Natural monoclonal autoantibodies against HERV-K102 Envelope-TM from SLE patients selectively eliminate autoreactive immune cells and cancer cells

In sharp contrast to immune dysfunction in cancer, autoimmune diseases such as systemic lupus erythematosus (SLE) exhibit excessive immune reactions characterized by high titers of autoantibodies to HERV-K102-envelope (HERV-K102-Env) neoantigens, which are frequently found in cancer patients but seldom elicit a strong immune response. Here we aim to address whether anti-HERV-K102-Env autoantibodies in SLE can effectively eliminate autoreactive immune cells and cancer cells expressing HERV-K102-Env neoantigens. We established world-first fully human autoantibody phage display library with 3.67x108 cfu using peripheral blood mononuclear cells (PBMCs) from SLE patients. Through high-throughput screening, we identified nineteen monoclonal autoantibodies (mAbs) targeting the conserved HERV-K102 Env-TM subunit. The EC50 values of these autoantibodies binding to the HERV-K102 Env-TM subunit ranged from 0.002436 g/ml to 1.798 g/ml. Remarkably, eleven of these mAbs not only recognized the HERV-K102 Env-TM glycoprotein on the cell surface but also effectively eliminated autoreactive B, T, and natural killer (NK) cells in SLE, as well as cancer cells. Our findings provide a conceptually new immunotherapy target HERV-K102 Env-TM subunit and open the era of using natural human autoantibodies to treat autoimmune disease and cancers. Several of these monoclonal autoantibodies show promise as potential diagnostic and therapeutic agents, paving the way for innovative approaches to treating SLE and various malignancies.