OUTLINE: Patients receive polysialic acid keyhole limpet hemocyanin (PSA-KLH) conjugate or N-propionylated PSA-KLH conjugate plus immunological adjuvant QS21 subcutaneously weekly on weeks 1-4 and on weeks 8 and 16 for a total of 6 vaccinations. Patients are followed at 2 weeks, and then every 3 months for up to 1 year.