In Vivo Gene Transfer in Mouse Skeletal Muscle Mediated by Baculovirus Vectors

Abstract

Baculovirus vectors are efficient tools for gene transfer into mammalian cells in vitro. However, in vivo gene delivery by systemic administration is hindered by the vector inactivation mediated by the complement system. To characterize further the gene transfer efficacy of baculovirus we examined the vector transduction efficiency in skeletal muscle. Vectors expressing vesicular stomatitis virus glycoprotein (VSV-G) in the viral envelope were generated by inserting the VSV-G coding sequence downstream of the polyhedrin promoter. Two viruses were constructed to carry either the Escherichia coliβ-galactosidase (β-Gal) gene or the mouse erythropoietin (EPO) cDNA cloned downstream of the cytomegalovirus immediate-early promoter and enhancer. The greater gene transduction efficiency of the Bac-G-βGal vector was confirmed by comparing the β-Gal expression level in a variety of human and mouse cell lines with that obtained on infection with Bac-βGal, a vector that lacks VSV-G. Similarly, a 5- to 10-fold increase in β-Gal expression between Bac-G-βGal and Bac-βGal was observed when mouse myoblasts and myotubes were infected. The same increase in β-Gal expression was detected on injection of the Bac-G-βGal vector in the quadriceps of BALB/c and C57BL/6 mice. In contrast, a 2-fold difference in transduction was observed between these two vectors in DBA/2J mouse strain. Last, expression of EPO cDNA was detected for at least 178 days in DBA/2J mice on Bac-G-EPO injection into the quadriceps whereas EPO expression declined to normal values by 35 days postinfection in BALB/c and C57BL/6 mice. Thus, these results indicate that baculovirus may be considered a useful vector for gene transfer in mouse skeletal muscle and that persistence of expression may depend on the mouse strain used.