Submitted to: Clinical and Diagnostic Laboratory Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 10, 1996
Publication Date: N/A
Interpretive Summary: Reproductive inefficiency causes over $ 200 million in annual losses to the U.S. beef and dairy cattle industry. Although the causes are many, neosporosis is known to be responsible for at least half of all neonatal abortions in the U.S. and worldwide. Neosporosis is a parasitic disease of many domestic animals, in particular cattle and sheep, caused by the protozoan Neospora caninum. Diagnosis of Neospora infection is hampered by the lack of a reliable, cost-effective method for corroborating clinical findings. The present study describes the cloning of DNA encoding a Neospora antigen which appears to be useful for identifying cows that are infected with the parasite. The recombinant antigen is produced in the bacterium Escherichia coli making the test inexpensive and useful for veterinarians attempting to diagnose neosporosis infection.
Neospora caninum is a recently described apicomplexan parasite which causes paralysis and death in dogs. Neospora parasites also cause abortion and neonatal morbidity in cattle, sheep, goats and horses, and neosporosis is emerging as an important cause of bovine abortion worldwide. The purpose of this study was to identify N. caninum cDNA clones encoding antigens that would be useful for the immunodiagnosis of bovine neosporosis. Two N. caninum tachyzoite cDNA clones expressing antigens that were recognized by serum from naturally and experimentally infected cattle were identified. The DNA sequences of these clones were determined and the inserts subcloned into the plasmid expression vector pTrcHis. Both recombinant antigens, expressed as fusion proteins with a (His)6 tag were purified on a nickel chelating affinity column and evaluated in separate enzyme-linked immunosorbent assays (ELISAs). Both recombinant antigen ELISAs were capable of distinguishing between sera from Neospora-infected cows and sera from normal control cows. Furthermore, both assays were able to detect an antibody response in animals that were experimentally inoculated with N. caninum. Neither antigen showed evidence of cross- reactivity with serum from animals inoculated with the closely related parasites Toxoplasma gondii, Sarcocystis cruzi, Sarcocystis hominis or Sarcocystis hirsuta.