To Investigate the Safety and Efficacy of UB-421 Monotherapy in HIV Infected Adults

Inclusion Criteria: * HIV-1 sero-positive * Aged 20 years or older * Have received HAART treatment * CD4+ T cell count ≧ 350 cells/mm3 * HIV-1 plasma RNA level remains below the limit of * Were not breastfeeding for women * Subjects with a negative serum pregnancy test result at screening visit for women of childbearing potential * Subjects agree on using birth control barrier (female or male condom) during the entire study period * Subjects sign the informed consent before undergoing any study procedures Exclusion Criteria: * Any active infection except for HIV, and required immediate therapy * Any active AIDS-defining illness per Category B and Category C conditions according to the U.S. Centers for Disease Control and Prevention (CDC) Classification System for HIV Infection * Any documented CD4+ T cell count \< 200 cells/mm3 within the past 12 weeks before screening visit * Any significant diseases (other than HIV-1 infection) or clinically significant findings, including psychiatric and behavioral problems, determined from screening, medical history, and/or physical examination that, in the investigator's opinion, would preclude the subject from participating in this study * Any vaccination within 8 weeks prior to the first dose of study drug * Any immunomodulating therapy (including interferon and steroid) or systemic chemotherapy within 12 weeks prior to the first dose of study drug * Any illicit intravenous drugs within 12 weeks prior to the first dose of study drug * Any current alcohol or illicit drug use that, in the investigator's opinion, will interfere with the subject's ability to comply with the dosing, visit schedules and protocol evaluations * More than one change of HAART regimen because of virologic failure