Report on the international workshop on alternative methods for Leptospira vaccine potency testing: State of the science and the way forward

• Potency testing of Leptospira vaccines is mostly conducted using a vaccination–challenge test.
• A workshop reviewed alternative methods for veterinary Leptospira vaccine potency testing.
• Product-specific validation using ELISAs for four Leptospira serogroups was recommended.
• Serology assays should be considered only after attempting in vitro assays.
• The potential for eliminating the back-titration procedure was highlighted.

Routine potency testing of Leptospira vaccines is mostly conducted using a vaccination–challenge test that involves large numbers of hamsters and unrelieved pain and distress. NICEATM, ICCVAM, and their international partners organized a workshop to review the state of the science of alternative methods that might replace, reduce, and refine the use of animals for veterinary Leptospira vaccine potency testing and to identify ways to advance improved alternative methods. Vaccine manufacturers were encouraged to initiate or continue product-specific validation using in vitro enzyme-linked immunosorbent assays as replacements for potency testing of four common Leptospira serogroups. Participants discussed the potential for eliminating the back-titration procedure in the hamster challenge assay, which could reduce animal use by 50% for each individual potency test. Further animal reduction may also be possible by using cryopreserved Leptospira stock to replace continual passaging through hamsters. Serology assays were identified as a way to further reduce and refine animal use but should be considered only after attempting in vitro assays. Workshop participants encouraged consideration of analgesics and use of earlier humane endpoints when the hamster vaccination–challenge potency assay is used. International harmonization of alternative potency methods was recommended to avoid duplicative potency testing to meet regionally different requirements.