Improved gene transfer efficiency in liver with vesicular stomatitis virusG-protein pseudotyped retrovirus after partial liver resection and thymidine kinase-ganciclovir pre-treatment

Liver-directed gene therapy is a promising alternative for the treatment of various liver diseases. Pseudotyped (VSV-G) retroviruses can be produced i n high titres which is essential to overcome the problem of low gene transf er efficiency detected previously with first generation Moloney murine (MML V) retroviruses and plasmid vectors. We compared the lacZ gene transfer eff iciency of MMLV retroviruses and VSV-G retroviruses in Watanabe heritable h yperlipidaemic rabbit liver using an intraportal administration route. Hepa tocyte proliferation was stimulated by a partial (10%) liver resection and a thymidine kinase-ganciclovir treatment. We also studied the safety of the gene transfer by clinical chemistry, tissue pathology and PCR analysis of lung, kidney, spleen and gonads. Gene transfer efficiency with the VSV-G re trovirus was significantly higher than with the traditional MMLV-based retr ovirus (9.5 +/- 5.26 vs 0.21 +/- 0.10 positive hepatocytes mm(-2) P < 0.05) . After a 12-month follow-up period no lacZ expression was detected in live r samples. No transgene was detected in plasma or in lung, kidney, spleen a nd gonads by PCR analysis 7 days after gene transfer. Transient increases w ere found in plasma c-reactive protein, aspartyl aminotransferase and alani ne aminotransferase levels shortly after the operation with both types of r etroviruses. VSV-G retrovirus was well tolerated and may become an efficien t new tool in liver gene therapy. The absence of transgene in systemic circ ulation or in extrahepatic tissues including gonads is an important safety feature required for in vivo gene therapy. (C) 1999 Academic Press.