Applications of nanobodies in the prevention, detection, and treatment of the evolving SARS-CoV-2

Resistance-based directed evolution of nanobodies for higher affinity in prokaryotes

A prokaryotic resistance-based directed evolution system leveraging protein-fragment complementation assay (PCA) was devised, and its proficiency in detecting protein-protein interactions and discriminating varying degrees of binding affinity was demonstrated by two well-characterized protein pairs. Furthermore, we constructed a random mutant library based on the GBPR36K/E45K mutant, characterized by almost no affinity towards EGFP. This library was subjected to PCA-based prokaryotic directed evolution, resulting in the isolation of back-mutated variants. In summary, we have established an expedited, cost-effective, and structural information-independent PCA-based prokaryotic directed evolution platform for nanobody affinity maturation, featuring tunable screening stringency via modulation of antibiotic concentrations.

A novel nanobody broadly neutralizes SARS-CoV-2 via induction of spike trimer dimers conformation

The ongoing mutations of the SARS-CoV-2 pose serious challenges to the efficacy of the available antiviral drugs, and new drugs with fantastic efficacy are always deserved investigation. Here, a nanobody called IBT-CoV144 is reported, which exhibits broad neutralizing activity against SARS-CoV-2 by inducing the conformation of spike trimer dimers. IBT-CoV144 was isolated from an immunized alpaca using the RBD of wild-type SARS-CoV-2, and it showed strong cross-reactive binding and neutralizing potency against diverse SARS-CoV-2 variants, including Omicron subvariants. Moreover, the prophylactically and therapeutically intranasal administration of IBT-CoV144 confers fantastic protective efficacy against the challenge of Omicron BA.1 variant in BALB/c mice model. The structure analysis of the complex between spike (S) protein, conducted using Cryo-EM, revealed a special conformation known as the trimer dimers. This conformation is formed by two trimers, with six RBDs in the "up" state and bound by six VHHs. IBT-CoV144 binds to the lateral region of the RBD on the S protein, facilitating the aggregation of S proteins. This aggregation results in steric hindrance, which disrupts the recognition of the virus by ACE2 on host cells. The discovery of IBT-CoV144 will provide valuable insights for the development of advanced therapeutics and the design of next-generation vaccines.

Therapeutic antibodies and alternative formats against SARS-CoV-2

The COVID-19 pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) heavily burdened the entire world. Despite a prompt generation of vaccines and therapeutics to confront infection, the virus remains a threat. The ancestor viral strain has evolved into several variants of concern, with the Omicron variant now having many distinct sublineages. Consequently, most available antibodies targeting the spike went obsolete and thus new therapies or therapeutic formats are needed. In this review we focus on antibody targets, provide an overview of the therapeutic progress made so far, describe novel formats being explored, and lessons learned from therapeutic antibodies that can enhance pandemic preparedness.

Nanobodies with cross-neutralizing activity provide prominent therapeutic efficacy in mild and severe COVID-19 rodent models

The weakened protective efficacy of COVID-19 vaccines and antibodies caused by SARS-CoV-2 variants presents a global health emergency, which underscores the urgent need for universal therapeutic antibody intervention for clinical patients. Here, we screened three alpacas-derived nanobodies (Nbs) with neutralizing activity from twenty RBD-specific Nbs. The three Nbs were fused with the Fc domain of human IgG, namely aVHH-11-Fc, aVHH-13-Fc and aVHH-14-Fc, which could specifically bind RBD protein and competitively inhibit the binding of ACE2 receptor to RBD. They effectively neutralized SARS-CoV-2 pseudoviruses D614G, Alpha, Beta, Gamma, Delta, and Omicron sub-lineages BA.1, BA.2, BA.4, and BA.5 and authentic SARS-CoV-2 prototype, Delta, and Omicron BA.1, BA.2 strains. In mice-adapted COVID-19 severe model, intranasal administration of aVHH-11-Fc, aVHH-13-Fc and aVHH-14-Fc effectively protected mice from lethal challenges and reduced viral loads in both the upper and lower respiratory tracts. In the COVID-19 mild model, aVHH-13-Fc, which represents the optimal neutralizing activity among the above three Nbs, effectively protected hamsters from the challenge of SARS-CoV-2 prototype, Delta, Omicron BA.1 and BA.2 by significantly reducing viral replication and pathological alterations in the lungs. In structural modeling of aVHH-13 and RBD, aVHH-13 binds to the receptor-binding motif region of RBD and interacts with some highly conserved epitopes. Taken together, our study illustrated that alpaca-derived Nbs offered a therapeutic countermeasure against SARS-CoV-2, including those Delta and Omicron variants which have evolved into global pandemic strains.

Ultrasensitive Electrochemical Immunosensors Using Nanobodies as Biocompatible Sniffer Tools of Agricultural Contaminants and Human Disease Biomarkers

Nanobodies (Nbs) are known as camelid single-domain fragments or variable heavy chain antibodies (VHH) that in vitro recognize the antigens (Ag) similar to full-size antibodies (Abs) and in vivo allow immunoreactions with biomolecule cavities inaccessible to conventional Abs. Currently, Nbs are widely used for clinical treatments due to their remarkably improved performance, ease of production, thermal robustness, superior physical and chemical properties. Interestingly, Nbs are also very promising bioreceptors for future rapid and portable immunoassays, compared to those using unstable full-size antibodies. For all these reasons, Nbs are excellent candidates in ecological risk assessments and advanced medicine, enabling the development of ultrasensitive biosensing platforms. In this review, immobilization strategies of Nbs on conductive supports for enhanced electrochemical immune detection of food contaminants (Fcont) and human biomarkers (Hbio) are discussed. In the case of Fcont, the direct competitive immunoassay detection using coating antigen solid surface is the most commonly used approach for efficient Nbs capture which was characterized with cyclic voltammetry (CV) and differential pulse voltammetry (DPV) when the signal decays for increasing concentrations of free antigen prepared in aqueous solutions. In contrast, for the Hbio investigations on thiolated gold electrodes, increases in amperometric and electrochemical impedance spectroscopy (EIS) signals were recorded, with increases in the antigen concentrations prepared in PBS or spiked real human samples.