Immunonological biomarkers of fatal coronavirus disease 2019 (covid-19): A study of 513 patients including hematological cases

Background: Knowledge on the immunopathobiology of COVID-19 is rapidly increasing but most studies analyzed relatively small series of patients and immune features predictive of fatal outcome are unavailable for routine stratification. Furthermore, an increased risk of death in patients with hematological cancer infected by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has been identified, but it remains unknown if this is related to possible immunosuppression caused by cancer itself and cytotoxic treatment. Aims: Characterize the immune response to SARS-CoV-2 in a large cohort of patients to identify high-risk immune biomarkers and evaluate the association between COVID-19 severity and immunosuppression in patients with hematological cancer. Methods: Multidimensional flow cytometry was used to conduct holistic and unbiased analyses of17 immune cell types on 780 peripheral blood samples obtained from 513 COVID-19 patients, 24 cases with non-SARS-CoV-2 infection and 36 age-matched healthy adults.167 COVID-19 patients had 207 longitudinal samples collected over time. RNA sequencing on FACSorted cells and high-resolution flow cytometry were used to perform a deeper characterization of various myeloid and lymphoid subsets in14 COVID-19 patients and4 healthy adults. Results: Immune profiles of COVID-19 patients were generally similar to those of age-matched patients with non-SARS-CoV-2 infection, but significantly different from those of age-matched healthy adults. When compared to the later, COVID-19 patients showed increased percentages of neutrophils, CD4+CD56+ T-cells, and plasmablasts, whereas levels of basophils, eosinophils, and non-classical monocytes, as well as double-negative, CD8loCD56-, CD8-/loCD56+ and CD8hiCD56- T-cells, and B-cells were decreased. Both transcriptional and immunophenotypic data in myeloid and lymphoid subsets suggested an association between COVID-19 severity and neutrophil activation, as well as significantly reduced levels of specific adaptive immune cell types. Unsupervised clustering analysis of 513 patients revealed three immunotypes in response to SARS-CoV-2 infection. One of them, present in14% of patients (n=74), was characterized by significantly lower percentages of all immune cell types except neutrophils and plasmablasts, and was significantly associated with more severe disease. Of note, 50% of COVID-19 patients with blood cancer displayed this immunotype. Accordingly, hematological patients showed a significantly higher frequency of admission into intensive care units (50% vs 5%, P<.001) and death (30% vs4%, P<.001) than patients without tumor did. On multivariate analysis incorporating age and comorbidities, the frequency of B-cells and non-classical monocytes were independent prognostic factors for overall survival. Indeed, <1% B-cells in peripheral blood was most strongly associated with risk of death. Among patients with immune monitoring during follow-up, significant changes in the relative distribution of eight immune cell types, including basophils, CD8loCD56- T-cells, and B-cells, were observed from the first to last peripheral blood sample between patients who survived or died. Summary/Conclusion: Our results accelerate our understanding of the immunopathobiology of COVID-19 and unveil an association between altered immune profiles in patients with hematological cancer and their poorer outcome. Reduced percentages of B-cells and non-classical monocytes are high-risk immune biomarkers that could be readily implemented in routine practice for risk-stratification of COVID-19.