Immunohistochemistry was performed to evaluate the distribution of PEDV antigen. Briefly, formalin-fixed paraffin-embedded tissues were sectioned at 4 μm, deparaffined in xylene, rehydrated in serially diluted ethanol, and proceeded to epitope retrieval with the Trilogy antigen retrieval system (Cell Marque, Rocklin, CA, USA). After being washed three times with Tris-buffered saline plus 0.1% Tween 20 (TBST), tissue slides were treated with 3% hydrogen peroxidase (KYB, New Taipei City, Taiwan) and 10% normal goat serum (Dako, Carpinteria, CA, USA) to block the endogenous peroxidase activity and non-specific signals, respectively. For antigen detection, an in-house anti-PEDV N antibody, DE-1, at a dilution of 1:1000 in 10% normal goat serum was applied to the slides for 1 h at RT followed by three times wash with TBST. The first antibodies were then captured using the polyclonal anti-rabbit/mouse immunoglobulin, EnVision-DAB+ system (Agilent Technologies, Santa Clara, CA, USA) at RT for 1 h and color was developed afterward with 3, 3′-diaminobenzidine (DAB) chromogen (Agilent Technologies, Santa Clara, CA, USA). The slides were counterstained with hematoxylin (MUTO, Tokyo, Japan), mounted in Entellan (Merck, Darmstadt, Germany) and cover slipped. Positive signals were visualized under an inverted light microscope (Nikon, Tokyo, Japan).