Transfer of IgG from long COVID patients induces symptomology in mice.

SARS-CoV-2 infections have led to a surge in long COVID, a post-infectious syndrome in which autoantibodies are proposed to play a pathogenic role, analogous to fibromyalgia. Here, we test this hypothesis by transferring total IgG from long COVID patients into mice. We stratified patients into three subgroups using plasma levels of glial fibrillary acidic protein (GFAP), neurofilament light chain (NFL), and interferon-β, with subgroup-specific pathways supported by plasma proteomics. Transfer of pooled total IgG induces pronounced and persistent mechanical hypersensitivity. Notably, IgG collected 2 years later from the same long COVID patients who remained symptomatic reproduced mechanical allodynia in mice, demonstrating longitudinal stability of pathogenic activity. Proteome-wide autoantibody profiling identifies elevated, subgroup-linked autoreactivities that persist over time and are validated by independent assays. Together, these findings demonstrate that long COVID IgG can induce mechanical hypersensitivity in mice, support a causal role for autoantibodies in long COVID pathogenesis, and may establish a murine model for therapeutic development.