Cytotoxic T cells targeting lytic KSHV gene products infiltrate Kaposi sarcoma tumors

Kaposi sarcoma-associated herpesvirus (KSHV) is the etiologic agent of Kaposi sarcoma (KS), primary effusion lymphoma (PEL), and KSHV-associated multicentric Castlemans disease (MCD), malignancies that predominantly arise in the context of T-cell deficiency. Unlike responses to other human herpesviruses such as EBV and CMV, KSHV-specific T-cell responses detected in blood have been described as heterogeneous and low-intensity. Hypothesizing that KSHV-specific T cells are recruited to KS tumors, we analyzed the T-cell receptor (TCR) repertoire of biopsies from 144 Ugandan adults with KS (106 people living with HIV [PLWH], 38 HIV-seronegative) and identified >4,000 {beta} TCRs with predicted specificity for KSHV- or HIV-encoded peptides presented by specific MHC alleles. We tested 14 putative KSHV- or HIV-specific TCRs for recognition of cells presenting cognate peptides in the predicted MHC context. Three novel HIV-specific TCRs, found only in tumors from PLWH, exhibited high-avidity, MHC-restricted recognition of HIV Vpr and Nef peptides previously identified as CD8+ T-cell targets. Four KSHV-specific TCRs, detected in tumors from both PLWH and HIV-seronegative individuals, recognized peptides encoded by the lytic KSHV genes ORF6, ORF57, and ORF59. The ORF6- and ORF57-specific TCRs were observed in multiple individuals and constitute the first examples of public T-cell responses to KSHV. We then confirmed that these four KSHV-specific TCRs recognized KSHV-infected cells undergoing lytic reactivation. Identification of TCRs specific for KSHV lytic gene products will enable the development of T-cell-based therapies for KS and other KSHV-associated diseases. Author summaryKaposi sarcoma-associated herpesvirus (KSHV) is the only oncogenic human virus for which there is no effective vaccine, antiviral, or immunotherapeutic strategy that directly targets the virus. KSHV is the causative agent of Kaposi sarcoma and primary effusion lymphoma, cancers that primarily affect immunocompromised individuals, most commonly people living with HIV in sub-Saharan Africa, where KSHV is endemic and HIV infection is prevalent. In this study we defined the antigenic specificity of novel, putative KSHV- and HIV-specific T-cell receptors (TCRs) that are carried in T cells commonly infiltrating KS tumor biopsies. We show that T cells engineered to express KSHV-specific TCRs exhibit high-avidity, MHC-restricted recognition of KSHV-infected cells presenting naturally processed peptides encoded by KSHV lytic genes. Our findings provide a blueprint for dissecting KSHV-specific T-cell immunity and advancing the development of immunotherapeutic strategies for the prevention or treatment of KSHV-associated diseases.