Monocyte Oxidative Stress Underlies Persistent Immune Activation in Long COVID Postural Orthostatic Tachycardia Syndrome

Long COVID Postural Orthostatic Tachycardia Syndrome (LCPOTS) is characterized by persistent orthostatic tachycardia and systemic symptoms following SARS-CoV-2 infection. Many features of LCPOTS suggest ongoing immune activation, but the mechanisms driving this response remain unclear. In this study, we show that patients with LCPOTS, compared with individuals who recovered from SARS-CoV-2 without POTS, exhibit increased monocyte mitochondrial content and superoxide production, along with downregulation of NRF2-dependent antioxidant enzymes. This is accompanied by a marked increase in the formation of isolevuglandins (IsoLGs) in monocytes, which modify self-proteins and act as neoantigens capable of activating T cells. Consistent with this, LCPOTS patients exhibit a 3-fold increase in circulating T cell-monocyte doublets with immunological synapse formation. T cells in these complexes display a proinflammatory effector-memory and TEMRA phenotype, producing IFN-γ and IL-17A, which correlated with symptom severity. Circulating cytokines, including IL-17A, IFN-γ, and TNF-α, are elevated in patients with LCPOTS by 1.5 to 3-fold. This immune response likely drives systemic inflammation and impaired cardiovagal regulation, hallmarks of LCPOTS. Our findings suggest that monocyte oxidative stress and IsoLG neoantigen formation sustain T cell activation, linking immune dysregulation to cardiovagal dysfunction. Targeting these pathways may offer novel therapeutic opportunities.