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.

Some biological properties of the human amniotic membrane interferon

Human amniotic interferon was investigated to define the species specificity of its antiviral action and compare its anti-cellular and NK cell stimulating activities with those of other human interferons. The antiviral effect was titrated in bovine (RV-IAL) and monkey (VERO) cells. Amniotic interferon exhibited, in bovine cells, 5% of the activity seen in monkey cells, while alpha interferon displayed 200%. No effect was detected with either beta or gamma interferon in bovine cells. Daudi cells were exposed to different concentrations of various interferons and the cell numbers were determined. The anticellular effect of the amniotic interferon reached its peak on the third day of incubation. Results suggested a higher activity for alpha and gamma interferons and a lower activity for beta when compared to amniotic interferon. Using total mononuclear cells as effector cells and K 562 as target cell in a 51Cr release assay, it was demonstrated that low concentrations of amniotic interferon consistently stimulated NK cell activity in cells derived from several donors, the results indicating a higher level of activity with this interferon than with alpha and beta interferons

Partial characterization of human amniotic membrane interferon

The molecular weight and the electrofocusing profile of human amniotic membrane interferon (IFN-AM) were determined. When submitted to gel filtration, IFN-AM showed a single 26-28 kDa component; in polyacrylamide gel electrophoresis one component of 19,500. In electrofocusing, IFN-AM displayed a terogeneity was reduced by previous treatment of IFN-AM with neuraminidase. IFN-AMis a siaglycoprotein similarto human beta IFN in terms of antigenicity but different from it in electrofocusing profile