Synovium changes were evaluated by light microscopy of fresh-frozen sections of the joints of euthanized animals, and conventional staining with haematoxylin and eosin (H&E). In comparison to the control joints treated with BVCAR or HAdV5-PUMA alone, the infiltrate was significantly reduced in the BVCARHAdV5-PUMA-treated joints (Fig. 5f). This effect was vector dose-dependent, with a lower number of infiltrating cells in ankle joints treated with 109 PFU compared to 107 PFU of BVCARHAdV5-PUMA (Figs 5f and 6).Fig. 6Histological analysis of ankle joints. Fresh-frozen sections (10 µm) of joints treated respectively with: a, BVCAR alone; b, HAdV5-PUMA alone (109 PFU); c, BVCARHAdV5-PUMA (107 PFU); d, BVCARHAdV5-PUMA (109 PFU); were stained with haematoxylin and eosin staining, and compared for the presence of synovial tissue infiltrates. The representative photograph from each group is provided at various magnifications (×200, left; ×400, middle; and ×800, right). The righmost panels are enlargements of the rectangular area delineated in the middle panels. Scale bar, 200 µm