Identification of a novel B. gibsoni 27-kDa protein as a serodiagnostic antigen

Abstract

A novel gene encoding 27-kDa protein was identified by the screening of Babesia gibsoni cDNA library with acutely infected dog serum. The BgP27 is a single copy gene with a predicted open reading frame of 762 bp and 254 amino acids. The phylogenic analysis of the deduced amino acid of BgP27 demonstrated considerable identities with members of Plasmodium berghei circumsporozoite protein family that ranged between 18.4% and 22.8%. The BgP27 was expressed as a glutathione S-transferase fusion protein in Escherichia coli. The serum raised in mice against the recombinant protein specifically reacted with a 27-kDa protein in the extracts of B. gibsoni parasites. Confocal laser scanning microscopic observation showed high fluorescent reactivity with both extracellular and intracellular merozoite. Furthermore, recombinant BgP27 was used as an antigen in an enzyme-linked immunosorbent assay (ELISA). Thus, the kinetics of the anti-BgP27 antibody was detected in serial serum samples collected from a B. gibsoni-infected dog. IgG levels were high throughout the course of infection. In addition, the ELISA was able to differentiate between B. gibsoni-infected dog serum and B. canis subspecies-infected dog serum or normal dog serum. The diagnostic performance of BgP27-ELISA revealed the potential use of the antigen for detection of infection in dogs.