PROPAGATION OF AN ATTENUATED VIRUS BY DESIGN - ENGINEERING A NOVEL RECEPTOR FOR A NONINFECTIOUS FOOT-AND-MOUTH-DISEASE VIRUS

To gain entry into cells, viruses utilize a variety of different cell- surface molecules. Foot-and-mouth disease virus (FMDV) binds to cell-s urface integrin molecules via an arginine-glycine-aspartic acid (RGD) sequence in capsid protein VP1. Binding to this particular cell-surfac e molecule influences FMDV tropism, and virus/receptor interactions ap pear to be responsible, in part, for selection of antigenic variants. To study early events of virus-cell interaction, we engineered an alte rnative and novel receptor for FMDV. Specifically, we generated a new receptor by fusing a virus-binding, single-chain antibody (scAb) to in tracellular adhesion molecule 1 (ICAM1). Cells that are normally not s usceptible to FMDV infection became susceptible after being transfecte d with DNA encoding the scAb/ICAM1 protein. An escape mutant (B2PD.3), derived with the mAb used to generate the genetically engineered rece ptor, was restricted for growth on the scAb/ICAM1 cells, but a variant of B2PD.3 selected by propagation on scAb/ICAM1 cells grew well on th ese cells. This variant partially regained wild-type sequence in the e pitope recognized by the mAb and also regained the ability to be neutr alized by the mAb. Moreover, RGD-deleted virions that are noninfectiou s in animals and other cell types grew to high titers and were able to form plaques on scAb/ICAM1 cells. These studies demonstrate the first production of a totally synthetic cell-surface receptor for a virus. This novel approach will be useful for studying virus reception and fo r the development of safer vaccines against viral pathogens of animals and humans.