Antigenicity assessment of the Theileria equi merozoite antigen (EMA-2) expressed in Pichia pastoris in mice and horses.

This study investigates the effectiveness of using a recombinant version of Theileria equi merozoite antigen-2 (rEMA-2) as a possible vaccine in combating equine theileriosis, a severe disease in horses found mostly in tropical and subtropical regions.

Introduction to the Study and Experimentation Process

• The study involves an examination into the effects of using a recombinant antigen of the Theileria equi protozoan organism – a key cause of equine theileriosis in horses, especially in tropical and subtropical regions.
• The antigen under study was rEMA-2 and was utilized as the principal immunogen.
• The experimental groups consisted of two sections of mice (10 each) and 60 mares – all separated into control and vaccinated groups. The mice and horses within the vaccinated groups were given doses of the rEMA-2 vaccine (50µg for mice and 200µg for horses) on the first day and then again on the 21st day of the experiment.

Evaluation and Findings

• To evaluate the antigen’s immunogenicity various tests were performed such as the ELISA (Enzyme-Linked Immunosorbent Assay) and IFAT (Indirect Fluorescent Antibody Test). These tests used serum samples collected from the vaccinated animals.
• The results of the tests showed significant variations (p<0.05) between the vaccinated groups and control groups at all the stages of the experiment.
• Additionally, the vaccine was seen to cause an increase in IgG (Immunoglobulin G – an antibody) levels within the subjects. Specifically, the antibody levels in the mice increased 3-fold on the 14th day and four-fold on the 28th day compared to the mice in the control group.
• The horses also demonstrated a substantial elevation in total IgG levels, registering significant increases from the 7th day and peaking on the 28th day with even higher significance (p < 0.001).
• Focusing on the isotypes, the IgG(T) (IgG3-5) had more elevated levels than other groups and were followed by IgGb (IgG4-7) and IgGa (IgG1).
• Furthermore, the IFAT detected a positive fluorescence, suggesting that the rEMA-2 protein could initiate an immune response and probably shared some similar epitopes with the native T. equi antigens found in the horses’ blood.

Conclusion

• Basing on the outcomes of the study, the researchers inferred that the rEMA-2 antigen can be considered a promising candidate for future vaccines against equine theileriosis.