Abstract: Objective To study the effeet of viral particle titer and the transgene length on the integration rate of transgenic mice mediated by lentiviral vector particles. Methods Eighteen kinds of lentiviral vectors particles, which carried various lengths of inserts, were used for subzonal injection of mouse fertilized eggs, followed with transplanting those eggs into the oviduct of pseudopregnanting mice. Neonates were then identified by PCR analysis. Results For short inserts (<2 kb), only 2 × 10⁸ of virus titer was needed to achieve a high integration rate. While the length of inserts were increase (4-5kb), 1 × 10⁹ viral particles were required for having a reasonable integration rate. However, transgenic mice was not able to be achieved when the inserts were longer than 6kb, in our hands. Conclusion Integration rate of transgenic mice was largely affected by both the viral titer and the length of inserts. It increases with the particle titer, while decreases with the length of inserts

Key words: Lentiviral vector, Transgenic mice, Integration rate, Viral particle titer, Insert length