| There are approximately thousands of biopharmaceuticals and vaccines that have been marketed and developing in the word. Now more and more attention has been paid to the safety issue of the gene therapy products. Transgenes and gene transfer vectors comprise gene therapy products. In one hand, when gene therapy products are transferred into target cells, they can express some proteins and cure some kind of diseases. In another hand, they will distribute to some non-target organs. Especially for replication-competent virus vectors, what is the situation of biodistribution, whether will they replicate inside the man body and how long will they last. All of the issues must be answered before the gene therapy products are used for clinical study.Although a great deal of attention has been focused on the time and dose dependency of expression of transgenes delivered to specific organs, very little attention has been paid to the biodistribution and pharmacokinetics of the gene therapy products . The biodistribution of the virus vectors is also essential and can be evaluated by molecular biology techniques, such as PCR. In the past, biodistribution of drug was studied mainly using transgene expression localization technique. Other techniques include nonquantitative or semiquantitative PCR, Southern blot and reporter gene expression (LacZ, luciferase and GFP). The TaqMan real time PCR technique was discoved by America PE Corporation, and now has been used widely in gene detection. The method provides very accurate and reproducible quantitation of gene copies, Unlike other quantitative PCR, real time PCR does not require post-PCR sample handing, preventing potential PCR product carry-over contamination and resulting in much faster and higer throughput assays. The real time PCR method has a very large dynamic range of starting target molecule determination. Real time quantitative PCR is extremely accurate and less labor intensive than current quantitative PCR mentods.
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