ABSTRACT
Introduction: After viral or bacterial sepsis, most intensive care unit (ICU) patients enter a state of profound immunosuppression contributing to patients' worsening. Transgene has developed an immunotherapy based on a viral vector encoding human interleukin-7 (hIL-7) to restore both innate and adaptive immune responses. Here, we assessed the capacity of hIL-7 to improve ex vivo T lymphocyte function from septic shock and COVID-19 patients. Methods: Primary human hepatocytes were transduced with MVAhIL- 7-Fc, a recombinant Modified Vaccinia virus Ankara (MVA) encoding the hIL-7 fused to the human IgG2 Fc fragment, or with empty MVA as control. Cell culture supernatants were harvested for further assays. T cells were collected from ICU patients (septic shock = 11, COVID- 19 = 29) and healthy donors (n = 21). STAT5 phosphorylation, cytokine production (ELISpot and intracellular staining) and cell proliferation were assessed upon TCR stimulation with supernatants containing or not hIL-7 produced after MVA transduction or with the counterpart recombinant hIL-7 (rhIL-7). Results: Patients with viral and bacterial sepsis display T lymphocyte alterations compared to healthy donors with a decreased production of cytokines and a decreased proliferation capacity. Supernatant containing hIL-7 induces STAT5 phosphorylation in CD3 lymphocytes of all patients. With 90% of responders, hIL-7 boosts cytokines production (single and double IFN-TNF) and T lymphocytes proliferation capacity at the same level as rhIL-7 in both cohorts whereas empty MVA has no effect. Conclusions: This study indicates that hIL-7-Fc produced after MVA transduction initiates IL-7 signaling through the phosphorylation of STAT5 and restores ex vivo human lymphocyte functions in cells from septic patients with acquired immunosuppression. This proof-of-concept study, along with experimental results in animal models, supports the clinical development of the MVA-hIL-7-Fc in sepsis immunosuppressed patients.