Integrin α 4 β 7 mediates the trafficking of leukocytes, including CD4 + T cells, to lymphoid tissues in the gut. Virus mediated damage to the gut is implicated in HIV and SIV mediated chronic immune activation and leads to irreversible damage to the immune system. We employed an immuno-PET/CT imaging technique to evaluate the impact of an anti-integrin α 4 β 7 mAb alone or in combination with ART, on the distribution of both SIV infected cells and CD4 + cells in rhesus macaques infected with SIV. We determined that α 4 β 7 mAb reduced viral antigen in an array of tissues of the lung, spleen, axillary, and inguinal lymph nodes. These sites are not directly linked to α 4 β 7 mediated homing; however, the most pronounced reduction in viral load was observed in the colon. Despite this reduction, α 4 β 7 mAb treatment did not prevent an apparent depletion of CD4 + T cells in gut in the acute phase of infection that is characteristic of HIV/SIV infection. However, α 4 β 7 mAb appeared to facilitate the preservation or restoration of CD4 + T cells in gut tissues at later stages of infection. Since damage to the gut is believed to play a central role in HIV pathogenesis, these results support further evaluation of α 4 β 7 antagonists in the study and treatment of HIV disease.