Immunohistochemical detection of HBsAg and HBcAg in tree shrew’s liver biopsies, DAB staining, ×400. A and B: Liver samples of animal no. 90-1 collected at the 167th-week after inoculation. A showed HBsAg-positive hepatocytes and B showed HBcAg-positive hepatocytes. C and D: Liver samples of animal no. 121-1 collected at the 60th-week after inoculation. C showed HBsAg-positive hepatocytes and D showed HBcAg-positive hepatocytes. E and F: Liver samples from an age-matched uninfected tree shrew. E showed HBsAg-negative hepatocytes and F showed HBcAg-negative hepatocytes.