Biological activity, binding site and affinity of monoclonal antibodies to the fusion protein of respiratory syncytial virus

The neutralizing activity and fusion-inhibition activity per unit weight of immunoglobulin were determined for each of a panel of 20 monoclonal antibodies (MAbs) to the fusion (F) protein of respiratory syncytial (RS) virus. Neutralization did not correlate with fusion-inhibiting activity, suggesting that the F protein plays at least two independent, antibody-sensitive roles in viral infection. Antibodies with the highest biological activity against A2, a subgroup A strain of RS virus, neutralized a subgroup B strain (8/60) poorly, suggesting a degree of antigenic variation that may be important in human infection. All but one fusion-inhibiting MAb bound to protein blots and binding was mapped to two areas on over-lapping F protein fragments. One MAb with relativel