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Background: The type 1 interferons (INF-α and INF-β) are potent antiviral agents. Albumin-INF-α and albumin-INF-β are novel recombinant proteins consisting of IFN-α or IFN-β genetically fused to human albumin. Methods: The in vitro antiviral activity of albumin-IFN-α was evaluated against representative bioterrorism viral agents and the severe acute respiratory syndrome virus. Antiviral activity was assessed using inhibition of cytopathic effect and neutral red staining. Results: EC50 values for albumin-IFN-α ranged from Conclusion: Further evaluation of these long-acting albumin-IFN fusion proteins as prophylactic or therapeutic agents against these viral agents of bioterrorism in relevant primate models is warranted.

A natural-product polyphenolic polymer of molecular weight 2,100 daltons designated SP-303, was found to have antiviral activity against respiratory syncytial virus (RSV) in the 2-10 microM range in plaque reduction assays and cytopathic-effect-inhibition assays. The material was also virucidal. The 50% effective concentration (EC50) for virucidal activity was 28 microM. Experiments were done to determine the mode(s) of RSV inhibition by SP-303. Interferon was not induced. SP-303 did not inhibit attachment at antiviral concentrations. However, the EC50 for inhibition of virus penetration by SP-303 was 0.48 +/- 0.19 microM. These data suggest that abolition of RSV penetration into host cells is one mechanism whereby SP-303 inhibits RSV replication.

SP-303, a natural plant flavonoid polymer of molecular weight 2,100 daltons, was found to have antiviral activity against two strains of type 1 herpes-type simplex virus, including a thymidine-kinase-deficient strain, and a strain of type 2 herpes simplex virus. The 50% effective concentrations (EC50s) were 1-2 microM. Acyclovir, which was run in parallel, had values of 4-28 microM. Surprisingly, the compound was inactive against human cytomegalovirus. SP-303 was also virucidal at 50 microM. Interferon was not induced. The mode of antiviral action of this biopolymer was through inhibition of virus penetration into cells (EC50 = 2.1 +/- 0.2 microM). SP-303 also significantly reduced lesion formation in a mouse vaginal model when applied topically at 5-10%.