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Title: IN VITRO SELECTION AND ANALYSIS OF FOOT-AND-MOUTH DISEASE VIRUS RECEPTOR NEUTRALIZATION ESCAPE MUTANTS

Author
item Rieder, Aida - Elizabeth
item Larocco, Michael
item Baxt, Barry

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 5/31/2006
Publication Date: 7/15/2006
Citation: Rieder, A.E., Larocco, M.A., Baxt, B. 2006. In vitro selection and analysis of foot-and-mouth disease virus receptor neutralization escape mutants. American Society for Virology Annual Meeting. 2006. P 209.

Interpretive Summary:

Technical Abstract: Foot-and-mouth disease (FMDV) initiates infection in vitro via recognition of at least four cell-surface integrin molecules: avb1, avb3, avb6 avb8 through the interaction of a highly conserved Arg-Gly-Asp (RGD) amino acid sequence motif located in the G-H loop of VP1. As part of an ongoing study on the role of viral receptors in FMDV pathogenesis in the natural host, we have isolated and characterized four FMDV mutants (rr) resistant to neutralization by a soluble bovine integrin receptor. After a limited number passages in the presence of a high concentration of soluble bovine avb6 integrin (ssavb6, 10 micrograms/ml), two classes of A24 Cruzeiro rr mutants were selected; a high-resistance class which resisted neutralization by 1000-5000 fold, and a low-resistant class which demonstrated a 300-500 fold increased resistance to neutralization by ssavb6 (20 micrograms/ml) compared to wild type virus. Sequence analysis of the mutations leading to the rr phenotype showed changes in the high resistance class in the RGD sequence alone (RGD > RDD) or in an additional residue downstream of the RGD (RGDMGSLAARVVK > RDDMGSLAARAVK). In the low resistance class one mutant had alterations in the RGD sequence and additional downstream residues (RGDMGSL > RDDM[V])GSL[P]), and the other mutant only had an alteration downstream of the RGD (RGDMGSL > RGDMGSR). Surprisingly, these mutants maintained the ability to enter and infect COS cells expressing bovine avb6. These findings, and patterns of resistance to integrin receptor neutralization, support the concept that sequences downstream the RGD modulate binding to the receptor. Because the resistance to ssavb6 did not prevent the virus from using avb6 attached to the cell-surface, the results indicate that the avb6 integrin, in its soluble form, may adopt a conformation that differs from the intact molecule attached to the cell membranes. These mutants provide useful tools for studying the regions of the capsid structure involved in attachment.