The high prevalence of Kaposi Sarcoma (KS) in immunosuppressed individuals, in particular
people living with HIV (PLWH), suggests that T-cell immunity is critical for tumor surveillance.
It has been previously shown that KS lesions harbor a lymphocytic infiltrate. However, the
specificity and immunophenotype of this infiltrate remains unclear. We hypothesized that
clonally expanded tumor infiltrating lymphocytes (TILs) have a role in controlling KS. We
applied a novel single cell TCR cloning platform to analyze the tissue TCR repertoire in subjects
affected by HIV associated KS. Alpha and beta clonal separate chains sequences isolated from
HIV-KS TILs were identified in public TCRs databases and showed similarity to TCRs recognising
EBV and CMV epitopes. In all subjects studied we identified clonal expansion within the TILs.
In one study participant we identified clonality of αβ paired TCR chains. A TCR-deficient cell
line (SKW3), transduced with the clonal TCR of interest, was cocultured with KSHV infected
target cells (autologous B-cell lines and partially HLA matching U2OS and HEK293T cell lines)
and no KSHV specific T-cell response was clearly detected with T-cell activation markers and
cytokines measurements. We observed a higher secretion of IL-2 and TNFα in KSHV-/EBV+
and KSHV+/EBV+ autologous B-cell lines in comparison to background which could be
explained by TCR cross reactivity between KSHV, EBV and CMV epitopes. We cannot fully
exclude an antigen specific immune response as it is possible that immune responses are
generated against lytic rather than latent viral epitopes or against non-viral epitopes within
the tumour. Lack of immunodominance in KSHV T-cell responses and immune suppressive
mechanisms, within the KS tumour microenvironment, could explain the results of the TCR
functional analysis.
Further characterisation of clonal TILs immune responses may have future translational
implications as TCR gene therapy for KS and other KSHV related malignancies