Advances in veterinary medicine
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Vaccination is the single most successful medical measure against infectious disease. However, the major barrier for achieving the full protective effect or immunization is how to render attenuated, killed, or subunit vaccines as immunogenic as the fully infectious versions of these microbes (Hughes and Babiuk, 1995; Rabinovich et al., 1994). In the case of PrV, infection with wild-type virus induces an immune response superior to vaccination with a live modified vaccine. ⋯ By providing cytokines such as IL-12 or IFN-gamma in combination with the vaccine inoculum, it is reasonable to expect that they will be able to direct the differentiation of T cells during the primary immune response. Modulation, in a predictable and desired manner of the quality and quantity of the induced protective immunity, should be achievable. The ability to manipulate a vaccine-induced immune response in the direction of a predominantly cellular response (Th1-like) instead of a predominantly humoral one (Th2-like) is perhaps best illustrated by the need to develop an effective vaccine against the porcine reproductive and respiratory syndrome (PRRS) virus, whose infectivity can be significantly enhanced in vitro and in vivo by antibody induced by vaccination
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Whatever strategy is adopted for the development of viral vectors for delivery of veterinary vaccines there are several key points to consider: (1) Will the vectored vaccine give a delivery advantage compared to what's already available? (2) Will the vectored vaccine give a manufacturing advantage compared to what's already available? (3) Will the vectored vaccine provide improved safety compared to what's already available? (5) Will the vectored vaccine increase the duration of immunity compared to what's already available? (6) Will the vectored vaccine be more convenient to store compared to what's already available? (7) Is the vectored vaccine compatible with other vaccines? If there is no other alternative available then the answer to these questions is easy. However, if there are alternative vaccines available then the answers to these questions become very important because the answers will determine whether a vectored vaccine is merely a good laboratory idea or a successful vaccine.