Infections with the human cytomegalovirus (HCMV) can cause life threatening illness in foetuses or patients after transplantation. Antiviral drugs are available but their use is limited due to adverse effects and development of resistance. Antibodies could serve as an alternative approach. From thousands of blood donors we have identified those with the highest activity against HCMV. Now, we aim to test whether plasma from these donors can raise the concentration of anti-HCMV antibody in patients after transplantation. If this is successful, we plan to isolate the antibody genes from the blood cells of the respective donors to enable production of such antibodies in the laboratory. This may help to develop alternative treatment options for HCMV-infected patients.