Immunotherapy with anti-PD-L1 improves CD8 T cell-mediated virus control without worsening spleen fibrosis in LCMV chronic infected mice. (a) Schematic representation of three different regimens of anti-PD-L1 (aPDL1) antibody treatment in chronic LCMV-infected mice. Untreated chronic infected mice were used as controls (ctr) and sampled at the same time points as the anti-PD-L1-treated mice. (b,c) Frequencies of LCMV gp33-responsive IFNγ-producing CD8+ T cells (b) and of Tim3+PD1+ exhausted CD8+ T cells (c) on days 30, 35 and 42 post-infection, after the three different aPDL1 regimens. (d) Viral loads in spleen from days 30, 35 and 42 post-infection, after the aPD-L1 regimens. (e,f) Spleen fibrosis score (e) and representative images of Masson’s Trichrome stained spleen sections (f) used to score the fibrosis in each group on days 30, 35 and 42 post-infection; the black arrows indicate deposits of collagen fibers (in blue—Masson trichrome stain) characteristic of fibrosis. Naive mouse spleen is stained as control. Data shown are the mean of n = 5 to 8 mice. * p ≤ 0.05; *** p ≤ 0.001; ns = not significant (unpaired two-tailed t-test).