Designing and Development of a Tandem Bivalent Nanobody against VEGF165

Background:

Inhibition of angiogenesis using monoclonal antibodies is an effective strategy in cancer therapy. However, they could not penetrate sufficiently into solid tumors. Antibody fragments have solved this issue. However, they suffer from short in vivo half-life. In the current study, a tandem bivalent strategy was used to enhance the pharmacokinetic parameters of an anti-VEGF165 nanobody.

Methods:

Homology modeling and MD simulation were used to check the stability of protein. The cDNA was cloned into pHEN6C vector and the expression was investigated in WK6 Escherichia coli (E. coli) cells by SDS-PAGE and western blot. After purification, the size distribution of tandem bivalent nanobody was investigated by dynamic light scattering. Moreover, in vitro antiproliferative activity and pharmacokinetic study were studied in HUVECs and Balb/c mice, respectively.

Results:

RMSD analysis revealed the tandem bivalent nanobody had good structural stability after 50 ns of simulation. A hinge region of llama IgG2 was used to fuse the domains. The expression was induced by 1 mM IPTG at 25°C for overnight. A 30 kDa band in 12% polyacrylamide gel and nitrocellulose paper has confirmed the expression. The protein was successfully purified using metal affinity chromatography. MTT assay revealed there is no significant difference between the antiproliferative activity of tandem bivalent nanobody and the native protein. The hydrodynamic radius and terminal half-life of tandem bivalent nanobody increased approximately 2-fold by multivalency compared to the native protein.

Conclusion:

Our data revealed that the physicochemical as well as in vivo pharmacokinetic parameters of tandem bivalent nanobody was significantly improved.

A nanobody-derived mimotope against VEGF inhibits cancer angiogenesis

Vascular Endothelial Growth Factor (VEGF) promotes angiogenesis in tumours of various cancers. Monoclonal antibodies and nanobodies are one of the potent agents in the treatment of cancer. Due to their high costs, researchers are considering to design and produce peptides as a substitute approach in recent years. The aim of the current study was designing a mimotope against VEGF and evaluate its effects on cell proliferation and tube formation in the HUVEC cell line. For this, a peptide was designed against VEGF and chemically produced. The effects of synthetic peptide and nanobody on the inhibition of proliferation of HUVEC cells were examined using MTT and tube formation assays. The data indicate that the peptide was able to significantly inhibit both HUVEC cell proliferation and tube formation through inhibition of VEGF, highlighting the potential of peptides as a ‘novel’ class of candidate drugs to inhibit angiogenesis.

Isolation and characterization of nanobodies against epithelial cell adhesion molecule as novel theranostic agents for cancer therapy

Epithelial cell adhesion molecule (EpCAM) plays an important role in tumorigenesis. Camelids produce functional antibodies composed of heavy chains only that bind to their antigens via a single domain variable fragment known as nanobody. Nanobodies show multiple advantages over traditional monoclonal antibodies. Isolation of functional anti-EpCAM nanobodies (Nbs) was the main aim of this study. An immune nanobody library containing 10⁸ members was constructed previously. Anti -EpCAM nanobodies were isolated from camel immune library using phage display. Four consecutive rounds of biopanning were performed on immobilized EpCAM. Four nanobodies (Nb4, Nb5, Nb22, and Nb23) with highest signal intensity in monoclonal phage ELISA were selected. Affinity of these selected nanobodies for EpCAM was in the nanomolar range. Selected nanobodies significantly inhibited proliferation of MCF-7 cells. The in vivo study revealed that a significant reduction in tumor size occurred when treated with nanobodies Nb4 and Nb5, after 14 days monitoring. Our data revealed that nanobodies Nb4 and Nb5 could be considered as attractive theranostic agents for EpCAM overexpressing cancers.

In vitro combination therapy of pathologic angiogenesis using anti-vascular endothelial growth factor and anti-neuropilin-1 nanobodies

OBJECTIVES

Emergence of resistant tumor cells to the current therapeutics is the main hindrance in cancer treatment. Combination therapy, which mixes two or more drugs, is a way to overcome resistant problems of cancer cells to current treatments. Nanobodies are promising tools in cancer therapy due to their high affinity as well as high penetration to tumor sites.

MATERIALS AND METHODS

Here, the inhibitory effect of mixtures of two nanobodies (anti-vascular endothelial growth factor (VEGF) and anti-neuropilin-1 (NRP-1) nanobodies) on tube formation of human endothelial cells in vitro and ex vivo were analyzed.

RESULTS

Results showed that combination of two drugs significantly inhibited proliferation and tube formation of human endothelial cells. In addition, mixtures of two nanobodies inhibited angiogenesis in chick chorioallantoic membrane (CAM) assay efficiently compared with each individual nanobody.

CONCLUSION

Results highlight the efficacy of combination therapy of cancer compared with mono-therapy and promises development of novel anti-cancer therapeutics based on nanobodies targeting two or more targets of tumor cells.

Evaluation of Laboratory Application of Camelid Sera Containing Heavy-Chain Polyclonal Antibody Against Recombinant Cytotoxic T-Lymphocyte-Associated Protein-4

Cytotoxic T-lymphocyte-associated protein-4 (CTLA-4) is a critical negative immunomodulatory receptor that is normally expressed in activated T cells and noticeably, in many cancerous cells. Indeed, molecular detection of CTLA-4 protein is crucial in basic research. In this work, the extracellular domain of the human CTLA-4 (hCTLA-4) protein was cloned, expressed, and purified. Subsequently, this protein was used as an antigen for camel (Camelus dromedarius) immunization to obtain polyclonal camelid sera against this protein. Furthermore, we evaluated the benefits of applying camelid hyperimmune sera containing heavy-chain antibodies in different antibody-based techniques. Our results indicated that hCTLA-4 protein was successfully expressed in the prokaryotic system. The polyclonal antibody (pAb) that raised against recombinant hCTLA-4 protein was able to detect the CTLA-4 protein in antibody-based techniques, such as enzyme-linked immunosorbent assay, western blotting, flow cytometry and immunohistochemistry (IHC) staining. This study shows that, due to the advantages such as multi-epitope-binding ability, camelid pAbs are potent to efficiently apply for molecular detection of CTLA-4 receptors in fundamental antibody-based researches such as IHC.

Protective responses of an engineered PspA recombinant antigen against Streptococcus pneumoniae

•

In this study, two immunogenic antigens based on recombinant PspA proteins were immunized mice.

•

The protective effects of developed anti-PspA antibodies in mice in intranasal and intraperitoneal challenges were proved.

•

Based on the obtained results, immunization with the B-regions of PspA antigens are crucial in protection of challenged mice with S. pneumoniae strains.

Streptococcus pneumoniae is a major pathogen in human respiratory tract which causes significant morbidity and mortality across from the world. Currently available vaccines are not completely effective and cannot cover all pathogenic strains so there is an important need to develop an alternative cost-effective vaccine, based on conserved protein antigens. Pneumococcal surface protein A (PspA) is one of interesting candidates for development of a serotype-independent vaccine against pneumococcal infections. PspA is grouped into two major families with five clades, and broad-reacting PspA-based vaccines should contain at least one functional fragment from each of the two families.

In this study, we developed two immunogenic antigens based on recombinant PspA proteins that including the different antigenic regions of PspA from both two families. The cross-reactivity of antibodies elicited against two PspA proteins PspAB1-5 and PspA₄ABC and their role in complement deposition with three strains of pneumococci were tested. The protective effects of developed anti-PspA antibodies in mice in intranasal and intraperitoneal challenges were evaluated using a strain from clade 2. Sera from immunized mice with PspAB_1-5 in comparison with PspA₄ABC was able to deposit more C3 complement component on surface of pneumococci bearing diverse PspA from both families 1 and 2, and immunized mice with the PspAB_1-5 showed a higher protection than PspA₄ABC in pneumococcal challenges.

The obtained results from this study indicate that a PspA-based antigen composed of B region from all clades in addition to conserved domains, can provide a significant protection against multiple strains of S. pneumoniae and may overcome the limitation of polysaccharide vaccines.

Development of a mono-specific anti-VEGF bivalent nanobody with extended plasma half-life for treatment of pathologic neovascularization

Vascular endothelial growth factor (VEGF) plays a crucial role in angiogenesis within solid cancers. Thus, targeting VEGF might be part of a feasible therapy for treating pathological neovascularization, and nanobodies - derived from heavy chain-only antibodies occurring within Camelidae - are a novel class of nanometer-sized antibodies possessing unique properties that could be developed into a promising therapeutic. However, nanobodies have a very short half-life in vivo due to their small size. Development of a bivalent nanobody is one way to remediate the half-life problem of nanobodies. Two identical anti-VEGF nanobodies were connected using the hinge region of llama IgG2c. The recombinant plasmid (pHEN6c-bivalent nanobody) was transformed into E.coli WK6 cells and expression of the bivalent nanobody construct was induced with 1mM Isopropyl β-D-1-thiogalactopyranoside (IPTG). Recombinant bivalent nanobody was purified using nickel affinity chromatography and its activity on human endothelial cells was assessed using 3-(4,5-Dimethylthiazol-2-yr)-2,5-diphenyltetrazolium bromide (MTT), tube formation, and cell migration assays. The pharmacokinetic study was performed after intravenous (i.v.) injection of recombinant bivalent nanobody into six-week-old C57BL/6 mice. Recombinant bivalent nanobody performed significantly better than monovalent nanobody in inhibiting proliferation, tube formation, and migration of human endothelial cells. Pharmacokinetic results showed a 1.8-fold longer half-life of bivalent nanobody in comparison with the monovalent nanobody. These results underscore the potential of recombinant anti-VEGF bivalent nanobody as a promising tool for development of a novel therapeutic with an extended plasma half-life for VEGF-related diseases.

Recombinant Expression of Zinc Transporter SLC39A6 and Its Functional Antibody Production

Zinc transporter ZIP6 (SLC39A6) or LIV-1 is a protein that belongs to a subfamily of proteins group that displays structural specifications of zinc transporters in the cell membrane. Overexpression of this protein is observed in breast, prostate, and kidney tumor cells. Lately, LIV-1 is a dependable marker for detection of estrogen receptor positive breast cancer, which can be used to detect luminal breast cancer type A. In this study, the gene construct containing extracellular domain of human LIV-1 gene was subcloned into pET22b expression vector, expressed and confirmed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis and western blotting. It was shown for the first time that the extracellular domain of LIV-1 could be expressed in bacterial systems and can be used for rabbit immunization. The reactivity of the resulted antibody was evaluated in flow cytometry and enzyme-linked immunosorbent assay. In conclusion, this protein can be used for animal immunization toward preparation of a new monoclonal antibody that can be introduced as a drug in the treatment of breast cancer.

Cell-specific targeting by engineered M13 bacteriophage expressing VEGFR2 nanobody

Objectives

Filamentous bacteriophage M13 was genetically engineered to specifically target mammalian cells for gene delivery purpose.

Materials and Methods

A vascular endothelial growth factor receptor 2 (VEGFR2)-specific nanobody was genetically fused to the capsid gene III of M13 bacteriophage (pHEN4/3VGR19). A mammalian expression construct containing Cop-green fluorescent protein (Cop-GFP), as a reporter gene, was amplified by PCR and then sub-cloned in the pHEN4/3VGR19 phagemid. The resulting construct was transfected into 293KDR cell. The recombinant phage was extracted and confirmed and then transduced into VEGFR2 expressing cell (293KDR).

Results

Seventy-two hr after transfection, green fluorescence was detected in 30% of the cells. About 1% of the cells which transduced by recombinant phages were able to express GFP.

Conclusion

It is hoped that the results from this study will help to find potential vectors to improve the efficiency of gene delivery. Taken together, we conclude that this newly-introduced vector can be used in cancer researches.

The inhibitory effect of the combination of two new peptides on biofilm formation by Acinetobacter baumannii

The emergence of extensively drug-resistant (XDR) Acinetobacter baumannii strains and the limited number of efficacious antibiotics demonstrate an urgent need to develop novel agents to treat infections caused by this dangerous pathogen. To find antimicrobial peptides against A. baumannii growing either in planktonic or in biofilm mode, biopanning was carried out with a peptide library on five XDR A. baumannii strains grown in the medium containing human blood (blood biopanning) and biofilms formed by these strains (biofilm biopanning). Two groups of peptides were identified, among which two peptides N10 (from blood biopanning) and NB2 (from biofilm biopanning) were selected and synthesized for more assessments. The selected peptides showed significant binding to A. baumannii rather than to the human cell line Caco-2. Both peptides were effective against A. baumannii and showed antibacterial activities (minimum inhibitory concentration (MIC) 500 μg/ml). In the biofilm inhibition assay, NB2 reduced biofilm more efficiently (75%) than N10 (50%). The combination of the two peptides could function better than each peptide alone to prevent biofilm formation by A. baumannii. Supplementation of conventional therapy with a mixture of peptides targeting A. baumannii or using peptides to deliver antibiotics specifically to the site of infection may be promising to control A. baumannii-related diseases.

An in-silico approach to find a peptidomimetic targeting extracellular domain of HER3 from a HER3 Nanobody

HER3 is an important therapeutic target in cancer treatments. HER3 Nanobodies (Nbs) are a novel class of antibodies with several competitive advantages over conventional antibodies. A peptidomimetic derived from these Nbs can be considered to be a small peptide mimicking some of the molecular recognition interactions of a natural peptide or protein in a three-dimensional (3D) space, with a receptor that has improved properties. In this study, we introduce a new approach to design a peptidomimetic derived from HER3 Nb through an in silico analysis. We propose that the complementarity determining region (CDR3) of HER3 Nb is large enough to effectively interact with HER3 antigen as well as with the entire Nb. A computational analysis has been performed using Nb models retrieved from SWISS-pdb Viewer 4.1.0 (spdbv) as a target spot and HER3 extracellular domain as its antigenic target to identify the interactions between them by the protein-protein docking method. Detailed analysis of selected models with docked complex help us to identify the interacting amino acid residues between the two molecules. The results of in silico analysis show that the CDR3 of HER3 Nb might be used by itself as a peptidomimetic drug instead of the full Nb. HER3 peptidomimetic-derived HER3 Nb may reduce Nb production costs and be used as a substitute for HER3 Nb after further experimental work. The paper demonstrates the feasibility of peptidomimetics designs using bioinformatic tools.

Antiadhesive and cytotoxic effect of Iranian Vipera lebetina snake venom on lung epithelial cancer cells

Background:

Cancer is one of the major health problems worldwide. Hence, finding potent therapeutics from natural sources seems necessary. Snake venom of Vipera lebetina contains potential component with anticancer activities such as antiproliferation, migration, invasion, adhesion, and angiogenesis effect. Evaluation of cytotoxic and antiadhesive effect of V. lebetina venom on lung epithelial cancer tumor cell (TC-1) was the main aim of this study.

Materials and Methods:

Here, we purified snake venom of V. lebetina by fast protein liquid chromatography (FPLC) using Sephacryl S-200 hr column. The fractions collected and evaluated by SDS-PAGE analysis. The cytotoxicity and antiadhesive effect of crude venom and fractions on TC-1 cells were demonstrated using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide and adhesion assay, respectively.

Results:

Our results showed six fractions in FPLC diagram. V. lebetina crude venom and fractions showed dose-dependent cytotoxic effect on TC-1 cells. Fractions 2 and 5 showed high cytotoxic effect with high IC50 value (IC50 = 6 μg/ml for fraction 2 and IC50 = 7.3 μg/ml for fraction 5). Fractions 2 and 5 selected for analysis antiadhesive effect on TC-1 cells. Furthermore, our results showed that both fractions 2 and 5 had antiadhesive effect on TC-1 cells.

Conclusion:

Because of potent cytotoxic and antiadhesive effect of V. lebetina fractions on lung epithelial cancer cell line, it could be promising tools for further analysis as anticancer therapeutic development.

Intrabody targeting vascular endothelial growth factor receptor-2 mediates downregulation of surface localization

Angiogenesis is among the most important mechanisms that helps cancer cells to survive, grow and undergo metastasis. Therefore, inhibiting angiogenesis will suppress tumor growth. Vascular endothelial growth factor (VEGF) and its receptor (VEGFR) are believed to be important players of angiogenesis. The goal of this study was to evaluate the success of a novel nanobody against VEGFR2 in tethering its target inside the endoplasmic reticulum and preventing its transport to the cell membrane. Nanobody sequence was cloned in a mammalian vector in fusion with green fluorescent protein and a KDEL retention signal. After transfection of 293KDR cells with this expression vector, surface localization of VEGFR2 was monitored by flow cytometry. This study demonstrates that our intrananobody is effective in targeting VEGFR2 receptor, and therefore, it is a powerful tool to downregulate a surface-exposed target protein, and in this capacity, it has potential to be used as a therapeutic protein to inhibit growth of tumors.

Recombinant expression and purification of functional vascular endothelial growth factor-121 in the baculovirus expression system

OBJECTIVE

To express human vascular endothelial growth factor121 (VEGF121) in insect cells.

METHODS

A gene construct containing VEGF was cloned in the pFastBac-HTA vector, followed by transformation in DH10BAC. The recombinant bacmid was then extracted, and transfected into Sf9 insect cells. The transfected cells were harvested, and then VEGF expression was confirmed by western blotting using specific antibodies. The tube formation assay was used for functional assessment of VEGF.

RESULTS

Our results showed that VEGF could be successfully expressed in the baculovirus system. Purified VEGF was able to stimulate in vitro tube formation of human endothelial cells.

CONCLUSIONS

Results from this study demonstrated that the recombinantly-produced VEGF can be considered as a promising candidate for therapeutic purposes.