The goal of this clinical trial is to demonstrate the benefit of a standardized immunotherapy (Interferon gamma) on the incidence of secondary infections. . It will also learn about the safety of Interferon-gamma. The main questions it aims to answer are:

Does Interferon-gamma:

• reduces the Incidence of secondary infection episodes at three months
• reduces the ICU mortality and at Day 90
• reduces the ICU and hospital length of stay
• induces Biological immune restoration at Day 10
• has cost-consequence and cost-effectiveness

Researchers will compare Interferon-gamma to a placebo (a look-alike substance that contains no drug) to see if Interferon-gamma works to treat sustained immunosuppression .

Participants will:

• Take Interferon-Gamma or a placebo for a maximum of 5 times between day 1 and day 9
• be monitored evety day until their ICU discharge and at day 30, 60 and 90

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