Kinetics of neutralization of two strains of Myxovirus Parainfluenza 3 in the presence of complement and anti-gammaglobulin-serum.

Using the kinetics of neutralization, it was established that two strains of Myxovirus Parainfluenza 3 of cattle and sheep origin which are immunologicaly identical have a different sensitivity to early neutralizing antibodies of reconvalescent calf sera. Complement-dependent neutralizing antibodies, supplied by adding 5% guinea pig serum to the calf serum, appear earlier than the usual neutralizing antibodies. Goat anti-cattle gammaglobulin serum decreases the neutralizing activity of early reconvalescent serum and release some of the neutralizing virus from the virus-antibody complex. It is believed that the lability of the virus-antibody complex depends not only on the activity of the antibody, but also on some properties of the strains. The addition of complement stabilizes this complex. The previous addition of adenovirus antigen to bivalent cattle serum against Myxovirus Parainfluenza 3 and cattle adenovirus, decreases the complement-dependent neutralizing antibody of the serum against Myxovirus Parainfluenza 3. It is suggested that this is the possible mechanism for the mutual activation of mixed virus infections.