Veterinary Vaccines
The technology of controlled release has always been attractive to veterinary vaccine developers as it has potential to bring a level of convenience, efficacy, and compliance to the use of vaccines. The ability to have in a single therapy or device all t
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Veterinary Vaccines Martin J. Elhay
Abstract The technology of controlled release has always been attractive to veterinary vaccine developers as it has potential to bring a level of convenience, efficacy, and compliance to the use of vaccines. The ability to have in a single therapy or device all that it is required to sensitize and protect an animal may deliver access to new markets, provide differentiation to existing products, and solve hitherto unmet needs in veterinary immunology. However, few controlled release vaccine formulations are available at this time despite the sophistication of the materials and devices used for controlled release of medical and veterinary therapeutics. Recent advances in our understanding of how the immune system is sensitized is beginning to allow us to apply new and old technology of controlled release to vaccines across a number of livestock and companion animal species. The technology allows us to control how antigen and adjuvant are presented to the host with increasing fidelity resulting in appropriate levels and duration of immunity. The discovery that many adjuvants work by stimulating the innate immune system has led to the development of molecular adjuvants, which are well suited to devices and controlled release formulations. As controlled release vaccine formulations near late development there are regulatory concerns that need to be addressed as familiar and unfamiliar vaccine components are presented to regulators in a persistent form.
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Introduction
The case of controlled release of veterinary vaccines in general is an interesting one in the realm of veterinary medicine. Unlike other preventative or therapeutic drugs, which may be directed toward a single biological target, the aim is to present to the
M.J. Elhay (*) Veterinary Medicines R&D, Pfizer Animal Health, Parkville, VIC, Australia e-mail: martin.elhay@pfizer.com M.J. Rathbone and A. McDowell (eds.), Long Acting Animal Health Drug Products: Fundamentals and Applications, Advances in Delivery Science and Technology, DOI 10.1007/978-1-4614-4439-8_14, © Controlled Release Society 2013
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immune system a package consisting of an immunogen and immunostimulatory molecules in a particular context that will afford relevant and, usually, sustained immunity. This does not necessarily mean that there needs to be continuous high levels of active ingredient but, rather, judicious presentation of antigen to the immune system in the context of appropriate immune signals. This is achieved normally by repeated immunization with vaccine formulations that characteristically are a mixture of antigen and adjuvant. An adjuvant is required to provide the host with a signal [1, 2] that indicates that the antigen should be treated by the body as foreign or a danger to the host and consequently neutralized by one or a number of immune mechanisms. The mechanisms of adjuvant action are beyond the scope of this chapter; however, it needs to be noted that adjuvants have a complex role in both activation of the imm
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