Evaluation of peptide- and recombinant protein-based assays for detection of anti-Ehrlichia ewingii antibodies in experimentally

Objective-To evaluate microtiter-plate format ELISAs constructed by use of different diagnostic targets derived from the Ehrlichia p28 outer membrane protein for detection of E ewingii antibodies in experimentally and naturally infected dogs. Sample Population-Serum samples from 87 kenneled dogs, 9 dogs experimentally infected with anti-E ewingii, and 180 potentially naturally exposed dogs from Missouri. Procedures-The capacities of the synthetic peptide and truncated recombinant protein to function as detection reagents in ELISAs were compared by use of PCR assay, western blot analysis, and a full-length recombinant protein ELISA. Diagnostic targets included an E ewingii synthetic peptide (EESP) and 2 recombinant proteins: a full-length E ewingii outer membrane protein (EEp28) and a truncated E ewingii outer membrane protein (EETp28). Results-A subset of Ehrlichia canis-positive samples cross-reacted in the EEp28 ELISA; none were reactive in the EESF and EETp28 ELISAs. The EESP- and EETp28-based ELISAs detected E ewingii seroconversion at approximately the same time after infection as the EEp28 ELISAs. In a field population, each of the ELISAs identified the same 35 samples as reactive and 27 samples as nonreactive. Anaplasma and E canis peptides used in a commercially available ELISA platform did not detect anti-E ewingii antibodies in experimentally infected dogs. Conclusions and Clinical Relevance The EESP and EETp28 ELISAs were suitable for specifically detecting anti-E ewingii antibodies in experimentally and naturally infected dogs. (Am J Vet Res 2010;71:1195-1200)