Phage Display Revealed the Complex Structure of the Epitope of the Monoclonal Antibody 10H10.

The annual number of reported human cases of flavivirus infections continues to increase. Measures taken by local healthcare systems and international organizations are not fully successful. In this regard, new approaches to treatment and prevention of flavivirus infections are relevant. One promising approach is to use monoclonal antibody preparations. The mouse mAb 10H10 is capable of interacting with viruses belonging to the genus Orthoflavivirus which are pathogenic to humans. ELISA and molecular modeling data can indicate that mAb 10H10 recognizes the fusion loop region of E protein. The KD of interaction between the mAb 10H10 and recombinant analogs of the E protein of the tick-borne encephalitis (TBEV), Zika (ZIKV) and dengue (DENV) viruses range from 1.5 to 4 nM. The aim of this study was to map the epitope of this antibody using phage display technology. After three rounds of biopanning, 60 individual phage clones were chosen. The amino acid sequences of the selected peptides were conveniently divided into five groups. Based on the selected peptides, bacteriophages were obtained carrying peptides on the surfaces of the pIII and pVIII proteins, which were tested for binding to the antibody in ELISA. Thus, the epitope of the mAb 10H10 is the highly conserved region 98-DRGWGNXXGLFGK-110 of the flavivirus E protein. The structures of the complexes of the identified peptides with the antibody paratope are proposed using the molecular docking and dynamics methods.

Are Hamsters a Suitable Model for Evaluating the Immunogenicity of RBD-Based Anti-COVID-19 Subunit Vaccines?

Currently, SARS-CoV-2 spike receptor-binding-domain (RBD)-based vaccines are considered one of the most effective weapons against COVID-19. During the first step of assessing vaccine immunogenicity, a mouse model is often used. In this paper, we tested the use of five experimental animals (mice, hamsters, rabbits, ferrets, and chickens) for RBD immunogenicity assessments. The humoral immune response was evaluated by ELISA and virus-neutralization assays. The data obtained show hamsters to be the least suitable candidates for RBD immunogenicity testing and, hence, assessing the protective efficacy of RBD-based vaccines.

Comparative Immunogenicity of the Recombinant Receptor-Binding Domain of Protein S SARS-CoV-2 Obtained in Prokaryotic and Mammalian Expression Systems.

The receptor-binding domain (RBD) of the protein S SARS-CoV-2 is considered to be one of the appealing targets for developing a vaccine against COVID-19. The choice of an expression system is essential when developing subunit vaccines, as it ensures the effective synthesis of the correctly folded target protein, and maintains its antigenic and immunogenic properties. Here, we describe the production of a recombinant RBD protein using prokaryotic (pRBD) and mammalian (mRBD) expression systems, and compare the immunogenicity of prokaryotic and mammalian-expressed RBD using a BALB/c mice model. An analysis of the sera from mice immunized with both variants of the protein revealed that the mRBD expressed in CHO cells provides a significantly stronger humoral immune response compared with the RBD expressed in E.coli cells. A specific antibody titer of sera from mice immunized with mRBD was ten-fold higher than the sera from the mice that received pRBD in ELISA, and about 100-fold higher in a neutralization test. The data obtained suggests that mRBD is capable of inducing neutralizing antibodies against SARS-CoV-2.