We identified, cloned, and functionally characterized a new avian hepadnavi
nus infecting storks (STHBV). STHBV has the largest DNA genome of all avian
hepadnaviruses and, based on sequence and phylogenetic analysis, is most c
losely related to, but distinct from, heron hepatitis B virus (HHBV). Uniqu
e for STHBV among the other avian hepadnaviruses is a potential HNF1 bindin
g site in the pries promoter. In common only with HHBV, STHBV has a myristy
lation signal on the S and not the preS protein, two C terminally located g
lycosylation sites on the precore/core proteins and lacks the phosphorylati
on site essential for the transcriptional transactivation activity of duck-
HBV preS protein. The cloned STHBV genomes were competent in gene expressio
n, replication, and viral particle secretion. STHBV infected primary duck h
epatocytes very inefficiently suggesting a restricted host range, similar t
o other hepadnaviruses. This discovery of stork infections unravels novel e
volutionary aspects of hepadnaviruses and provides new opportunities for he
padnavirus research. (C) 2001 Academic Press.