Assessment of the presence of cytomegalovirus-neutralizing antibody by a plaque-reduction assay.

Evaluation of the in vitro neutralizing activity of 30 immunoglobulin G (IgG) preparations and seven batches of pooled plasma against human cytomegalovirus (CMV) was performed by plaque-reduction assays. There were definite differences detected by these methods that could permit the selection of preparations with highest titers for clinical trials. The addition of guinea pig complement to the plaque-reduction assay enhanced inhibition of CMV; thus, guinea pig complement should be used in assays of IgG preparations. There was no relationship between the ELISA-derived optical density values of the IgG samples and the titers determined by plaque neutralization. These data suggest that the results of plaque-reduction neutralization assays provide important information about preparations of antibody that may be selected for patient administration. The preparations selected for their high titers by neutralization assays differ significantly from those identified by another method.