Background: Veterinary autogenous vaccines, similar to all injectable pharmaceutical products, must be tested to assess endotoxin concentrations. The Limulus Amebocyte Lysate Test (LAL test) is widely used in in vitro quality control assays for endotoxin detection, although it presents some ethical issues related to the production of reagents and is also characterized by a low specificity due to other contaminants that can activate the reaction. For all these reasons, a new recombinant factor C LAL test was developed. Aim: In this study, we described the comparison between two LAL test methods for in vitro quality control of veterinary autogenous vaccines, with the aim of evaluating the most suitable method and establishing an endotoxin concentration range for two different matrices. Methods: Two hundred batches of two different vaccine matrices were tested using the kinetic chromogenic LAL test and recombinant factor C endotoxin detection assay commercial kits. Results and Conclusions: Statistical analysis conducted after the validation of the recombinant factor C test exhibited a statistically significant correlation between the two methods and for both vaccine matrices, suggesting that the animal-free assay can be used as a routine quality control test for veterinary autogenous vaccines.

Background: Veterinary autogenous vaccines (AVs) are emergency tools produced in a short timeframe from bacterial/viral/fungal isolates when commercial vaccines are not available and undergo strict quality assurance and safety tests before release. In accordance with the European Directive 2010/63/EU and the 3R principles, we evaluated for the first time the possible substitution of the final toxicity in vivo test (abnormal toxicity test) with an alternative cell-based and embryo-based assay. Methods: The five most requested different autogenous matrices (adopted to produce a customizable number of lots requested from customers) were tested in vitro in parallel for residual toxicity by in vitro fish embryo acute toxicity (FET) test and cytotoxicity assay (MTS) using serial dilutions, together with the authorized in vivo test. Results: Statistical analysis revealed different outcomes between the two in vitro methods, highlighting the greater discriminatory power of the MTS assay compared to the other, with results more like the observed in vivo ATT outcome (pass/negative). Conclusions: In this preliminary first dataset, FET appeared poorly compatible with several complex autogenous vaccine matrices, while the L929 MTS assay yielded interpretable viability thresholds for all tested matrices. These findings support further qualification of MTS as part of an integrated non-animal batch characterization strategy, but they do not yet establish replacement of the in vivo test for veterinary autogenous vaccine quality control.

Background/Objectives: European Brown Hare Syndrome (EBHS) is an acute and highly contagious viral disease of hares that causes considerable economic losses on wild and captive-reared hares. No preventive treatments are currently available to defeat the disease. Immunoprophylactic and biosafety measures could be applied to prevent EBHS only in captive-reared hares, where vaccination is proposed as an effective strategy. Due to the lack of a cellular substrate for virus growth, commercially available vaccines are autovaccines produced from inactivated liver suspensions of hares dead for EBHS. Therefore, using a recombinant vaccine based on VP60 major capsid protein seems a viable alternative to overcome such a problem. Methods: the 6xHis C-terminal tagged VP60 protein of EBHSV was expressed and produced in baculovirus, purified by affinity chromatography and the self-assembled recombinant (rEVP60-His₆) protein. To establish the protective properties of rEVP60-His₆-based VLPs, hares were immunised with 50 and 100 µg of VLPs and parenterally challenged with EBHSV. Results: all hares vaccinated with 100 µg of VLPs survived after the experimental infection, demonstrating the excellent protective ability of this prototype VLPs-based vaccine. Conclusions: self-assembled EBHSV rEVP60-His₆ protein was successfully produced following a rapid, simple, low-cost protocol. Although the protective efficacy of such VLPs were experimentally demonstrated, some key aspects remain to be clarified, including the duration of protection, the entity of the antibody response, and the ability to stimulate cell-mediated response. Last, an additional aspect to be evaluated is whether the use of an adjuvant can determine whether its presence improves the performance of the recombinant VLPs vaccine.