Profound reduction in MuLV-induced pain hypersensitivity did not correlate with major changes in virus titers or host immunopathogenesis (splenomegaly, immunosuppression, cytokine induction) since these parameters were comparable in WT and IDO1-KO mice (S1C–S1F Fig), as reported previously [7]. This evidence concerns the gene IDO1 and Splenomegaly.