title: Factors associated with seroconversion to the major piroplasm surface protein of the bovine haemoparasite Theileria orientalis.
abstract: BACKGROUND
  Bovine theileriosis caused by Theileria orientalis is an emerging disease of cattle in the Asia-Pacific region where it causes a significant economic burden to meat and milk production. While host immunological responses to the lymphocyte-transforming species of Theileria, T. parva and T. annulata, have been well studied, little is known about the immune response to this non-transforming species.
  
  
  METHODS
  We developed a recombinant antigen ELISA based on the major piroplasm surface protein (MPSP) of T. orientalis and investigated whether seroconversion to the MPSP was associated with clinical factors (anaemia), parasite burden and parasite genotype. We also examined the dynamics of seroconversion in animals acutely infected with T. orientalis.
  
  
  RESULTS
  In cattle testing qPCR positive for T. orientalis, seroconversion was more frequent in anaemic compared to normal cattle (P < 0.0001). The ELISA ratio (ER) was highly correlated with total parasite burden as measured by qPCR (r = 0.69; P < 0.0001); however when loads of individual genotypes of the parasite were examined, only the pathogenic Ikeda genotype was highly correlated with ER. Conversely, seroconversion was less frequently detected in the presence of benign T. orientalis genotypes. Temporal measurement of the serological response, parasite burden and packed cell volume (PCV) in acutely infected animals revealed that seroconversion to the MPSP occurs within 2-3 weeks of the initial qPCR detection of the parasite and coincides with a peak in infection intensity and a declining PCV.
  
  
  CONCLUSIONS
  Whether the serological response to the MPSP is immunoprotective against re-infection or recrudescence requires further investigation; however the MPSP represents a promising target for a subunit vaccine given that genetic variability within the MPSP results in differential pathogenicity of T. orientalis.
authors.affiliation: NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW, 2568, Australia. cheryl.jenkins@dpi.nsw.gov.au.
authors.forename: Cheryl
authors.initials: C
authors.lastname: Jenkins
authors.affiliation: NSW Department of Primary Industries, Elizabeth Macarthur Agricultural Institute, Menangle, NSW, 2568, Australia. daniel.bogema@dpi.nsw.gov.au.|The ithree institute, University of Technology, Sydney, Ultimo, NSW, 2007, Australia. daniel.bogema@dpi.nsw.gov.au.
authors.forename: Daniel R
authors.initials: DR
authors.lastname: Bogema
mesh_terms: D000818:Animals; D000913:Antibodies, Protozoan / Q000097:blood*; D000953:Antigens, Protozoan / Q000235:genetics / Q000276:immunology*; D001208:Asia; D002417:Cattle; D002418:Cattle Diseases / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D010139:Pacific Islands; D015800:Protozoan Proteins / Q000235:genetics / Q000276:immunology*; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D000069078:Seroconversion; D013801:Theileriasis / Q000276:immunology*
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D015800:Protozoan Proteins; D011994:Recombinant Proteins; C115173:major piroplasm surface protein, Theileria