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Immunodiagnosis of Ehrlichia canis infection with recombinant proteins
J W McBride1, R E Corstvet, E B Breitschwerdt
1Department of Pathology and WHO Collaborating Center for Tropical Diseases, University of Texas Medical Branch, Galveston, Texas 77555, USA.
Abstract:
Ehrlichia canis causes a potentially fatal rickettsial disease of dogs that requires rapid and accurate diagnosis in order to initiate appropriate therapy leading to a favorable prognosis. We recently reported the cloning of two immunoreactive E. canis proteins, P28 and P140, that were applicable for serodiagnosis of the disease. In the present study we cloned a new immunoreactive E. canis surface protein gene of 1,170 bp, which encodes a protein with a predicted molecular mass of 42.6 kDa (P43). The P43 gene was not detected in E. chaffeensis DNA by Southern blot, and antisera against recombinant P43 (rP43) did not react with E. chaffeensis as detected by indirect fluorescent antibody (IFA) assay. Forty-two dogs exhibiting signs and/or hematologic abnormalities associated with canine ehrlichiosis were tested by IFA assay and by recombinant Western immunoblot. Among the 22 samples that were IFA positive for E. canis, 100% reacted with rP43, 96% reacted with rP28, and 96% reacted with rP140. The specificity of the recombinant proteins compared to the IFAs was 96% for rP28, 88% for P43 and 63% for P140. The results of this study demonstrate that the rP43 and rP28 are sensitive and reliable serodiagnostic antigens for E. canis infections.
Insights
A new Ehrlichia canis surface protein, P43, shows promise for diagnosing canine ehrlichiosis. Recombinant P43 (rP43) and rP28 are sensitive and reliable antigens for serodiagnosis of this potentially fatal dog disease.
Area of Science:
- Veterinary Medicine
- Molecular Biology
- Immunology
Background:
- Ehrlichia canis causes a severe, potentially fatal disease in dogs.
- Accurate and rapid diagnosis is crucial for effective treatment and favorable outcomes.
- Previous studies identified P28 and P140 as immunoreactive antigens for serodiagnosis.
Purpose of the Study:
- To clone and characterize a new immunoreactive Ehrlichia canis surface protein (P43).
- To evaluate the diagnostic potential of P43 and previously identified antigens (P28, P140) for canine ehrlichiosis.
Main Methods:
- Cloning of the 1,170 bp P43 gene from E. canis.
- Southern blot analysis to assess P43 gene specificity against E. chaffeensis DNA.
- Indirect fluorescent antibody (IFA) assay and recombinant Western immunoblotting using recombinant P43 (rP43), rP28, and rP140.
- Testing of 42 dogs with clinical signs of ehrlichiosis.
Main Results:
- The P43 gene was specific to E. canis and not detected in E. chaffeensis.
- Antisera against rP43 did not cross-react with E. chaffeensis.
- Among 22 IFA-positive samples, 100% reacted with rP43, 96% with rP28, and 96% with rP140.
- Specificities were 96% for rP28, 88% for rP43, and 63% for rP140 compared to IFA.
Conclusions:
- Recombinant P43 (rP43) and rP28 are highly sensitive and reliable antigens for the serodiagnosis of Ehrlichia canis infections.
- These antigens can aid in the rapid and accurate diagnosis of canine ehrlichiosis, facilitating timely treatment.