Myeloid-Driven Immune Suppression Subverts Neutralizing Antibodies and T Cell Immunity in Severe COVID-19.

The objective of this study was to better understand immune failure mechanisms during severe acute respiratory syndrome coronavirus 2, SARS-CoV-2 infection, which are critical for developing targeted vaccines and effective treatments. We collected 34 cases representing different disease severities and performed high-quality single-cell TCR/BCR sequencing to analyze the peripheral immune cell profiles. Additionally, we assessed antibody-neutralizing activity through in vitro experiments. Our integrated multiomics analysis uncovers a profound immune paradox in severe COVID-19: hyperinflammation coexists with immunosuppression, driven by distinct yet interconnected dysregulatory mechanisms. Severe patients develop robust humoral immunity, evidenced by clonally expanded plasma cells producing neutralizing antibodies (e.g., IGHG1-dominated responses) and antigen-specific T cell activation. However, these protective responses are counteracted by myeloid-driven immunosuppression, particularly CD14+ HMGB2+ monocytes exhibiting metabolic reprogramming and HLA-DR downregulation, coupled with progressive T cell exhaustion characterized by IFN-γ/TNF-α hyperactivation and impaired antigen presentation. Importantly, prolonged viral persistence in severe cases arises from a failure to coordinate humoral and cellular immunity-antibody-mediated neutralization cannot compensate for defective cytotoxic T cell function and monocyte-mediated immune suppression. These findings highlight the necessity for therapeutic strategies that simultaneously enhance antibody effector functions (e.g., Fc optimization), restore exhausted T cells, and reverse myeloid suppression. They also highlight the importance of vaccines designed to elicit balanced B cell memory and durable T cell responses, which are critical to preventing severe disease progression. By addressing the dual challenges of hyperinflammation and immunosuppression, such approaches could restore immune coordination and improve outcomes in severe COVID-19.