Neutralising human recombinant antibodies to human cytomegalovirus glycoproteins gB and gH

Antibody Phage Display Technology for Sensor-Based Virus Detection: Current Status and Future Prospects

Viruses are widespread in the environment, and many of them are major pathogens of serious plant, animal, and human diseases. The risk of pathogenicity, together with the capacity for constant mutation, emphasizes the need for measures to rapidly detect viruses. The need for highly sensitive bioanalytical methods to diagnose and monitor socially significant viral diseases has increased in the past few years. This is due, on the one hand, to the increased incidence of viral diseases in general (including the unprecedented spread of a new coronavirus infection, SARS-CoV-2), and, on the other hand, to the need to overcome the limitations of modern biomedical diagnostic methods. Phage display technology antibodies as nano-bio-engineered macromolecules can be used for sensor-based virus detection. This review analyzes the commonly used virus detection methods and approaches and shows the prospects for the use of antibodies prepared by phage display technology as sensing elements for sensor-based virus detection.

Developing Recombinant Antibodies by Phage Display Against Infectious Diseases and Toxins for Diagnostics and Therapy

Antibodies are essential molecules for diagnosis and treatment of diseases caused by pathogens and their toxins. Antibodies were integrated in our medical repertoire against infectious diseases more than hundred years ago by using animal sera to treat tetanus and diphtheria. In these days, most developed therapeutic antibodies target cancer or autoimmune diseases. The COVID-19 pandemic was a reminder about the importance of antibodies for therapy against infectious diseases. While monoclonal antibodies could be generated by hybridoma technology since the 70ies of the former century, nowadays antibody phage display, among other display technologies, is robustly established to discover new human monoclonal antibodies. Phage display is an in vitro technology which confers the potential for generating antibodies from universal libraries against any conceivable molecule of sufficient size and omits the limitations of the immune systems. If convalescent patients or immunized/infected animals are available, it is possible to construct immune phage display libraries to select in vivo affinity-matured antibodies. A further advantage is the availability of the DNA sequence encoding the phage displayed antibody fragment, which is packaged in the phage particles. Therefore, the selected antibody fragments can be rapidly further engineered in any needed antibody format according to the requirements of the final application. In this review, we present an overview of phage display derived recombinant antibodies against bacterial, viral and eukaryotic pathogens, as well as microbial toxins, intended for diagnostic and therapeutic applications.

Anti-Proliferative Effect of Specific Anti-EGFR Single Chain Antibody on Triple Negative Breast Cancer Cells

Background

Targeted therapy is an important treatment strategy that is widely used for cancer therapy. Epidermal growth factor receptor (EGFR) is overexpressed in a significant percentage of Triple-negative breast cancer (TNBC) patients. Although Cetuximab, which targets EGFR, has shown some inhibitory effects on TNBC cells, Cetuximab resistance cases due to ligand-independent activating mutations in the EGFR gene limit its application. Due to various benefits of single chain antibodies (scFvs), the use of these antibodies in cancer targeted therapy is increasing. In this study, a specific anti-EGFR antibody was isolated and evaluated.

Methods

Panning procedure was used against an immunodominant epitope of EGFR in its dimerization arm using a diverse phage library. Polymerase Chain Reaction (PCR) and fingerprinting were applied to identify the specific clones. The MTT tetrazolium assay was performed to evaluate the inhibitory effects of selected anti- EGFR scFv phage antibody on MDA-MB-468, a TNBC cell line.

Results

After four round of panning, one dominant pattern was observed in DNA fingerprinting with frequency of 85%. The growth of MDA-MB-468 cells was decreased dose-dependently after treatment with anti-EGFR scFv phage antibody. No significant inhibitory effect of M13KO7 helper phage as negative control on the cell growth of MDA-MB-468 was observed (p> 0.05).

Conclusion

The selected anti-EGFR scFv with high anti proliferative effect on TNBC cells offers an effective alternative for TNBC targeted therapy. The antibody, which binds to the dimerization arm of EGFR and inhibits EGFR dimerization, could also overcome TNBC cases with Cetuximab resistance due to ligandindependent activating mutations.

Cell growth inhibition and apoptotic effects of a specific anti-RTFscFv antibody on prostate cancer, but not glioblastoma, cells

Background: Single chain antibody (scFv) has shown interesting results in cancer immunotargeting approaches, due to its advantages over monoclonal antibodies. Regeneration and tolerance factor (RTF) is one of the most important regulators of extracellular and intracellular pH in eukaryotic cells. In this study, the inhibitory effects of a specific anti-RTF scFv were investigated and compared between three types of prostate cancer and two types of glioblastoma cells.  Methods: A phage antibody display library of scFv was used to select specific scFvs against RTF using panning process. The reactivity of a selected scFv was assessed by phage ELISA. The anti-proliferative and apoptotic effects of the antibody on prostate cancer (PC-3, Du-145 and LNCaP) and glioblastoma (U-87 MG and A-172) cell lines were investigated by MTT and Annexin V/PI assays.  Results: A specific scFv with frequency 35% was selected against RTF epitope. This significantly inhibited the proliferation of the prostate cells after 24 h. The percentages of cell viability (using 1000 scFv/cell) were 52, 61 and 73% for PC-3, Du-145 and LNCaP cells, respectively, compared to untreated cells. The antibody (1000 scFv/cell) induced apoptosis at 50, 40 and 25% in PC-3, Du-145 and LNCaP cells, respectively. No growth inhibition and apoptotic induction was detected for U-87 and A172 glioblastoma cells.  Conclusions: Anti-RTFscFv significantly reduced the proliferation of the prostate cancer cells. The inhibition of cell growth and apoptotic induction effects in PC-3 cells were greater than Du-145 and LNCaP cells. This might be due to higher expression of RTF antigen in PC-3 cells and/or better accessibility of RTF to scFv antibody. The resistance of glioblastoma cells to anti-RTF scFv offers the existence of mechanism(s) that abrogate the inhibitory effect(s) of the antibody to RTF. The results suggest that the selected anti-RTF scFv antibody could be an effective new alternative for prostate cancer immunotherapy.

Neutralizing human recombinant antibodies against herpes simplex virus type 1 glycoproteins B from a phage-displayed scFv antibody library

The HSV-1 envelope glycoprotein B (gB) plays a critical role in virus entry into host cells. Neutralizing antibodies can therefore potentially prevent virus entry into target cells and cell-to-cell spread of infection. Our present study focused on the selection of neutralizing single-chain Fv (scFv) antibodies of a phage-displayed nonimmune human scFv antibody library against gB of HSV-1. To enrich specific scFvs, two phage antibodies were isolated against amino acid residues 31–43 derived from the N-terminal part of gB using panning technique. Two scFvs, scFv-gB₁ and scFv-gB₂, with frequencies of 45% and 20% were obtained from scFv clones after performing PCR and MvaI fingerprinting. In phage ELISA analysis, both gB₁ and gB₂ scFvs demonstrated high reactivity with the gB peptide. In the neutralization assay, scFv-gB₁ and scFv-gB₂ represented neutralizing effects of 55% and 59%, respectively. Upon further enhancement of the neutralizing effects of these antibodies, they can be considered as new potential alternatives in the treatment and prophylaxis of HSV-1 infections.

Recombinant antibodies for diagnostics and therapy against pathogens and toxins generated by phage display

Antibodies are valuable molecules for the diagnostic and treatment of diseases caused by pathogens and toxins. Traditionally, these antibodies are generated by hybridoma technology. An alternative to hybridoma technology is the use of antibody phage display to generate recombinant antibodies. This in vitro technology circumvents the limitations of the immune system and allows—in theory—the generation of antibodies against all conceivable molecules. Phage display technology enables obtaining human antibodies from naïve antibody gene libraries when either patients are not available or immunization is not ethically feasible. On the other hand, if patients or immunized/infected animals are available, it is common to construct immune phage display libraries to select in vivo affinity‐matured antibodies. Because the phage packaged DNA sequence encoding the antibodies is directly available, the antibodies can be smoothly engineered according to the requirements of the final application. In this review, an overview of phage display derived recombinant antibodies against bacterial, viral, and eukaryotic pathogens as well as toxins for diagnostics and therapy is given.

Global Mapping of O-Glycosylation of Varicella Zoster Virus, Human Cytomegalovirus, and Epstein-Barr Virus

Herpesviruses are among the most complex and widespread viruses, infection and propagation of which depend on envelope proteins. These proteins serve as mediators of cell entry as well as modulators of the immune response and are attractive vaccine targets. Although envelope proteins are known to carry glycans, little is known about the distribution, nature, and functions of these modifications. This is particularly true for O-glycans; thus we have recently developed a "bottom up" mass spectrometry-based technique for mapping O-glycosylation sites on herpes simplex virus type 1. We found wide distribution of O-glycans on herpes simplex virus type 1 glycoproteins and demonstrated that elongated O-glycans were essential for the propagation of the virus. Here, we applied our proteome-wide discovery platform for mapping O-glycosites on representative and clinically significant members of the herpesvirus family: varicella zoster virus, human cytomegalovirus, and Epstein-Barr virus. We identified a large number of O-glycosites distributed on most envelope proteins in all viruses and further demonstrated conserved patterns of O-glycans on distinct homologous proteins. Because glycosylation is highly dependent on the host cell, we tested varicella zoster virus-infected cell lysates and clinically isolated virus and found evidence of consistent O-glycosites. These results present a comprehensive view of herpesvirus O-glycosylation and point to the widespread occurrence of O-glycans in regions of envelope proteins important for virus entry, formation, and recognition by the host immune system. This knowledge enables dissection of specific functional roles of individual glycosites and, moreover, provides a framework for design of glycoprotein vaccines with representative glycosylation.

Single Chain Antibodies Against gp55 of Human Cytomegalovirus (HCMV) for Prophylaxis and Treatment of HCMV Infections

Background:

Immunotherapy is a promising prospective new treatment for cytomegalovirus (CMV) infections. Neutralizing effects have been reported using monoclonal antibodies. Recombinant single chain antibodies (scFvs) due to their advantages over monoclonal antibodies are potential alternatives and provide valuable clinical agents.

Objectives:

The aim of this study was to select specific single chain antibodies against gp55 of CMV and to evaluate their neutralizing effects. In the present study, we selected specific single chain antibodies against glycoprotein 55 (gp55) of CMV for their use in treatment and diagnosis.

Materials and Methods:

Single chain antibodies specific against an epitope located in the C-terminal part of gp55 were selected from a phage antibody display library. After four rounds of panning, twenty clones were amplified by the polymerase chain reaction (PCR) and fingerprinted by MvaI restriction enzyme. The reactivities of the specific clones were tested by the enzyme-linked immunosorbent assay (ELISA) and the neutralizing effects were evaluated by the plaque reduction assay.

Results:

Fingerprinting of selected clones revealed three specific single chain antibodies (scFv1, scFv2 and scFv3) with frequencies 25%, 20 and 20%. The clones produced positive ELISA with the corresponding peptide. The percentages of plaque reduction for scFv1, scFv2 and scFv3 were 23.7, 68.8 and 11.6, respectively.

Conclusions:

Gp55 of human CMV is considered as an important candidate for immunotherapy. In this study, we selected three specific clones against gp55. The scFvs reacted only with the corresponding peptide in a positive ELISA. The scFv2 with 68.8% neutralizing effect showed the potential to be considered for prophylaxis and treatment of CMV infections, especially in solid organ transplant recipients, for whom treatment of CMV is urgently needed. The scFv2 with neutralizing effect of 68.8%, has the potential to be considered for treatment of these patients. The specific scFv1 and scFv3 with lower neutralizing effects can be used for diagnostic purposes.

Antiproliferative and apoptotic effects of a specific antiprostate stem cell single chain antibody on human prostate cancer cells

Prostate stem cell antigen (PSCA) is a highly glycosylated cell surface protein which is overexpressed in several malignancies including prostate, pancreas, and urinary bladder cancers. Tumor suppression has been reported by anti-PSCA antibody. Small and high affinity single chain antibodies (scFv) have been introduced as effective agents for cancer immunotargeting approaches. In the present study, we used a phage antibody display library of scFv and selected two antibodies against two immunodominant epitopes of PSCA by panning process. The reactivity of the scFvs for the corresponding epitopes was determined by phage ELISA. The binding specificity of antibodies to PSCA-expressing prostate cancer cell line, DU-145, was analyzed by flow cytometry. The antiproliferative and apoptotic induction effects were evaluated by MTT and Annexin-V assays, respectively. Results represented functional scFv C5-II which could bind specifically to DU-145 cells and significantly inhibited the proliferation of these cells (61%) with no effect on PSCA-negative cells. The antibody also induced apoptosis in the PSCA expressing cells. The percentage of the apoptotic cells after 24 hrs of exposure to 500 scFv/cell was 33.80%. These results demonstrate that the functional anti-PSCA scFv C5-II has the potential to be considered as a new agent for targeted therapy of prostate cancer.

Deregulation of HER2 downstream signaling in breast cancer cells by a cocktail of anti-HER2 scFvs

Human epidermal growth factor receptor 2 (HER2) is overexpressed in 30% of patients with breast cancer. HER2 targeting is the mainstay of targeted therapy for the treatment of invasive breast cancers. Due to biological and therapeutic advantages, single chain fragment variable (scFv) antibodies have emerged as promising alternative therapeutics. In this study, we assessed the capability of three scFvs against HER2 extracellular domains (II, III, IV) in deregulation of some key signaling mediators that have important roles in growth, survival, angiogenesis, and cell migration of breast tumor cells. Downregulation of activated Akt (p-Akt), increase of p27 protein levels, and downregulation of HER1, HER2, HER3 and epidermal growth factor (EGF), CXCR3, CXCL10, and MMP2 were observed following treatment of breast cancer cells (SKBR3 cell line) with the scFvs and their combination. Our results suggest that the combination of the three scFvs could be considered as an effective cocktail on HER2 tumorgenic signaling pathways that leads to tumor growth suppression and death.

Down-regulation of vascular endothelial growth factor expression by anti-Her2/neu single chain antibodies

HER-2/neu is overexpressed in 25-30% of breast tumors. Signaling through HER-2/neu leads to an increase in the production of vascular endothelial growth factor (VEGF) and enhances angiogenesis. We evaluated the effects of three specific anti-HER2/neu single chain-Fv (scFv) antibodies on the expression level of VEGF in HER2/neu-expressing breast cancer cell lines. A nonimmunized human scFv library was panned against three epitopes of HER2/neu. BT-474 human breast cancer cell line was treated with three specific anti-HER2/neu scFv antibodies and the amount of VEGF gene transcript was determined by quantitative real-time PCR. The expression of VEGF protein was analyzed by western blot. All three scFv antibodies along with their combination inhibited VEGF expression at both the gene and protein levels. Our results show that anti-HER2/neu recombinant antibodies can be considered as anti-angiogenic agents in HER2/neu-positive breast cancers.

Recombinant human monoclonal antibodies to human cytomegalovirus glycoprotein B neutralize virus in a complement-dependent manner

Human antibodies specific for HCMV are currently considered as potential anti-HCMV therapeutic agents. In this study, we used a combinatorial human antibody library to isolate and characterize complete human monoclonal antibodies that effectively neutralize HCMV in a complement-dependent manner. One hundred and six clones were isolated in two independent screens using HCMV virions and recombinant glycoprotein B, gB654, as antigens. All of the clones recognized the same molecule gB and were classified into 14 groups based on the amino acid sequence of the V(H) region. Seven representative clones from these 14 groups had a strong gB654 binding affinity by surface plasmon resonance (SPR). A pairwise binding competition analysis suggested that there were three groups based on differences in the gB recognition sites. Although Fab fragments of the seven groups showed strong affinity for gB, none of the Fab fragments neutralized HCMV infectivity in vitro. In contrast, complete human IgG(1) antibodies of at least three groups neutralized HCMV in a complement-dependent manner. These data suggest that potent therapeutic antibodies can be obtained from a human antibody library, including most of the functional antibodies that mediate humoral immunity to the selected pathogen.

Recombinant human IgG antibodies against human cytomegalovirus

OBJECTIVE

To study the passive immunization with human monoclonal antibodies as for prophylaxis of human cytomegalovirus (HCMV) infection.

METHODS

Fab monoclonal antibodies to HCMV were recovered by repertoire cloning of mRNA from a HCMV infected individual. Antigen binding specificity, CDR sequence of V(H) and V(L) and neutralizing activity on HCMV AD169 stain were analyzed in vitro. The light and heavy chain Fd fragment genes of Fab antibodies were further cloned into a recombinant baculovirus expression vector pAC-kappa-Fc to express intact IgG. Secreted products were purified with affinity chromatography using protein G.

RESULTS

SDS-PAGE and Western blot confirmed the expression of the intact IgG. Immuno-blotting and -precipitation were used to identify HCMV proteins. One Fab monoclonal antibody recognized a conformational HCMV protein.

CONCLUSION

IgG antibodies can neutralize the HCMV AD169 strain efficiently at a titer of 2.5 microg/mL and may prove valuable for passive immunoprophylaxis against HCMV infection in humans.

Novel microneutralization assay for HCMV using automated data collection and analysis

In addition to being sensitive and specific, an assay for the assessment of neutralizing antibody activity from clinical trial samples must be amenable to automation for use in high-volume screening. To that effect, we developed a 96-well microplate assay for the measurement of HCMV-neutralizing activity in human sera using the HCMV-permissive human cell line HEL-299 and the laboratory strain of HCMV AD169. The degree to which neutralizing antibodies diminish HCMV infection of cells in the assay is determined by quantifying the nuclei of infected cells based on expression of the 72 kDa IE1 viral protein. Nuclear IE1 is visualized using a highly sensitive immunoperoxidase staining and the stained nuclei are counted using an automated ELISPOT analyzer. The use of Half Area 96-well microplates, with wells in which the surface area of the well bottom is half the area of a standard 96-well microplate plate, improves signal detection compared with standard microplates and economizes on the usage of indicator cells, virus, and reagents. The staining process was also streamlined by using a microplate washer and data analysis was simplified and accelerated by employing a software program that automatically plots neutralization curves and determines NT₅₀ values using 4-PL curve fitting.

The optimized assay is not only fast and convenient, but also specific, sensitive, precise and reproducible and thus has the characteristics necessary for use in measuring HCMV-neutralizing activity in the sera of vaccine trial subjects such as the recipients of Vical's HCMV pDNA vaccine candidates.

The production and application of single-chain antibody fragments

This review discusses methods for the single-chain antibody fragment ($cFv) generation and scFv expression systems, and describes potential applications of scFv in the therapy of viral diseases and cancer, with emphasis on intracellularly expressed scFvs (intrabodies), application of scFvs in detection and diagnostics, and their use in proteomics.