Molecular characterization of a synthetic neutralizing antibody targeting p67 of Theileria parva

Abstract The Theileria parva sporozoite surface antigen p67 is a target of the bovine humoral immune response that generates antibodies capable of providing protection against subsequent infection. As a result, p67 has been the subject of efforts aimed at the development of an anti‐sporozoite subunit vaccine. Previous studies have identified neutralizing epitopes in the N‐ and C‐terminal regions of the full‐length protein and shown that immunization with a C‐terminal fragment of p67 (p67C) alone is capable of eliciting protection. To identify additional neutralizing epitopes in p67C, selections were conducted against it using a phage‐displayed synthetic antibody library. An antibody that neutralized the sporozoite in vitro was identified, and the crystal structure of a Fab:peptide complex was elucidated. Mutagenesis studies aimed at validating and further characterizing the Fab:peptide interaction identified critical residues involved in binding and neutralization. This study also validates distinct epitopes for previously reported neutralizing antibodies.