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Ultraviolet (UV) irradiation of type I poliovirus resulted in a modified (M) particle that had lost infectivity, lacked ability to adsorb to HeLa cells, lacked VP4, and reduced in S value. Additional irradiation resulted in the loss of VP2, further reduction in S value, and permeability of the capsid to RNAse, This particle (C) as well as M contain the genome. Acid pH (5.5-65) and sulfhydryl-reducing substances (dithiothreitol. reduced glutathione, and L-cysteine) inhibited UV-induced modification of the capsid. UV irradiation at alkaline pH (7.5-8.5) resulted in more extensive modification of the capsid than irradiation at neutral pH. Ionic compounds were found to inhibit the modifying reaction.

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Interferon produced by rainbow trout gonadal cells (RTG-2) was partially purified. The physical, chemical, and biological properties of this in vitro produced fish cell interferon were studied. Purification was achieved by ultracentrifugation, molecular sieve gel chromatography, ion exchange chromatography, and polyacrylamide gel electrophoresis. The isoelectric point of RTG-2 interferon, as determined by CM-Sephadex (C-0O) chromatography, was 7.1. Filtration through Sephadex G-150 showed that RTG-2 interferon had a molecular weight of 94,000. The partially purified material was not sedimented at 105,000 x g for 2 h at 4 C. The fish cell interferon was non-dialyzable and exhibited heat and pH stability. The partially purified material was inactivated by treatment with trypsin or 2-mercaptoethanol, but was resistant to treatment with deoxyribonuclease or ribonuclease. RTG-2 interferon which was induced by infectious pancreatic necrosis virus exhibited antiviral activity against challenge with infectious hematopoietic necrosis virus or infectious pancreatic necrosis virus. Partially purified RTG-2 interferon exhibited greater species specificity than the crude material.

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