Monitoring monocyte HLA-DR expression and CD4 + T lymphocyte count in dexamethasone-treated severe COVID-19 patients

Abstract

Background: A 10-day dexamethasone regimen has emerged as the internationally adopted standard-of-care for severe COVID-19 patients. However, the immune response triggered by SARS-CoV-2 infection remains a complex and dynamic phenomenon, leading to various immune profiles and trajectories. The immune status of severe COVID-19 patients following complete dexamethasone treatment has yet to be thoroughly documented.

Results: To analyze monocyte HLA-DR expression (mHLA-DR) and CD4 + T lymphocyte count (CD4) in critically ill COVID-19 patients after a dexamethasone course and evaluate their association with 28-day ICU mortality, adult COVID-19 patients (n = 176) with an ICU length of stay of at least 10 days and under dexamethasone treatment were included. Associations between each biomarker value (or in combination) measured at day 10 after ICU admission and 28-day mortality in ICU were evaluated. At day 10, the majority of patients presented decreased values of both parameters. A significant association between low mHLA-DR and 28-day mortality was observed. This association remained significant in a multivariate analysis including age, comorbidities or pre-existing immunosuppression (adjusted Hazard ratio (aHR) = 2.86 [1.30-6.32], p = 0.009). Similar results were obtained with decreased CD4 + T cell count (aHR = 2.10 [1.09-4.04], p = 0.027). When combining these biomarkers, patients with both decreased mHLA-DR and low CD4 presented with an independent and significant elevated risk of 28-day mortality (i.e., 60%, aHR = 4.83 (1.72-13.57), p = 0.001).

Conclusions: By using standardized immunomonitoring tools available in clinical practice, it is possible to identify a subgroup of patients at high risk of mortality at the end of a 10-day dexamethasone treatment. This emphasizes the significance of integrating immune monitoring into the surveillance of intensive care patients in order to guide further immumodulation approaches.

Keywords: CD4; COVID-19; Dexamethasone; HLA-DR; Immunomonitoring; Monocyte; Sepsis.

Fig. 1

Study flow chart Patients included in the RICO clinical study before July 6th, 2020 (i.e. publication date of the RECOVERY clinical trial) were first excluded. Then exclusion criteria included a dexamethasone treatment duration below 7 days and an ICU length of stay below 10 days. Patients with dexamethasone treatment of at least 7 days and ICU length of stay of at least 10 days discharged alive from the ICU but who died with 28 days were excluded. Finally the cohort was divided between patients who were still alive at D28 and those who died in the ICU within 28 days after admission

Fig. 2

Kinetics of mHLA-DR and CD4 + T cell counts measured in D28 Survivors vs Non-Survivors critically ill COVID-19 patients. Values of monocyte HLA-DR expression (expressed as numbers of antibody bound per cell: AB/C, reference values: 13 500–45 000 AB/C) and CD4 + T cell absolute count (expressed as numbers of cells per µL, reference values: 365–1 345 cells/µL) measured in non-survivors (n = 38, red lines) and survivors (n = 138, blue lines) over time are shown. Patients were sampled within the first 48h after ICU admission (Day 0: D0), between 72 and 96h (D3), between D7 and D9 (D7), between D12 and D15 (D12), between D20 and D25 (D20). Results are presented as means and interquartile ranges (Q1-Q3). The numbers of available values for mHLA-DR and CD4 + count were 37 at D0 and at D3, 35 at D7, 27 at D12 and 10 at D20 in non-survivors. The numbers of available values were 132 for mHLA-DR and 134 for CD4 at D0, 130 for mHLA-DR and 128 for CD4 + at D3, 127 at D7, 102 for mHLA-DR and 103 for CD4 at D12 and 74 at D20 in survivors

Fig. 3

Association between mHLA-DR at D10 and mortality at D28 in critically ill COVID-19 patients. A. Based on cut-off value calculated using Youden index (i.e., 5 479 AB/C) from ROC curve analysis, patients were separated in 2 groups to build Kaplan–Meier survival curves. The Log-rank test was used to test the differences between these curves. B. Univariate and multivariate Cox regressions were used to identify the variables associated with the risk of death before day 28 and assessed by crude hazard ratio (HR) and adjusted HR (aHR) with their 95% confidence intervals (95%CI). Variables with a p value ≤ 0.20 in univariate analysis were entered in the multivariate models. mHLA-DR at day 10 in critically ill COVID-19 patients treated by dexamethasone was the predicted values from mathematical modeling of the change of this variable over time (n = 176)

Fig. 4

Association between CD4 + T lymphocyte count at D10 and mortality at D28 in critically ill COVID-19 patients. A. Based on cut-off value calculated using Youden index (i.e., 225 cells/µL) from ROC curve analysis, patients were separated in 2 groups to build Kaplan–Meier survival curves. Log-rank test was used to test the differences between these curves. B. Univariate and multivariate Cox regressions were used to identify the variables associated with the risk of death before Day 28 and assessed by crude hazard ratio (HR) and adjusted HR (aHR) with their 95% confidence intervals (95%CI). Variables with a p value ≤ 0.20 in univariate analysis were entered in the multivariate models. Number of circulating CD4 + T cells at day 10 in critically ill COVID-19 patients treated by dexamethasone was the predicted values from mathematical modeling of the change of this variable over time (n = 176)

Fig. 5

Association between the combination of mHLA-DR and CD4 + T lymphocyte count at D10 and mortality at D28 in critically ill COVID-19 patients. A. Patients were categorized into three groups based on mHLA-DR and CD4 + T cell count at day 10: Group 1 = both markers (mHLA-DR and CD4) above their respective cut-off values calculated using Youden index (i.e. 5 479 AB/C for mHLA-DR and 225 cells/µL for CD4 + T cell count) (black line); Group 2 = at least one marker (either mHLA-DR or CD4) above its cut-off value (red line); Group 3 = Both markers below their cut-off values (green line). Log-rank test was used to test the differences between these curves. B. Univariate and multivariate Cox regressions were used to identify the variables associated with the risk of death before Day 28 and assessed by crude hazard ratio (HR) and adjusted HR (aHR) with their 95% confidence intervals (95%CI). Variables with a p value ≤ 0.20 in univariate analysis were entered in the multivariate models. Monocyte HLA-DR expression and number of circulating CD4 + T cells at day 10 in critically ill COVID-19 patients treated by dexamethasone were calculated based mathematical modeling