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J. Virol., 07 1997, 5115-5123, Vol 71, No. 7
D Sa-Carvalho, E Rieder, B Baxt, R Rodarte, A Tanuri and PW Mason
Isolates of foot-and-mouth disease virus (FMDV) exist as complex mixtures
of variants. Two different serotype O1 Campos preparations that we examined
contained two variants with distinct plaque morphologies on BHK cells: a
small, clear-plaque virus that replicates in BHK and CHO cells, and a
large, turbid-plaque virus that only grows in BHK cells. cDNAs encoding the
capsids of these two variants were inserted into a genome-length FMDV type
A12 infectious cDNA and used to produce chimeric viruses that exhibited the
phenotype of the original variants. Analyses of these viruses, and hybrids
created by exchanging portions of the capsid gene, identified codon 56 in
VP3 (3056) as the critical determinant of both cell tropism and plaque
phenotype. Specifically, the CHO growth/clear-plaque phenotype is dependent
on the presence of the highly charged Arg residue at 3056, and viruses with
this phenotype and genotype were selected during propagation in tissue
culture. The genetically engineered Arg 3056 virus was highly attenuated in
bovines, but viruses recovered from animals inoculated with high doses of
this virus had lost the ability to grow in CHO cells and contained either
an uncharged residue at 3056 or a negatively charged Glu substituted for a
Lys at a spatially and antigenically related position on VP2 (2134).
Comparison of these animal-derived viruses to other natural and engineered
viruses demonstrated that positively charged residues are required at both
2134 and 3056 for binding to heparin. Taken together, these results
indicate that in vitro cultivation of FMDV type O selects viruses that bind
to heparin and that viruses with the heparin-binding phenotype are
attenuated in the natural host.
Copyright © 1997, American Society for Microbiology
Tissue culture adaptation of foot-and-mouth disease virus selects viruses that bind to heparin and are attenuated in cattle
Plum Island Animal Disease Center, Agricultural Research Service, North Atlantic Area, U.S. Department of Agriculture, Greenport, New York 11944, USA.
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