Molecular characterization of a novel 32-kDa merozoite antigen of Babesia gibsoni with a better diagnostic performance by enzyme-linked immunosorbent assay

Abstract

We cloned and expressed 3 novel gene encoding a 32-kDa merozoite protein of Babesia gibsoni (BgP32). The length of nucleotide sequence of the cD;\' A \\'3. 1-1-6-1 bp with an open reading frame of 969 bp. The truncated recombinant BgP32 (rBgP32) without a signal peptide and Cvterrninal hydrophobic sequence was expressed in Escherichia coli as a oluble glutathione- -rran ferase (GST) fusion protein. We stern blotting demonstrated that the native protein was 32-kDa, consistent with molecular weight of thc predicted mature polypeptide. Enzyme-linked irnmunosorbent assay (ELISA) using rBgP32 detected specific antibodi s from 8 days to 541 days post-infection in the sequential sera from a dog experimentally infected wirh B. gibsoni. Moreover. the antigen did not cross-react with B. canis subspecies and closely related protozoan parasites, indicating that rBgP32 is a specific diagnostic antigen. Analysis of 47 era taken from dogs with anaemic signs re ealed that rBgP32 detected a higher proportion of B. gibson! seroposirive sample' (77%) than its previou Iy identified rBgPSO (68%) homologue. These results indicate that the BgP32 is a novel immunodominant antigen of B. gibsoni, and rBgP32 might be useful for diagno is of B. gibsoni infection