Immune Profiling Panel Gene Set Identifies Critically Ill Patients With Low Monocyte Human Leukocyte Antigen-DR Expression: Preliminary Results From the REAnimation Low Immune Status Marker (REALISM) Study

Abstract

Objectives: There is a crucial unmet need for biomarker-guided diagnostic and prognostic enrichment in clinical trials evaluating immune modulating therapies in critically ill patients. Low monocyte expression of human leukocyte antigen-DR (mHLA-DR), considered as a reference surrogate to identify immunosuppressed patients, has been proposed for patient stratification in immunostimulation approaches. However, its widespread use in clinic has been somewhat hampered by technical constraints inherent to flow cytometry technology. The objective of the present study was to evaluate the ability of a prototype multiplex polymerase chain reaction tool (immune profiling panel [IPP]) to identify immunosuppressed ICU patients characterized by a low mHLA-DR expression.

Design: Retrospective observational cohort study.

Setting: Adult ICU in a University Hospital, Lyon, France.

Patients: Critically ill patients with various etiologies enrolled in the REAnimation Low Immune Status Marker study (NCT02638779).

Interventions: None.

Measurements and main results: mHLA-DR and IPP data were obtained from 1,731 blood samples collected from critically ill patients with various etiologies and healthy volunteers. A partial least square regression model combining the expression levels of IPP markers was trained and used for the identification of samples from patients presenting with evidence of immunosuppression, defined here as mHLADR less than 8,000 antibodies bound per cell (AB/C). The IPP gene set had an area under the receiver operating characteristic curve (AUC) of 0.86 (95% CI 0.83-0.89) for the identification of immunosuppressed patients. In addition, when applied to the 123 patients still in the ICU at days 5-7 after admission, IPP similarly enriched the number of patients with ICU-acquired infections in the immunosuppressed group (26%), in comparison with low mHLA-DR (22%).

Conclusions: This study reports on the potential of the IPP gene set to identify ICU patients presenting with mHLA-DR less than 8,000 AB/C. Upon further optimization and validation, this molecular tool may help in the stratification of patients that could benefit from immunostimulation in the context of personalized medicine.

Figure 1.

Distribution of monocyte expression of human leukocyte antigen-DR (mHLA-DR) levels. mHLA-DR measurement was available in 1,731 samples distributed as follows: 163 samples from healthy volunteers (HVs), and 1,568 samples from 106 sepsis, 136 trauma, 109 surgery patients. mHLA-DR values ranged from 439 to 80,066 AB/C. The vertical line corresponds to the value of 8,000 AB/C. mHLA-DR was below 8,000 antibodies bound per cell (AB/C) in 591 patients samples (34%) and above 8,000 AB/C in 1,140 samples (66%), of which 977 samples were from patients, and 163 from HV.

Figure 2.

Concordance between monocyte expression of human leukocyte antigen-DR (mHLA-DR) and immune profiling panel (IPP) classification in the test set, including healthy volunteers (n = 510). Groups of samples based on mHLA-DR value (< 8,000 antibodies bound per cell [AB/C] for immunosuppressed and ≥ 8,000 AB/C for immunocompetent status) are represented on the left of each alluvial plot, and prediction using IPP gene set is represented on the right. Concordance is 80% on the test set.