Mice immunized with EBNA-1 protein produce antibodies that cross-react with double stranded DNA (129.5)

Abstract

Systemic Lupus Erythematosus (SLE) is characterized by the production of antibodies to nuclear antigens, in particular antibodies to double stranded DNA (dsDNA). The etiology of these autoantibodies is unknown but one theory suggests that viruses may play a role. One virus that has been shown to have an association with SLE is the Epstein Barr Virus (EBV). We previously demonstrated that mice immunized with an EBNA-1 expression vector or with purified EBNA-1 protein develop antibodies to dsDNA as well as to the viral antigen. We have recently demonstrated that these antibodies are pathogenic and deposit in the kidney and induce moderate proteinuria. We hypothesized that since EBNA-1 is a dsDNA binding protein, it could complex with chromosomal dsDNA in order to render it immunogenic and elicit an anti-dsDNA response. To test this hypothesis we generated recombinant EBNA-1 protein that lacks the 3 known chromosomal binding sites and immunized mice with it. We observed that mice immunized with this mutated EBNA-1 protein still develop an anti-dsDNA response. We have now generated hybridomas producing anti-EBNA-1 antibodies from these mice and observed that 10 out of 18 monoclonal anti-EBNA-1 antibodies actually cross-react with dsDNA. These results suggest that a viral protein determinant can mimic chromatin and elicit an anti-dsDNA response that can lead to autoimmunity. Future studies will analyze the molecular basis of this cross-reactivity.