Systemic evaluation of immune cells and cytokines in patients with different clinical severity of Omicron infection

Immune cells and inflammatory cytokines play pivotal roles in immune response against viral infections. Herein, we performed a comprehensive immunocyte profiling to delineate the variations in immunocyte populations and cytokine levels among patients infected with Omicron presenting different clinical severities. Whole blood samples were collected from a cohort of 109 participants who sought medical assistance at Peking Union Medical College Hospital between December 2022 and February 2023 in China. Study participants were categorized into three groups based on clinical severity determined by their oxygen requirements: those without the need for oxygen supplementation (No O2, n = 30), those requiring supplemental oxygen as maximal respiratory support (O2, n = 35), and those requiring assisted ventilation (VENT, n = 44). Flow cytometry was used to evaluate the levels of immune cells and cytokines. Patients requiring oxygen supplementation and those requiring assisted ventilation exhibited widespread CD28 downregulation across T-cell subsets, along with elevated expression of CD38, HLA-DR, and CD279. Further characterization revealed reduced Th1-like and Th2-like cell frequencies and increased Th17-like cell frequencies in patients requiring either oxygen supplementation or assisted ventilation. We also observed a trend toward B-cell subset alterations and changes in innate immune populations across groups. Notably, significantly higher levels of IL-6, IL-8, and IL-10, along with lower levels of IL-1β, were observed in patients with more severe disease. This study offers valuable insights into systemic immunocyte profiling among Omicron-infected patients with varying clinical severity, which may contribute to a deeper understanding of the immunopathology of COVID-19 and inform future prospective studies.