Vaccine efficacy, veterinary vaccines

The results presented in this chapter demonstrate that enhanced immunogenic efficacy can be achieved by using liposphere-based formulations, indicating the potential usefulness of lipospheres in the formulation of human and veterinary vaccines. The liposphere approach employs the fat-lipid environment to achieve several goals to serve as a carrier to protect the antigen, to serve as a depot, and to provide a surface interphase necessary for adjuvant activity. The ability to provide different surface... 

Many compounds with adjuvant activity are presently known (shown in Table 12.2) but only a few are applied routinely in human and veterinary vaccines. The application of the novel adjuvants are limited for several reasons, such as disappointing efficacy in the target animal species, insufficient safety, problems with large-scale preparations, and limited stability of the final formulations. Many studies have reported on O/W and W/O emulsions used as adjuvants and delivery systems for immunization (Hilgers et al., 1994a, b, 1999). The adjuvanticity of the W/O/W makes this type of multiple emulsion a suitable delivery system for immunization with prolonged release, and its interesting preparation is presented below. 

The types of veterinary vaccine products available difler from country to country. This not only reflects commercial considerations but also disease patterns, which vary depending on location. As with human medicine, animal diseases difler with climactic conditions and so different vaccines are required in equatorial conditions when compared with those needed in northern Europe. Table 14.1 is neither comprehensive nor is it representative of every climactic area. In fact, it is largely (but not entirely) based on the United Kingdom and the vaccine products commercially available there. The table also shows that in the UK there only three enzootic disease vaccines available which are capable of causing disease in humans. Such vaccines are usually authorised, in spite of the obvious hazards and associated risks, either because the inactivated versions are not effective or if they are, they are not as efficacious as the live version. 

Veterinary vaccines are frequently complex formulations. In addition to one or more antigens, they also contain a solvent or solvent system. To achieve maximum efficacy, these products usually contain an adjuvant. The nature of these adjuvants can vary widely but the most common ones are aluminium compounds, mineral oil, saponins and nanoparticles, and although their activities are poorly understood they may have immunomodulatory effects or... 

Harrison, G.B., Shakes, T.R., Robinson, C.M., Lawrence, S.B., Heath, D.D., Dempster, R.P., Lightowlers, M.W. and Rickard, M.D. (1999) Duration of immunity, efficacy and safety in sheep of a recombinant Taenia ovis vaccine formulated with saponin or selected adjuvants. Veterinary Immunology and Immunopathology 70, 1 61 -1 72. 

RUANGPAN, L., KITAO, T. and YOSIHDA, T. (1986) Protective efficacy of Aeromonas hydrophila vaccines in Nile tilapia. Veterinary Immunology and Immunopathol-ogy 12,345-350. 

---