Many infectious agents persist in the patient because of an insufficient immune response. Natural viral capsids are highly immunogenic but often they do not induce neutralizing antibodies or a CTL response. Using genetic methods protective B and T cell epitopes can be introduced into capsid proteins and expressed in bacteria or yeast. It is planned to encapsidate in vitro into such chimeric capsids genes encoding cytokines which favour Th1 and subsequent CTL responses. Recognition of such capsids by B cells would lead to efficient antibody production and Th1 cell epitope presentation in a favourable cytokine milieu. The suitability of such hepatitis B and polyoma virus capsid vectors shall be tested in cell cultures, and in mouse models.