SUMMARYA recombinant interferon (IFN) hybrid has been found to have a broad host-range of activity in an antiviral assay (plaque reduction of vesicular stomatitis virus) and also high efficacy as an antiviral agent in at least 12 different animal cell species. The IFN hybrid consists of amino acids 1 to 60 from HulFN-c~B and amino acids 61 to 166 from HuIFN-c~D. The profile of cross-species activity of the IFN-,B/D hybrid has been compared with that of HulFN-c~F, and of the parents HulFN-c~B and -c~D. When both IFN-c~B and -aD were active in a cell species, the hybrid IFN had comparable or better activity than the more active parental IFN. The hybrid shared a broad cross-species activity with IFN-c~D. However, the IFN-c~B/D hybrid was 10-fold more active on human cells, 30-fold more active on rabbit cells, and 50-fold more active on mouse cells than IFN-~D.Numerous studies using crude or partially purified mixtures of interferon (IFN) have shown that these preparations usually exert antiviral activity in a defined variety of cell species (for review, see Stewart, 1981). These studies were refined when recombinant IFN became available, when it was observed that the profile of host-range specificity could vary widely between individual species of IFN (Streuli et al., 1981;Yelverton et al., 1981;. Cross-species efficacy has proved to be a useful biological parameter to discriminate between IFN-c~ hybrids constructed by combining gene fragments of individual species of HulFN-c~. In particular, the spectrum of activity of some IFN-~A/D hybrids is different from that of either parent (Streuli et al., 1981;Rehberg et al., 1982; Weck et al., 1981b). The construction of human hybrid molecules with high specific activity on unrelated animal species might provide a useful tool for studying the biology of the IFN system in various animal species.The purpose of this report is to describe the antiviral properties of a recombinant human IFN hybrid which has not only a very broad host-range of activity but also a high efficacy. The hybrid comprises amino acids 1 to 60 from IFN-c~B and amino acids 61 to 166 from IFN-c~D as previously described (Meister et al., 1986).The types of recombinant IFN (> 90~ pure) used in this study were produced in yeast, and their final purification involved affinity immunochromatography using monoclonal antibodies. IFN titres calibrated against HulFN-c~ (NIH standard G 023-901-527) on human diploid cells were: IFN-c~B/D hybrid (0.5 x 108 IU/mg), IFN-c~B (2.5 x 108 IU/mg), IFN-c~D (4 x 10 ° IU/mg) and IFN-c~F (0.5 x 108 IU/mg). Whenever possible, the target cells were diploid cells with a finite life span in tissue culture. They were obtained by digestion of tissues with a neutral protease (Dispase, Boehringer-Mannheim) at pH 6.7 in phosphate-buffered saline. All cells were propagated in Eagle's MEM supplemented with 10~o foetal bovine serum and antibiotics. Primary cells and established cell lines were subcultured using a solution of trypsin (1:250) in EDTA (Gibco).The cross-species activity of IFN ...

We have defined some characteristics of the mouse Mx protein as a marker of biological response to interferon (IFN) and to virus infection in A2G mice. The Mx protein has been detected and quantitated by Western immunoblot analysis. Upon induction by poly(I):poly(C) or with Newcastle disease virus, the Mx protein is expressed and accumulated in a variety of organs, such as liver, lungs, spleen, kidneys, heart, and brain. In some organs the expression of the Mx protein is detected readily, as soon as 4 h after treatment. The highest protein level is reached at 24 h, and it remains stable for several days declining slowly to return to preinduced levels 2-3 weeks after treatment. Infection with an hepatotropic or a pneumotropic strain of influenza virus resulted in a systemic induction of Mx protein, the highest levels being found in the target organ for virus replication. Our results indicate that the Mx protein is a sensitive, quantitative, and stable marker to follow IFN activity or virus infection in an animal model.

The sensitivity of influenza virus to the action of natural human interferon (IFN)‐α+β and ‐γ, and to the action of highly purified recombinant HuIFN‐αB, ‐αD, and ‐αF, has been investigated. A plaque assay for the fowl‐plague strain of influenza A virus has been established using human embryonic foreskin (HEF) cells. The sensitivity of influenza virus to all IFNs tested in this assay was comparable to that shown by vesicular stomatitis virus (VSV) which was taken as the reference standard. The high sensitivity to IFN action found for the fowl‐plague strain was confirmed for the WSN strain of human origin in a yield reduction assay.