Neomount

For IHC, lung tissue sections (3-4 mm) were mounted on SuperFrostPlus © slides (Menzel-Gl€ aser, Braunschweig, Germany). The avidin-biotin-complex peroxidase method was used for the detection of infectious agents. Following dewaxing and rehydration, antigen retrieval was achieved by heating the slides in citrate buffer (pH 6.0) in a microwave oven, except for FHV-1, where the slides were placed in 0.1% pronase (Protease type XIV, Sigma Aldrich, Steinheim, Germany) for 5 min at 37 8C. Endogenous peroxidase activity was blocked with 0.3% H 2 O 2 in methanol for 30 min. The sections were then incubated with a 1:10 dilution of normal goat serum (Vector Laboratories, Burlingame, CA, USA) for 60 min, followed by overnight incubation with the diluted primary antibody (Table 1). After washing in phosphate-buffered saline, the tissues were incubated with a 1:400 dilution of biotinylated anti-mouse or anti-rabbit IgG, depending on the origin of the primary antibody, for 30 min, followed by the Vectastain ABC kit (Vector Laboratories) for 60 min. The reaction was visualised with DAB Substrate Kit for Peroxidase (Vector Laboratories). After counterstaining with haemalum and dehydration, the slides were placed under coverslips with Neomount (VWR, Vienna, Austria). Each run was accompanied by respective positive controls.