Abstract: Novel proteins of the Chicken Anemia Virus are described and compositions for preventing or treating infections with that virus (CAV), in particular vaccines less pathogenic than the CAV itself, but yet leading to neutralizing antibodies in the immunized animal. Besides, there are described compositions containing antibodies against parts of the CAV for the control of infections with CAV and anti-idiotype antibodies. The invention also provides antibodies and test kits for the detection of CAV. Recombinant DNA molecules derived from CAV and host cells transfected therewith and vaccines based on these host cells are made possible by this invention. The invention also comprises living virus vaccines in which a piece of DNA is brought into a virus infectious to the host. Besides, the invention provides uses of proteins of CAV in the induction of apoptosis, in particular in tumor cells. It further provides the induction of cell death by means of gene therapy.