This is a single-center, single arm, open-label pilot study evaluating the safety, anti-tumor effect, and immunogenicity of neoadjuvant MGA271 given prior to radical prostatectomy in men with intermediate and high-risk localized prostate cancer. Patients will be recruited from the outpatient Urology clinic. Eligible patients will receive MGA271 at a dose of 15mg/kg IV given weekly for 6 doses beginning 50 days prior to radical prostatectomy. 14 days after the last dose of MGA271, prostate glands will be harvested at the time of radical prostatectomy, and prostate tissue will be examined for the secondary endpoints. Follow-up evaluation for adverse events will occur 30 days and 90 days after surgery. Patients will then be followed by their urologists according to standard institutional practices, but will require PSA evaluations every 3 (±1) months during year 1 and every 6 (±2) months during years 2-3.