This year, an unexpected finding of sustained remission of plasma viremia level (PVL) to below quantifiable assay limits in a rhesus macaque SIV infection model of AIDS was reported. The envelope of SIV (and HIV) appears to interact with α4β7 integrin, a lymphocyte homing receptor for trafficking to gut mucosal-associated lymphoid tissue (GALT) that was the target of mAb treatment in this study. This study showed that in animals treated with the mAb while discontinuing ART there was a diminished rebound and sustained remission of PVL, and less GALT associated viral load for a long-lasting period of at least 24 months. The mechanism of this unexpected post-treatment effect is unknown. In humans infected with HIV, such an effect sustained over time with continued remission of progressive immunodeficiency would meet definitional criteria of "functional cure" of HIV/AIDS. The results observed in the SIV model reveal a promising avenue for investigation in this area of research towards control of HIV infection in absence of ART. We propose to assess the safety and tolerability of anti-α4β7 integrin monoclonal antibody in healthy HIV-infected adults on ART, to assess the safety of ATI and whether anti-α4β7 integrin monoclonal antibody treatment can induce sustained virologic remission in the absence of ART.