Liver targeting of interferon through pullulan conjugation.

Purpose: The purpose of this study was to actively target interferon (IFN) to the liver through its chemical conjugation with pullulan, a water-soluble polysaccharide with a high affinity for the liver.

Methods: Chemical conjugation of IFN with pullulan was achieved by a cyanuric chloride method. Following intravenous injection of the conjugates to mice, their body distribution and the activity of an IFN-induced enzyme, 2', 5'-oligoadenylate (2-5A) synthetase in the liver and other organs, were evaluated.

Results: The cyanuric chloride method enabled us to prepare an IFN-pullulan conjugate that retained approximately 7-9% of the biological activity of IFN. Pullulan conjugation enhanced the liver accumulation of IFN and the retention period with the results being reproducible. When injected intravenously to mice, the IFN-pullulan conjugate enhanced the activity of 2-5A synthetase in the liver. The activity could be induced at IFN doses much lower than those of free IFN injection. In addition, the liver 2-5A synthetase induced by conjugate injection was retained for 3 days, whereas it was lost within the first day for the free IFN-injected mice.

Conclusions: IFN-pullulan conjugation was promising for IFN targeting to the liver with efficient exertion of its antiviral activity therein.