Increasing disease resistance in transgenic domestic animals

Novel approaches to modify disease resistance or susceptibility in livestock are justified by economical and animal welfare reasons. Currently research on the improvement of disease resistance by gene transfer focuses on three main issues: (i) somatic gene transfer, i.e. nucleic acid vaccines, (ii) deletive or replacement germline gene transfer, i.e. gene knockout or targeted introduction of novel alleles and (iii) additive germline gene transfer. The strategies aim at the transient or stable expression of components known to influence innate or adaptive host defence mechanisms or the disruption and/or replacement of genes known to cause susceptibility to disease. Referring to the source of the effective agent and the site and mode of action the additive gene transfer strategies are termed 'genetic', 'congenital', 'intracellular' and 'extracellular' immunisation.