Engineering analysis of ex vivo retroviral transduction system

The overall dynamics of the retrovirus-cell encounter under a static retroviral transduction system can be described in terms of the process of uptake (adsorption/ internalization), decay, and diffusion. In this study, a mathematical model illustrating these processes was derived assuming a semi-infinite domain and solved analytically using the Laplace transform. The closed-form solutions for retroviral concentrations and time course profile of transduced cell colonies are presented to clarify the contributions of the processes involved in the retroviral transduction system. To manifest the usefulness of the closed-form solutions, the neomycin-resistant gene encoding retroviruses produced by two different packaging cells (human 293 cells and murine GP+ E86/LNCX cells) were employed to transduce NIH 3T3 cells, which formed neomycin-resistant colonies after G418 selection. The experimental results were curve fitted with the model-derived analytical solutions to quantitatively determine transduction rate constant k and initial concentration of infectious retrovirus C0. Our study showed that the vesicular stomatitis virus G protein pseudotyped retrovirus produced from 293 packaging cells exhibited much higher transduction rate (k = 0.0480 cm/h) than the ecotropic retrovirus (k = 0.0102 cm/h) produced from GP + E86/LNCX cells. The fitted values of C0 are approximately two orders of magnitude higher than the experimentally estimated titers for both retroviruses.