A luminescence-based assay for evaluating bactericidal antibody to Borrelia burgdorferi in vaccinated horses' serum.
Authors: Lee J J, Hsieh C L, Widman J, Mingala C, Ardeza Villanueva M, Feng H, Divers T, Chang Y-F
Journal: Equine veterinary journal
Summary
# Editorial Summary: A Luminescence-Based Assay for Evaluating Bactericidal Antibody to *Borrelia burgdorferi* in Vaccinated Horses The ability to distinguish between antibodies that actually kill *Borrelia burgdorferi* and those that merely indicate exposure has long been a limitation of conventional serological testing for Lyme disease in horses. Lee and colleagues developed a luminescence-based serum bactericidal assay (L-SBA) using genetically modified spirochetes expressing luciferase; viable bacteria produce a measurable light signal when incubated with patient serum and complement, allowing quantification of genuinely bactericidal activity rather than simple antibody presence. Their validation work on 238 vaccinated horses and archived samples revealed a moderate positive correlation (r = 0.423) between L-SBA titres and anti-OspA antibody levels, whilst systematically optimising reaction conditions including spirochete source, complement origin and concentration to ensure reproducibility. The assay proved sensitive and practical to operate, though the authors appropriately note that batch-to-batch variation in commercial complement sources requires standardisation, and that protective thresholds for bactericidal antibody levels in horses remain undetermined. For practitioners assessing vaccine responses or investigating potential Lyme disease exposure, this method represents a meaningful advance toward evaluating true immune protection rather than relying solely on conventional antibody titres.
Read the full abstract on PubMed
Practical Takeaways
- •Practitioners can now use L-SBA as a more specific tool than conventional serological tests to verify that horses have mounted a functionally protective immune response to Borrelia vaccination, rather than just an antibody response
- •Vaccination efficacy in horses can be better monitored with this assay, potentially improving decision-making about booster vaccination timing and protocol effectiveness
- •Standardization of complement source and batch testing will be essential for consistent results if L-SBA is adopted in clinical diagnostic settings
Key Findings
- •A luminescence-based serum bactericidal assay (L-SBA) successfully distinguished bactericidal antibodies to B. burgdorferi from non-functional antibody responses in vaccinated horses
- •L-SBA titres correlated with anti-OspA antibody levels (r = 0.423) in vaccinated horses, establishing a relationship between the two measurement methods
- •Commercial complement immunoreactivity varied between batches, requiring standardization for reliable assay performance
- •The L-SBA provided a sensitive, easy-to-operate platform for evaluating vaccine efficiency against B. burgdorferi in horses