Kaposi's sarcoma-associated herpesvirus (KSHV) is a virus that is linked to the development of a type of cancer known as Kaposi's sarcoma (KS) in individuals with compromised immune systems. KS is one of the top 10 cancers identified in men, women and children in South Africa, where it is the third most common cancer in African men. Despite this, there are no specific or effective treatments for KS that target the KSHV virus directly. As KS is an AIDS-defining disease, controlling HIV/AIDS and improving immune function using antiretroviral agents has been investigated as a possible treatment for KS. However, this is not always effective as many patients with well-controlled HIV infection still develop KS, and some individuals can experience life-threatening side-effects once they start antiretroviral therapy. Consequently, focused, specific and effective anti-KSHV therapies are urgently needed. KSHV is a member of the herpesvirus family and has two distinct life cycles in cells, a persistent life-long infection where the virus is mainly dormant (known as latency) and an infectious cycle that produces new viruses from the host cells (known as lytic replication). Uniquely for KSHV, both the latent and lytic replication cycles contribute to the development of KSHV-associated cancers. Therefore, it is essential to study the virus-host cell interactions which regulate both latent and lytic phases to fully understand KSHV-related disease. Moreover, inhibiting either or both phases may provide an opportunity to develop novel antiviral strategies to inhibit KS formation. This project focuses on a family of proteins found in host cells known as molecular chaperones. Molecular chaperones are needed for KSHV to undergo both latent and lytic replication cycles, acting as broad host cell factors for viral function. Molecular chaperones are themselves regulated by a family of host proteins known as co-chaperones, which are accessory proteins that fine-tune the function of chaperone systems. We have exciting preliminary data implicating the host co-chaperone STIP1 in multiple aspects of KSHV biology. This proposal will investigate how STIP1 functions during the KSHV latent and lytic phases and develop new ways to inhibit STIP1's function for use as KSHV-targeted therapeutics. We will apply a combination of molecular virology and drug discovery to describe in detail the viral and human cell processes controlled by STIP1 during KSHV latency and lytic replication. We will then use that information to design molecules capable of inhibiting STIP1 function in KSHV, which could subsequently be developed into KSHV-specific antivirals in future.