Submitted to: Journal of Virology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/16/2004
Publication Date: 9/1/2004
Citation: Duque, H., Larocco, M., Golde, W.T., Baxt, B. 2004. Interactions of foot-and-mouth disease virus with soluble bovine alphavbeta3 and alphavbeta6 integrins. Journal of Virology. 78:9773-9781. Interpretive Summary: Foot-and-mouth disease is a highly contagious foreign animal disease of livestock, which results in large economic losses to countries where it occurs. As part of an overall FMD control strategy we are examining host and viral targets which may be useful in the development of antiviral compounds to be used in conjunction with vaccination. The virus initiates infection in cells by first binding to a specific molecule on the cell surface, called a receptor. We have shown that the specific receptor used by FMDV is part of a large family of membrane proteins called integrins. Interference with this virus-receptor interaction is one of a number of antiviral strategies we are investigating. To this end, we have examined the interactions of cloned FMDV receptors, which we have engineered to be soluble, with virus. We found that one of the FMDV receptors, a molecule called integrin alphaVbeta6 (aVb6), can bind to virus in a soluble form and prevent it from infecting cells by blocking binding of virus to the receptor on the cell surface. This finding now be expanded to examine the role of small molecules which mimic the receptor (mimetics) as possible anti-viral agents, and also to perform structural studies which will be useful in antiviral drug design.
Technical Abstract: At least three members of the integrin family of receptors, alphaVbeta1 (aVb1), alphaVbeta3 (aVb3), and alphaVbeta6 (aVb6) have been identified as receptors for foot-and-mouth disease virus (FMDV)in vitro. We have recently shown that efficiency of receptor usage appears to be related to the viral serotype. To further examine these differences, we generated soluble aVb3 and aVb6 integrins. cDNA plasmids encoding the individual complete integrin aV, b3, and b6 subunits were used to amplify sequences encoding the subunits' signal peptide and ectodomain. Plasmids encoding the soluble aV subunit and either the soluble b3 or b6 subunits were transiently expressed in COS-1 cells. Complete subunit heterodimeric integrins were secreted into the media, as determined by radioimmunoprecipitation with specific monoclonal and polyclonal antibodies. For the examination of the integrins' biological activity, stable cell lines producing the soluble integrins were generated in 293A cells and interactions of the soluble integrins, secreted into the culture media, with FMDV were analyzed. In the presence of divalent cations, soluble aVb6 bound to types A12 or O1 virus, and significantly inhibited viral replication, as determined by plaque-reduction assays. In contrast soluble aVb3 was unable to bind to or neutralize virus of either serotype. Incubation of soluble aVb6 with labeled FMDV resulted in inhibition of virus adsorption to BHK cells, while soluble aVb3 caused a low, but consistent, inhibition of adsorption. Virus incubated with soluble aVb6 had a lower sedimentation rate than native virus on sucrose density gradients, but the particles retained all of their structural proteins and contained bound integrin, therefore not exhibiting the characteristics of a picornaviral A particle.