Emulsion Adjuvants for Use in Veterinary Vaccines

Development and efficacy evaluation of a novel water-in-oil-in-water adjuvant for an inactivated foot-and-mouth disease vaccine

To develop a novel water-in-oil-in-water (W/O/W) adjuvant and evaluate the effect on foot-and-mouth disease (FMD) inactivated vaccine, in this study, we prepared the novel nano-emulsion adjuvant based on QS-21 (BEA) which is composed of the mixture of mineral oil Marcol52, surfactant Tween80, oleate polyoxyethylene ether ester, polyoxyethylene palmitic acid ester and span80, cosurfactant polyethylene glycol and QS-21. The two-step emulsification method formed the W/O/W nano-emulsion with two films and three-phase structures. The effective particle diameter of the BEA was about 184 nm, and it has good thermal stability. Then, BEA was emulsified as an adjuvant to prepare for the inactivated FMDV vaccine, and BALB/c mice and pigs were immunized to evaluate its safety and immunization effect. The results showed that the inactivated BEA-FMDV vaccine significantly increased BALB/c mice and pigs' antibodies and cytokine IFN-γ in serum. Meanwhile, the pig-neutralizing antibodies were higher than control group. Safety tests found no symptoms of FMD or significant toxic reactions. After 28 days of immunization, the protection rate can reach 93.3%. The BEA vaccine had good stability at 4 °C, no stratification after 180 days, and the content of 146S in the vaccine did not decrease. In conclusion, the BEA prepared in this study is suitable for FMDV inactivated vaccine and is an effective adjuvant.

New Formulation of a Subunit Vaccine Candidate against Lawsonia intracellularis Increases Humoral and Cellular Immune Responses

Previously, we designed a subunit vaccine candidate based on three L. intracellularis antigens with promising results in pigs. In this study, antigens were produced individually to achieve an even antigen ratio in the formulation. The emulsion characterization included the drop size and the mechanical and thermal stability. Immune response was evaluated by indirect and sandwich ELISAs, qPCR, and flow cytometry. The vaccine candidate's safety was assessed by histopathology and monitoring the clinical behavior of animals. The average production yielded for the chimeric antigen as inclusion bodies was around 75 mg/L. The formulation showed mechanical and thermal stability, with a ratio Hu/Ho > 0.85 and a drop size under 0.15 nm. Antigens formulated at a ratio of 1:1:1 induced a significant immune response in inoculated pigs that persisted until the end of the experiment (week 14). The dose of 200 μg significantly activated cellular response measured by transcriptional and translational levels of cytokines. The cell proliferation assay revealed an increment of lymphocytes T CD4+ at the same dose. Animals gained weight constantly and showed proper clinical behavior during immunization assays. This research demonstrated the immunological robustness of the new subunit vaccine candidate against Porcine Proliferative Enteropathy evenly formulated with three chimeric antigens of L. intracellularis.

Skin-Based Vaccination: A Systematic Mapping Review of the Types of Vaccines and Methods Used and Immunity and Protection Elicited in Pigs

The advantages of skin-based vaccination include induction of strong immunity, dose-sparing, and ease of administration. Several technologies for skin-based immunisation in humans are being developed to maximise these key advantages. This route is more conventionally used in veterinary medicine. Skin-based vaccination of pigs is of high relevance due to their anatomical, physiological, and immunological similarities to humans, as well as being a source of zoonotic diseases and their livestock value. We conducted a systematic mapping review, focusing on vaccine-induced immunity and safety after the skin immunisation of pigs. Veterinary vaccines, specifically anti-viral vaccines, predominated in the literature. The safe and potent skin administration to pigs of adjuvanted vaccines, particularly emulsions, are frequently documented. Multiple methods of skin immunisation exist; however, there is a lack of consistent terminology and accurate descriptions of the route and device. Antibody responses, compared to other immune correlates, are most frequently reported. There is a lack of research on the underlying mechanisms of action and breadth of responses. Nevertheless, encouraging results, both in safety and immunogenicity, were observed after skin vaccination that were often comparable to or superior the intramuscular route. Further research in this area will underlie the development of enhanced skin vaccine strategies for pigs, other animals and humans.