IMPROVED GENE TRANSFER EFFICIENCY IN LIVER WITH VESICULAR STOMATITIS VIRUS G-PROTEIN PSEUDOTYPED RETROVIRUS AFTER PARTIAL LIVER RESECTION AND THYMIDINE KINASE-GANCICLOVIR PRE-TREATMENT

Abstract

Liver-directed gene therapy is a promising alternative for the treatment of various liver diseases. Pseudotyped (VSV-G) retroviruses can be produced in high titres which is essential to overcome the problem of low gene transfer efficiency detected previously with first generation Moloney murine (MMLV) retroviruses and plasmid vectors. We compared thelacZ gene transfer efficiency of MMLV retroviruses and VSV-G retroviruses in Watanabe heritable hyperlipidaemic rabbit liver using an intraportal administration route. Hepatocyte 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 retrovirus was significantly higher than with the traditional MMLV-based retrovirus (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 liver samples. No transgene was detected in plasma or in lung, kidney, spleen and gonads by PCR analysis 7 days after gene transfer. Transient increases were found in plasma c-reactive protein, aspartyl aminotransferase and alanine aminotransferase levels shortly after the operation with both types of retroviruses. VSV-G retrovirus was well tolerated and may become an efficient new tool in liver gene therapy. The absence of transgene in systemic circulation or in extrahepatic tissues including gonads is an important safety feature required for in vivo gene therapy.