Autoimmune Encephalitis is a disorder of the central nervous system caused by bodily substances, called antibodies. Antibodies normally help the body to prevent infections. However, in this disorder, the antibodies turn against the body itself and especially against cells in the brain and disturb the normal brain function. They are therefore called autoantibodies. There is no specific therapy for patients with autoimmune encephalitis so far. At the moment, the symptoms are treated with approved medications such as cortisone and immunotherapies also used in oncology. These therapies are unspecified and aim to reduce the number of autoantibodies and to contain the autoimmune process. In this trial we aim to test a new therapy option: in this therapy the body cells producing autoantibodies will be specifically targeted by a substance called bortezomib. The trial addresses patients with severe autoimmune encephalitis. The aim of the trial is to evaluate the efficacy and safety of bortezomib in patients with severe autoimmune encephalitis.