The Panning And Identification Of Single Domain Antibodies Agnsit Foot And Mouse Disease Virus And The Utilization Of Single Domain Antibody For Detection Of Foot And Mouth Disease

Foot-and-mouth disease(FMD) is a highly contagious disease that affects cloven-hoofed animals and causes significant economic losses to husbandry worldwide. FMDV is divided into seven immunologically distinct serotypes: A, O, C, Asia I, and South African Territories(SAT1, SAT 2, and SAT3). Serotype O is the most globally prevalent of the seven serotypes of FMDV. Several outbreaks of serotype O have recently occurred in China and neighboring countries, suggesting the urgent need to prevent this FMDV serotypeApart from these conventional antibodies, naturally occurring and functional antibodies that are devoid of light chains are also found in the sera of camelids.The variable domain of the heavy chain from heavy-chain antibodies(VHHs or single domain antibodies, sdAbs) are single-domain antigen-binding fragments derived from camelid heavy-chain antibodies. Given their small size, high physicochemical stability, facile genetic manipulation, these antibodies have various medical and biotechnological applications, such as in cancer therapy.In this work, camels were immuned with inactived FMD vaccine and an immune phage display library was constructed. The capacity of this library was 1.2×108 pfu/mL.Two sdAbs against FMD virus(FMDV) serotype O were selected from a camelid phage display immune library and expressed in Escherichia coli. The serotype specificity and affinity of the sdAbs were identified through enzyme-linked immunosorbent assay and surface plasmon resonance assay. Moreover, the sdAbs were conjugated with quantum dots to constitute probes for imaging FMD virions. Results demonstrated that the two sdAbs were specific for serotype O and shared no cross-reactivity with serotypes A and Asia 1. The equilibrium dissociation constant(KD) values of the two sdAbs ranged from 6.23 nM to 8.24 nM, which indicated high affinity to FMDV antigens. Co-localization with the sdAb-AF488 and sdAb-QD probes indicated the same location of FMDV virions in baby hamster kidney-21(BHK-21) cells. Also, we made the tentative exploration of utilization of sdAb-magnetic bead for detection FMD.