单抗TIGTC—Ⅲ片段F(ab')2的制备及其放射免疫显像研究

目的:将抗人原发性肝癌(PLC)单抗TIGTC-Ⅲ,用胃蛋白酶法消化成F(ab′)2片段,标记131I后进行裸鼠人肝癌移植瘤的体内定位研究.方法:采用胃蛋白酶消化法,进行裸鼠体内核素显像.结果:消化产率为31.7%±2.4%,经细胞结合实验证明F(ab′)2具有良好的免疫活性,抗体片段进入裸鼠体内后,与完整抗体比,进入肿瘤的速度快,生物学分布特异性高,定位指数上升,血清本底下降迅速,生物半衰期明显缩短.结论:F(ab′)2与全抗体比较可使成像时间提前,定位清晰.     

单克隆抗体及其F(ab′)_2片段在小鼠体内的药物动力学及肿瘤显像研究

放射性同位素标记的抗肿瘤单克隆抗体(McAb)可用于体内肿瘤的定位显像及导向治疗。我们用~(125)I标记抗人小细胞肺癌单克隆抗体2F7和相应片段F(ab’)_2,比较它们在荷瘤裸鼠模型中的定位显像及经静脉(iv)或腹腔(ip)注射后在正常小鼠体内     

抗血小板单克隆抗体片段的抗栓效应研究

目的 :研究抗血小板膜糖蛋白IIIa(GPIIIa)单克隆抗体 (mAb)SZ 2 1F(ab′) 2 片段的抗血栓效应。方法 :用木瓜蛋白酶在偏酸条件下 ( pH5 .5 )消化 2 0h ,经DEAE 5 2NaCl梯度洗脱消化产物 ,以得到F(ab′) 2 片段。收集产物经SDS PAGE鉴定 ,并通过ELISA和血小板聚集抑制试验 ,观察所获F(ab′) 2 片段免疫原活性和抗栓活性。结果 :该法制备F(ab′) 2 片段的得率为 6 0 .32 % ;酶免法测定其效价为 0 .8× 10 -9mol/L ;体外血小板聚集抑制半数有效剂量 (ED5 0 )为 3.395mg/L。F(ab′) 2 片段与血小板的结合性及对血小板聚集功能的抑制效果均高于完整的IgG。 结论 :利用木瓜蛋白酶制备的抗血小板mAbSZ 2 1的F(ab′) 2 片段 ,产率高且其抗栓活性与免疫原活性均优于完整的mAbIgG ,为mAbSZ 2 1用于临床抗血栓治疗展现了良好的前景     

~(131)I标记抗胃癌单克隆抗体(MG_7)在荷人胃癌裸鼠体内的分布及显像研究

本文观察~(131)I标记的抗胃癌的MG_7-McAb及其片段在移植人胃癌或结肠癌裸鼠体内的生物学分布及放射免疫显象。MG_7抗体在结肠癌(无关肿瘤)移植片 中无明显定位分布,静脉注射4只鼠的六种主要脏器及体液的肿瘤与非肿瘤比活性比值(T/NT)平均为1.32。该抗体及其片段在胃癌移植片中有明显定位浓集,其中F(ah′)_2段的浓集量(T/NT=4.9)大于全抗体(T/NT=3.0)。注射标记McAb后48～72h作放射免疫显象可见肿瘤的阳性图象,胃癌移植片的显像比结肠癌密集、清晰,注射标记F(ah′)_2片段者,胃癌的清晰显像时间可提前至注射后24h。     

人单核细胞趋化因子受体5(CCR5)N-端膜外第一襻特异抗体F(ab′)2的制备及鉴定

目的 :研究人 β趋化因子受体 5 (huCCR5 )NH2 端膜外第一襻特异抗体F(ab′) 2 的制备及鉴定方法。方法 :计算机分析定位超基因家族中同源顺序最低的结构域NH2 端膜外第一襻 ,PCR扩增出该基因片段后克隆到原核表达载体pGEX 1N中 ,经测序鉴定正确后 ,在E coli中表达 ,纯化后免疫新西兰白兔。经A蛋白 SepharoseCL 4B亲和层析纯化后 ,用胃蛋白酶消化IgG ,经S 2 0 0凝胶过滤柱分离制备F(ab′) 2 。结果 :经还原和非还原聚丙烯酰胺凝胶电泳和ELISA阻断实验分析证明得到抗huCCR5NH2 端的特异性抗体。结论 :这一简捷快速的特定功能结构域抗体F(ab′) 2 的制备方法 ,对研究该基因在体内的表达及生物学功能提供了重要的实验材料 ,同时也对超基因家族中亚家族特异抗体研制提供了一种研究思路和方法。     

人单核细胞趋化因子受体5〔CCR5）N—端膜外第一襻特异抗体F〔ab′）2的制备及鉴定

目的：研究人β趋化因子受体5(huCCR5)NH2端膜外第一襻特异抗体F(ab′)2的制备及鉴定方法。方法：计算机分析定位超基因家族中同源顺序最低的结构域NH2端膜外第一襻，PCR扩增出该基因片段后克隆到原核表达载体pGEX-1N中，经测序鉴定正确后，在E．coli中表达，纯化后免疫新西兰白兔。经A蛋白-Sepharose CL-4B亲和层析纯化后，用胃蛋白酶消化IgG，经S—200凝胶过滤柱分离制备F(ab′)2。结果：经还原和非还原聚丙烯酰胺凝胶电泳和ELISA阻断实验分析证明得到抗huCCR5NH2端的特异性抗体。结论：这一简捷快速的特定功能结构域抗体F(ab′)2的制备方法，对研究该基因在体内的表达及生物学功能提供了重要的实验材料，同时也对超基因家族中亚家族特异抗体研制提供了一种研究思路和方法。     

抗人肝癌mAbHAb18F(ab′)2半成品的制备与质量控制

目的制备符合人用标准的抗人肝癌mAbHAb18F(ab′)2 片段。方法用胃蛋白酶消化经硫酸铵盐析的腹水抗体 ,然后在快速蛋白液相色谱(FPLC)上用Phenyl SepharoseHP疏水柱纯化并进行质检。结果经Phenyl SepharoseHP疏水柱纯化后 ,F(ab′)2 片段的纯度可达98.8% ;回收率大于50 % ;免疫活性为1∶8000;细菌、热原质检测均呈阴性。结论本制备工艺周期短、易于质控 ,适宜进行中试放大及半成品生产。     

中和性马抗体对SARS-CoV感染的防治作用

目的探讨马抗SARSCoV中和性抗体是否对SARSCoV感染有防治作用。方法用SARSCoV(BJ01株)免疫马匹,从免疫马血清中制备IgGs及其F(ab’)2片段。通过细胞病变法(CPE)、MTT法和空斑形成实验(PFU)等方法,在体外培养的VeroE6细胞中检测F(ab’)2片段对SARSCoV感染的预防性和治疗性作用。再在Balb/c小鼠体内模型中,用CPE法和定量RTPCR方法检测该抗体的保护性效应。结果CPE、MTT和PFU三种方法证实来自三匹马的血清F(ab’)2的中和滴度均达到1∶1600以上。体内实验证实,50μg的F(ab’)2片段可以完全中和1×104TCID50SARSCoV。结论马抗SARSCoV抗体在体内外均能有效地中和SARSCoV和预防其感染宿主细胞,为马抗体将来在大的灵长类动物或人体内进行实验提供实验依据。     

~(131)I标记抗胃癌单克隆抗体(MG_7)在荷人胃癌裸鼠体内的分布及显像研究

本文观察~(131)I标记的抗胃癌的MG_7-McAb及其片段在移植人胃癌或结肠癌裸鼠体内的生物学分布及放射免疫显像。MG_7抗体在结肠癌(无关肿瘤)移植片中无明显定位分布,静脉注射4只鼠的六种主要脏器及体液的肿瘤与非肿瘤比活性比值(T/NT)平均为1:32。该抗体及其片段在胃癌移植片中有明显定位浓集,其中F(ab’)_2段的浓集量(T/NT=4.9)大于全抗体(T/NT=3.0)。注射标记McAb后48～72h作放射免疫显像可见肿瘤的阳性图像,胃癌移植     

抗SARS-CoV免疫球蛋白F(ab′)_2治疗性抗体对SARS-CoVBJ-01株的中和作用

目的观察马抗SARS-CoV免疫球蛋白F(ab′)2治疗性抗体对SARS-CoVBJ-01毒株的中和作用。方法采用细胞病变法(cytopathiceffect,CPE)、四甲基偶氮唑盐(methylthiazolyltetrazoliumassay,MTT)测定马抗SARS-CoV免疫球蛋白F(ab′)2对SARS-CoVBJ-01株的中和作用。结果三批马抗SARS-CoV免疫球蛋白F(ab′)2对SARS-CoVBJ-01株有很好的中和作用,CPE和MTT法测得中和效价分别为1∶6400、1∶6400、1∶12800。结论研制的马抗SARS-CoV免疫球蛋白F(ab′)2对SARS-CoVBJ-01株有很好的中和作用,并且两种方法结果一致,为SARS的治疗提供了可靠的依据。     

Autoantibodies to calcium channels in type 1 diabetes mediate autonomic dysfunction by different mechanisms in colon and bladder and are neutralized by antiidiotypic antibodies

Autoantibodies (Abs) directed against L-type voltage-gated calcium channels (VGCCs) have been shown to contribute to autonomic dysfunction of the gastrointestinal tract and bladder in patients with Type 1 diabetes mellitus (T1D). We used a passive transfer model to determine whether the functional activity of the Ab requires crosslinking of channels in colon and bladder and can be neutralized by intravenous immunoglobulin (IVIg). Mice were injected with mono- and divalent F(ab) fragments of patient IgG with anti-VGCC activity and tested for gut and bladder function using a colonic migrating motor complex (MMC) assay and bladder-filling cystometry. The ability of IVIg to neutralize anti-VGCC IgG-mediated autonomic dysfunction was investigated by injection of mice with an equimolar concentration of IVIg prior to T1D IgG injection, or by injection with T1D IgG passed over a sepharose 4B column coupled with F(ab')(2) from IVIg. Passive transfer of T1D IgG and its F(ab')(2) or F(ab) fragments reduced the amplitude of spontaneous colonic motility. In contrast, intact IgG and F(ab')(2,) but not F(ab), produced the urodynamics features of an overactive bladder. T1D IgG-mediated colonic and bladder dysfunction was neutralized in vivo by prior injection of animals with equimolar IVIg. Moreover, anti-VGCC activity was depleted by preabsorption of patient IgG on a IVIg F(ab')(2) column. The activity of anti-VGCC IgG is mediated by the antigen-binding site consistent with a true functional Ab. The pathogenic effect on the bladder requires crosslinking of the channel, whereas monovalent binding of Ab is sufficient for disruption of colon motility. The anti-VGCC Abs are neutralized by antiidiotypic antibodies present in IVIg that may prevent the emergence of these Abs in healthy individuals.     

An investigation into the mechanism of protection by local passive immunization with monoclonal antibodies against Streptococcus mutans.

Local oral passive immunization with Streptococcus mutans-specific monoclonal antibody (MAb) (Guy's 13) prevented recolonization by indigenous S. mutans in human volunteers who had first been treated with a conventional antibacterial agent (chlorhexidine). The F(ab')2 fragment of the MAb was as protective as the intact immunoglobulin G, but the Fab fragment of the molecule failed to prevent recolonization of S. mutans. In subjects receiving the MAb Fab fragment, S. mutans levels in dental plaque and saliva reappeared at a similar rate to that found in sham-immunized subjects who received either saline or a nonprotective MAb. In vitro, MAb had no bacteriostatic or bacteriocidal effect on S. mutans. However, S. mutans grown in the presence of either intact immunoglobulin G MAb or the F(ab')2 fragment formed very long chains, which resulted in clumping of the cells. S. mutans grown with either saline or the MAb Fab fragment formed significantly shorter chains, more characteristic of streptococcal growth in liquid media. The results suggest that the two binding sites of the MAb molecule may be an essential feature for preventing streptococcal colonization but that the ability to bind to phagocytes and activate complement which resides in the Fc fragment is not essential. Protection against colonization by S. mutans lasting up to 2 years was observed in immunized subjects, although MAb was applied over a period of only 3 weeks. Furthermore, functional MAb was detected up to 3 days following application of MAb to the teeth. The long-term protection could not be accounted for by a persistence of MAb on the tooth surface, and we have suggested that it may be due to a shift in the balance of the oral flora which discouraged recolonization by S. mutans. However, examination of the proportions of Streptococcus sanguis and veillonella species in the recolonization experiments failed to reveal a significant change in the proportions of either organism, which returned to approximately the preexperimental levels in both the immunized and control groups. These findings confirm the in vivo functional specificity of the MAb to S. mutans but are not consistent with the suggestion that S. sanguis or veillonella take over the niche vacated by S. mutans, unless the shift in the proportion of these organisms cannot be detected by the method used.     

Identification and characterization of a Mycoplasma hyopneumoniae adhesin.

An adhesin of Mycoplasma hyopneumoniae was identified and characterized in this study. A monoclonal antibody (MAb), F2G5, and its F(ab')2 fragments inhibited the adherence of M. hyopneumoniae to porcine tracheal cilia, the natural targets to which the mycoplasma binds during infection. MAb F2G5 detected multiple bands, but predominantly recognized a 97-kDa (P97) protein of M. hyopneumoniae on immunoblots. Affinity chromatography, conducted with immobilized MAb F2G5, mainly purified P97. The purified proteins were able to bind to cilia and blocked the adherence of intact M. hyopneumoniae cells to cilia. Immunolabeling of mycoplasmas with MAb F2G5 under electron microscopy demonstrated that the proteins recognized by MAb F2G5 were located at the surface of the mycoplasma, predominantly on a surface fuzzy layer. These results indicate that P97 functions as an adhesin of M. hyopneumoniae. The N-terminal amino acid sequence of P97 did not have significant homology with any known bacterial or mycoplasmal adhesins, suggesting that P97 is a novel protein. The predominant proteins detected by MAb F2G5 in different strains varied in size, indicating that the antigen bearing the epitope for MAb F2G5 undergo intraspecies size variation. Antigenic variation of adhesins may be a pathogenic mechanism utilized by M. hyopneumoniae to evade the porcine immune system.     

Detection of human auto-anti-idiotypic antibodies (Ab2). I. Isolation and characterization of Ab2 in the serum of a ragweed immunotherapy-treated patient

This study documents, by means of both solid and liquid phase assays, the presence of anti-idiotypic antibodies (Ab2) in the serum of one allergic individual undergoing ragweed immunotherapy. Serum from this individual was collected and F(ab')2 fragments specific for ragweed antigen E (AgE) were prepared (Ab1). These AgE-specific F(ab')2 Ab1, following absorption with normal immunoglobulin, were studied for their capacity to specifically bind autologous Ab2. The binding of Ab1 to Ab2 was demonstrated to be inhibitable by ragweed AgE but not by another allergen (oak) to which the patient reacted. These findings demonstrate the presence and binding specificities of Ab2 in the serum of a ragweed immunotherapy patient and may serve as a model to study the role of Ab2 in the regulation of Ab1 in allergic patients.     

Immunization procedures for anti-idiotypic antibody induction in mice and rats

Anti-idiotypic antibodies (Ab2) mimicking antigens (Ags)-defined by antibodies (Ab1) directed to tumors or pathogens have elicited Ag-specific humoral, cellular and/or protective immunity in experimental animals and in humans. In immunizations of rodents with Ab1, factors such as animal species, form of Ab1 and choice of adjuvant are crucial for the successful induction of Ab2 as candidate vaccines against tumors and pathogens. Here we survey the outcome of 362 fusion events (each event representing one animal), using nine immunization schedules in mice and seven schedules in rats and including 10 different Ab1 directed against human tumor- and immunodeficiency virus (HIV-1)-associated Ags. Ab1 IgG or F(ab')2 were administered uncoupled or coupled to keyhole limpet hemocyanin (KLH). As adjuvants, complete and incomplete Freund's adjuvant (CFA/IFA), lipid A, aluminum hydroxide, TiterMax or vaccinia virus were used. In syngeneic immunizations with murine Ab1 in mice, F(ab')2 coupled to KLH and emulsified in CFA/IFA preferentially induced Ab2 mimicking tumor or HIV-1 associated epitopes. In xenogeneic immunizations with mouse Ab1 in rats, various forms of Ab1 and adjuvants successfully induced Ab2 mimicking tumor Ags.     

Activation and proliferation signals in mouse B cells. V.A. comparison of the effects of intact (IgG) and F (ab')2 anti-mu or anti-delta antibodies.

This study compares the effects of soluble intact (IgG) and F(ab')2 rabbit anti-mu and anti-delta antibodies on mouse B cells. The results show that while the F(ab')2 antibodies to both isotypes induce polyclonal B cell proliferation, the IgG antibodies are not mitogenic, but rather inhibit DNA synthesis induced by the homologous F(ab')2 fragments. Furthermore, intact anti-mu antibodies inhibit mitogenesis induced by F(ab')2 anti-delta, and vice versa. However, the intact antibodies to both isotypes promote early changes characteristic of B-cell activation, namely, increased Ia antigen expression, and priming for a facilitated proliferative response to F(ab')2 anti-Ig. In addition, F(ab')2 anti-mu and anti-delta both induce the breakdown of phosphatidylinositol phospholipids in B cells, an early consequence of Ig receptor cross-linking which may be involved in the induction of cell growth. These results therefore indicate that stimulating mature B cells via IgM or IgD receptors produces indistinguishable early effects, and that cross-linking Fc and surface Ig receptors by intact anti-Ig generates a dominant inhibitory signal, regardless of which isotype is involved.     

A new monoclonal antibody reactive with several Ly49 NK cell receptors mediates redirected lysis of target cells

We produced a novel hamster monoclonal antibody (MAb), 14B11, that recognizes the majority of mouse natural-killer (NK) cells. Transfection studies demonstrated that 14B11 MAb binds a subset of Ly49 receptors, including three putative inhibitory receptors, Ly49F, I, and C. No binding to Ly49A, B, D, or G was detected. In addition, 14B11 was shown to bind the putative activating receptor Ly49H, which required co-transfection of the signaling molecule DAP12 for detectable cell surface expression. Thus, 14B11 is the first reported MAb to bind Ly49H and F. At the functional level, 14B11 MAb enhanced the lysis by IL-2 activated NK cells of an FcR+ target cell line (Daudi), but not an FcR- target cell (EL-4). Because F(ab')2 fragments of 14B11 failed to enhance lytic activity, the enhancement of lysis by intact antibody is apparently due to "redirected lysis," in which stimulatory receptors on the NK cell are bridged by antibody to Fc receptors on the target cell. Cell separation experiments demonstrated that the 14B11-dependent redirected lysis was markedly increased using NK cell populations that had been depleted of Ly49F,+ I,+ or C+ NK cells. Because such depletions are expected to enrich for Ly49H+ NK cells, these results suggest that the enhancement of lysis mediated by 14B11 MAb may be due to stimulation of the activating Ly49H receptor. In conjunction with other anti-Ly49 MAbs, the 14B11 MAb will be useful in further studies of Ly49 receptor function and specificity.     

Detection and enumeration of immunoglobulin secreting cells

A method is described in which sheep red blood cells (SRBC) are coated with anti-immunoglobulin (Ig) antibodies (Ab) for use in reverse hemolytic plaque assays (RHPA) as follows. The non-complement fixing F(ab')2 fragments of rabbit anti-mouse Ig Ab are derivatized with the N-hydroxysuccinimide ester of palmitate. The hydrophobic palmitate tails spontaneously insert into the SRBC membranes, thus coating the cells with anti-Ig F(ab')2 molecules. The SRBC are lysed by successive additions of mouse Ig, rabbit anti-mouse Ig and complement. When this procedure is carried out in agar gel, Ig-secreting mouse cells produce localized hemolytic areas (plaques). The procedure is more reproducible and more sensitive than RHPA performed with protein A-coated SRBC. In principle, this procedure should be adaptable to the detection of cells secreting any molecule for which specific antibodies are available.     

Immunotherapy of murine leukemia. IX. The requirement for the Fc portion of antibody for successful passive serum therapy of Friend leukemia virus-induced disease

The possible role of an antibody-dependent cellular cytotoxicity (ADCC)-type mechanism in the passive serum therapy of Friend leukemia virus (FLV)-induced erythroleukemia has been investigated by determining whether successful serum protection requires an intact Fc portion on the administered antibody. F(ab')2 fragments of IgG extracted from chimpanzee anti-FLV and goat anti-FLV gp71 antisera were prepared and compared with whole serum and uncleaved IgG for their capacity to protect DBA/2 mice against challenge with leukemogenic dose of FLV. Despite demonstrating in vitro virus neutralizing activity equivalent to that seen with antiviral serum or IgG, the virus-specific F(ab')2 preparations were devoid of protective activity. Given that passively administered F(ab')2 of goat origin have been reported to persist at stable levels in the mouse circulation, the failure of these F(ab')2 preparations to protect against virus challenge cannot be ascribed to rapid clearance from the treated animals. These results indicate that the passive serum therapy of FLV-induced disease is Fc dependent, consistent with the involvement of an ADCC-type mechanism, as well as confirming the previous suggestion that virus neutralization does not represent the sole mechanism of serum protection in this system.