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J. Virol., Dec 1996, 8872-8878, Vol 70, No. 12
RW Renshaw, C Soine, T Weinkle, PH O'Connell, K Ohashi, S Watson, B Lucio, S Harrington and KA Schat
Chicken infectious anemia virus (CIAV) is a unique infectious agent with an
amino acid composition that has been found to be remarkably conserved even
in isolates from different parts of the world. We have characterized field
isolates of CIAV which vary significantly in terms of their abilities to
replicate in culture, demonstrating a biological difference between
isolates. Two sublines of MDCC-MSB1 cells that differ in their abilities to
support CIAV were identified. In the MSB1(S) subline the CIA-1 isolate of
CIAV was found to be less cytopathogenic than the prototype Cux-1(C)
isolate; the MSB1(L) subline, which supports Cux-1(C) replication, was
found to be nonpermissive for CIA-1. Alignments of the VP1 sequences of
previously examined isolates with those of the field isolates CIA-1 and
L-028 and the culture-adapted ConnB isolate revealed a previously
unreported hypervariable region spanning amino acid positions 139 to 151.
Chimeras of Cux-1(C) and CIA-1 were constructed to examine the potential
for this region to affect cytopathogenicity. Transfer of a 316-bp region of
Cux-1(C) open reading frame 1 into CIA-1 produced a virus with a
cytopathogenic profile typical of Cux-1(C), indicating that one or both of
the amino acid differences at positions 139 and 144 affect the rate of
replication or the spread of infection. Transfection experiments with
additional chimeras indicated that the inability of CIA-1 to replicate in
MSB1(L) cells is mediated by a larger region of the genome which contains
the hypervariable region in addition to upstream amino acid differences.
Analysis of chimeras excluding the entire region of open reading frame 1
suggested the presence of a secondary mediator in the progression of
infection in culture that was localized to a region containing a single
nucleotide difference which results in amino acid differences in both VP2
(V-153) and the nuclear localization signal of VP3 (C-118).
Immunofluorescence assays indicated an increased cytoplasmic distribution
of VP3 and a general lack of VP3-associated apoptotic bodies in infections
of CIA-1 and chimeras containing V-153 or C-118, as opposed to a primarily
nuclear distribution and association with well-formed apoptotic bodies in
Cux-1(C)-infected cells.
Copyright © 1996, American Society for Microbiology
A hypervariable region in VP1 of chicken infectious anemia virus mediates rate of spread and cell tropism in tissue culture
Department of Microbiology and Immunology, College of Veterinary Medicine, Cornell University, Ithaca, New York 14853, USA.
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