Preliminary evaluation of a dual antigen ELISA to distinguish vaccinated from Leptospira infected horses.
Authors: Velineni S, Timoney J F
Journal: The Veterinary record
Summary
# Editorial Summary: Distinguishing Leptospiral Infection from Vaccination in Horses Leptospirosis poses a significant diagnostic challenge in horses because conventional serology cannot reliably differentiate protective vaccine-induced immunity from active infection. Velineni and Timoney (2016) exploited a key biological difference: proteins upregulated during natural infection (Sph1, LigA, Hsp15 and LipL45) are expressed minimally or not at all in cultured vaccine organisms, whereas LipL32 is abundant in both. Their investigation compared antibody responses in naturally infected horses against those vaccinated with a serovar Pomona bacterin, screening IgG reactivity across six recombinant leptospiral antigens and whole-organism sonicate. Critically, infection sera showed strong reactivity to Sph1, LigA and a truncated LigA fragment (Lk90), while vaccine sera did not; conversely, both infection and vaccine sera responded robustly to LipL32 and sonicate, rendering these unsuitable as discriminators on their own. A dual-antigen ELISA combining a broadly reactive antigen (sonicate or LipL32) with infection-specific markers (Sph1 and Lk90) therefore offers practitioners a rational approach to serological interpretation—enabling differentiation of vaccinated from infected animals and clarifying the clinical significance of positive leptospiral titres in individual cases.
Read the full abstract on PubMed
Practical Takeaways
- •A new diagnostic ELISA can help distinguish between horses infected with Leptospira and those protected by vaccination, improving disease surveillance and management decisions
- •Culture-based vaccines do not stimulate antibodies to infection-induced proteins, allowing for serological differentiation that wasn't previously possible
- •This test could reduce unnecessary treatment or quarantine of vaccinated horses while identifying truly infected animals requiring intervention
Key Findings
- •Infection sera reacted strongly with host-induced proteins Sph1, LigA, and Lk90, while vaccine sera did not
- •LipL32 and Lk sonicate reacted strongly with both infection and vaccine sera, making them unsuitable for differentiation alone
- •LipL45 and Hsp15 showed moderate reactivity with infection sera and weak reactivity with vaccine sera
- •A dual antigen ELISA combining LipL32/Lk sonicate with host-induced Sph1 and Lk90 can differentiate infection from vaccination responses