Isolierung und Charakterisierung von Iridoviren

We describe the isolation and characterization of an iridescent
virus from commercially produced colonies of Gryllus bimaculatus in
Germany, which showed apparent mortality. Transmission electron
microscopy studies on adult cricket specimens revealed the
paracrystalline assembly of icosahedral virus particles in the
cytoplasm of hypertrophied abdominal fat body cells. The infecting
agent could be cultivated in the lepidopteran cell line sf-9, where
it caused cytopathogenic effects such as cell hypertrophy,
cytoplasmic vacuolization, and cell death within 8 days
postinfection. Negatively stained virus particles (n = 100) had
dimensions of 172 +/- 6 nm (apex to apex) and 148 +/- 5nm (side to
side). SDS-polyacrylamide gel electrophoresis of virus proteins
showed more than 20 distinct polypeptides with a major species of
approximately 50 kDa. Analysis of the restriction fragment length
profiles from digestion of purified viral DNA with the
endonucleases EcoRI, BamHI, and HindIII showed marked differences
from the profiles of iridoviruses of lower vertebrates (genus
Ranavirus), e.g., Rana esculenta Iridovirus and Frog virus 3.
Restriction enzyme digests with the endonucleases MspI and HpaII
indicated the lack of methylation of viral DNA. Polymerase chain
reaction led to the amplification of a 420-bp gene fragment with 97
% sequence homology to the major capsid protein gene of
Invertebrate iridescent virus 6 (IIV-6). The data indicate, that
this new isolate, which is the first iridescent virus reported from
Germany, belongs to the genus Iridovirus of the family
Iridoviridae. It is proposed to be termed Gryllus bimaculatus
iridescent virus (GbIV). The investigation of four other
iridescent-like viruses which were obtained in 1998, 1999 and 2000
from various tissues of three reptile species, e.g. Pogona
vitticeps, Chamaeleo quadricornis, and Chamydosaurus kingii,
revealed cytoplasmic desoxyriboviruses with the exact morphological
and molecular biological characteristics of the formerly described
GbIV. We conclude that all five isolates of iridescent-like viruses
from Germany are identical and represent variants or strains of the
type species of the genus Iridovirus, IIV-6. The data indicate,
that GbIV, an invertebrate iridescent virus, is able to replicate
in reptiles.