Th17 immune microenvironment in Epstein-Barr virus-negative Hodgkin lymphoma: implications for immunotherapy

Classical Hodgkin lymphoma (CHL) is a neoplasm characterized by robust inflammatory infiltrates and heightened expression of the immunosuppressive PD-1/PD-L1 pathway. Although anti-PD-1 therapy can be effective in >60% of patients with refractory CHL, improved treatment options are needed for CHLs which are resistant to anti-PD-1 or relapse after this form of immunotherapy. A deeper understanding of immunologic factors in the CHL microenvironment might support the design of more effective treatment combinations based on anti-PD-1. In addition, because the Epstein-Barr virus (EBV) residing in some CHL tumors is strongly immunogenic, we hypothesized that characteristics of the tumor immune microenvironment in EBV⁺ CHL would be distinct from EBV^- CHL, with specific implications for designing combination treatment regimens. Employing immunohistochemistry for immune cell subsets and checkpoint molecules, as well as gene expression profiling, we characterized 32 CHLs from the Johns Hopkins archives, including 12 EBV⁺ and 20 EBV^- tumors. Our results revealed a dichotomous cellular and cytokine immune milieu in EBV⁺ vs EBV^- CHL. EBV⁺ tumors displayed a T helper 1 (Th1) profile typical of effective antitumor immunity, with increased infiltration of CD8⁺ T cells and coordinate expression of the canonical Th1 transcription factor Tbet (TBX21), interferon-γ (IFNG), and the IFN-γ-inducible immunosuppressive enzyme indoleamine 2,3-dioxygenase. In contrast, EBV^- tumors manifested a pathogenic Th17 profile and ongoing engagement of the interleukin-23 (IL-23)/IL-17 axis, with heightened phosphorylated signal transducer and activator of transcription 3 expression in infiltrating lymphocytes. These findings suggest that drugs blocking the IL-23/IL-17 axis, which are already in the clinic for treating certain autoimmune disorders, may enhance the therapeutic impact of anti-PD-1 therapy in EBV^- CHL.