Prevention of Secondary Infections by Interferon Gamma in ICU-acquired Sustained Immune-suppression

Inclusion Criteria: * Adult patient hospitalized in the ICU for at least 1 week * Expected length of stay in the ICU greater than 10 days at screening * At least 1 episode of multiple organ failure, defined as a SOFA ≥ 6 (excluding the respiratory component when related to a neurological failure), during the first 1 week of ICU hospitalization * Immunosuppression defined as an mHLA-DR \< 8000 Ab/c and a lymphopenia \< 1000/mm3 within a 96 hours time window * Patient or the legal representative giving consent must be able to understand the trial in its entirety * Patient affiliated to the social security system * For female participants of childbearing potential, agreement to use dual methods of contraception until Day 90 * For male participants with female partners of childbearing potential, agreement to use barrier method of contraception until Day 90. Exclusion Criteria: * Uncontrolled secondary infections ongoing at the time of screening * Participation in another research clinical trial within 30 days * Chemotherapy / radiation therapy within the last 6 weeks * Apache II ≥ 30 at screening * History of autoimmune disease * Organ or bone marrow transplant * History of hematologic malignancy * History of hepatitis C * HIV stage C within the last 12 months * Patients under legal protection * History of or ongoing tuberculosis * Chronic hepatitis B * Patients receiving immunosuppressive medications including patient receiving a steroid dose greater than 1mg/kg/day of prednisone equivalent for more than 1 week and patient that have been on corticosteroid for more than 3 months * Patient with thrombocytopenia below 50,000/mm3 * Patient with traumatic brain and spinal injury * Pregnancy or breast feeding * Subjects with a history hypersensitivity to interferon gamma or excipient (Mannitol, Sodium succinate dibasic hexahydrate, Succinic acid, polysorbate 20), known latex hypersensitivity or other interferon * Hepatic cytolysis with AST/ALT \> 5 times ULN (local laboratory) * Suspected acute pancreatitis with lipase or amylase \> 3 times ULN (local laboratory) * Severe chronic renal failure (eGFR\<10 ml/min/1.73m2 CKP-EPI method) * Acute ECG abnormality such as myocardial infarction or any acute life-threatening ECG abnormalities (e.g: ventricular fibrillation, ventricular tachycardia…) * Mental state rendering the person giving consent incapable of understanding the trial * Patient deprived of liberty by judicial or administrative decision * Patient being the investigator, or any member of the team or relative of the investigator directly involved in the trial, including assistant doctors, pharmacists, nurses, trial coordinators