抑制T细胞增殖的抗CD45单克隆抗体的建立

目的寻找能调节T细胞功能的相关分子,进行与T细胞介导的自身免疫性疾病相关的研究。方法从BALB/c小鼠骨髓中收集树突状细胞,免疫Wistar大鼠,进行细胞融合,建立杂交瘤细胞系。筛选得到很多株能调节T细胞功能的杂交瘤细胞系,对其中一株最能抑制T细胞增殖的杂交瘤细胞系进行了进一步的深入研究。结果显示其目标分子是CD45,同时增殖实验结果显示该抗体能显著抑制T细胞增殖反应。结论抗CD45单克隆抗体能有效抑制T细胞增殖,有望将本抗体用于T细胞介导的自身免疫性疾病的相关预防及治疗中。     

抑制T细胞增殖的抗CD98重链单克隆抗体的建立

目的寻找能调节T细胞功能的相关分子,进行与T细胞介导的自身免疫性疾病相关的研究。方法收集BALB/c小鼠脾细胞,免疫Wistar大鼠,进行细胞融合,建立杂交瘤细胞系。筛选得到43株能调节T细胞功能的杂交瘤细胞系,对其中一株最能抑制T细胞增殖的杂交瘤细胞系进行了进一步的深入研究。结果显示其目标分子是CD98重链,同时后续实验显示抗CD98单克隆抗体能抑制纤连蛋白介导的细胞分布,但不影响氨基酸转运。而且混合淋巴细胞反应显示该抗体能显著抑制T细胞增殖反应。结论抗CD98单克隆抗体能有效抑制T细胞增殖,有望将本抗体用于T细胞介导的自身免疫性疾病的相关预防及治疗中。     

抗CD52单克隆抗体中残留蛋白AELISA定量检测方法的验证

目的验证抗CD52单克隆抗体(单抗)中残留蛋白A(Protein A,Pro A)ELISA定量检测方法。方法使用Cygnus公司的Mix-N-Go Protein A检测试剂盒,对抗CD52单抗中的Pro A残留量进行检测,并验证该方法的专属性、准确度、精密度、线性及定量限。结果亲和填料(Mab Select SuRe)稀释1 000倍后仍检测到含有Pro A 1.9 ng/m L;制剂及抗CD52单抗细胞发酵液中未检出Pro A;3种不同Pro A加标质量浓度6次试验的加标回收率均在80%~120%之间;3种不同Pro A加标质量浓度重复性检测结果及中间精密度检测结果 RSD均<20%;分别对3次Pro A残余检测结果绘制的四参数标准曲线,R2均>0.990;定量限为0.16 ng/m L。结论经验证,抗CD52单抗中Pro A残留量的ELISA定量检测方法专属性好,准确度、精密度高且线性良好。     

Targeting properties of an anti-CD16/anti-CD30 bispecific antibody in an in vivo system

Bispecific antibodies are currently being used in clinical trials in increasing numbers in the areas of breast cancer, prostate cancer, non-Hodgkin's lymphoma and Hodgkin's lymphoma. We have previously performed two clinical trials in patients with Hodgkin's disease with an anti-CD30/anti-CD16 bispecific antibody and demonstrated a 30% response rate in a cohort of patients otherwise resistant to standard therapeutic modalities. However, no surrogate marker could be defined in these trials indicative of optimal antibody dosing/scheduling or predictive for favorable response. In order to evaluate accurately the potential biodistribution properties of bispecific antibody in patients, we have performed a detailed analysis of the binding properties and animal model in vivo characteristics of these constructs. For this purpose, the parental antibodies (anti-CD30 and anti-CD16) and the bispecific antibody (anti-CD30/anti-CD16) were radiolabeled with either ¹²⁵I or ¹¹¹In. Antibody integrity and binding properties after labeling were confirmed by Scatchard plot and Lindmo analysis. ¹¹¹In-labeled antibodies revealed superior targeting properties in a standard SCID mouse tumor model. Both the bivalent parental anti-CD30 monoclonal antibody and the monovalent anti-CD30/anti-CD16 bispecific antibody showed excellent uptake in CD30⁺ tumors which did not differ significantly between the two (maximum uptake 16.5% ± 4.2% vs. 18.4% ± 3.8% injected dose/gram tissue). The equivalent targeting properties of the bispecific antibody compared with the parental anti-CD30 antibody encourages the further clinical development of this bispecific antibody, and might help to explain the clinical responses seen with this antibody so far in patients suffering from Hodgkin's disease. Received: 26 October 2000 / Accepted: 15 December 2000     

表达重组抗CD52单克隆抗体CHO细胞灌流培养基的筛选

目的筛选重组抗CD52单克隆抗体CHO细胞株培养和连续灌流表达用培养基,以提高抗体表达量。方法通过调整原有批培养用培养基中谷氨酰胺和植物水解蛋白,获得5种培养基配比。使用模拟灌注方式进行细胞培养,分析细胞密度、活细胞比率和目标蛋白表达,筛选连续灌流细胞培养和表达用培养基。最后在7 L反应器中采用灌注培养方式对筛选获得的培养基进行验证。结果使用50 mL细胞培养管进行模拟灌注培养时,活细胞比率较高,达到90%以上;CHO细胞在添加谷氨酰胺至4.0 mmol/L和植物水解蛋白至5.0 g/L的批培养用培养基中生长速度最快;在基础培养基中抗体表达量比优化前高15%。20 d培养周期内,优化的培养基在7 L反应器中可以维持CHO细胞密度在(2 727±253)万个/mL,活细胞比率在95%以上。结论通过模拟灌注培养,筛选获得了一种在7 L反应器灌流培养中适宜于重组抗CD52单克隆抗体CHO细胞表达的培养基。     

Characterization of anti-CD20 monoclonal antibody produced by transgenic silkworms (Bombyx mori)

In response to the successful use of monoclonal antibodies (mAbs) in the treatment of various diseases, systems for expressing recombinant mAbs using transgenic animals or plants have been widely developed. The silkworm (Bombyx mori) is a highly domesticated insect that has recently been used for the production of recombinant proteins. Because of their cost-effective breeding and relatively easy production scale-up, transgenic silkworms show great promise as a novel production system for mAbs. In this study, we established a transgenic silkworm stably expressing a human-mouse chimeric anti-CD20 mAb having the same amino acid sequence as rituximab, and compared its characteristics with rituximab produced by Chinese hamster ovary (CHO) cells (MabThera®). The anti-CD20 mAb produced in the transgenic silkworm showed a similar antigen-binding property, but stronger antibody-dependent cell-mediated cytotoxicity (ADCC) and weaker complement-dependent cytotoxicity (CDC) compared to MabThera. Post-translational modification analysis was performed by peptide mapping using liquid chromatography/mass spectrometry. There was a significant difference in the N-glycosylation profile between the CHO− and the silkworm-derived mAbs, but not in other post-translational modifications including oxidation and deamidation. The mass spectra of the N-glycosylated peptide revealed that the observed biological properties were attributable to the characteristic N-glycan structures of the anti-CD20 mAbs produced in the transgenic silkworms, i.e., the lack of the core-fucose and galactose at the non-reducing terminal. These results suggest that the transgenic silkworm may be a promising expression system for the tumor-targeting mAbs with higher ADCC activity.     

In vitro and in vivo antitumour activity of a chimeric anti-CD19 antibody

Mouse monoclonal antibodies to CD19 detect an antigenic determinant expressed exclusively on the surface of B lymphocytes, and have previously been shown to be potentially useful therapeutic reagents for human B cell lymphoma. We report the production and characterization of a mouse/human chimeric antibody, cCD19, with potent in vivo antitumour activity. The genes encoding the variable domains for heavy (V_H) and light (V_L) chains were subcloned into eukaryotic expression vectors containing human constant region genes (IgG1 and ), and co-transfected into non-secreting Sp2/0 mouse myeloma cells. Intraperitoneal administration of cCD19 produced inhibition of growth of subcutaneous CD19⁺ Sultan human B lymphoma tumours inscid/scid mice. When the antibody was administered 18 and 20 days after subcutaneous tumour inoculation, an approximately 30% reduction in tumour size was noted by day 29. cCD19 faithfully mimicked the in vitro binding characteristics of mCD19 as (a) the chimeric antibody was shown by flow cytometry to bind exclusively to cell lines that expressed CD19, (b) cCD19 was able to inhibit the binding of mCD19 on CD19⁺ cells completely and (c) the affinity of binding of the two antibodies was not significantly different [K _a=(2.03±1.5)×10⁸]. In biodistribution studies, up to 14.8% of the total injected antibody dose per gram of tissue was localized in CD19⁺ Sultan tumours at 24 h approximately, 14.4% was present in the tumors at 48 h and about 13.7% at 72 h. These levels were comparable to mCD19 administered in the same fashion. cCD19 conjugated to idarubicin was specifically and strongly cytotoxic to CD19⁺ cells cultured in vitro, and demonstrated an IC₅₀ of 0.17 M, similar to that of mCD19 (0.32 M) and approximately 14-fold greater than the IC₅₀ of free idarubicin. The specific cytotoxic capacity of cCD19 and its likely reduced immunogenicity suggest that it may potentially be of use in the treatment of refractory B cell lymphoma in humans.     

Characterization of anti-CD20 monoclonal antibody produced by transgenic silkworms (Bombyx mori)

In response to the successful use of monoclonal antibodies (mAbs) in the treatment of various diseases, systems for expressing recombinant mAbs using transgenic animals or plants have been widely developed. The silkworm (Bombyx mori) is a highly domesticated insect that has recently been used for the production of recombinant proteins. Because of their cost-effective breeding and relatively easy production scale-up, transgenic silkworms show great promise as a novel production system for mAbs. In this study, we established a transgenic silkworm stably expressing a human-mouse chimeric anti-CD20 mAb having the same amino acid sequence as rituximab, and compared its characteristics with rituximab produced by Chinese hamster ovary (CHO) cells (MabThera®). The anti-CD20 mAb produced in the transgenic silkworm showed a similar antigen-binding property, but stronger antibody-dependent cell-mediated cytotoxicity (ADCC) and weaker complement-dependent cytotoxicity (CDC) compared to MabThera. Post-translational modification analysis was performed by peptide mapping using liquid chromatography/mass spectrometry. There was a significant difference in the N-glycosylation profile between the CHO? and the silkworm-derived mAbs, but not in other post-translational modifications including oxidation and deamidation. The mass spectra of the N-glycosylated peptide revealed that the observed biological properties were attributable to the characteristic N-glycan structures of the anti-CD20 mAbs produced in the transgenic silkworms, i.e., the lack of the core-fucose and galactose at the non-reducing terminal. These results suggest that the transgenic silkworm may be a promising expression system for the tumor-targeting mAbs with higher ADCC activity.     

A peptide mimetic of an anti-CD4 monoclonal antibody by rational design

The development of rational methods to design 'continuous' sequence mimetics of discontinuous regions of protein sequence has, to now, been only marginally successful. This has been largely due to the difficulty of constraining the recognition elements of a mimetic structure to the relative conformational and spatial orientations present in the parent molecule. Using peptide mapping to determine 'active' antigen recognition residues, molecular modeling, and a molecular dynamics trajectory analysis, we have developed a peptide mimic of an anti-CD4 antibody, containing antigen contact residues from multiple CDRs. The design described is a 27-residue peptide formed by juxtaposition of residues from 5 CDR regions. It displays an affinity for the antigen (CD4) of 0.9nM, compared to 2nM for the parent antibody ST40. Nevertheless, the mimetic shows low biological activity in an anti-retroviral assay.     

Evolution of anti-CD20 monoclonal antibody therapeutics in oncology

Approval of an anti-CD20 chimeric monoclonal antibody, rituximab, has revolutionized cancer treatment and also validated CD20 targeting for providing benefit and improvement of overall response rate in B cell malignancies. Although many patients have benefited from the treatment of rituximab, there are still significant numbers of patients who are refractory or develop resistance to the treatment. Here we discuss pre-clinically well-defined potential mechanisms of action for rituximab and review the ways next generation anti-CD20 monoclonal antibodies can potentially exploit them to further enhance the treatment of B cell malignancies. Although the relative importance of each of these mechanism remains to be established in the clinic, well-designed clinical trials will help to define the efficacy and understanding of which effector activity of modified next generation anti-CD20 mAb will be important in the treatment of B-cell malignancies.Key words: CD20, NHL, CLL, monoclonal antibody, next generation anti-CD20 antibodies, ADCC, CDC, ADCP, PCD, rituximab     

Dilute-and-shoot analysis of therapeutic monoclonal antibody variants in fermentation broth: a method capability study

Monoclonal antibodies (mAbs) are widely applied as highly specific and efficient therapeutic agents for various medical conditions, including cancer, inflammatory and autoimmune diseases. As protein production in cellular systems inherently generates a multitude of molecular variants, manufacturing of mAbs requires stringent control in order to ensure safety and efficacy of the drugs. Moreover, monitoring of mAb variants in the course of the fermentation process may allow instant tuning of process parameters to maintain optimal cell culture conditions. Here, we describe a fast and robust workflow for the characterization of mAb variants in fermentation broth. Sample preparation is minimal in that the fermentation broth is shortly centrifuged before dilution and HPLC-MS analysis in a short 15-min gradient run. In a single analysis, N-glycosylation and truncation variants of the expressed mAb are identified at the intact protein level. Simultaneously, absolute quantification of mAb content in fermentation broth is achieved. The whole workflow features excellent robustness as well as retention time and peak area stability. Additional enzymatic removal of N-glycans enables determination of mAb glycation levels, which are subsequently considered in relative N-glycoform quantification to correct for isobaric galactosylation. Several molecular attributes of the expressed therapeutic protein may thus be continuously monitored to ensure the desired product profile. Application of the described workflow in an industrial environment may therefore substantially enhance in-process control in mAb production, as well as targeted biosimilar development.     

表达抗-CD25单克隆抗体的GS-NS0骨髓瘤细胞无血清培养及代谢特性

抗-CD25单克隆抗体作为免疫抑制剂拥有广阔的市场前景和巨大的经济价值。本实验以表达抗?CD25单克隆抗体的GS-NS0细胞为研究对象,开发了支持其大规模培养和抗体表达的无血清低蛋白培养基,批培养最大活细胞密度和最大抗体浓度分别达3×106cells/mL和300mg/L以上,比商业无血清培养基(Excell 620+0.2% primatone)分别提高了100%和46%。通过批培养实验,研究了细胞的生长、葡萄糖和氨基酸代谢、以及产物表达特点,并揭示了批培养过程中初始葡萄糖浓度对GS-NS0细胞生长与代谢的影响规律。为优化GS-NS0细胞培养过程和抗CD25单抗成功迈向产业化提供了重要的科学依据。     

抗CD52单克隆抗体ADCC转基因测活方法的建立

目的 建立转基因细胞法测定抗CD52单克隆抗体(单抗)的抗体依赖细胞介导的细胞毒性作用(antibody-dependentcell-mediatedcytotoxicity,ADCC)生物学活性检测方法。方法 ①以Ramos细胞系作为靶细胞,以Jurkat-hFcγRⅢa/FcεRIγ-NFAT转基因细胞系作为效应细胞,通过荧光素酶检测系统(Bright-GloTM luciferase Assay System)建立抗CD52单抗的ADCC生物学活性检测方法;②对靶细胞、量效范围、效靶比及诱导时间进行优化并进行方法学验证;③研究建立的方法应用于对不同抗CD52单抗的ADCC生物学活性检测。结果 建立抗CD52单抗的ADCC生物学活性检测方法,抗CD52单抗在该方法中存在量效关系,符合四参数方程:y=(A-D)/[1+(x/C)B]+D;经优化后确定抗体量效范围为起始质量浓度360μg/mL,4倍系列稀释9个稀释度;效靶比为3∶1,诱导时间为6.0h;该方法具有良好的专属性;4个不同稀释组回收率样品经3次测定,相对效价分别为(45.58±4.67)%、(71.61±9.45)%、(122.92±7.92)%和(149.94±14.58)%;对应的回收率分别为(91.16±9.34)%、(95.49±12.60)%、(98.34±6.34)%和(99.96±9.72)%,上述结果的变异系数(coefficientofvariation,CV)均小于15%;且该方法也适用于不同抗CD52单抗的ADCC效应评价。结论 利用转基因细胞法成功建立了抗CD52单抗ADCC生物学活性检测方法,该方法专属性强、准确性高、重复性好,可用于评价抗CD52单抗的ADCC生物学活性。     

A recombinant human monoclonal antibody to human metapneumovirus fusion protein that neutralizes virus in vitro and is effective therapeutically in vivo

Human metapneumovirus (hMPV) is a recently discovered paramyxovirus that is a major cause of lower-respiratory-tract disease. hMPV is associated with more severe disease in infants and persons with underlying medical conditions. Animal studies have shown that the hMPV fusion (F) protein alone is capable of inducing protective immunity. Here, we report the use of phage display technology to generate a fully human monoclonal antibody fragment (Fab) with biological activity against hMPV. Phage antibody libraries prepared from human donor tissues were selected against recombinant hMPV F protein with multiple rounds of panning. Recombinant Fabs then were expressed in bacteria, and supernatants were screened by enzyme-linked immunosorbent assay and immunofluorescent assays. A number of Fabs that bound to hMPV F were isolated, and several of these exhibited neutralizing activity in vitro. Fab DS7 neutralized the parent strain of hMPV with a 60% plaque reduction activity of 1.1 mug/ml and bound to hMPV F with an affinity of 9.8 x10(-10) M, as measured by surface plasmon resonance. To test the in vivo activity of Fab DS7, groups of cotton rats were infected with hMPV and given Fab intranasally 3 days after infection. Nasal turbinates and lungs were harvested on day 4 postinfection and virus titers determined. Animals treated with Fab DS7 exhibited a >1,500-fold reduction in viral titer in the lungs, with a modest 4-fold reduction in the nasal tissues. There was a dose-response relationship between the dose of DS7 and virus titer. Human Fab DS7 may have prophylactic or therapeutic potential against severe hMPV infection.     

Properties and characteristics of an anti-human chorionic gonadotropin monoclonal antibody

The product of a hybrid cell clone, P₃W₈₀, obtained as ascites fluid from mouse peritoneal cavity had high titres of anti-human chorionic gonadotropin antibodies e.g. 30 to 40% binding of¹²⁵I-human chorionic gonadotropin at 10⁷ dilution in a radioimmunoassay. The antiserum SB₆ (raised against Β-human chorionic gonadotropin distributed by National Institutes of Health, USA gave similar binding at 5000 dilution in parallel runs. The monoclonal antibody recognized best human chorionic gonadotropin (0.3 mlU of hormone/tube withB/B ₀ 75%), but also bound Β and a subunits of human chorionic gonadotropin, 12 and 800 folds lower than human chorionic gonadotropin respectively No binding was observed with carboxy terminal peptides of Β-human chorionic gonadotropin ranging from 93 to 145 amino acid residues, indicating the lack of recognition of the C-terminal region. No cross-reaction with human leutinizing hormone was obtained at the physiological surge levels, a significant competition (B/B ₀75 %. obtainable only at 60 mlU of LER 960 human leutinizing hormone/ tube. The antibody had heavy chain of IgG₁ and light chain of kappa type. It neutralized the bio-activity of human chorionic gonadotropin bothin vitro and invivo.     

In vitro and in vivo fitness of respiratory syncytial virus monoclonal antibody escape mutants

Respiratory syncytial virus (RSV) is the only infectious disease for which a monoclonal antibody (MAb) is used in humans. Palivizumab (PZ) is a humanized murine MAb to the F protein of RSV. PZ-resistant viruses appear after in vitro and in vivo growth of RSV in the presence of PZ. Fitness for replication could be a determinant of the likelihood of dissemination of resistant viruses. We assessed the fitness of two PZ-resistant viruses (F212 and MP4). F212 grew less well in cell culture than the parent A2 virus and was predicted to be less fit than A2. Equal amounts of F212 and A2 were mixed and passaged in cell culture. F212 disappeared from the viral population, indicating it was less fit than the A2 virus. The MP4 virus grew as well as A2 in culture and in cotton rats. A2/MP4 virus input ratios of 1:1, 10:1, 100:1, and 1,000:1 were compared in competitive replication. For all input ratios except 1,000:1, the MP4 virus became dominant, supplanting the A2 virus. The MP4 virus also dominated the A2 virus during growth in cotton rats. Thus, the mutant MP4 virus was more fit than A2 virus in both in vitro and in vivo competitive replication. Whether this fitness difference was due to the identified nucleotide substitutions in the F gene or to mutations elsewhere in the genome is unknown. Understanding the mechanisms by which mutant virus fitness increased or decreased could prove useful for consideration in attenuated vaccine design efforts.     

不同细胞系表达的抗EGFR单抗糖基化结构对比分析

真核表达系统造就了单克隆抗体药物的广泛异质性,这些异质性通常是由翻译后修饰引起,而糖基化修饰则是关键的翻译后修饰,其对治疗性蛋白的安全性和有效性有着深远的影响,为探索细胞表达系统的改变对单抗糖基化所带来的影响,应用液相色谱-电喷雾离子化四极杆飞行时间质谱技术(LC-ESI-Q-Tof),通过交替高低碰撞能量扫描、源内诱导解离及二级质谱的方法从释放的寡聚糖水平研究聚糖结构,对比分析由两种不同细胞系制备的抗表皮生长因子受体(EGFR)单抗,然后结合外切糖苷酶逐级消化的方法对两种蛋白的糖链结构作进一步确证分析。分析结果表明,在Fc区域的糖基化修饰,两种表达系统表达的该抗体未发生明显的改变,而在Fab区域,由小鼠骨髓瘤细胞SP2/0制备的抗EGFR单抗的聚糖结构中含有大量α半乳糖(α-Gal),且末端唾液酸形式主要是N-羟乙基神经氨酸(NGNA),具有极高的免疫原性风险。而通过中国仓鼠卵巢细胞CHO表达系统制备的抗EGFR单抗Fab区域聚糖结构中不含有α-Gal,且末端唾液酸形式主要是N乙酰神经氨酸(NANA),免疫原性风险极大降低。本研究在一定程度上可以预测由CHO表达系统制备的抗EGFR单抗具备较好的临床耐受性,超敏反应发生风险低,CHO细胞可以作为该抗体改良型生物类似药(Biobetter)的优选表达系统。     

Humanization of an anti-CD34 monoclonal antibody by complementarity-determining region grafting based on computer-assisted molecular modelling

4C8 is a new mouse anti-human CD34 monoclonal antibody (mAb), which recognizes class II CD34 epitopes and can be used for clinical hematopoietic stem/progenitor cell selection. In an attempt to improve its safety profiles, we have developed a humanized antibody of 4C8 by complementarity-determining region (CDR) grafting method in this study. Using a molecular model of 4C8 built by computer-assisted homology modelling, framework region (FR) residues of potential importance to the antigen binding were identified. A humanized version of 4C8, denoted as h4C8, was generated by transferring these key murine FR residues onto a human antibody framework that was selected based on homology to the mouse antibody framework, together with the mouse CDR residues. The resultant humanized antibody was shown to possess antigen-binding affinity and specificity similar to that of the original murine antibody, suggesting that it might be an alternative to mouse anti-CD34 antibodies routinely used clinically.     

Novel human monoclonal antibody combination effectively neutralizing natural rabies virus variants and individual in vitro escape mutants

The need to replace rabies immune globulin (RIG) as an essential component of rabies postexposure prophylaxis is widely acknowledged. We set out to discover a unique combination of human monoclonal antibodies (MAbs) able to replace RIG. Stringent criteria concerning neutralizing potency, affinity, breadth of neutralization, and coverage of natural rabies virus (RV) isolates and in vitro escape mutants were set for each individual antibody, and the complementarities of the two MAbs were defined at the onset. First, we identified and characterized one human MAb (CR57) with high in vitro and in vivo neutralizing potency and a broad neutralization spectrum. The linear antibody binding site was mapped on the RV glycoprotein as antigenic site I by characterizing CR57 escape mutants. Secondly, we selected using phage display a complementing antibody (CR4098) that recognized a distinct, nonoverlapping epitope (antigenic site III), showed similar neutralizing potency and breadth as CR57, and neutralized CR57 escape mutants. Reciprocally, CR57 neutralized RV variants escaping CR4098. Analysis of glycoprotein sequences of natural RV isolates revealed that the majority of strains contain both intact epitopes, and the few remaining strains contain at least one of the two. In vitro exposure of RV to the combination of CR57 and CR4098 yielded no escape mutants. In conclusion, a novel combination of human MAbs was discovered suitable to replace RIG.