Development and Utilization of VHH Antibodies Derived from Camelus Dromedarius Against Foot-and-Mouth Disease Virus

A review on camelid nanobodies with potential application in veterinary medicine

The single variable domains of camelid heavy-chain only antibodies, known as nanobodies, have taken a long journey since their discovery in 1989 until the first nanobody-based drug's entrance to the market in 2022. On account of their unique properties, nanobodies have been successfully used for diagnosis and therapy against various diseases or conditions. Although research on the application of recombinant antibodies has focused on human medicine, the development of nanobodies has paved the way for incorporating recombinant antibody production in favour of veterinary medicine. Currently, despite many efforts in developing these biomolecules with diversified applications, significant opportunities exist for exploiting these highly versatile and cost-effective antibodies in veterinary medicine. The present study attempts to identify existing gaps and shed light on paths for future research by presenting an updated review on camelid nanobodies with potential applications in veterinary medicine.

Characterization of Foot-and-Mouth Disease Virus Serotype O-Specific Single Domain Antibody Expressed in the pET Expression System

Foot and mouth disease (FMD) is an extremely contagious disease of cloven-hoofed domesticated and wild animals, resulting in significant economic losses in many parts of the world. FMD virus (FMDV) serotype O is responsible for approximately 70% of global outbreaks. For detection of FMDV antigen or antibody, ELISAs are used worldwide and have several limitations, such as batch-to-batch variation in generating immunobiologicals, high production cost and ethical concerns over animal sacrifice. The use of single domain antibody (sdAb) or variable N-terminal domain of the heavy chain of heavy chain antibody (VHH) found naturally in camels has proven their effectiveness in diagnostics and therapeutics. In the present study, the anti-FMDV serotype O-specific VHH-C1 gene sequence (Accession no. KJ751546) was retrieved from the NCBI database. The gene was synthesized commercially in the pBluescript KS+ cloning vector and expressed in E. coli BL21 (DE3) cells using the pET303/CT-His expression system with a C-terminal 6X-His tag. The expressed sdAb, verified by SDS‒PAGE and western blotting, was purified by Ni-chelate chromatography and used as a coating antibody in double antibody sandwich (DAS) ELISA for FMDV detection and typing. The sdAb exhibited a high binding affinity for FMDV serotype O, without any cross-reactivity toward serotypes A and Asia-1. It exhibited better thermostability up to 85 °C than conventional rabbit polyclonal anti-FMDV sera. The potential of sdAbs thus produced without sacrificing lab animals could be explored for replacing polyclonal sera in DAS-ELISA as well as for developing biosensors or lateral flow devices for FMDV type O detection.

Nanobodies in the limelight: Multifunctional tools in the fight against viruses

Antibodies are natural antivirals generated by the vertebrate immune system in response to viral infection or vaccination. Unsurprisingly, they are also key molecules in the virologist's molecular toolbox. With new developments in methods for protein engineering, protein functionalization and application, smaller antibody-derived fragments are moving in focus. Among these, camelid-derived nanobodies play a prominent role. Nanobodies can replace full-sized antibodies in most applications and enable new possible applications for which conventional antibodies are challenging to use. Here we review the versatile nature of nanobodies, discuss their promise as antiviral therapeutics, for diagnostics, and their suitability as research tools to uncover novel aspects of viral infection and disease.

VHH Structural Modelling Approaches: A Critical Review

V_HH, i.e., VH domains of camelid single-chain antibodies, are very promising therapeutic agents due to their significant physicochemical advantages compared to classical mammalian antibodies. The number of experimentally solved V_HH structures has significantly improved recently, which is of great help, because it offers the ability to directly work on 3D structures to humanise or improve them. Unfortunately, most V_HHs do not have 3D structures. Thus, it is essential to find alternative ways to get structural information. The methods of structure prediction from the primary amino acid sequence appear essential to bypass this limitation. This review presents the most extensive overview of structure prediction methods applied for the 3D modelling of a given V_HH sequence (a total of 21). Besides the historical overview, it aims at showing how model software programs have been shaping the structural predictions of V_HHs. A brief explanation of each methodology is supplied, and pertinent examples of their usage are provided. Finally, we present a structure prediction case study of a recently solved V_HH structure. According to some recent studies and the present analysis, AlphaFold 2 and NanoNet appear to be the best tools to predict a structural model of V_HH from its sequence.

Advances in the Diagnosis of Foot-and-Mouth Disease

Foot-and-mouth disease (FMD) is a devastating livestock disease caused by foot-and-mouth disease virus (FMDV). Outbreaks of this disease in a country always result in conspicuous economic losses to livestock industry and subsequently lead to serious socioeconomic damages due to the immediate imposition of trade embargo. Rapid and accurate diagnoses are imperative to control this infectious virus. In the current review, enzyme-linked immunosorbent assay (ELISA)-based methods used in FMD diagnosis are extensively reviewed, particularly the sandwich, liquid-phase blocking, and solid-phase competition ELISA. The differentiation of infected animals from vaccinated animals using ELISA-based methods is also highlighted, in which the role of 3ABC polyprotein as a marker is reviewed intensively. Recently, more studies are focusing on the molecular diagnostic methods, which detect the viral nucleic acids based on reverse transcription-polymerase chain reaction (RT-PCR) and RT-loop-mediated isothermal amplification (RT-LAMP). These methods are generally more sensitive because of their ability to amplify a minute amount of the viral nucleic acids. In this digital era, the RT-PCR and RT-LAMP are progressing toward the mobile versions, aiming for on-site FMDV diagnosis. Apart from RT-PCR and RT-LAMP, another diagnostic assay specifically designed for on-site diagnosis is the lateral flow immunochromatographic test strips. These test strips have some distinct advantages over other diagnostic methods, whereby the assay often does not require the aid of an external device, which greatly lowers the cost per test. In addition, the on-site diagnostic test can be easily performed by untrained personnel including farmers, and the results can be obtained in a few minutes. Lastly, the use of FMDV diagnostic assays for progressive control of the disease is also discussed critically.