Comparative stability and analytical performance of anti-miroestrol recombinant antibody in different cassettes.

Immunoassays are efficient for the phytochemical analysis of various matrices. However, producing an appropriate recombinant antibody for small molecules is challenging, resulting in costly analyses. In this study, we aimed to develop recombinant fragment antigen-binding (Fab) antibodies against miroestrol, a potent phytoestrogen marker of Pueraria candollei. Two expression cassettes of Fab were established for the production of active Fab antibodies using SHuffle® T7 Escherichia coli cells. The orientation of variable fragment heavy chain (VH) and variable fragment light chain (VL) in the expression vector constructs influences the reactivity, stability, and binding specificity of the resultant Fab. Stability testing of antibodies demonstrated that Fab is a more stable form of recombinant antibody than a single-chain variable fragment (ScFv) antibody in all conditions. Based on the obtained Fab, the ELISA specifically detected miroestrol in the range of 39.06-625.00 ng/mL. The intra- and inter-assay precisions were 0.74-2.98% and 6.57-9.76%, respectively. The recovery of authentic miroestrol spiked into samples was 106.70-110.14%, and the limit of detection was 11.07 ng/mL. The results for P. candollei roots and products determined using our developed ELISA with Fab antibody and an ELISA with anti-miroestrol monoclonal antibody (mAb) were consistent (R2 = 0.9758). The developed ELISA can be applied for the quality control of miroestrol derived from P. candollei. Therefore, the appropriate expression platform of Fab resulted in the stable binding specificity of the recombinant antibody and was applicable for immunoassays.Key points• ELISAs with Fab has higher sensitivity than that with ScFv.• Fab is more stable than ScFv.• Fab-based ELISA can be used for miroestrol determination of Pueraria candollei.

Different expression systems resulted in varied binding properties of anti-paclitaxel single-chain variable fragment antibody clone 1C2.

The binding properties of recombinant antibody fragments, such as affinity and specificity, determine their usefulness for therapeutic and analytical applications. Anti-paclitaxel single-chain variable fragment clone 1C2 (anti-PT scFv1C2) was expressed using Escherichia coli cell and Bombyx mori larvae expression systems. The binding characteristics of the scFvs were evaluated using indirect competitive ELISA. The linear range of binding between anti-PT scFv1C2 and paclitaxel was significantly different between the anti-PT scFv1C2s derived from E. coli (1.056-5.700 µg/ml) and B. mori (7.813-1000 ng/ml), which indicated that different expression systems resulted in different sensitivities for paclitaxel determination. In addition, the binding specificity of anti-PT scFv1C2 varied between expression systems. This finding implied that the expression system significantly affects the binding properties of recombinant antibodies, especially antibodies against low-molecular-weight targets.

Therapeutic treatment with scFv-PLGA nanoparticles decreases pulmonary fungal load in a murine model of paracoccidioidomycosis.

Paracoccidioidomycosis (PCM) is a systemic mycosis with lymphatic dissemination that is caused by Paracoccidioides species. Treatment of PCM consists of chemotherapeutics such as itraconazole, trimethoprim, sulfamethoxazole or amphotericin B. However, several studies are aiming to develop therapeutic alternatives for the treatment of fungal infection using new molecules as adjuvants. The single-chain variable fragments (scFv) from an antibody that mimics the main fungal component incorporated within poly(lactide-co-glycolic) acid (PLGA) nanoparticles helped treat the fungal disease. After expressing the scFv in Picchia pastoris (P. pastoris), the recombinant molecules were coupled with PLGA, and the BALB/c mice were immunized before or after infection with yeast Paracoccidioides brasiliensis (P. brasiliensis). Our results showed decreased disease progression and decreased fungal burden. Taken together, our results showed an increased of IFN-γ and IL-12 cytokine production and an increased number of macrophages and dendritic cells in the pulmonary tissue of BALB/c mice treated with a high concentration of our molecule. Our data further confirm that the scFv plays an important role in the treatment of experimental PCM.

Human scFv antibodies (Afribumabs) against Africanized bee venom: Advances in melittin recognition.

Africanized Apis mellifera bees, also known as killer bees, have an exceptional defensive instinct, characterized by mass attacks that may cause envenomation or death. From the years 2000-2013, 77,066 bee accidents occurred in Brazil. Bee venom comprises several substances, including melittin and phospholipase A2 (PLA2). Due to the lack of antivenom for bee envenomation, this study aimed to produce human monoclonal antibody fragments (single chain fragment variable; scFv), by using phage display technology. These fragments targeted melittin and PLA2, the two major components of bee venom, to minimize their toxic effects in cases of mass envenomation. Two phage antibody selections were performed using purified melittin. As the commercial melittin is contaminated with PLA2, phages specific to PLA2 were also obtained during one of the selections. Specific clones for melittin and PLA2 were selected for the production of soluble scFvs, named here Afribumabs: prefix: afrib- (from Africanized bee); stem/suffix: -umab (fully human antibody). Afribumabs 1 and 2 were tested in in vitro and in vivo assays to assess their ability to inhibit the toxic actions of purified melittin, PLA2, and crude bee venom. Afribumabs reduced hemolysis caused by purified melittin and PLA2 and by crude venom in vitro and reduced edema formation in the paws of mice and prolonged the survival of venom-injected animals in vivo. These results demonstrate that Afribumabs may contribute to the production of the first non-heterologous antivenom treatment against bee envenomation. Such a treatment may overcome some of the difficulties associated with conventional immunotherapy techniques.

Expression of anti-tumor necrosis factor alpha (TNFα) single-chain variable fragment (scFv) in Spirodela punctata plants transformed with Agrobacterium tumefaciens.

Therapeutic antibodies against tumor necrosis factor alpha (TNFα) have been considered effective for some of the autoimmune diseases such as rheumatoid arthritis, Crohn's diseases, and so on. But associated limitations of the current therapeutics in terms of cost, availability, and immunogenicity have necessitated the need for alternative candidates. Single-chain variable fragment (scFv) can negate the limitations tagged with the anti-TNFα therapeutics to a greater extent. In the present study, Spirodela punctata plants were transformed with anti-TNFα through in planta transformation using Agrobacterium tumefaciens strain, EHA105. Instead of cefotaxime, garlic extract (1 mg/mL) was used to remove the agrobacterial cells after cocultivation. To the best of our knowledge, this report shows for the first time the application of plant extracts in transgenic plant development. 95% of the plants survived screening under hygromycin. ScFv cDNA integration in the plant genomic DNA was confirmed at the molecular level by PCR. The transgenic protein expression was followed up to 10 months. Expression of scFv was confirmed by immunodot blot. Protein expression levels of up to 6.3% of total soluble protein were observed. ß-Glucuronidase and green fluorescent protein expressions were also detected in the antibiotic resistant plants. The paper shows the generation of transgenic Spirodela punctuata plants through in planta transformation.

Llama nanoantibodies with therapeutic potential against human norovirus diarrhea.

Noroviruses are a major cause of acute gastroenteritis, but no vaccines or therapeutic drugs are available. Llama-derived single chain antibody fragments (also called VHH) are small, recombinant monoclonal antibodies of 15 kDa with several advantages over conventional antibodies. The aim of this study was to generate recombinant monoclonal VHH specific for the two major norovirus (NoV) genogroups (GI and GII) in order to investigate their potential as immunotherapy for the treatment of NoV diarrhea. To accomplish this objective, two llamas were immunized with either GI.1 (Norwalk-1968) or GII.4 (MD2004) VLPs. After immunization, peripheral blood lymphocytes were collected and used to generate two VHH libraries. Using phage display technology, 10 VHH clones specific for GI.1, and 8 specific for GII.4 were selected for further characterization. All VHH recognized conformational epitopes in the P domain of the immunizing VP1 capsid protein, with the exception of one GII.4 VHH that recognized a linear P domain epitope. The GI.1 VHHs were highly specific for the immunizing GI.1 genotype, with only one VHH cross-reacting with GI.3 genotype. The GII.4 VHHs reacted with the immunizing GII.4 strain and showed a varying reactivity profile among different GII genotypes. One VHH specific for GI.1 and three specific for GII.4 could block the binding of homologous VLPs to synthetic HBGA carbohydrates, saliva, and pig gastric mucin, and in addition, could inhibit the hemagglutination of red blood cells by homologous VLPs. The ability of Nov-specific VHHs to perform well in these surrogate neutralization assays supports their further development as immunotherapy for NoV treatment and immunoprophylaxis.

The protective effects and underlying mechanism of an anti-oligomeric Aß42 single-chain variable fragment antibody.

Oligomeric Aß42 aggregates have been identified as one of the major neurotoxic components of Alzheimer's disease (AD). Immunotherapy targeted against these Aß42 aggregates has been proposed as an appropriate therapeutic approach for the treatment of AD. Here, we report an anti-oligomeric Aß42 single-chain variable fragment (scFv) antibody, named MO6, obtained from the human antibody library of a healthy donor. ScFv MO6 specifically recognized and bound to the oligomeric Aß42 (Aß42 oligomers and immature protofibrils; 18-37 kDa), and reduced their levels mainly by blocking their formation, although scFv MO6 also induced disaggregation of Aß42 aggregates. More importantly, scFv MO6 ameliorated or attenuated Aß42-induced cytotoxicity and increased cell viability by up to 33%. Furthermore, scFv MO6 efficiently passed through an in vitro blood-brain barrier (BBB) model with a delivery efficiency of 66% after 60 min post-administration. ScFv MO6 is a monovalent antibody with an affinity constant (KD) of 5.2×10(-6) M for Aß42 oligomers. Molecular docking simulations of Aß42 to scFv MO6 revealed that the approach and specific binding of scFv MO6 to oligomeric Aß42 aggregates was achieved by conformational recognition and directed induction, which resulted in a more dynamic adaptation of Aß42 to scFv MO6, occurring mainly in the N-terminal (3-4), middle (12-19) and C-terminal (34-42) regions of Aß42. This binding mode of scFv MO6 to Aß42 explains its protective effects against oligomeric Aß42. Our findings may be applied for the design of a smaller antibody specific for Aß42 oligermers.

High-density IgE recognition of the major grass pollen allergen Phl p 1 revealed with single-chain IgE antibody fragments obtained by combinatorial cloning.

The timothy grass pollen allergen Phl p 1 belongs to the group 1 of highly cross-reactive grass pollen allergens with a molecular mass of ∼25-30 kDa. Group 1 allergens are recognized by >95% of grass pollen allergic patients. We investigated the IgE recognition of Phl p 1 using allergen-specific IgE-derived single-chain variable Ab fragments (IgE-ScFvs) isolated from a combinatorial library constructed from PBMCs of a grass pollen-allergic patient. IgE-ScFvs reacted with recombinant Phl p 1 and natural group 1 grass pollen allergens. Using synthetic Phl p 1-derived peptides, the binding sites of two ScFvs were mapped to the N terminus of the allergen. In surface plasmon resonance experiments they showed comparable high-affinity binding to Phl p 1 as a complete human IgE-derived Ab recognizing the allergens' C terminus. In a set of surface plasmon resonance experiments simultaneous allergen recognition of all three binders was demonstrated. Even in the presence of the three binders, allergic patients' polyclonal IgE reacted with Phl p 1, indicating high-density IgE recognition of the Phl p 1 allergen. Our results show that multiple IgE Abs can bind with high density to Phl p 1, which may explain the high allergenic activity and sensitizing capacity of this allergen.

Multiple independent IgE epitopes on the highly allergenic grass pollen allergen Phl p 5.

BACKGROUND: Group 5 allergens are small proteins that consist of two domains. They belong to the most potent respiratory allergens. OBJECTIVE: To determine the binding sites and to study allergic patients' IgE recognition of the group 5 allergen (Phl p 5) from timothy grass pollen using human monoclonal IgE antibodies that have been isolated from grass pollen allergic patients. METHODS: Using recombinant isoallergens, fragments, mutants and synthetic peptides of Phl p 5, as well as peptide-specific antibodies, the interaction of recombinant human monoclonal IgE and Phl p 5 was studied using direct binding and blocking assays. Cross-reactivity of monoclonal IgE with group 5 allergens in several grasses was studied and inhibition experiments with patients' polyclonal IgE were performed. RESULTS: Monoclonal human IgE showed extensive cross-reactivity with group 5 allergens in several grasses. Despite its small size of 29 kDa, four independent epitope clusters on isoallergen Phl p 5.0101, two in each domain, were recognized by human IgE. Isoallergen Phl p 5.0201 carried two of these epitopes. Inhibition studies with allergic patients' polyclonal IgE suggest the presence of additional IgE epitopes on Phl p 5. CONCLUSIONS & CLINICAL RELEVANCE: Our results reveal the presence of a large number of independent IgE epitopes on the Phl p 5 allergen explaining the high allergenic activity of this protein and its ability to induce severe allergic symptoms. High-density IgE recognition may be a general feature of many potent allergens and form a basis for the development of improved diagnostic and therapeutic procedures in allergic disease.

Towards effective and safe thrombolysis and thromboprophylaxis: preclinical testing of a novel antibody-targeted recombinant plasminogen activator directed against activated platelets.

RATIONALE: Fibrinolysis is a valuable alternative for the treatment of myocardial infarction when percutaneous coronary intervention is not available in a timely fashion. For acute ischemic stroke, fibrinolysis is the only treatment option with a very narrow therapeutic window. Clinically approved thrombolytics have significant drawbacks, including bleeding complications. Thus their use is highly restricted, leaving many patients untreated. OBJECTIVE: We developed a novel targeted fibrinolytic drug that is directed against activated platelets. METHODS AND RESULTS: We fused single-chain urokinase plasminogen activator (scuPA) to a small recombinant antibody (scFvSCE5), which targets the activated form of the platelet-integrin glycoprotein IIb/IIIa. Antibody binding and scuPA activity of this recombinant fusion protein were on par with the parent molecules. Prophylactic in vivo administration of scFvSCE5-scuPA (75 U/g body weight) prevented carotid artery occlusion after ferric chloride injury in a plasminogen-dependent process compared with saline (P<0.001), and blood flow recovery was similar to high-dose nontargeted urokinase (500 U/g body weight). Tail bleeding time was significantly prolonged with this high dose of nontargeted urokinase, but not with equally effective targeted scFvSCE5-scuPA at 75 U/g body weight. Real-time in vivo molecular ultrasound imaging demonstrates significant therapeutic reduction of thrombus size after administration of 75 U/g body weight scFvSCE5-scuPA as compared with the same dose of a mutated, nontargeting scFv-scuPA or vehicle. The ability of scFvSCE5-scuPA to lyse thrombi was lost in plasminogen-deficient mice, but could be restored by intravenous injection of plasminogen. CONCLUSIONS: Targeting of scuPA to activated glycoprotein IIb/IIIa allows effective thrombolysis and the potential novel use as a fibrinolytic agent for thromboprophylaxis without bleeding complications.

Generation of a nanobody targeting the paraflagellar rod protein of trypanosomes.

Trypanosomes are protozoan parasites that cause diseases in humans and livestock for which no vaccines are available. Disease eradication requires sensitive diagnostic tools and efficient treatment strategies. Immunodiagnostics based on antigen detection are preferable to antibody detection because the latter cannot differentiate between active infection and cure. Classical monoclonal antibodies are inaccessible to cryptic epitopes (based on their size-150 kDa), costly to produce and require cold chain maintenance, a condition that is difficult to achieve in trypanosomiasis endemic regions, which are mostly rural. Nanobodies are recombinant, heat-stable, small-sized (15 kDa), antigen-specific, single-domain, variable fragments derived from heavy chain-only antibodies in camelids. Because of numerous advantages over classical antibodies, we investigated the use of nanobodies for the targeting of trypanosome-specific antigens and diagnostic potential. An alpaca was immunized using lysates of Trypanosoma evansi. Using phage display and bio-panning techniques, a cross-reactive nanobody (Nb392) targeting all trypanosome species and isolates tested was selected. Imunoblotting, immunofluorescence microscopy, immunoprecipitation and mass spectrometry assays were combined to identify the target recognized. Nb392 targets paraflagellar rod protein (PFR1) of T. evansi, T. brucei, T. congolense and T. vivax. Two different RNAi mutants with defective PFR assembly (PFR2RNAi and KIF9BRNAi) were used to confirm its specificity. In conclusion, using a complex protein mixture for alpaca immunization, we generated a highly specific nanobody (Nb392) that targets a conserved trypanosome protein, i.e., PFR1 in the flagella of trypanosomes. Nb392 is an excellent marker for the PFR and can be useful in the diagnosis of trypanosomiasis. In addition, as demonstrated, Nb392 can be a useful research or PFR protein isolation tool.

Expression and purification of a novel therapeutic single-chain variable fragment antibody against BNP from inclusion bodies of Escherichia coli.

Abnormal brain natriuretic peptide (BNP) secretion is regarded as the dominating mechanism of cerebral salt wasting syndrome (CSW), which results from a renal loss of sodium and water during intracranial disease leading to hyponatremia. Scale preparation of therapeutic single-chain variable fragment (scFv) that can neutralize elevated circulating BNP may have potential value for clinical use. In this report, we used a recently isolated humanized anti-BNP scFv fragment (3C1) as model antibody (Ab) to evaluate the potential of scale production of this therapeutic protein. The truncated gene encoding for scFv fragment cloned in pET22b (+) was mainly overexpressed as inclusion bodies in Escherichia coli (E. coli) Rosetta (DE3) pLysS cells. The insoluble fragment was solubilized and purified by Ni-NTA agarose resin under denaturation conditions, and recovered via an effective refolding buffer containing 50 mM Tris-HCl, pH 8.0, 0.15 M NaCl, 1 mM EDTA, 0.5 M arginine, 2 mM GSH, 1 mM GSSG, and 5% glycerol. The refolded scFv fragment was concentrated by PEG20000, and dialyzed in PBS (containing 5% glycerol, pH 7.4). The final yield was approximately 10.2 mg active scFv fragment per liter of culture (3.4 g wet weight cells). The scFv fragment was more than 95% pure assessed by SDS-PAGE assay. Recombinant scFv fragment with His tag displayed its immunoreactivity with anti-His tag Ab by western blotting. ELISA showed the scFv fragment specifically bound to BNP, and it displayed similar activity as the traditional anti-BNP monoclonal Ab (mAb). Thus, the current strategy allows convenient small-scale production of this therapeutic protein.

Delayed targeting of CD39 to activated platelet GPIIb/IIIa via a single-chain antibody: breaking the link between antithrombotic potency and bleeding?

The ecto-nucleoside triphosphate diphosphohydrolase CD39 represents a promising antithrombotic therapeutic. It degrades adenosine 5'-diphosphate (ADP), a main platelet activating/recruiting agent. We hypothesized that delayed enrichment of CD39 on developing thrombi will allow for a low and safe systemic concentration and thus avoid bleeding. We use a single-chain antibody (scFv, specific for activated GPIIb/IIIa) for targeting CD39. This should allow delayed enrichment on growing thrombi but not on the initial sealing layer of platelets, which do not yet express activated GPIIb/IIIa. CD39 was recombinantly fused to an activated GPIIb/IIIa-specific scFv (targ-CD39) and a nonfunctional scFv (non-targ-CD39). Targ-CD39 was more effective at preventing ADP-induced platelet activation than non-targ-CD39. In a mouse carotid artery thrombosis model, non-targ-CD39, although protective against vessel occlusion, was associated with significant bleeding on tail transection. In contrast, targ-CD39 concentrated at the thrombus site; hence, a dose ∼10 times less of CD39 prevented vessel occlusion to a similar extent as high-dose non-targ-CD39, without prolonged bleeding time. An equimolar dose of non-targ-CD39 at this low concentration was ineffective at preventing vessel occlusion. Thus, delayed targeting of CD39 via scFv to activated platelets provides strong antithrombotic potency and yet prevents bleeding and thereby promotes CD39 toward clinical use.

Determination of allergen specificity by heavy chains in grass pollen allergen-specific IgE antibodies.

BACKGROUND: Affinity and clonality of allergen-specific IgE antibodies are important determinants for the magnitude of IgE-mediated allergic inflammation. OBJECTIVE: We sought to analyze the contribution of heavy and light chains of human allergen-specific IgE antibodies for allergen specificity and to test whether promiscuous pairing of heavy and light chains with different allergen specificity allows binding and might affect affinity. METHODS: Ten IgE Fabs specific for 3 non-cross-reactive major timothy grass pollen allergens (Phl p 1, Phl p 2, and Phl p 5) obtained by means of combinatorial cloning from patients with grass pollen allergy were used to construct stable recombinant single chain variable fragments (ScFvs) representing the original Fabs and shuffled ScFvs in which heavy chains were recombined with light chains from IgE Fabs with specificity for other allergens by using the pCANTAB 5 E expression system. Possible ancestor genes for the heavy chain and light chain variable region-encoding genes were determined by using sequence comparison with the ImMunoGeneTics database, and their chromosomal locations were determined. Recombinant ScFvs were tested for allergen specificity and epitope recognition by means of direct and sandwich ELISA, and affinity by using surface plasmon resonance experiments. RESULTS: The shuffling experiments demonstrate that promiscuous pairing of heavy and light chains is possible and maintains allergen specificity, which is mainly determined by the heavy chains. ScFvs consisting of different heavy and light chains exhibited different affinities and even epitope specificity for the corresponding allergen. CONCLUSION: Our results indicate that allergen specificity of allergen-specific IgE is mainly determined by the heavy chains. Different heavy and light chain pairings in allergen-specific IgE antibodies affect affinity and epitope specificity and thus might influence clinical reactivity to allergens.

Generation and functional characterization of the anti-transferrin receptor single-chain antibody-GAL4 (TfRscFv-GAL4) fusion protein.

BACKGROUND: The development of vectors for cell-specific gene delivery is a major goal of gene therapeutic strategies. Transferrin receptor (TfR) is an endocytic receptor and identified as tumor relative specific due to its overexpression on most tumor cells or tissues, and TfR binds and intakes of transferrin-iron complex. We have previously generated an anti-TfR single-chain variable fragments of immunoglobulin (scFv) which were cloned from hybridoma cell line producing antibody against TfR linked with a 20 aa-long linker sequence (G4S)4. In the present study, the anti-TfR single-chain antibody (TfRscFv) was fused to DNA-binding domain of the yeast transcription factor GAL4. The recombinant fusion protein, designated as TfRscFv-GAL4, is expected to mediate the entry of DNA-protein complex into targeted tumor cells. RESULTS: Fusion protein TfRscFv-GAL4 was expressed in an E. coli bacterial expression system and was recovered from inclusion bodies with subsequent purification by metal-chelate chromatography. The resulting proteins were predominantly monomeric and, upon refolding, became a soluble biologically active bifunctional protein. In biological assays, the antigen-binding activity of the re-natured protein, TfRscFv-GAL4, was confirmed by specific binding to different cancer cells and tumor tissues. The cell binding rates, as indicated by flow cytometry (FCM) analysis, ranged from 54.11% to 8.23% in seven different human carcinoma cell lines. It showed similar affinity and binding potency as those of parent full-length mouse anti-TfR antibody. The positive binding rates to tumor tissues by tissue microarrays (TMA) assays were 75.32% and 63.25%, but it showed weakly binding with hepatic tissue in 5 cases, and normal tissues such as heart, spleen, adrenal cortex blood vessel and stomach. In addition, the re-natured fusion protein TfRscFv-GAL4 was used in an ELISA with rabbit anti-GAL4 antibody. The GAL4-DNA functional assay through the GAL4 complementary conjugation with the GAL4rec-GFP-pGes plasmid to verify the GLA4 activity and GAL4rec-recognized specificity functions. It also shows the complex, TfRscFv-GAL4-GAL4rec-GFP-pGes, could be taken into endochylema to express the green fluorescent protein (GFP) with 8 to 10-fold transfection efficiency. CONCLUSIONS: Results of our study demonstrated that the biofunctianality of genetically engineered fusion protein, TfRscFv-GAL4, was retained, as the fusion protein could both carry the plasmid of GAL4rec-pGes and bind TfR on tumour cells. This product was able to transfect target cells effectively in an immuno-specific manner, resulting in transient gene expression. This protein that can be applied as an effective therapeutic and diagnostic delivery to the tumor using endogenous membrane transport system with potential widespread utility.

Targeted tumor therapy with a fusion protein of an antiangiogenic human recombinant scFv and yeast cytosine deaminase.

In adults, endothelial cell division occurs only in wound healing, during menstruation, or in diseases such as wet age-related macular degeneration or development of benign or malignant tissues. Angiogenesis is one of the major requirements to supply the fast developing tumor tissue with oxygen and nutrients, and enables it to spread into other tissues far from its origin. We selected the extradomain B (ED-B), a splice variant of fibronectin, which is exclusively expressed in ovaries, uterus, during wound healing, and in tumor tissues, as a target for the development of an innovative antiangiogenic, prodrug-based targeted tumor therapy approach. We designed a fusion protein termed L19CDy-His, consisting of the antibody single chain fragment L19 for targeting ED-B and yeast cytosine deaminase for the conversion of 5-fluorocytosine into cytotoxic 5-fluorouracil. We purified high amounts of the fusion protein from Pichia pastoris that is stable, enzymatically active, and retains 75% of its activity after incubation with human plasma for up to 72 hours. The binding of L19CDy-His to ED-B was confirmed by an enzyme-linked immunosorbent assay and quantified by surface plasmon resonance spectroscopy determining a KD value of 81±7 nM. L19CDy-His successfully decreased cell survival of the murine ED-B-expressing teratocarcinoma cell line F9 upon addition of the prodrug 5-fluorocytosine. Our data demonstrate the suitability of targeting ED-B by L19CDy-His for effective prodrug-based tumor therapy.

In vivo visualization and attenuation of oxidized lipid accumulation in hypercholesterolemic zebrafish.

Oxidative modification of LDL is an early pathological event in the development of atherosclerosis. Oxidation events such as malondialdehyde (MDA) formation may produce specific, immunogenic epitopes. Indeed, antibodies to MDA-derived epitopes are widely used in atherosclerosis research and have been demonstrated to enable cardiovascular imaging. In this study, we engineered a transgenic zebrafish with temperature-inducible expression of an EGFP-labeled single-chain human monoclonal antibody, IK17, which binds to MDA-LDL, and used optically transparent zebrafish larvae for imaging studies. Feeding a high-cholesterol diet (HCD) supplemented with a red fluorescent lipid marker to the transgenic zebrafish resulted in vascular lipid accumulation, quantified in live animals using confocal microscopy. After heat shock-induced expression of IK17-EGFP, we measured the time course of vascular accumulation of IK17-specific MDA epitopes. Treatment with either an antioxidant or a regression diet resulted in reduced IK17 binding to vascular lesions. Interestingly, homogenates of IK17-EGFP-expressing larvae bound to MDA-LDL and inhibited MDA-LDL binding to macrophages. Moreover, sustained expression of IK17-EGFP effectively prevented HCD-induced lipid accumulation in the vascular wall, suggesting that the antibody itself may have therapeutic effects. Thus, we conclude that HCD-fed zebrafish larvae with conditional expression of EGFP-labeled oxidation-specific antibodies afford an efficient method of testing dietary and/or other therapeutic antioxidant strategies that may ultimately be applied to humans.

The development of a high-yield recombinant protein bioreactor through RNAi induced knockdown of ATP/ADP transporter in Solanum tuberosum.

There is an increased need for high-yield protein production platforms to meet growing demand. Tuber-based production in Solanum tuberosum offers several advantages, including high biomass yield, although protein concentration is typically low. In this work, we investigated the question whether minor interruption of starch biosynthesis can have a positive effect on tuber protein content and/or tuber biomass, as previous work suggested that partial obstruction of starch synthesis had variable effects on tuber yield. To this end, we used a RNAi approach to knock down ATP/ADP transporter and obtained a large number of transgenic lines for screening of lines with improved tuber protein content and/or tuber biomass. The initial screening was based on tuber biomass because of its relative simplicity. We identified a line, riAATP1-10, with minor (less than 15%) reduction in starch, that had a nearly 30% increase in biomass compared to wild-type, producing both more and larger tubers with altered morphological features compared to wild-type. riAATP1-10 tubers have a higher concentration of soluble protein compared to wild-type tubers, with nearly 50% more soluble protein. We assessed the suitability of this line as a new bioreactor by expressing a human scFv, reaching over 0.5% of total soluble protein, a 2-fold increase over the highest accumulating line in a wild-type background. Together with increased biomass and increased levels in total protein content, foreign protein expression in riAATP1-10 line would translate into a nearly 4-fold increase in recombinant protein yield per plant. Our results indicate that riAATP1-10 line provides an improved expression system for production of foreign proteins.

Isolation of functional single domain antibody by whole cell immunization: implications for cancer treatment.

Carcinoembryonic antigen related cell adhesion molecule (CEACAM) 6 is over-expressed in different types of cancer cells. In addition, it has also been implicated in some infectious diseases. Targeting this molecule by an antibody might have applications in diverse tumor models. Single domain antibody (sdAb) is becoming very useful format in antibody engineering as potential tools for treating acute and chronic disease conditions such as cancer for both diagnostic as well as therapeutic application. Generally, sdAbs with good affinity are isolated from an immune library. Discovery of a new target antigen would require a new immunization with purified antigen which is not always easy. In this study, we have isolated, by phage display, an sdAb against CEACAM6 with an affinity of 5 nM from a llama immunized with cancer cells. The antibody has good biophysical properties, and it binds to the cells expressing the target antigen. Furthermore, it reduces cancer cells proliferation in vitro and shows an excellent tumor targeting in vivo. This sdAb could be useful in diagnosis as well as therapy of CEACAM6 expressing tumors. Finally, we envisage it would be feasible to isolate good sdAbs against other interesting tumor associated antigens from this library. Therefore, this immunization method could be a general strategy for isolating sdAbs against any surface antigen without immunizing the animal with the antigen of interest each time.

Single-chain variable fragment (scFv) antibodies optimized for environmental analysis of uranium.

Recombinant single-chain variable fragment antibodies (scFv) were specifically generated and selected for the measurement of environmental uranium with an antibody-based sensor. These sFvs, which recognized UO(2)(2+) complexed to 2,9-dicarboxyl-1,10-phenanthroline-acid (DCP), were produced using genetic material obtained from the spleen cells of rabbits immunized with UO(2)(2+)-DCP conjugated to keyhole limpet hemocyanin. Immunoglobulin light chain and heavy chain genes were amplified and cloned into the phagemid pSD3 for generation of a recombinant antibody library and phage-displayed antibodies. The screening process was designed to isolate antibodies that bound to a "loaded" noncovalent complex with high affinity, while selecting against binding to an "unloaded" complex. After five rounds of panning, individual positive scFv clones were used to infect E. coli TG1 and soluble scFv antibodies were purified and characterized. Binding studies showed that the best scFv bound tightly to the UO(2)(2+)-DCP complex (K(d), 19.6 nM). However, because of the depletion experiments performed on this library during the panning process, this scFv bound 1200-fold less tightly (K(d), 23.5 µM) to metal-free DCP. This scFv (clone 3A) was subsequently used to accurately determine the UO(2)(2+) concentrations in environmental water samples using a sensor based on kinetic exclusion analysis. The present studies demonstrate that recombinant scFvs with properties engineered for specific applications (i.e., biosensor-based measurement of metals in groundwater) can be prepared if the correct genetic material and techniques are employed. The phage display system permitted the generation of proteins with very specific binding properties (in this case, high affinity for a metal-chelate complex and low affinity for metal-free chelator). The recombinant scFvs isolated in these studies will be the basis for rapid and affordable assays for the detection of residual uranium in environmental water samples.