3Rs implementation in veterinary vaccine batch-release testing: Current state-of-the-art and future opportunities. A webinar and workshop report.

Regulatory authorities require veterinary batch-release testing to confirm vaccine potency and safety, but these tests have traditionally relied on large numbers of laboratory animals. Advances in vaccine research and development offer increasing opportunities to replace in vivo testing, and some stakeholders have made significant progress in incorporating 3Rs elements in quality control strategies. A three-part event series entitled "3Rs Implementation in Veterinary Vaccine Batch-Release Testing: Current state-of-the-art and future opportunities" was jointly organized by the Animal-Free Safety Assessment Collaboration, HealthforAnimals, and the International Alliance of Biological Standardization. Two webinars and a workshop aimed to outline the state-of-the-art non-animal approaches for veterinary batch-release testing. The events included information on the state of the deletion of obsolete safety testing and the current initiatives implemented by European, North American, and Asian-Pacific stakeholders on 3Rs implementation and regulatory acceptance. The events contributed to a better understanding of the barriers to 3Rs implementation. Participants highlighted the need for open communication, continued collaboration between stakeholders, and international harmonization of regulatory requirements to help accelerate acceptance. Despite the challenges, the countries represented at this three-part event have shared their commitments to advancing the acceptance of alternative methods.

BCG Vaccination Induces Robust CD4+ T Cell Responses to Mycobacterium tuberculosis Complex-Specific Lipopeptides in Guinea Pigs.

A new class of highly antigenic, MHC-II-restricted mycobacterial lipopeptides that are recognized by CD4-positive T lymphocytes of Mycobacterium tuberculosis-infected humans has recently been described. To investigate the relevance of this novel class of mycobacterial Ags in the context of experimental bacille Calmette-Guérin (BCG) vaccination, Ag-specific T cell responses to mycobacterial lipid and lipopeptide-enriched Ag preparations were analyzed in immunized guinea pigs. Lipid and lipopeptide preparations as well as complex Ag mixtures, such as tuberculin, mycobacterial lysates, and culture supernatants, all induced a similar level of T cell proliferation. The hypothesis that lipopeptide-specific T cells dominate the early BCG-induced T cell response was corroborated in restimulation assays by the observation that Ag-expanded T cells specifically responded to the lipopeptide preparation. A comparative analysis of the responses to Ag preparations from different mycobacterial species revealed that the antigenic lipopeptides are specific for strains of the M. tuberculosis complex. Their intriguing conservation in pathogenic tuberculous bacteria and the fact that these highly immunogenic Ags seem to be actively released during in vitro culture and intracellular infection prompt the urgent question about their role in the fine-tuned interplay between the pathogen and its mammalian host, in particular with regard to BCG vaccination strategies.

Recommendations of the VAC2VAC workshop on the design of multi-centre validation studies.

Within the Innovative Medicines Initiative 2 (IMI 2) project VAC2VAC (Vaccine batch to vaccine batch comparison by consistency testing), a workshop has been organised to discuss ways of improving the design of multi-centre validation studies and use the data generated for product-specific validation purposes. Moreover, aspects of validation within the consistency approach context were addressed. This report summarises the discussions and outlines the conclusions and recommendations agreed on by the workshop participants.

Development and validation of a serological potency test for the release of Leptospira vaccines--requirements in the European Union.

Both European Pharmacopoeia Monograph 01/2008:0447 "Canine Leptospirosis vaccine (inactivated)" and the more recent Monograph 01/2008:1939 "Bovine Leptospirosis vaccine (inactivated)" explicitly allow for a sero-response test to assess batch potency. Test setup and requirements for in vivo and in vitro validation are described. Furthermore, the two main strategies to assess batch potency and their specific demands are addressed.

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

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.

Potency testing of veterinary vaccines: the way from in vivo to in vitro.

Current quality control of inactivated animal vaccines still focuses on the potency of final products in a batch-wise manner. Animal welfare concerns as well as scientific considerations have led to the '3Rs-concept' that comprises the refinement of animal procedures, the reduction of animal numbers, and the replacement of animal models. Although the 3Rs-concept has been widely accepted as a fundamental principle, the number of approved alternatives for in vivo tests is still limited. To promote further progress, the international scientific workshop 'Potency Testing of Veterinary Vaccines: The Way from in vivo to in vitro' was held at the Paul-Ehrlich-Institut in Langen, Germany, on 01-03 December 2010. More than 130 participants from industry, academia and regulatory authorities discussed the current state of the 3Rs-concept, examples of its successful implementation as well as still existing hurdles. Special emphasis was laid on the 'consistency approach' that aims to ensure relevant quality attributes of vaccine batches by in vitro analyses during production rather than by in vivo potency tests on the final product. This report provides an overview of the insights gained, including the recommendations produced at the end of the workshop.

Three Rs Approaches in the Production and Quality Control of Fish Vaccines.

The workshop on Three Rs Approaches in the Production and Quality Control of Fish Vaccines aimed a) to identify animal tests currently stipulated for the production and quality control of fish vaccines and to highlight animal welfare concerns associated with these tests; b) to identify viable options to replace, reduce, and refine animal use for fish vaccine testing; and c) to discuss the way forward and set out how the Three Rs may be implemented without jeopardizing the quality of the vaccines. The workshop participants - experts from academia, regulatory authorities, a scientific animal welfare organization, and the fish vaccine industry - agreed that efforts should be undertaken to replace the vaccination-challenge batch potency testing with tests based on antigen quantification or antibody response tests. Regulatory requirements of questionable scientific value and relevance for the quality of fish vaccines, such as the re-testing of batches produced outside Europe, or the double-dose batch safety test, should be re-considered. As an immediate measure the design of the current animal tests should be evaluated and modified in the light of refinement and reduction, for example, the number of unprotected control fish in vaccination-challenge tests should be reduced to the minimum.

A new lymphocyte proliferation assay for potency determination of bovine tuberculin PPDs.

The tuberculin skin test is the method of choice for tuberculosis surveillance in livestock ruminants. The exact definition of the biological activity of bovine tuberculin purified protein derivatives (bovine tuberculin PPDs) is essential for the reliability of a test system. PPDs consist of heterogeneous mixtures of mycobacterial antigens, making it difficult to determine their potency in vitro. The commonly used batch potency test is therefore based on the evaluation of skin reactions in mycobacteria-sensitized guinea pigs. Aim of the present study was to test an alternative in vitro method that reliably quantifies tuberculin PPD potency. This novel approach may prevent animal distress in the future. To this end a flow cytometry-based lymphocyte proliferation assay using peripheral blood mononuclear cells (PBMCs) from sensitized guinea pigs was established. Potency estimates for individual PPD preparations were calculated in comparison to an international standard. The comparison with results obtained from the guinea pig skin test revealed that the lymphocyte proliferation assay is more precise but results in systematically higher potency estimates. However, with a manufacturer specific correction factor a correlation of over 85% was achieved, highlighting the potential of this in vitro method to replace the current guinea pig skin test.