Improved understanding of the HIV reservoir in tissues is critical to curative efforts. Progress in understanding the HIV reservoir has been hampered by difficulty to access clinically relevant tissue samples for HIV cure research. We have overcome this challenge through innovative cohort design and a long-standing collaboration at the heart of the global HIV epidemic in KwaZulu Natal, South Africa. There we have established the FRESH (Females Rising through Education, Support and Health) Study that allow us to access large blood volumes and tissue samples from persons who initiate therapy very early in Fiebig Stage I-II, some of whom have interrupted therapy during their participation in a bNAB intervention study. We propose to use samples from these cohorts to determine the barriers to HIV eradication in lymph nodes and the gut, and to test novel approaches of overcoming these barriers using the lymph-node-on-a-chip technology. This grant builds on the firm foundation laid by compelling data generated in the previous funding period, including the discovery that HIV persists in germinal center T follicular helper cells (GC TFH) mainly within the B cell follicles (BCFs) even after more than 3 years. We also showed that a stronger virus specific CD8+ T cell response in LNs is associated with reduced persistence, however, the lack of cytolytic potential by CD8+ T cells that infiltrate the BCF allows the virus to persist. We will now use the best-in-class imaging and omics technologies to determine the molecular barriers to HIV eradication in the BCFs, testing the hypothesis that HIV induced immune regulatory environment in the BCL mitigates cytotoxic activity of follicular CD8+ T cells. We will use serial excisional LN, gut biopsies and match blood samples to identify cellular and signaling processes that impede immune mediated eradication of HIV in tissues. Additionally, we will create the first known model of the HIV infected human BCF in vitro using the organ on a chip microfluidics technology and use it to test the impact of IL-15 and IL-10 blockade on enhance CTL mediated eradication of the HIV reservoir the BCF. If successful, these studies will lead to the discovery of novel therapies for HIV eradication in secondary lymphoid organs which must be a critical component of an HIV cure strategy.