Arch Virol (2001) 146: 1991–2007
Rescue of infectious bursal disease virus from mosaic full-length
clones composed of serotype I and II cDNA
H. J. Boot, A. A. H. M. ter Huurne, S. A. Vastenhouw, A. Kant,
B. P. H. Peeters, and A. L. J. Gielkens
Institute for Animal Science and Health, Department of Avian Virology,
Lelystad, The Netherlands
Accepted February 22, 2001
Summary. Infectious Bursal Disease Virus (IBDV) is the causative agent of
one of the most important and wide-spread infectious diseases among commer-
cial chicken ﬂocks. IBDV causes a depletion of B-lymphoid cells in the bursa
of Fabricius, inducing immunosuppression, morbidity, or even acute mortality.
Because currently used live IBDV vaccines are derivatives from ﬁeld isolates no
serologic discrimination between ﬁeld isolates and livevaccines can be made. The
recently developed reverse genetics techniques for IBDV allows one to generate
genetically modiﬁed IBDVs which might have altered biological and antigenic
properties. Here, we describe the rescue of mosaic serotype I IBDVs, of which
the polyprotein encoding region was partly replaced by the corresponding region
of a serotype II strain. A mosaic virus, containing the C-terminal part of serotype
II VP3 showed only a slightly delayed release of progeny virus compared to un-
modiﬁed serotype I virus, while maximum viral titers at 25 h post infection were
equal. Since serotype speciﬁc epitope(s) are present in the C-terminal part of
VP3, we were able to discriminate this rescued virus from serotype I and II IBDV
strains. These ﬁndings make the use of a chimeric VP3 a promising approach to
develop an IBDV marker vaccine.
Infectious Bursal Disease Virus (IBDV), a member of the Birnaviridae Genus
Avibirnavirus, is the causative agent of a highly contagious disease of chickens.
This disease is also known as Gumboro, named after the place where the ﬁrst
outbreak of IBDV was reported . The double stranded RNA (dsRNA) genome,
which is divided over two segments , is packed within a capsid, consisting
of two viral proteins (VP2 and VP3). The resulting single-shelled naked virus
particle has a diameter of 60 nm and an icosahedral (T = 13) symmetry .