Replication of duck hepatitis B virus in extrahepatic tissue such as pancreas, kidney and spleen has been well documented. To assess whether there is more widespread extrahepatic virus replication, we assayed brain, heart, lung, thymus, pancreas, kidney, spleen and intestine of 1-to 16-wk-old ducklings for the presence of duck hepatitis B virus DNA and mRNA by blotting and in situ methods. Replicative intermediates and single-stranded duck hepatitis B virus DNA and RNA transcripts were detected in the brain, lung, heart, intestine, kidney, pancreas and spleen. In situ hybridization showed evidence of viral replication in the lung epithelium, germinal center of spleen, acinar cell of pancreas and tubular epithelium of kidney.
These data suggest that extrahepatic duck hepatitis B virus replication is more widespread than previously thought. It is yet to be determined whether widespread extrahepatic replication is unique to duck hepatitis B virus infection or is a common feature of other mammalian hepatitis B-like viruses. (HEPA- TOLOGY 1wlk44-48.)
Hepadnaviruses (hepatitis B-like viruses) are so named because of their hepatotropic features. However, recent studies have suggested that hepadnaviruses also replicate in extrahepatic sites (1-9). We and others have previously studied the extrahepatic replication of duck hepatitis B virus (DHBV) and observed viral replication in pancreas, kidney and spleen (10, 11). To test whether there is more widespread extrahepatic viral replication, we assayed brain, heart, lung, thymus, kidney, pancreas, spleen and intestine of 1-to 16-wk-old ducklings for the presence of DHBV DNA and mRNA by blotting and in situ methods.
Methods
Ducklings. Six 1-day-old white Pekin ducklings were inoculated with 50 p,l of serum from DHBV carrier ducks as previously described (12). Another group of three ducklings was injected with 20 pg of head-to-tail dimer DHBV DNA directly in the liver (in uiuo transfection). The diluted DNA