  (D) H&E (top panels) and immunohistochemical staining for CMV IE1 antigen (bottom panels). These parameters were used to assess CMV-related pathology and CMV viremia. Cytomegalic cells (top panel) or CMV IE1⁺ cells (brown staining cells in bottom panels) are marked by a filled triangle. Portal tract expansion by an inflammatory cell infiltrate is marked by a filled arrowhead. Areas of hepatic necrosis (filled arrow) and hemorrhagic necrosis (open arrow) are shown. (E) Hepatic necrosis scores (see “Materials and Methods”) and numbers of CMV inclusions are shown. (F) Liver function was assessed at day 6 PI by measuring plasma ALT, AST, and bilirubin levels. (G) Viral loads in the liver and lungs were measured over the course of infection by plaque assay. (A-B) n = 4 to 5 mice per group; (C-E) n = 5 to 8 mice per group; (F) n = 9 to 15 mice per group; (G) n = 5 to 10 mice per group. Data in C-G are representative of, or pooled from, at least 2 independent experiments. *P = .01-.05; **P = .001-.01; ***P = .0001-.001; ****P < .0001.