#2033 First small steps…a pilot study on changes in Immunoglobulin G N-glycome during immunosuppressive treatment of ANCA-associated vasculitis

Abstract Background and Aims ANCA-associated vasculitis (AAV) activity during and after the treatment lacks adequate biomarkers. Immunoglobuline G (IgG) N-glycome is an enzymatically attached oligosaccharides network crucial for IgG functional “phenotype”. Glicosylation is necessary in inflammatory reactions in which changes occur to glycosylation of numerous plasma proteins including IgG. Recently published paper by Wojcik I et al. pointed to specific IgG glycosylation differences preceding relapse in PR3-AAV patients both with and without ANCA titre rise. By presenting the pilot results of our GlycANVasc (Glycans in ANCA-associated vasculitis) study, evaluating IgG N-glycome changes during the immunosuppressive treatment, we wish to invite collaborators to join in. Method The pilot cases were two female patients, aged 63 (MPO-AAV) and 67 (PR3-AAV), both with lung and renal involvement. Serum was collected at four-time points: The first and second points (both patients) were the at the induction treatment (cyclophosphamide + methylprednisolone) and remission achievement. The third point (only the first patient) was maintenance treatment Rituximab (RTX) administration (three months later), and the fourth point (only the first patient) was one month after RTX. N-glycans were enzymatically released from isolated IgG, fluorophore-labeled, separated using capillary gel electrophoresis, and the glycan traits were calculated using the individual glycans' relative abundances. Results During induction treatment in the “MPO-AAV” patient, the relevant relative changes were the increase in digalactosylated glycans (12.2%) and the decrease in agalactosylated (8.5%) and afucosylated (12.3%). An analogous pattern was present between the second and third samples. Still, the changes were lower: digalactosylated glycans went up by 3.8%, with a reduction of 4.4% in agalactosylated and 2.0% in afucosylated traits. A month after the RTX administration, the relative decreases in the disialylated (8.8%) and monosialylated (3.8%) glycans appeared, while the abundance of (a)galactosylated and afucosylated glycans remained stationary. The “PR3-AAV” during the induction treatment, showed a relative increase in digalactosylated glycans (79.7%) and bisecting GlcNAc of (43.5%), accompanied by a relative decrease in agalactosylated glycans (45.4%). Conclusion The pilot cases evidenced IgG N-glycome changes during immunosuppressive treatment administered in both AAV subtypes. The increase in the galactosylated glycans during remission achievement could indicate a transition towards anti-inflammatory IgG “phenotype” both in MPO and PR3 AAV. The interpretation might be similar for the increase in bisecting GlcNAc in PR3 AAV, while for afucosylation and sialylation, straightforward assumptions would be challenging. These pilot data justify further “mining” of IgG N-glycome changes in the search for AAV activity biomarker candidates.