Immunodominant epitopes of alpha 3(IV)NC1 induce autoimmune glomerulonephritis in rats

Immunodominant epitopes of alpha 3(IV)NC1 induce autoimmune glomerulonephritis in rats.BackgroundThe major Goodpasture antibody binding epitopes have been localized to the amino-terminal third of the noncollagenous domain (NC1) of the alpha 3 chain of type IV collagen [ alpha 3(IV)NC1]. The present study determined whether the same epitopes induce glomerulonephritis in rats.MethodsWe immunized Wistar Kyoto (WKY) rats with human alpha 3(IV)/ alpha 1(IV)NC1 chimeric proteins or full-length recombinant alpha 3(IV)NC1 ( alpha 3 sub(732)). Chimeric protein constructs were thirds of alpha 3(IV)NC1 (CP333) replaced by corresponding sequences of homologous nonreactive alpha 1(IV)NC1 (CP111). All chimeric proteins contained 30 amino acids of type X collagen at the amino terminus except alpha 3 sub(732.) Two other constructs, T195 EA (EA) and T194 EB (EB), were entirely alpha 1(IV)NC1, except for antibody-immunodominant amino acids from the first and second thirds of alpha 3(IV)NC1.ResultsConstruct immunized animals developed specific antibody responses to recombinant proteins and native human, bovine and rat NC1. CP311 immunized rats, as well as alpha 3 sub(732) rats, had glomerular IgG, fibrin, and glomerulonephritis with proteinuria by 3 weeks. CP331 produced more severe disease, comparable to positive controls. CP111 produced no disease. EA, but not EB, induced severe glomerulonephritis. Half-dose each of EA plus EB induced disease identical to full-dose EA alone.ConclusionThe amino third of alpha 3(IV)NC1 which contains the major epitope for Goodpasture antibody binding, also induces glomerulonephritis in rats. The middle third of alpha 3(IV)NC1 does not induce glomerulonephritis but appears to enhance disease with the amino terminal third. Finally, the presence of the collagen X leader sequence appears to convey greater nephritogenicity. These studies suggest that not only the nephritogenic epitope itself, but flanking sequences and the conformational context of the nephritogenic epitope may influence its ability to cause glomerulonephritis.Kidney International (2003) 64, 2108-2120; doi:10.1046/j.1523-1755.2003.00332.x