Objective:To establish VSV-G qPCR assay for detection of replication competent lentivirus(RCL) and verify its application.Methods:A real-time fluorescent quantitative PCR for VSV-G envelope gene was developed. Several parameters including specificity, linear, amplification efficiency, precision, trueness, dynamic range, limit of detection, limit of quantification and robustness were verified. Preliminary application on CAR-T cells, end of production cells and the harvest of lentivirus vector was performed by using the method developed.Results:The real-time fluorescent quantitative PCR assay for VSV-G was specific for the detection VSV-G without specific amplification on 293T, PBMC and C8166 cells. The linear range of the assay was 1×10 2 copies/test-1×10 9 copies/test with a R2 value more than 0.998 and amplification efficiency between 93% and 98%. The precision (relative standard deviation) of the assay was less than 12% and the trueness (the rate of recovery) of the assay was between 85% and 106%. The limit of detection (LOD) and limit of quantification (LOQ) of the assay was 5 copies/test and 40 copies/test. In addition, the robustness of the assay was also well. All the results of validation illustrated that the assay could meet the detection requirements. All of the 54 samples including CAR-T cells, lentivirus vector and end of product cells after amplification and passage on C8166 cells were negative of RCL by using the established assay. Conclusions:The real-time fluorescent quantitative PCR for VSV-G were established successfully. All of the validation results illustrated that the assay could meet the detection requirements. The application of the assay was conducive to further enhance the safety of the lentivirus vector related products.

支原体是生物制品的最常见外源因子污染物之一,《中国药典》2015年版收录的两种支原体检测方法虽然可灵敏地检测出活的支原体,但因检测时间较长,对实验室设置及实验室人员的技术均有一定要求,且对一些特定的样本及需要快速放行的样本有一定的局限性,如目前研究热点之一的CAT-T细胞治疗产品的过程或放行检验.因此,越来越多的新兴领域的研发者更倾向于采用支原体污染快速检测方法用于中间品放行检测,甚至作为CAR-T细胞等治疗产品的放行检验的补充或替代方法.由此,也带来了另一个药品监管机构所关注的重要问题安全性,即所用的方法是否具有与经典方法相同的灵敏度可以保证产品的安全性.本文总结了近年来我国生物制品采用药典方法检测的支原体污染的现状,分析了支原体核酸检测(NAT)方法的需求与研究现状以及国内外法规对支原体核酸检测方法使用的态度,简述了国外法规对支原体验证的相关要求,并针对目前我国支原体核酸检测法方法学验证的现状提出解决的思路,以期对我国支原体核酸扩增法检测的研发者及使用者提供借鉴.

一 引言 嵌合抗原受体T细胞(Chimeric antigen receptor T cell,CAR-T),是指通过基因修饰技术,将带有特异性抗原识别结构域及T细胞激活信号的遗传物质转入T细胞,使T细胞通过直接与肿瘤细胞表面的特异性抗原相结合而激活,通过释放穿孔素、颗粒酶素B等直接杀伤肿瘤细胞,同时还通过释放细胞因子募集人体内源性免疫细胞杀伤肿瘤细胞,从而达到治疗肿瘤的目的,而且还可形成免疫记忆T细胞从而获得特异性的抗肿瘤长效机制.目前,CAR-T细胞对多种血液肿瘤显示了非常好的临床效果,对实体瘤治疗也表现出了非常大的潜力.

嵌合抗原受体T细胞(CAR-T细胞)因其在血液肿瘤中的显著疗效已成为肿瘤免疫治疗领域中的国际研究新热点,成为肿瘤治愈新的希望.目前,在CAR-T细胞产品的生产中,通常是利用逆转录病毒载体或慢病毒载体将CAR基因高效地导入T细胞中,但在使用这些病毒载体的同时也带来了CAR-T产品污染复制型逆转录病毒(RCR)或复制型慢病毒(RCL)的潜在风险.虽然随着病毒载体设计及生产体系的不断改进,这种风险已大大降低,但仍不能完全排除.因此,监管机构要求对于临床使用的慢病毒或逆转录病毒载体、转导的CAR-T细胞产品以及患者均要进行复制型病毒的检测.本文主要通过分析复制型病毒污染检测的必要性、降低复制型病毒污染风险的措施、复制型病毒检测的阶段以及检测方法等方面,提出在CAR-T细胞生产过程中控制RCR/RCL的策略,以供CAR-T细胞产品研发者参考.

Objective To optimize and compare four in vitro cytotoxicity assays in order to find a relatively rapid assay that can replace the traditional 51Cr release assay to evaluate the cytotoxicity of immune cells prepared for immunotherapy.Methods Four assays including BATDA, CAM (calcein acetoxymethyl ester), CytoTox-Glo and PKH were optimized and used to measure the in vitro cytotoxicity of NK-92 cells to K562 cell line.Intra-and inter-assay reproducibility of these assays and their correlation with 51Cr release assay were analyzed.Results After optimization, all of the four cytotoxicity assays showed good correlation with effector to target (E/T) ratio in a certain range.Compared with the other three assays, CytoTox-Glo assay showed obvious hook effect at a high E/T ratio of 40∶1.BATDA assay could detect the significant cytotoxicity of NK-92 cells to K562 cells after incubating them for one hour and that was the shortest time taken by the four assays to detect in vitro cytotoxicity.Both CAM and PKH assays took about four hours and CytoTox-Glo assay took six to eight hours to detect the significant cytotoxic potency.All of the four assays, especially BATDA and CAM assays, showed good intra-and inter-assay reproducibility.Among these assays, BATDA assay showed the best correlation with the traditional 51Cr release assay.BATDA assay, as compared with the other three assays, could be used to detect the cytotoxicity of Caov3 cells, an adherent cell line, and showed good results in evaluating the cytotoxic potency of autologous primary NK cells and CD19-CAR T cells.Conclusion Compared with the other three assays, BATDA assay shows the best linear correlation with 51Cr release assay and has the advantages of time-saving and good reproducibility.Besides, it is a better assay for detecting the cytotoxicity of adherent cells.BATDA assay is a promising substitute for 51Cr release assay in evaluating the in vitro cytotoxic potency of NK cells and other immune cells.

Objective To establish an assay for the detection of Torque teno sus virus ( TTSuV) strains and to analyze its preliminary application to biologics.Methods Primers and probe were designed according to the conserved sequences.A fluorescent PCR assay for the detection of TTSuV strains was estab-lished.Several parameters including the specificity, linearity, accuracy, sensitivity and anti-interference of the established assay were verified.The fluorescent PCR assay was performed to detect the samples of por-cine blood, cell substrate and rotavirus vaccine.The porcine blood samples positive for TTSuV strains were further genotyped.Results The established fluorescent PCR assay was confirmed to have high specificity as no cross-reactions with parvovirus virus of various species, SV40 and porcine circovirus strains were detec-ted.The linear range of the assay was 1×109-1×103 copies/μl for TTSuV1 genotype and 1×109-1×102 cop-ies/μl for TTSuV2 genotype with a R2 value more than 0.993.The sensitivity of the fluorescent PCR assay was 1×103 copies/μl for TTSuV1 genotype and 1×102 copies/μl for TTSuV2 genotype.The intra-and inter-CVs were both less than 7%in Ct values and less than 25% and 45% respectively in copies.No interfer-ence was found in the detection of TTSuV nucleic acids from cell samples.8 out of 20 porcine blood samples were positive for TTSuV strains, among which one sample was positive for TTSuV1 genotype, four samples were positive for TTSuV2 genotype and the rest were positive for both TTSuV1 and TTSuV2 genotypes.Com-pared with the reference strain, strains genotyped as TTSuV1 and TTSuV2 were respectively shared 98%-99%and 98%homologies in sequences.All of the cell substrate and rotavirus vaccine samples detected by the fluorescent PCR assay were negative for TTSuV strains.Conclusion The fluorescent PCR assay for the detection of TTSuV was established successfully, the application of which would further improve the safety of biologics.

Abstract] Objective To establish an assay for the detection of porcine parvovirus ( PPV) and to verify its application for monitoring cells used for production.Methods A pair of primers and one probe were designed according to the conserved sequence encoding non-structural protein 1 (NS1).Based on the designed primers, a real-time fluorescent quantitative PCR assay for the detection of PPV was developed. Several parameters including the linearity, precision, minimum detection limit and anti-interference of the established assay were evaluated.A stock of PPV strains was prepared by infecting swine testicle ( ST) cells with PPV strains.An assay for the detection of PPV infection was developed by using ST cells as sensitive cells.A combined ST cell infection-PCR test was developed by combining the ST cell infection assay with the real-time fluorescent quantitative PCR assay.The sensitivity of ST cell infection-PCR test was analyzed.The cell samples used for production of biological products were detected by using the established assay.Results The real-time fluorescent quantitative PCR assay was specific for the detection of PPV without cross-reaction to other species of parvovirus virus, SV40 virus and other porcine viruses.The linear range of the assay was 1×109-1×104 copies/μl with a R2 value more than 0.98.The sensitivity of the real-time quantitative PCR assay was 1×104 copies/μl.Both of the intra-and inter-coefficient of variation (CV) were less than 5%in Ct values.The intra-and inter-CV in copies of detection were 5%-15% and 30%-40% respectively.The minimum detection limit of the real-time fluorescent quantitative PCR assay was 1CCID50/ml.The PPV strains were detected in cell samples with no interference.The sensitivity of ST cells infection-PCR test was 0.01CCID50/ml.All of the 22 cell samples were negative for PPV by using the real-time fluorescent quanti-tative PCR assay.Conclusion The real-time fluorescent quantitative PCR and the ST cell infection-PCR test for the detection of PPV in cells were established successfully.The application of the two assays was conducive to further enhance the safety of using cells for production and therapy.