Distinct antigenic subtypes of human beta interferon can be distinguished by neutralization

Different molecular configurations of human beta interferon were titrated with the standard reference antiserum of the National Institutes of Health (NIH) which had been prepared with natural beta fibroblast interferon in order to determine to what extent differences in these configurations would influence the neutralization of the antiviral action of interferon. Neutralization tests were carried out in Vero cells by diluting both interferon and antiserum. Encephalomyocarditis virus was employed as challenge virus. The neutralization titer was considered to have been reached when the effect of eight units of interferon was reduced to one. Two natural beta interferons prepared from fibroblasts and from amniotic membranes gave similar high titers. However, titers were reduced five-fold with recombinant interferons expressed in Escherichia coli, which do not contain carbohydrate, one with the natural sequence and a mutant with a single amino acid substitution (cysteine for serine). The NIH antiserum did not neutralize the effect of a protein fraction from amniotic membranes antigenically different from the human alpha, beta or gamma interferons but having the biological activity of interferon. We conclude that the carbohydrate moieties of human beta interferons are essential for their recognition by the NIH antiserum and that antibodies specific for human recombinant beta interferon, which does not contain carbohydrate, are needed.