Determination of the Affinity and Kinetic Constants for the Interaction between the Human Virus Echovirus 11 and Its Cellular Receptor, CD55

The biochemical properties of the molecular interactions mediating viral-cell recognition are poorly characterized. In this study, we use surface plasmon resonance to study the affinity and kinetics of the interaction of echovirus 11 with its cellular receptor decay-accelerating factor (CD55). As reported for interactions between cell-cell recognition molecules, the interaction has a low affinity (KD ∼3.0 μm) as a result of a very fast dissociation rate constant (kon∼105m−1·s−1,koff ∼0.3 s−1). This contrasts with the interaction of soluble ICAM-1 (sICAM-1, CD54) with human rhinovirus 3 which has been reported to have a similar affinity but 102–103-fold slower kinetics (Casasnovas, J. M., and Springer, T. A. (1995) J. Biol. Chem.270, 13216–13224). The extracellular portion of decay-accelerating factor comprises four short consensus repeat domains (domains 1–4) and a mucin-like stalk. By comparison of the binding affinity for echovirus 11 of various fragments of decay-accelerating factor, we are able to conclude that short consensus repeat domain 3 contributes ∼80% of the binding energy.