Vaccine Therapy Plus QS21 in Treating Patients With Prostate Cancer

DISEASE CHARACTERISTICS: * Histologically confirmed prostate cancer * Disease progression after primary surgery (radical prostatectomy) or radiotherapy with or without prior neoadjuvant androgen ablation * Minimum of 3 rising PSA values, taken at least 2 weeks apart, with more than a 50% rise in PSA level above the baseline value (1.0 ng/mL post -prostatectomy or 2.0 ng/mL post-radiotherapy) * Received prior intermittent hormonal therapy after prior primary therapy * Non-castrate levels of testosterone (more than 50 ng/mL) * Evaluable disease (by serial changes in PSA) * No radiographic evidence of metastatic disease * No active CNS or epidural tumor * No soft tissue and/or bone disease * No androgen-independence with no evidence of radiographic disease * May not be symptomatic or anticipated to develop symptoms within 6 months of study entry PATIENT CHARACTERISTICS: Age: * 18 and over Performance status: * Karnofsky 70-100% Life expectancy: * At least 6 months Hematopoietic: * WBC at least 3,500/mm\^3 * Platelet count at least 100,000/mm\^3 Hepatic: * Bilirubin less than 2.0 mg/dL * SGOT less than 3 times upper limit of normal Renal: * Creatinine no greater than 2.0 mg/dL OR * Creatinine clearance at least 40 mL/min Cardiovascular: * No clinically significant cardiac disease (New York Heart Association class III or IV) Pulmonary: * No severe debilitating pulmonary disease Other: * No allergy to seafood (shellfish) * No other active malignancy within the past 5 years except nonmelanoma skin cancer * No infection requiring antibiotics * No narcotic-dependent pain * No positive stool guaiac unless associated with hemorrhoids or prior documented radiation-induced proctitis PRIOR CONCURRENT THERAPY: Biologic therapy: * Not specified Chemotherapy: * At least 4 weeks since prior chemotherapy Endocrine therapy: * See Disease Characteristics * See Chemotherapy * At least 2 weeks since change in hormonal therapy (e.g., prednisone or dexamethasone) except to maintain castrate levels of testosterone Radiotherapy: * See Disease Characteristics * At least 4 weeks since prior radiotherapy * No concurrent irradiation of only measurable lesion Surgery: * See Disease Characteristics * No concurrent surgery of only measurable lesion Other: * Recovered from prior therapy * At least 8 weeks since prior suramin and/or documented plasma concentration of suramin if less than 50 micrograms/mL (replacement hydrocortisone allowed) * No other concurrent oncolytic agents * No concurrent immunosuppressive therapy