Mapping of minimal motifs of B-cell epitopes on human zona pellucida glycoprotein-3

The human zona pellucida glycoprotein-3 (hZP3) by virtue of its critical role during fertilization has been proposed as a promising candidate antigen to develop a contraceptive vaccine. In this direction, it is imperative to map minimal motifs of the B cell epitopes (BCEs) so as to avoid ZP-specific oophoritogenic T cell epitopes (TCEs) in the ZP3-based immunogens. In this study, based on known results of mapping marmoset and bonnet monkey ZP3 (mstZP3 and bmZP3), two predictable epitopes(23-30  and  301-320) on hZP3 were first confirmed and five minimal motifs within four epitopes on hZP3 were defined using serum to recombinant hZP3a(22-176) or hZP3b(177-348) as well as a biosynthetic peptide strategy. These defined minimal motifs were QPLWLL(23-28) for hZP3(23-30), MQVTDD(103-108) for hZP3(93-110), EENW(178-181) for hZP3(172-190), as well as SNSWF(306-310) and EGP(313-315) for hZP3(301-320), respectively. Furthermore, the antigenicity of two peptides for hZP3(172-187) and hZP3(301-315) and specificity of the antibody response to these peptides were also evaluated, which produced high-titer antibodies in immunized animals that were capable of reacting to ZP on human oocytes, r-hZP3b(177-348) protein, as well as r-hZP3(172-190), r-hZP3(303-310), and r-hZP3(313-320) epitope peptides fused with truncated GST188 protein.