Effect of p40 tax trans -Activator of Human T Cell Lymphotropic Virus Type I on Expression of Autoantigens

The possibility of a retroviral etiology has long been raised in a number of autoimmune disorders. More recently, Sjögren's syndrome and rheumatoid arthritis were noted in transgenic mice carrying the tax gene of human T cell leukemia virus type I (HTLV-I). To evaluate the involvement of HTLV-I Tax in autoimmunity, its effect on expression of autoantigens was investigated. A metallothionein promoter-driven p40 ^tax expression plasmid, pMAXRHneo-1, was stably transfected into Molt4 and Jurkat cells and the p40 ^tax protein was induced with CdCl2. trans-Activation or trans-repression of autoantigens by HTLV-I Tax was studied by Western blot analysis utilizing autoantigen-specific murine monoclonal and rabbit polyvalent antibodies as well as sera from 161 autoimmune patients. Induction of p40 ^tax of HTLV-I had no significant effect on levels of expression of common autoantigens Ul snRNP, Sm, Ro, La, HSP-70, topoisomerase I/Scl70, PCNA, and HRES-1. Expression of two potentially novel autoantigens, 44 and 46 kDa, was induced by p40 ^tax as detected by sera of progressive systemic sclerosis patients, BAK and VAR. By contrast, expression of 24- and 34-kDa proteins was suppressed in response to induction of p40 ^tax as detected by sera of systemic lupus erythematosus patients PUS and HOR. Because none of these patients were infected by HTLV-I, a protein functionally similar to p40 ^tax may be involved in eliciting autoantigen expression and a subsequent autoantibody response in a minority of patients with PSS and SLE. Sera of autoimmune patients may also be utilized to detect novel proteins trans-activated or trans-repressed by p40 ^tax of HTLV-I.