ORF44-04 - Beyond Perilipin-1: Proteome-Wide Antibody Profiling Reveals Novel Shared Target Autoantigens in Acquired Lipodystrophy Syndromes

Introduction:
Acquired lipodystrophy syndromes (LD) are often idiopathic and diagnosed after adipose tissue loss with associated metabolic complications. There is growing evidence of an autoimmune association; yet, disease markers are still lacking. Identification of perilipin-1 (PLIN1)-antibodies suggests that dysregulated immune response with involvement of autoantibodies may contribute to disease development or serve as disease biomarkers. The purpose of this study is to discover novel autoantibody biomarkers specific to acquired LD.

Methods:
We included 16 patients with acquired LD (M/F, 3/13; mean age, 41±11 years; partial/generalized, 7/9) and 108 healthy controls (M/F, 31/77; mean age 35±13). In patients with LD, autoimmune and rheumatologic conditions were most common (n=8), followed by a prior malignancy history with treatment exposure (n=5) and gastrointestinal diseases (n=3). Antibody reactome profiling was performed using Molecular Indexing of Proteins by Self-Assembly method, to screen whole human proteome, including 15,091 full-length human proteins and 353,914 overlapping peptides to quantify antibodies (IgG, IgA, and IgM) targeting self-proteins (autoantigens). To assess reproducibility across populations, we then compared our antibody reactome findings with an independent LD cohort (M/F, 3/8; mean age, 29±21 years; partial/generalized, 9/2) to identify overlapping autoantibody signals.

Results:
Analysis of the LD cohort identified IgG, IgA, and IgM responses to 3,667 (1.04%), 381 (0.11%), and 234 (0.07%) peptides and to 796 (5.27%), 327 (2.17%), and 377 (2.50%) full-length proteins, respectively. All patients in both groups were responsive to at least one autoantigen and the number of positive antibodies per individual did not differ between patients and healthy controls (p=0.270). Two patients demonstrated LMNA autoantibody positivity, one with a history of malignancy and the other with multiple autoimmune disorders. After filtering out antibodies shared with healthy controls, PLIN1 (n=2), Ras GTPase-activating protein 1 (RASA1; n=3), thyroid hormone–responsive protein (THRSP; n=1), growth arrest-specific protein 2 (GAS2; n=1), and FYVE, RhoGEF, and PH domain-containing protein 2 (FGD2) were identified as autoantigens unique to the LD cohort. The two PLIN1 autoantibody-positive patients also had unique antibodies against solute carrier proteins (SLC51B and SLC22A7), spermatogenesis-associated serine-rich protein 2 (SPATS2), and methyltransferase-like protein 17 (METTL17). Notably, THRSP autoantibody positivity was also observed in the confirmatory LD cohort.

Conclusion:
Using a proteome-wide, antibody screening approach, we demonstrate that patients with acquired LD exhibit numerous autoantibodies beyond PLIN-1. Further work is needed to determine the pathogenic significance and clinical utility of these profiles.