Humoral immune response to cytomegalovirus Towne vaccine strain and to Toledo low-passage strain.

Neutralization and immunoblot or immunoprecipitation assays of serum samples from seronegative or seropositive volunteers immunized with the attenuated Towne and challenged with the virulent Toledo cytomegalovirus strains were carried out. Titers of neutralizing antibodies differed as a function of the strain used for immunization. All serum samples with neutralizing activity detected a 58-kDa protein that is the abundant component of the major glycoprotein complex of the envelope, suggesting that this protein complex is involved in the induction of neutralizing antibodies. Complement-independent neutralizing activity was found to develop later than complement-dependent activity, and no correlation was observed between complement-independent titers of neutralizing antibodies and antibody to the 86-kDa protein, which bears a complement-independent neutralizing epitope. Antibodies to the 66-kDa major tegument protein were present early after infection but were not correlated with serum neutralizing activity.