Immune response of adult horses, pregnant mares and foals to an experimental vaccine with recombinant EMA-2 protein of Theileria equi.

This research article explores the potential of a vaccine using the EMA-2 protein from the Theileria equi protozoan to treat equine theileriosis, a widespread disease in horses. Different groups of horses, including adult, pregnant, and young foals, were vaccinated and their immune responses studied.

Study Design and Methodology

The research involved a study cohort of 46 horses categorised into specific groups:

• Twelve geldings or castrated adult male horses
• Fourteen pregnant mares – female horses
• Fourteen foals or baby horses

The horses in each group were randomized into either a control or a vaccinated arm. They evaluated the immune response by measuring the level of serum specific anti-rEMA-2 IgG (an antibody), its subclasses and the transcription of specific cytokines, which are key immune cells.

For a real-world challenge to the vaccine, six-month-old foals from the study were infected with Theileria equi taken from a theileriosis-infected horse’s blood.

Immunity Response Findings

Both geldings and pregnant mares showcased continuous IgG production until 130 and 140 days respectively post-vaccination. The three IgG subclasses most frequently found in the vaccinated horses were IgG3/5, IgG4/7, and IgG1.

Additionally, the transcription of important cytokines including IL2, IL10, IL12, IL17, IFN-γ, and TNF-α were the highest in vaccinated horses when stimulated with rEMA-2.

Vaccine Challenge Results

The vaccinated foals’ total IgG increased by 33% four days post-blood transfusion from the theileriosis-infected horse, while there was no significant response in the unvaccinated foals. This result suggests that the vaccine-derived antibodies could potentially recognize the EMA-2 protein in the natural T. equi antigen.

Thus, the research concludes that Theileria equi’s recombinant EMA-2 protein stimulates both cellular and humoral immunity similar to natural parasite infection responses, marking it as a promising antigen for vaccine development against equine theileriosis.