The need for a novel generation of vaccines

Although empirical vaccine development was highly successful, it has now re ached its limits. Vaccines are only efficacious against those pathogens whi ch are primarily controlled by antibodies. Protection against many infectio us agents, however, strongly depends on T lymphocytes. Thus, novel vaccines have to stimulate the combination of T lymphocytes that is required for an optimum protective immune response. Although identification of antigens re mains crucial, novel vaccine design also needs to consider the best way of introducing these antigens to the immune system. Intracellular antigen comp artmentalisation, the early cytokine milieu and the appropriate surface exp ression of co-stimulatory molecules are of major relevance for understandin g how novel vaccines could induce a protective immune response mediated by T lymphocytes. Intracellular bacteria are controlled by T lymphocytes and e fficacious vaccines against these pathogens are not available yet. In this treatise, two experimental vaccination strategies will be described in more detail. These encompass recombinant vaccine carriers expressing, and naked DNA constructs encoding, heterologous antigens. Both vaccination strategie s proved to be protective in the model of experimental listeriosis of mice.