DISEASE CHARACTERISTICS:

• Histologically confirmed metastatic adenocarcinoma of the prostate
• HLA-A2 positive

• Progressive measurable systemic disease

  • PSA at least 5 ng/mL with 2 consecutive rising PSA levels at least 1 week apart and no measurable disease OR
  • Objective evidence of disease progression by a 20% increase in the sum of longest diameter of all target lesions or evidence of new lesions by CT or bone scan regardless of PSA status
  • Lesions must be at least 1 cm to be considered measurable
  • Progressive systemic disease after discontinuation of anti-androgen therapy

• Previously treated with orchiectomy (testosterone less than 50 ng/mL) OR luteinizing hormone-releasing hormone (LHRH) analogue therapy with or without anti-androgens

  • If on LHRH analogue therapy, must continue therapy during study
• Brain metastases allowed if previously treated, clinically stable, and weaned from prior corticosteroids

PATIENT CHARACTERISTICS:

Age:

• Over 18

Performance status:

• Karnofsky 70-100%

Life expectancy:

• At least 12 weeks

Hematopoietic:

• Absolute neutrophil count greater than 1,500/mm^3
• Hemoglobin greater than 9 g/dL
• Platelet count greater than 100,000/mm^3
• No active gastrointestinal bleeding

Hepatic:

• Bilirubin less than 1.5 times upper limit of normal (ULN)
• SGPT normal
• Hepatitis B surface antigen negative

Renal:

• Creatinine less than 1.5 times ULN
• Calcium less than 11 mg/dL

Cardiovascular:

• No significant cardiovascular disease
• No cardiac arrhythmia requiring therapy

Other:

• Fertile patients must use effective barrier contraception
• No intrinsic immunosuppression
• HIV negative
• No serious concurrent infection
• No psychiatric illness that would preclude study compliance
• No clinically significant autoimmune disease
• No uncontrolled peptic ulcer disease
• No history of inflammatory bowel disease

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• At least 4 weeks since prior biologic therapy

Chemotherapy:

• Not specified

Endocrine therapy:

• See Disease Characteristics
• At least 4 weeks since prior flutamide
• At least 6 weeks since prior bicalutamide or nilutamide
• No concurrent systemic corticosteroids except physiologic replacement doses

Radiotherapy:

• Not specified

Surgery:

• See Disease Characteristics

Other:

• No concurrent immunosuppressive drugs (e.g., cyclosporine)