Selection of single-chain antibodies that specifically interact with vesicular stomatitis virus (VSV) nucleocapsid and inhibit viral RNA synthesis

Generation and characterization of avian single chain variable fragment against human Alpha-Enolase

Overexpression of human alpha-enolase (hEno1)has been reported in a wide range of cancers and is tightly associated with poor prognosis, making it a remarkable biomarker and therapeutic target. In this study, polyclonal yolk-immunoglobulin (IgY) antibodies purified from hEno1-immunized chickens showed a noticeable specific humoral response. Phage display technology was used to construct two antibody libraries of IgY gene-derived single-chain variable fragments (scFvs) containing 7.8 × 10⁷ and 5.4 × 10⁷ transformants, respectively. Phage-based ELISA indicated that specific anti-hEno1 clones were significantly enriched. The nucleotide sequences of scFv-expressing clones were determined and classified into seven groups either in the short linker or the long linker. Moreover, higher mutation rates were revealed in the CDR regions, especially in the CDR3. Three distinguish antigenic epitopes were identified on the hEno1 protein. The binding activities of selected anti-hEno1 scFv on hEno1-positive PE089 lung cancer cells were confirmed using Western blot, flow cytometry, and immunofluorescence assay. In particular, hEnS7 and hEnS8 scFv antibodies significantly suppressed the growth and migration of PE089 cells. Taken together, these chicken-derived anti-hEno1 IgY and scFv antibodies have great potential to develop diagnostic and therapeutic agents for the treatment of lung cancer patients with high expression levels of hEno1 protein.

An approach towards development of monoclonal IgY antibodies against SARS CoV-2 spike protein (S) using phage display method: A review

The present state of diagnostic and therapeutic developmental race for vaccines against the SARS CoV-2 (nCOVID-19) focuses on prevention and control of this global pandemic which also represents a critical challenge to the global health community. Although development of novel vaccines can prevent the SARS CoV-2 infections, it is still impeded by several other factors and therefore novel approaches towards treatment and management of this disease is the urgent need. Passive immunotherapy plays a vital role as a possible alternative to meet this challenge and among various antibody sources, chicken egg yolk antibodies (IgY) can be used as an alternative to mammalian antibodies which have been previously studied against SARS CoV outbreak in China. In this review, we discuss the strategies for the use of chicken egg yolk (IgY) antibodies in the development of rapid diagnosis and immunotherapy against SARS CoV-2. Also, IgY antibodies have previously been used against various respiratory bacterial and viral infections in humans and animals. Compared to mammalian antibodies (IgG), chicken egg yolk antibodies (IgY) have greater binding affinity to specific antigens, ease of extraction and lower production costs, hence possessing remarkable pathogen-neutralizing activity of pathogens in respiratory and lungs. We provide an overall importance for the use of monoclonal chicken egg yolk antibodies (IgY) using phage display method describing their potential passive immunotherapeutic application for the treatment and prevention of SARS CoV-2 infection which is simple, fast and safe way of approach for treating patients effectively.

Cytosolic 5'-triphosphate ended viral leader transcript of measles virus as activator of the RIG I-mediated interferon response

BACKGROUND

Double stranded RNA (dsRNA) is widely accepted as an RNA motif recognized as a danger signal by the cellular sentries. However, the biology of non-segmented negative strand RNA viruses, or Mononegavirales, is hardly compatible with the production of such dsRNA.

METHODOLOGY AND PRINCIPAL FINDINGS

During measles virus infection, the IFN-beta gene transcription was found to be paralleled by the virus transcription, but not by the virus replication. Since the expression of every individual viral mRNA failed to activate the IFN-beta gene, we postulated the involvement of the leader RNA, which is a small not capped and not polyadenylated RNA firstly transcribed by Mononegavirales. The measles virus leader RNA, synthesized both in vitro and in vivo, was efficient in inducing the IFN-beta expression, provided that it was delivered into the cytosol as a 5'-trisphosphate ended RNA. The use of a human cell line expressing a debilitated RIG-I molecule, together with overexpression studies of wild type RIG-I, showed that the IFN-beta induction by virus infection or by leader RNA required RIG-I to be functional. RIG-I binds to leader RNA independently from being 5-trisphosphate ended; while a point mutant, Q299A, predicted to establish contacts with the RNA, fails to bind to leader RNA. Since the 5'-triphosphate is required for optimal RIG-I activation but not for leader RNA binding, our data support that RIG-I is activated upon recognition of the 5'-triphosphate RNA end.

CONCLUSIONS/SIGNIFICANCE

RIG-I is proposed to recognize Mononegavirales transcription, which occurs in the cytosol, while scanning cytosolic RNAs, and to trigger an IFN response when encountering a free 5'-triphosphate RNA resulting from a mislocated transcription activity, which is therefore considered as the hallmark of a foreign invader.

A dominant antigenic epitope on SARS-CoV spike protein identified by an avian single-chain variable fragment (scFv)-expressing phage

Severe acute respiratory syndrome (SARS) is a newly emergent human disease, which requires rapid diagnosis and effective therapy. Among antibody sources, immunoglobulin Y (IgY) is the major antibody found in chicken eggs and can be used as an alternative to mammalian antibodies normally used in research and immunotherapy. In this study, phage-expressing chicken monoclonal scFv antibody was chosen and characterized with phage display antibody technology. Truncated fragments of SARS-CoV spike protein were cloned in pET-21 vector and expressed in BL-21 Escherichia coli (E. coli) cells. After purification, the purity of these recombinant spike proteins was examined on SDS-PAGE and their identity verified with Western blot analysis using anti-his antibodies and sera from convalescent stage SARS-CoV-infected patients. Using these bacteria-derived proteins to immunize chickens, it was found that polyclonal IgY antibodies in the egg yolk and sera were highly reactive to the immunogens, as shown by Western blot and immunocytochemical staining analysis. A phage displaying scFv library was also established from spleen B cells of immunized chicken with 5 x 10(7) clones. After four panning cycles, the eluted phage titer showed a 10-fold increase. In sequence analysis with chicken germline gene, five phage clones reacted, with large dissimilarities of between 31 and 62%, in the complementarity-determining regions, one dominant phage 4S1 had strong binding to fragment Se-e, located between amino acid residues 456-650 of the spike protein and this particular phage had significantly strong binding to SARS-CoV-infected Vero E6 cells. Based on the results, we conclude that generating specific scFv-expressing phage binders with the phage display system can be successfully achieved and that this knowledge can be applied in clinical or academic research.

Recombinant single chain Fv antibodies specific for glycoprotein D of equid herpesvirus 1

Single chain Fv (scFv) molecules generated by phage-display technology represent a new and efficient tool in the research and diagnostics of infectious diseases. The recombinant glycoprotein D of Equid herpesvirus 1 was successfully expressed in E. coli cells. The protein was produced predominantly in soluble fraction and was then purified on a nickel-agarose column. The scFv antibodies against the glycoprotein were selected and several clones of glycoprotein D-specific scFv-antibodies were identified; t of them was expressed as a soluble scFv molecule, purified by immobilized metal-affinity chromatography and used as reagent in an immunofluorescence test.