Analysis on integrity of target nucleic acid in recombinant adeno-associated virus
Objective To explore a method for detecting the integrity of target nucleic acid in recombinant adeno-associated virus(rAAV),and establish a preliminary analysis algorithm.Methods The free DNA fragment of rAAV was digested,and the virus genome was extracted.Five pairs of overlapping primers were designed,using the orthogonal array method,which were detected by digital PCR respectively,with conventional conditions:20 μL reaction system with EveGreen and 4 μL template,and digital PCR conditions:95 ℃ 5 min;95 ℃ 15 s,55 ℃ 30 s,72 ℃ 90 s for 45 cycles.The enhance-ment condition of ultra-long nucleic acid fragment was 25 µL reaction system with Mix B-2 000 bp and 2 μL template,and the quantitative analysis was performed by using the software attached to the instrument.Using the least square method,the number of full-length fragments was fitted and analyzed,and then the integrity distribution of target nucleic acid was inter-preted.Results The fragments with the distance between primers of no more than 1 200 nt were amplified effectively,and a series of effective copies of fragments with a length of about 1 000 nt were obtained by systematic analysis.The copy number of common fragments was fitted and analyzed by the least square method.It was estimated that the full-length fragments in the sample were no more than 1 234 copies/μL,and there was a signficant difference(P＜0.05)between this value and the maximum measured value of 1 443 copies/µL,with the difference of approximately 16.9％.Conclusion A preliminary detection method for the integrity of target nucleic acid in rAAV has been developed,and a certain amount of incomplete target nucleic acids were analyzed in the test sample,laying a foundation for further in-depth research.
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