ANTIBODY-BINDING TO INDIVIDUAL SHORT CONSENSUS REPEATS OF DECAY-ACCELERATING FACTOR ENHANCES ENTEROVIRUS CELL ATTACHMENT AND INFECTIVITY

Decay-accelerating factor (DAF), a widely expressed membrane complemen t-regulatory protein, is utilized as a cellular receptor by many human enteric pathogens, We show here that the binding of two enteroviruses to individual short consensus repeats (SCR) of DAF on the cell surfac e is greatly augmented by mAb binding to an alternate SCR: Coxsackievi rus A21 binding to the SCR1 of DAF is increased by Ab binding to SCR3 and, conversely, Echovirus 7 binding to SCR3 is enhanced severalfold b y Ab binding to SCR1, These Ab-induced increases in viral binding also resulted in increased viral infectivity, Using purified soluble DAF i n a solid phase assay it was found that Ab binding to SCR1 is increase d greatly in the presence of an Ab against SCR3 and, reciprocally, Ab against SCR1 greatly increases Ab binding to SCR3, In contrast to the results obtained with the larger viral particles, however, this recipr ocal Ab-induced enhancement of binding is not seen when measuring Ab b inding to membrane-bound DAF SCR on the cell surface. These findings p rovide a possible explanation for functional differences between membr ane-bound and soluble DAF with implications for a potential role for D AF-binding molecules in regulating DAF function, This is the first dem onstration of enhancement of viral infectivity mediated by Ab against the viral receptor.