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.

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.

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In Europe, use of non-animal methods is encouraged and being informed is key.

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Manufacturers should engage in validation studies at an early stage.

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Participants in validation studies can use data for product-specific validation.

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More regulatory guidance on setting specifications and validity criteria needed.

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Communication of key players crucial for implementation/acceptance of methods.

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.

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.

Quantification of the herpesvirus content in various tissues and organs, and associated post mortem lesions of psittacine birds which died during an epornithic of pacheco's parrot disease (PPD)

This paper reports on the viral content of up to 52 tissue and organ samples of 18 individual large psittacines which died during an epornithic of Pacheco's parrot disease (PPD) caused by psittacid herpesvirus 1 (PsHV1). Associated clinical signs and pathological lesions are described. The large spectrum of samples found to be positive for PsHVl suggests that birds succumb to PPD during viraemia. Tissues and organs from which the virus could be isolated included the integument and associated structures, the muscular, respiratory and circulatory system, bone marrow, the nervous system, thyroid and adrenal glands, spleen and liver, the urogenital tract and the gastro-intestinal tract. Nevertheless, individual and organ (but not species)-specific variation does occur. Virus isolation appears to be most promising from the respiratory, vascular and nervous system and the liver. Highest titres were obtained from heart blood and liver (up to 7.6 log(10)/g tissue), airsac, Nervus vagus and pulp and quill of pin feathers. Pin feathers may therefore be suitable for in-vivo diagnosis. In contrast, HV could not be isolated from any of the feather vanes examined. For the most part, post mortem lesions do not reflect the organ pattern found to be most permissive for virus replication as judged by the success of virus isolation and virus titres. A closer quantitative correlation is indicated for the lungs, spleen and liver, only. Corresponding findings as to frequency of gross pathological lesions and virus quantification appear to be restricted to the liver. In accordance with clinical observations and experimental findings, tissue virus content indicates that horizontal spread of herpesviruses is mediated by cloacal contents or secretions from the respiratory system.

Towards in vitro potency testing of inactivated erysipelas vaccines

Ph. Eur. Monograph 0064 "Swine erysipelas vaccine (inactivated)" currently advises mouse serology for batch potency testing. However, technological advances in vaccine production, improved quality control systems and comprehensive post marketing surveillance increasingly promote the acceptance of non-animal approaches for batch release testing. Protein and immune profiles of inactivated swine erysipelas vaccines obtained by SDS-PAGE and Western Blot might offer a convenient global and functional in vitro alternative. Characteristic and consistent protein and immune profiles could be obtained for aluminium-adjuvanted vaccines. Immunoreactivity of polyclonal sera raised in mice differs markedly from reactivity of swine sera.

[100 years of erysipelas prophylaxis: significance and reduction of animal experiments]

The history of erysipelas prophylaxis began in 1882 when Pasteur first discovered the attenuating effect of rabbit passages on the erysipelas bacterium. Ten years later, the German veterinarian Lorenz demonstrated the protecting effect of erysipelas antiserum. He developed a method of serovaccination which was successfully used in Germany for more than 50 years. Both scientists employed laboratory animals for the development of their live vaccines. Lorenz additionally recommended an animal model with grey mice to control the potency of erysipelas sera. In 1944, Fortner and Dinter published the results of their investigation on a skin scarification test in swine. This modus of infection was the basis of the first reliable model for efficacy testing of erysipelas vaccines in domestic animals. Shortly after World War II, the first inactivated erysipelas vaccines were being developed. At that time, also a strict quality control was introduced for this product group which required extensive animal experiments in laboratory mice and pigs for the determination of efficacy. WHO established International Standards for erysipelas vaccines and antisera concerning potency testing in mice. These animal models were finally incorporated in pharmacopoeia monographs. Animal experiments have played an important role in the development and quality control of erysipelas vaccines. And the success of this quality control based on animal experiments has had a significant impact on the quality control systems for veterinary vaccines in general. Today, we have a far more detailed knowledge about pathogenesis and immunology of swine erysipelas. This knowledge now allows the introduction of alternative methods according to the 3R concept. With these new methods, animal numbers can be decreased and suffering caused by challenge infection can be reduced. The ultimate goal, i.e. quality control of erysipelas vaccines carried out without routine performance of animal experiments, should be achieved in the near future.

Comparative studies of diagnostic bacteriological methods for the recovery of Salmonella from faecal samples from flocks of layers

Several conventional culture procedures were compared for the recovery of Salmonella from faecal samples of layer flocks. The cultural media employed consisted of Rappaport-Vassiliadis and tetrathionate broth for selective enrichment and three different plating media (Brilliant Green, Xylose-Lysine-Desoxycholate and modified semisolid Rappaport-Vassiliadis medium). The initial enrichment and plating procedures were repeated in a four-stage secondary enrichment. Selective enrichment in Rappaport-Vassiliadis or tetrathionate broth followed by plating on modified semisolid Rappaport-Vassiliadis medium (selective motility enrichment) resulted in a significantly higher isolation rate for Salmonella from faecal samples of layers compared to Brilliant Green and Xylose-Lysine-Desoxycholate medium. The selective enrichment yielded additional Salmonella isolates up to the second stage. Further enrichment did not increase the isolation rate.

Review of the literature and investigations on the prevalence and consequences of yeasts in reptiles

Ninety-one reptiles were examined for the presence of yeasts by standard protocols and pathohistological methods. Yeasts were isolated from 42 of the animals. Representatives of herbivorous families (Testudinidae and Iguanidae) carried yeasts more often than animals belonging to carnivorous taxa (Boidae and Emydidae). Yeasts were most often isolated from the gastrointestinal tract, and in 24-6 per cent of cases they could be cultured from the oral cavity and/or cloaca of living animals. Postmortem examination revealed that the intestines of 80-6 per cent of the animals carried yeasts. In all, 56 isolates, belonging to the genera Candida (32), Trichosporon (11), Torulopsis (9) and Rhodotorula (3), and one perfect yeast were obtained. The species included taxa potentially pathogenic to man. However, no sufficiently reliable criteria could be established to prove that positive culture results were associated with disease. In the reptiles examined postmortem, three cases of dermatomycosis were detected histologically. No case of organ mycosis was identified.

[Polyostotic hyperostosis in a plum-headed parakeet (Psittacula cyanocephala L., 1766]

With emphasis on a case report, the clinical and pathological findings commonly associated with polyostotic hyperostosis as well as its etiology are discussed, and the available literature is reviewed. The diagnostic specifics of the disease are detailed, and a survey of possible differential diagnoses is given.