Establishment and validation of a method for determination of interesting protein expression level in cells infected with recombinant adeno-associated virus
Objective To establish and validate a method for the determination of the interesting protein expression level of recombinant adeno-associated virus(rAAV)infected cells,so as to monitor the product quality in different stages of rAAV9 production process.Methods After incubation of serial diluted rAAV samples with infection enhancer Envirus-AAV,the human malignant glioblastoma cells(U87-MG)pretreated with hydroxyurea(HU)were infected.Using rAAV9 reference as the standard,the expression level of glutaryl-CoA dehydrogenase(GCDH)was detected by ELISA,and the specificity,accuracy,precision,linear range,limit of quantitation(LOQ)and durability of the method were verified.Eight batches of rAAV9 samples were detected by the established method.Results The A450-A630 value of the sample buffer was 0.3,which was slightly lower than the lowest dilution point(1 ng/mL)of the four-parameter standard curve for protein quantification.The average recoveries of samples with 150％,100％and 50％theoretical relative titer levels were in the range of 100.0％-107.3％.The RSDs of the target protein expression level of the samples with three theoretical relative titer levels detected by the same experimenter three times and different experimenters were all less than 25％.There was a good linear relationship between rAAV9 samples and the target protein expression levels in the range of 50％-150％theoretical relative titer levels,and the linear regression equation was y=1.077 x-0.022,R2=0.984.The LOQ of the method was 0.59,namely 6.0 × 1012 vg/mL.After U87-MG cells were incubated with HU for different time(18,21,24 h),and the culture supernatant was stored under different conditions(room temperature for 0.5 h,below-60 ℃ for 12 h,below-60 ℃ for 24 h).The RSDs of target protein expression levels were all less than 25％.The target protein expression levels of 1-8 batches of rAAV9 samples were 111％,121％,72％,65％,86％,75％,102％and 91％,respectively.Conclusion The established method for the deter-mination of the target protein expression level after rAAV infection has good specificity,accuracy,precision and durability,and can be used for the quality control of products in different stages of rAAV9 production.
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