Characteristics of the New Respiratory Viruses (Adenoviruses)

Summary Neutralization titrations carried out with types 1–4 APC-RI viruses and type-specific rabbit sera, as well as human convalescent sera, indicated that preliminary incubation of virus-serum mixtures at 22° or 37°C was necessary to obtain maximum titers. Prolongation of the incubation period beyond 30 min did not increase the neutralization titer appreciably; with human convalescent sera, neutralization titers were similar whether a mixture of serum and either type 3 or 4 virus was incubated 30 min at 4°C or 120 min at 37°C. Investigation of the quantitative aspects of the neutralization reaction with the new respiratory viruses and type-specific immune sera indicates that the reaction between the two components, expressed as logarithms to the base 10, describes a linear relationship. The ratio between the two variables, the logarithm of the quantity of virus neutralized and the logarithm of the serum dilution end point, was 1.0 for types 3 and 4 viruses and 2.0 for types 1 and 2 viruses. The species of animal from which serum was obtained for the neutralization titrations did not influence the slope of the neutralization line.