Project Summary/Abstract Despite being a pressing human health problem, very little has been done thus far to develop specific therapeutics against Kaposi’s sarcoma-associated Herpesvirus (KSHV) infection and its associated diseases. Interestingly, the KSHV genome carries a viral homolog of cellular G-protein coupled receptor (GPCR). As essential mediators of cell signaling, GPCRs are involved in nearly all aspects of human biology. Their clinical relevance is thus underscored by the fact that 30-40% of all FDA approved drugs target GPCRs. The KSHV GPCR (vGPCR) is essential for virus-mediated oncogenesis: its expression is sufficient to transform cells in vitro and induce tumor formation in vivo. The fact that vGPCR plays a key role in KSHV oncogenesis and that it is a member of protein family frequently targeted by FDA-approved drugs makes vGPCR a promising target for therapeutic intervention. We will use biochemical methods and signaling assays to understand structural insight of vGPCR and to develop novel therapeutic nanobodies for inhibiting the oncogenic function of vGPCR.