A new antigenic site of poliovirus recognized by an intertypic cross-neutralizing monoclonal antibody.

A monoclonal antibody (mAb 7J6) neutralizing poliovirus type 2 (PV2) and poliovirus type 1 (PV1) was obtained after immunization of BALB/c mice with infectious PV2, strain MEF-1. Preincubation of mAb 7J6 with PV1 inhibited its binding to PV2 and vice versa. Neutralization-resistant variants of PV2 and PV1 were selected. Nucleotide sequencing of the RNAs of some variants revealed mutations in the loop of amino acid residues 239 to 245 in VP2 and in the loop of amino acid residues 195 to 207 in VP3. This is the first evidence that these two loops contribute to a neutralization antigenic site (N-Ag) for poliovirus. Moreover, this new site on PV2 induced intertypic cross-neutralizing antibodies.