Paillot, R., et al. Antibody Titres to Strangvac Antigens Correlate with Protection and Duration of Immunity Against Experimental Infection with Streptococcus equi Subspecies equi. Vaccines (Basel), 2026 Jun 16, 14(6):533. PMID: 42347654
This study investigates the immunological correlates of protection induced by Strangvac®, a recombinant fusion protein vaccine containing antigens from Streptococcus equi and formulated with a saponin-based adjuvant, in ponies challenged with high doses of the pathogen. The research highlights that antibody titers to specific antigens: IdeE, Eq85, and CCE are robust correlates of protection and can predict the duration of immunity, up to at least one year post-vaccination. This paper advances knowledge on how saponin adjuvants may contribute to durable, antigen-specific humoral responses, providing valuable insights for the development and evaluation of adjuvanted vaccines.
What makes this paper unique is its comprehensive retrospective analysis across multiple controlled trials, establishing quantitative antibody thresholds linked to effective protection and demonstrating that these antibody levels sustained with the saponin adjuvant can confer long-term immunity.
The study concludes that antibody titers to the vaccine antigens IdeE, Eq85, and CCE are strong correlates of protection against clinical disease following experimental S. equi challenge in ponies vaccinated with Strangvac®. These antibody levels, measured up to one year post-vaccination, remain predictive of significant long-term protection, supporting the vaccine’s ability to confer durable immunity and aligning with observed field efficacy.
Click here to access the full scientific paper.
