The Retrovirus titer set is designed to quantitate viral RNA transcribed from retrovirus vectors based on the murine leukemia virus (MLV). The kit is based on real-time RT-PCR method to quantitate MLV RNA and accurately determine the virus titer. Use of this kit with the One Step TB Green PrimeScript RT-PCR Kit (Cat. #RR066A), provides a direct measurement of RNA titer from virus supernatant with a relatively rapid protocol (approximately 4 hours).

RNA titers of almost all MLV-based retrovirus vector can be measured because using the MLV packaging signal region as an amplification target. In contrast, the conventional method for measuring the infection titer of a retrovirus vector involves calculating the biological titer by infecting an indicator cell with the retrovirus and using fluorescence or drug resistance to measure infection efficiency. This method requires several days to complete, and cannot be used to measure a retroviral vector that lacks a marker or drug-resistance gene. In addition, when determined multiplicity of infection (MOI) based on biological titer, the procedure requires several days; thus, the virus supernatant must be kept frozen until infection. Freeze/thaw cycles can lower the virus titer and alter the MOI, and additional manipulations increase the likelihood of contamination.

The Retrovirus titer set can measure retrovirus titer without marker or drug-resistance genes because it quantitates retroviral vector RNA. Because results can be obtained within several hours, infection at the obtained MOI is possible without freezing the virus supernatant. The One Step TB Green PrimeScript RT-PCR Kit (Perfect Real Time) is recommended for use with the kit. One Step TB Green PrimeScript RT-PCR Kit is a one-step, real-time RT-PCR system that includes TB Green dye and combines PrimeScript reverse transcriptase, which has excellent fidelity and a rapid elongation rate, with Takara Ex Taq hot-start polymerase, a highly efficient, specific PCR enzyme.