Quantitation of the residual DNA from rice-derived recombinant human serum albumin

Development and Validation of Quantitative Real-Time PCR for the Detection of Residual CHO Host Cell DNA and Optimization of Sample Pretreatment Method in Biopharmaceutical Products

Background

The presence of residual DNA carried by biological products in the body may lead to an increased oncogenicity, infectivity, and immunomodulatory risk. Therefore, current agencies including WHO, EU, and the FDA limited the accepted amounts of residual DNA (less than 10 ng or 100 pg/dose). Among the methods of detecting residual DNA, qPCR is considered to be the most practical for residual DNA quantitation due to its sensitivity, accuracy, precision, and time-saving.

Results

In this study, the detection capacity of this method was determined by comparing the detected concentration of the commercial kit and the self-designed primer/probe set after the same treatment of the extraction method. Then, a universal sample pretreatment method based on a co-precipitant was optimized. The validation results demonstrated that the method has appropriate specificity, sensitivity, accuracy, and precision according to ICH guidelines. The limit of detection and quantitation reached 3 fg/ul and 0.3 pg/reaction respectively, which satisfies the requirement of limit of residual DNA detection in biologics. Spike recovery (82.3–105.7%) showed that the proposed qPCR assay was accurate and has good extraction efficiency. Moreover, the precision of the method based on intra- and inter-assay was 0.065–0.452% and 0.471–1.312%, respectively.

Conclusions

These results all indicated that the method for determination of residual DNA in biological products expressed from CHO cells is sensitive, accurate and robust.

Electronic supplementary material

The online version of this article (10.1186/s12575-019-0105-1) contains supplementary material, which is available to authorized users.

Design and validation of a new method to detect and quantify residual host cell DNA in human recombinant erythropoietin (rEPO)

During the purification of human recombinant erythropoietin (rEPO) from host cells, residual DNA may remain in final products. This contamination is a risk factor for patients and may result in the inactivation of some tumor suppressor genes or activation of oncogenes if its concentration is more than the standard defined by WHO. Based on WHO's criteria, acceptable level of residual DNA in biopharmaceuticals is less than 10-100 pg/dose. In this study, we have designed a sensitive and specific quantitative real-time polymerase chain reaction (PCR) assay for the detection of residual DNA in human rEPO products. All reported sequences of CHO's GAPDH gene were retrieved from GenBank, and a multiple alignment was performed using Mega 6 software to find conserved regions of the gene. Primers and probe were designed by AlleleID7 software for the highly conserved region. Quantitative real-time PCR showed an R² value more than 0.99 and the efficiency equal to 101% indicating a highly accurate and efficiency of the reaction, respectively. Based on the standard curve, the limit of detection of the assay was determined to be 10 copies/µL (0.00967 fg/µL). In addition, the inter- and intra-assay of the test were determined to be 1.14% and 0.65%, respectively, which are in acceptable range according to the WHO's guidelines.