Induction of mucosal and systemic antibody specific for SeMF3 of Streptococcus equi by intranasal vaccination using a sucrose acetate isobutyrate based delivery system.

The research explores how use of a substance called sucrose acetate isobutyrate (SAIB) can enhance the immune response in horses vaccinated against Streptococcus equi, the bacterium causing the respiratory infection equine strangles. The method involves intranasal administration of the vaccine.

Introduction and Background

• The study is focused on the bacterial disease equine strangles, which affects the upper respiratory tract of horses. It is caused by the bacterium Streptococcus equi. This disease is highly contagious and results in a powerful immune response.
• One of the surface proteins of the bacteria, SeM, is an important part of this immune response, helping to trigger both mucosal and systemic antibodies – important components of the immune system.

Methodology

• The research explores the potential of a high viscosity substance called sucrose acetate isobutyrate (SAIB) to improve the antibody response generated by intranasal immunisation with a peptide of the SeM protein, called SeMF3.
• SAIB works by providing a controlled release of the biologically active substance (in this case, the SeMF3 peptide). This is administered via the nose to 11 horses on two separate occasions (on day 0 and day 28), while a second group of seven horses are given the SeMF3 peptide without SAIB.

Findings

• The study found that SAIB allowed for a more powerful immune response than just the SeMF3 peptide on its own. SeMF3 by itself only prompted a short-term IgA response in the mucosa (an essential antibody for immune response), and did not stimulate a system-wide immune response.
• Samples taken from the nasal mucosa of horses vaccinated with SeMF3 and SAIB showed this approach triggered both a quantitative and qualitative response similar to what is seen in horses recovering naturally from the disease. This response included the activation of similar linear epitopes of SeM (regions of the protein which antibodies bind to).
• Epitope analysis also suggested a difference between the nasal and systemic response, indicating the mucosal response as potentially more targeted.
• Upon a second vaccination, a booster response was observed, suggesting the intranasal delivery and usage of SAIB elicited a robust immunological response.

Conclusion

• The study concluded that using SAIB as a delivery system for intranasal immunisation has potential for improving the vaccine’s efficacy against Streptococcus equi. This offers hope for better prevention and control of equine strangles.