Experimental antiglomerular basement membrane GN induced by a peptide from actinomyces

Abstract

Background: Antiglomerular basement membrane (anti-GBM) disease is associated with HLA-DRB1∗1501 (the major predisposing genetic factor in the disease), with α3127-148 as a nephritogenic T and B cell epitope. Although the cause of disease remains unclear, the association of infections with anti-GBM disease hasbeenlong suspected. Methods: To investigate whether microbesmight activate autoreactive T and B lymphocytes via molecular mimicry in anti-GBM disease, we used bioinformatic tools, including BLAST, SYFPEITHI, and ABCpred, for peptide searching and epitope prediction. We used sera from patients with anti-GBM disease to assess peptides recognized by antibodies, and immunized WKY rats and a humanized mouse model (HLA-DR15 transgenic mice) with each of the peptide candidates to assess pathogenicity. Results: Onthe basis of the criticalmotif, the bioinformatic approach identified 36 microbial peptides thatmimic human α3127-148. Circulating antibodies in sera from patients with anti-GBM recognized nine of them. One peptide, B7, derived from Actinomyces species, induced proteinuria, linear IgG deposition on the GBM, and crescent formation when injected into WKY rats. The antibodies to B7 also targeted human and rat α3127-148. B7 induced T cell activation from human α3127-148-immunized rats. T cell responses to B7 were detected in rats immunized by Actinomyces lysate proteins or recombinant proteins. We confirmed B7's pathogenicity in HLADR15 transgenic mice that developed kidney injury similar to that observed in a3135-145-immunized mice. Conclusions: Sera from patients with anti-GBM disease recognizedmicrobial peptides identified through a bioinformatic approach, and a peptide fromActinomycesinduced experimental anti-GBMGNbyTandBcell crossreactivity. These studies demonstrate that anti-GBM disease may be initiated by immunization with a microbial peptide.