Antibodies to the Epstein-Barr virus nuclear antigen and to rheumatoid arthritis nuclear antigen identify the same polypeptide.

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Patients with seropositive rheumatoid arthritis (RA) have elevated titers of precipitating antibody toward an antigen designated RA nuclear antigen (RANA). Anti-RANA reactivity has been associated with prior Epstein-Barr virus (EBV) infection. Using the protein blot technique, we have identified, in extracts of WI-L2, an EBV+ nonproducer B-lymphoblast line, a Mr 80,000 polypeptide that is reactive with anti-RANA-containing sera. This same polypeptide can be recovered from RANA precipitin bands. The Mr 80,000 polypeptide appears to be EBV-associated, as a homologous antigen was detected in two other EBV+ cell lines, Daudi and Raji, but was not present in three EBV- human cell lines tested, HeLa, BJAB, and Ramos. Anti-RANA antibodies and antibodies reactive with the Mr 80,000 polypeptide also appear coincidently in the sera of individuals exhibiting an EBV infection (infectious mononucleosis). Further analysis of the RANA-associated Mr 80,000 polypeptide suggested its identity with the previously recognized EBV-associated nuclear antigen designated EBNA. The Mr 80,000 antigen shares with EBNA the properties of being a heat-stable, DNA binding protein. EBNA is traditionally assayed by a complement fixation reaction and anti-Mr 80,000 antibodies were shown to be reactive when a complement fixation assay was used in the immunoblot. Finally, when the Mr 80,000 antigen was used to absorb an anti-RANA/anti-EBNA serum, both antibodies were reduced.

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