Screening and Anti-angiogenesis Activity of Chiloscyllium plagiosum Anti-human VEGFR2 Single-domain Antibody.

Recently, the incidence of malignant tumors is on the rise and searching for new treatments on it has become the research priority. Blocking the vascular endothelial growth factor (VEGF) and its receptor (VEGFR) is one of the treatment strategies that used in the development of specific anti-angiogenic drugs. The deficiencies in tissue penetration and affinity maturation become the weakness of these drugs in anti-tumors applications. The single heavy chain antibody found in Chiloscyllium plagiosum, which has a low molecular weight and superior tissue penetration of variable region (VNARs), was considered to have the high antigen binding activity and stability. This type of antibody has a simple structure that can be prokaryoticaly expressed, which makes it easily to produce new antiangiogenic target drugs. Specific anti-IgNAR rabbit multiple antibodies have been used to assess the level of VNARs in sharks and have shown a significant enrichment of IgNAR after triple immunization. An anti-VEGFR2 phage library was used for the targeted VNARs screening, and five candidate VNARs sequences were subsequently obtained by phage screening, followed by combined screening with the transcriptome library, and analysis of conserved regions along with 3D modelling matched the VNAR profile. ELISA and cell-based assays showed that two of the VNARs, VNAR-A6 and VNAR-E3, had a superior antigen affinity and anti-angiogenic activity thereby being able to inhibit human Umbilical Vein Endothelial Cells proliferation and migration. The anti-VEGFR2 VNARs derived from the immunized Chiloscyllium plagiosum and screened by phage library, which provide the new research ideas and specific approaches for the development of new drugs. The anti-VEGFR2 VNARs are capable for blocking the VEGF-VEGFR pathway, which of these may contribute to expanding the use of anti-angiogenic drugs.

Antigen specific VNAR screening in whitespotted bamboo shark (Chiloscyllium plagiosum) with next generation sequencing.

IgNAR exhibits significant promise in the fields of cancer and anti-virus biotherapies. Notably, the variable regions of IgNAR (VNAR) possess comparable antigen binding affinity with much smaller molecular weight (∼12 kDa) compared to IgNAR. Antigen specific VNAR screening is a changeling work, which limits its application in medicine and therapy fields. Though phage display is a powerful tool for VNAR screening, it has a lot of drawbacks, such as small library coverage, low expression levels, unstable target protein, complicating and time-consuming procedures. Here we report VANR screening with next generation sequencing (NGS) could effectively overcome the limitations of phage display, and we successfully identified approximately 3000 BAFF-specific VNARs in Chiloscyllium plagiosum vaccinated with the BAFF antigen. The results of modelling and molecular dynamics simulation and ELISA assay demonstrated that one out of the top five abundant specific VNARs exhibited higher binding affinity to the BAFF antigen than those obtained through phage display screening. Our data indicates NGS would be an alternative way for VNAR screening with plenty of advantages.

Screening and anti-glioma activity of Chiloscyllium plagiosum anti-human IL-13Rα2 single-domain antibody.

Glioblastoma is a common and fatal malignant tumour of the central nervous system, with high invasiveness. Conventional treatments for this disease, including comprehensive treatment of surgical resection combined with chemoradiotherapy, are ineffective, with low survival rate and extremely poor prognosis. Targeted therapy is promising in overcoming the difficulties in brain tumour treatment and IL-13Rα2 is a widely watched target. The development of new therapies for glioma, however, is challenged by factors, such as the unique location and immune microenvironment of gliomas. The unique advantages of single-domain antibodies (sdAbs) may provide a novel potential treatment for brain tumours. In this study, Chiloscyllium plagiosum was immunized with recombinant IL-13Rα2 protein to produce sdAb and sdAb sequences were screened by multi-omics. The targeted sdAb genes obtained were efficiently expressed in the Escherichia coli prokaryotic expression system, showing a significant binding capacity to IL-13Rα2 in vitro. The cell proliferation and migration inhibitory effects of recombinant variable domain of the new antigen receptor (VNAR) on glioma cells were detected by CCK-8 and cell scratch assays. The sdAb obtained in this study showed high in vitro activity and favourable cell proliferation inhibitory effect on glioma cells, with potential clinical application value. The present study also provides a new direction and experimental basis for the development of targeted therapies for glioma.

IgNAR characterization and gene loci identification in whitespotted bamboo shark (Chiloscyllium plagiosum) genome.

Single domain antibodies (sdAb) are promising candidates in cancer and anti-virus biotherapies for their unique structure characters. Though VHH and IgNAR have been discovered in camelidae and nurse shark (Ginlymostoma cirratum) respectively serval decades ago, expense of these large animals still limits the studies and applications of sdAb. Recently, IgNAR has been found in whitespotted bamboo shark (Chiloscyllium plagiosum), a small-sized sharks, while how to characterize and achieved the IgNAR of whitespotted bamboo shark is still unclear. In our research, we identified four IgNAR coding gene loci in whitespotted bamboo shark chromosome 44 (NC_057753.1), and primers were designed for single domain variable regions of IgNAR (VNAR) libraries preparation. Following sequencing results revealed that all plasmids constructed with our predicted VNAR libraries contained VNAR coding sequences, which confirmed the specificities of our primers in VNAR amplification. To our surprise, ≥90% VNAR sequences were encoded by IgNAR1, which suggests IgNAR1 is the most active IgNAR transcription locus in whitespotted bamboo shark. Interestingly, we found IgNAR(ΔC2-C3) were encoded by IgNAR3. Our findings gave a new sight of whitespotted bamboo shark IgNAR, which would broad the way of IgNAR studies and applications in biotherapies.

Shark IgNAR: The Next Broad Application Antibody in Clinical Diagnoses and Tumor Therapies?

Antibodies represent a relatively mature detection means and serve as therapeutic drug carriers in the clinical diagnosis and treatment of cancer-among which monoclonal antibodies (mAbs) currently occupy a dominant position. However, the emergence and development of small-molecule monodomain antibodies are inevitable due to the many limitations of mAbs, such as their large size, complex structure, and sensitivity to extreme temperature, and tumor microenvironments. Thus, since first discovered in Chondroid fish in 1995, IgNAR has become an alternative therapeutic strategy through which to replace monoclonal antibodies, thus entailing that this novel type of immunoglobulin has received wide attention with respect to clinical diagnoses and tumor therapies. The variable new antigen receptor (VNAR) of IgNAR provides an advantage for the development of new antitumor drugs due to its small size, high stability, high affinity, as well as other structural and functional characteristics. In that respect, a better understanding of the unique characteristics and therapeutic potential of IgNAR/VNAR in clinical and anti-tumor treatment is needed. This article reviews the advantages of its unique biochemical conditions and molecular structure for clinical diagnoses and novel anti-tumor drugs. At the same time, the main advantages of the existing conjugated drugs, which are based on single-domain antibodies, are introduced here, thereby providing new ideas and methods for the development of clinical diagnoses and anti-tumor therapies in the future.