Generation and Characterization of Single-Domain Antibodies Against the D-Antigen of Sabin Poliovirus Types 2 and 3

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A panel of monoclonal nanobodies (VHH) specific to poliovirus Sabin strains types 2 and 3 has been generated and characterized. For poliovirus Sabin type 2, a panel of four serotype-specific single-domain antibodies was obtained. Notably, two of these antibodies, S2-C5 and S2-D5, were able to discriminate between D- and H-antigens. Three nanobodies specifically neutralized poliovirus Sabin type 2 and exhibited no neutralizing activity against the homologous wild-type MEF-1 strain or other poliovirus serotypes. Among the four nanobodies selected against Sabin type 3, S3-A2 and S3-G1 demonstrated high serotype specificity in ELISAs. When used as a capture antibody in the ELISA, S3-G1 showed preferential binding to D-antigen over H-antigen. However, the type 3 nanobodies did not display virus-neutralizing activity. The obtained antibodies represent promising tools for improving existing immunoassays based on polyclonal antibodies by increasing D-antigen specificity and may facilitate the development of next-generation ELISA systems for the quality control of inactivated polio vaccines.