The adsorption and degradation of foot-and-mouth disease virus by isolated BHK-21 cell plasma membranes

Foot-and-mouth disease virus (FMDV) was examined for its ability to adsorb specifically to plasma membranes isolated from BHK-21 cells. The membranes were prepared by the polyethylene glycol-dextran method, and characterized by increases in specific activity of ouabain-sensitive Na +K +-ATPase and 5′-nucleotidase, and by enrichment in 3H-fucose over unfractionated homogenates. The membranes adsorbed purified radiolabeled FMDV type A 12119 with kinetics characteristic of intact cells. Plasma membranes prepared from cells pretreated with trypsin were unable to adsorb virus. The adsorption of labeled FMDV was inhibited by unlabeled virus. Treatment of virus with trypsin, which cleaves capsid protein 3, greatly reduced its ability to adsorb to both plasma membranes and intact cells. After adsorption of virus to membranes at 4°, subsequent incubation at 37° under physiological conditions resulted in a rapid elution of bound virus in an unmodified form which reached approximately 80% by 1 hr. Incubation of the membrane-virus complex at 33° under low-salt conditions degraded the virus particles to intact and fragmented viral RNA and 12 S protein subunits. Membrane-induced viral degradation did not occur at 4° but was observed within 5 min after shifting to 33°. Thus, isolated plasma membranes from BHK-21 cells retain receptors for FMDV possessing uncleaved capsid protein 3. In addition, the eclipse and uncoating of FMDV in intact cells probably occurs at the plasma membrane, and in confirmation of previously reported results, the postadsorptive degradation, unlike that of other picornaviruses, occurs in a single step without the production of intermediate subviral particles.