Epitope Mapping of Human α3(IV)NC1-Induced Membranous Nephropathy in Mice.

BACKGROUND AND AIM: Primary membranous nephropathy (pMN) is the most common cause of nephrotic syndrome in adults. Recent studies suggested that immunization of DBA/1 mice with the main antigen of antiglomerular basement membrane disease (GBM) disease, α3(IV)NC1, could lead to MN lesions. This study aimed to explore the pathogenic epitopes for mouse MN.

METHODS

Twenty-four linear peptides were synthesized spanning human α3(IV)NC1. Male DBA/1 mice aged 6-8 weeks were immunized with the peptides 200 μg/mouse in Freund's complete adjuvant subcutaneously and boosted 3 times with the peptides in Freund's incomplete adjuvant in weeks 3, 5, and 7. The blood and 24-h urine samples were assessed every 2 weeks. The kidneys were examined when the mice were sacrificed at 18 weeks.

RESULTS

All the mice immunized with human α3(IV)NC1 and the 24 peptides produced circulating antibodies against the immunogens at 2 weeks and achieved the maximum titers at 8 weeks. About 5/6 (83%) mice immunized with α3(IV)NC1 and (3/6) 50% of the mice immunized with peptide 23 (α3141-154) showed proteinuria at 8-10 weeks and increased continuously. The kidneys showed granular depositions of IgG, C3, and C5b-9 along the glomerular capillary loops. The major IgG subclass was IgG1 (equivalent to human IgG4). GBM thickening with the formation of spikes and subepithelial electron-dense deposits were observed under electron microscope.

CONCLUSION

The linear peptide of α3141-154 could induce clinical and histopathological features of MN in DBA/1 mice, which might give clues to the mechanism of MN in combination with anti-GBM disease.