The purpose of this study is to assess the safety and tolerability of 2 or 4 doses of MDX-010 in HIV-infected subjects

Inclusion Criteria:

• Detectable HIV viremia (HIV-1 RNA level between 1,000 and 100,000 copies/mL)
• CD4 count greater than or equal to 100 cells/mm3
• Current antiretroviral therapy regimen following at least 2 previous changes for documented virologic failure
• Documented resistance tests demonstrating the presence of at least 1 mutation to each major therapeutic class of antiretroviral therapy
• No significant organ compromise

Exclusion Criteria:

• Initiation of any new medications that might reasonably affect the immune response or viral load within 4 weeks prior to screening
• Tetanus booster immunization within 2 months of screening, or a history of anaphylaxis or severe local reaction to the tetanus vaccine
• History of autoimmune disease at risk for recurrence
• Current malignancy, except Stage A or B cervical carcinoma or basal cell carcinoma
• Chronic viral hepatitis, due to Hepatitis B or Hepatitis C undergoing current treatment or Hepatitis B DNA greater than 25 pg/cc or Hepatitis C RNA greater than 20,000 IU/cc
• Currently undergoing treatment or prophylaxis for tuberculosis infection
• Chronic active infectious disease (other than HIV)