Diagnostic application of recombinant equine merozoite surface antigen-1 in elisa for detection of Theileria equi specific antibodies.

The research article presents a study on the development of a new diagnostic tool, based on a specific antigen found in Theileria equi, to detect antibodies against T. Equi in horses.

Development of EMA-1-based ELISA Test

• Researchers have developed an ELISA (Enzyme-Linked Immunosorbent Assay) based on the EMA-1 (Equine Merozoite Antigen-1) recombinant antigen.
• The EMA-1 gene fragment contains a high hydrophilic antigenic region allowing it to be used in diagnostic tests.
• The fragment, consisting of 547 base pairs (bp), was expressed with a glutathione-S-transferase tag in a prokaryotic system. The purified protein, resulting in a 43kDa size, was then used for development of this ELISA test.

Efficiency of the EMA-1-based ELISA Test

• The EMA-1t/ELISA was able to distinctly identify T. equi-infected horse serum from Babesia caballi-infected horse serum or normal horse serum.
• The test was validated by comparing the results with a previously developed (EMA-2) ELISA on serum samples already confirmed for T. equi infection. The relative percent positivity (RPP) values found a very high correlation, indicating the reliability of the new test.
• The diagnostic sensitivity of the EMA-1t/ELISA test was measured to be 0.92, indicating a high probability of detecting true positive cases. Additionally, the specificity was 1.0, indicating a high accuracy in ruling out false positives, therefore marking suitability of this test for sero-epidemiological studies.

Field Application of the EMA-1-based ELISA Test

• Researchers applied this assay on serum samples taken from 240 field horses in northern India. The results indicated a high prevalence of T. equi antibodies, particularly in samples from Haryana state (74%) and Uttarakhand state (36.31%).

Future Implications

• The findings of the study suggest that the 43kDa EMA-1 expressed protein could serve as a reliable immunodiagnostic antigen in ELISA for T. equi sero-prevalence studies, providing a valuable tool for diagnosing and controlling equine piroplasmosis.