ARLINGTON - Biologists
from The University of Texas at Arlington have uncovered virus fragments from
the same family as the modern Hepatitis B virus locked inside the genomes of
songbirds such as the modern-day zebra finch.
Gilbert and Feschotte
they've been sitting there for at least 19 million years, far longer than
anyone previously thought this family of viruses had been in existence," say
Cédric Feschotte and Clément Gilbert, co-authors of the new study being published today
in PLoS Biology, the flagship journal
of the Public Library of Science. Feschotte is an associate professor and member of the UT Arlington Genome
Biology Group. Gilbert is a post-doctoral research associate in the group.
article, entitled "Genomic Fossils Calibrate the Long-Term
Evolution of Hepadnaviruses,"
marks the first time that endogenous hepadnaviruses have been found in any
organism. An endogenous virus is one that deposits itself or fragments of
itself into the chromosome of an organism, allowing it to be passed from
generation-to-generation. Previously, most of these known "fossilized" virus
sequences came from retroviruses.
and Gilbert's results also suggest that the birds could be carriers of these
types of viruses today.
Gilbert and Feschotte dated the
hepadnavirus fragments by locating them in the same spot on the genome of five
species of passerine birds and then tracing those species to a common ancestor
that lived more than 19 million years ago.
Eddie Holmes, a distinguished
professor of biology at Penn State University's Eberly College of Science and
an expert in the field of viral evolution, said Feschotte and Gilbert's work "provides a glimpse into an ancient viral world that we never
"The results they obtained were
remarkable; whereas we previously thought of hepadnavirus evolution on
time-scales of only a few thousand years, this paper shows that the true
time-scale is in fact many million years. Therefore, hepadnavirues, and likely
many other viruses as well, are far older than we previously thought." Holmes
another surprising finding, the older versions of the hepadnaviruses are
remarkably similar to today's viruses. Feschotte believes that the slow
evolution of the hepadnaviruses observed in birds indicates that the viruses
are, in the long run, better adapted to their hosts than what is suggested by
study of the disease-causing Hepatitis B viruses.
"Genomic fossils like the remarkable
hepadnaviral fossils found by Gilbert and Feschotte have the prospect of
completely revising our preconceived notions about the age and evolution of
such viruses," said Harmit Singh Malik, an associate member of the Fred
Hutchinson Cancer Research Center in Seattle and one of the leaders in the new
field of ‘paleovirology'. "They provide an unexpectedly clear lens on an
ancient time when these viruses were prevalent and abundant."
study also opens avenues for research that might help predict and prevent human
viral pandemics originating in bird species.
"Given that they were infected in the past, it
is legitimate to think that some of these birds may still carry such viruses
today," said Gilbert. "We can therefore use this discovery as a guide to screen
targeted groups of bird species for the presence of new circulating Hepatitis
B-like viruses. "
University of Texas at Arlington is a comprehensive undergraduate and graduate
institution of more than 30,000 students in the heart of North Texas. The work
of Feschotte and Gilbert is representative of the research under way as UT
Arlington becomes a nationally recognized research institution.
more information, visit www.uta.edu.