Recombinant Major Antigenic Protein 2 ofEhrlichia canis: a Potential Diagnostic Tool

Open Access
Publisher Website
Google Scholar
Abstract
The major antigenic protein 2 (MAP2) ofEhrlichia caniswas cloned and expressed. The recombinant protein was characterized and tested in an enzyme-linked immunosorbent assay (ELISA) format for potential application in the serodiagnosis of canine monocytic ehrlichiosis. The recombinant protein, which contained a C-terminal polyhistidine tag, had a molecular mass of approximately 26 kDa. The antigen was clearly identified by Western immunoblotting using antihistidine antibody and immune serum from an experimentally infected dog. The recombinant MAP2 (rMAP2) was tested in an ELISA format using 141 serum samples fromE. canisimmunofluorescent antibody (IFA)-positive and IFA-negative dogs. Fifty-five of the serum samples were from dogs experimentally or naturally infected withE. canisand were previously demonstrated to contain antibodies reactive withE. canisby indirect immunofluorescence assays. The remaining 86 samples, 33 of which were from dogs infected with microorganisms other thanE. canis, were seronegative. All of the samples from experimentally infected animals and 36 of the 37 samples from naturally infected animals were found to contain antibodies against rMAP2 ofE. canisin the ELISA. Only 3 of 53 IFA-negative samples tested positive on the rMAP2 ELISA. There was 100% agreement among IFA-positive samples from experimentally infected animals, 97.3% agreement among IFA-positive samples from naturally infected animals, and 94.3% agreement among IFA-negative samples, resulting in a 97.2% overall agreement between the two assays. These data suggest that rMAP2 ofE. caniscould be used as a recombinant test antigen for the serodiagnosis of canine monocytic ehrlichiosis.