Characterization of a monoclonal antibody resistant variant of MHV.

A monoclonal antibody resistant (MAR) variant of MHV was isolated after infection of hybridoma cells secreting the neutralizing and fusion-inhibiting monoclonal antibody, mAb 11F. The isolated variant was able to mediate syncytia formation even in the presence of high concentrations of mAb 11F. The S gene of the variant was cloned and sequenced. There were three nucleotide exchanges in comparison to the wild-type S gene, resulting in two amino acid alterations. However, both amino acid substitutions (at positions 255 and 1116) were located outside the binding site of mAb 11F.