DEVELOPEMENT OF A NOVEL LIVER-SPECIFIC GENE TRANSFER METHOD USING HEPATIC-RECEPTOR IMAGING AGENT

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Neogalactosylalbumin (GSA) was activated and reacted with dendrimer (G4), which was known to make electrostatic complex with DNA, to construct GSA-G4 compound as a carrier of oligoDNA (olDNA) to the liver. GSA-G4 was then mixed with ^<111>In-labeled olDNA, and the formed GSA-G4/olDNA complex was intravenously administered into normal mice. Although GSA-G4/olDNA complex showed an accumulation to the liver, it also showed high uptake in the kidney, lung, and spleen, probably because of the instability of the GSA-G4/olDNA complex in the bloodstream (i.e. detachment of olDNA, which accumulated in the kidney) and also because of the formation high-molecular weight complexes and their aggregate, which were trapped in the lung and spleen.Then, avidin (Av), a highly glycosilated protein which is also known to accumulate in the liver, was introduced as an alternate to GSA. Two Av-olDNA conjugates were constructed and their biodistribution were studied. First Av was mixed with biotinylated olDNA (bt-olDNA) to form Av-bt-olDNA. Second, Av was reacted with biotinylated G4 (bt-G4) to form Av-bt-G4, and then mixed with olDNA to make Av-bt-G4/olDNA complex. After intravenous injection into normal mice, Av-bt-olDNA showed a specific and high hepatic uptake of ^<111>In-labeled olDNA with low uptake to other normal organs, resulting in very high liver-to-background radioactivity ratios. Although Av-bt-G4/olDNA complex showed relatively high hepatic uptake, it showed extremely high uptake in the lung. This may be because of the formation of large molecular weight complexes and their aggregates, which were trapped in the lung.Present investigations demonstrated that avidin had the potential as a carrier of oligoDNA to the liver. Av-bt-G4/olDNA complex, however, has a problem of making large aggregates and the change in administration route, such as intraportal injection, is necessary.