SUMMARYInterferon produced by mouse L-929 cells by incubation with poly(rI), poty(rC) is known to be composed of a mixture of MuIFN-c~ and MuIFN-fl. The c~ component was separated from the fl species by affinity chromatography over a monoclonal antiMuIFN-fl agarose column and partially purified by gel filtration. MuIFN-c~, prepared by this method was separated into at least five subspecies by chromatofocusing. The approximate pI values of these components are >~ 7.5, 6.5, 6.2, 5-9 and 5.6, respectively. Component 3 (pI 6.2) was the most prominent subspecies present in our MulFN-~ preparations, representing 40 to 50 ~o of the total antiviral activity. Component 1 (pI /> 7.5) which accounted for about 5~ of the antiviral activity on mouse cells, differed in some properties from the other interferon subspecies. It showed a relatively high antiviral activity on heterologous cells and it was eluted from a Sephadex column after the other c¢ subspecies. Furthermore, it showed a diminished binding to heparin as compared to the other MulFN-c¢ subspecies, indicating a lower affinity for polynucleotides.

A monoclonal antibody against murine interferon-beta (MuIFN-beta) was prepared using standard methods. Antibodies were immobilized by coupling to Sepharose and used for large-scale purification of poly(I) . poly(C)-induced mouse L cell IFN. Antibodies isolated from the serum of one nude mouse which was transplanted with the anti-MuIFN-beta antibodies producing hybridoma were able to bind at least 7 X 10(7)U MuIFN-beta. In one single antibody affinity chromatography step MuIFN-alpha was separated from MuIFN-beta and a 1000-fold purification of MuIFN-beta was obtained. The purified material had a specific activity of 5 X 10(8)U/mg protein. The recovery from the antibody column was 100%. SDS-PAGE analysis of the purified material revealed the presence of one single protein band with a molecular weight of 33 kD, representing MuIFN-beta.

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SUMMARYWe have studied the relationship between Friend spleen focus-forming virus (SFFV) and its helper lymphoid leukaemia virus (LLV) by comparing RNase T1 fingerprints of genomic RNAs. Our data indicate that about 70% of the SFFV sequence is a perfect copy of parts of the helper genome. We conclude that our SFFV and LLV isolates have co-evolved very closely and that SFFV-specific sequences are not identical in different Friend virus isolates.