AUTOANTIGENS INTERACT WITH CIS-ACTING ELEMENTS OF RUBELLA-VIRUS RNA

Rubella virus (RV) infections in adult women can be associated with ac ute and chronic arthritic symptoms. In many autoimmune individuals, an tibodies are found targeting endogenous proteins, called autoantigens, contained in ribonucleoprotein complexes (RNPs). In order to understa nd the molecular mechanisms involved in the RV-associated pathology, w e investigated the nature of cellular factors binding RV RNA and wheth er such RNPs were recognized by antibodies in infected individuals. Pr eviously, we noted that cellular proteins associated with the RV 5'(+) stem-loop (SL) RNA are recognized by serum with Ro reactivity. To bet ter understand the nature of the autoantigens binding RV cis-acting el ements, serum samples from individuals with various autoimmune disease s were tested for their ability to immunoprecipitate RNPs containing l abeled RV RNAs. A subset of serum samples recognizing autoantigen La, or Ro and La, immunoprecipitated both the RV 5'(+)SL and 3'(+)SL RNA-p rotein complexes. Autoantigens binding the RV 5'(+)SL and 3'(+)SL RNAs differed in molecular mass, specificities for respective RNA binding substrates, and sensitivity to alkaline phosphatase treatment. The La autoantigen was found to interact with the RV 5'(+)SL RNA as determine d by immunological techniques and binding reactions with mixtures cont aining recombinant La protein. To test whether there is a correlation between La binding to an RV RNA element and the appearance of an anti- La response, we measured anti-La titers in RV-infected individuals. Si gnificant anti-La activity was detected in approximately one-third of RV-infected individuals 2 years postinfection.