Modification of lupus-associated 60-kDa Ro protein with the lipid oxidation product 4-hydroxy-2-nonenal increases antigenicity and facilitates epitope spreading

Systemic lupus erythematosus (SLE) is a Chronic autoimmune disease with autoantibodies as a near Universal feature of the disease. The Ro ribonucleoprotein particle, composed of a 60-kDa protein noncovatently associated with human cytoplasmic RNA, is the target of antibodies in 25-40% of lupus patients. Purified human 60-kDa Ro was found to be oxidatively modified. Earlier investigations from our laboratory revealed increased oxidative damage in SLE patients. Therefore we hypothesized that oxidation by-products, Such as 4-hydroxy-2-nonenal (HNE), Could lead to neoantigens like HNE-modified 60-kDa RO, Which Could in turn initiate autoimmunity or drive epitope spreading. To test this hypothesis we immunized rabbits with either HNE-modified 60-kDa Ro Or the unmodified Ro. Intramolecular epitope spreading within the Ro molecule and intermolecular epitope spreading to La, double-stranded DNA, nRNP, and Sin occurred preferentially in HNE-Ro-imminized animals. Nonspecific anti-FINE antibody, generated by immunization with HNE-keyhole limpet hemocyanin conjugate, did not significantly bind to these autoantigens. These data May suggest a hitherto unappreciated mechanism by which oxidative stress facilitates epitope spreading in SLE. (C) 2004 Elsevier Inc. All rights reserved.