Autoimmune reactivity in sheep induced by the visna retrovirus

Sheep, either naturally or experimentally infected with visna virus, were examined for the production of autoantibodies. Elevated titres of IgM and IgG antiglobulins and rheumatoid factors as well as antibodies to ssDNA, cardiolipin or histones were found in serum of both groups of animals using ELISA techniques. IgA autoantibodies were usually absent or present in low titres. The specificity of the autoantibody reactivities was confirmed by inhibition assays, affinity chromatography, Western blotting and agglutination methods. Antiglobulin titres were slightly elevated in synovial fluids, although the levels of the other autoantibodies were not raised. No significant correlations were observed between autoantibody and immunoglobulin concentrations. In a separate group of sheep infected experimentally, small but significant rises in the levels of all IgM autoantibodies, except anti-histone antibodies, were observed during and subsequent to the primary immune response to the virus. The autoantibody profiles tended to parallel each other, suggesting a common stimulus for their induction and/or a high degree of polyreactivity. The results thus show that the visna retrovirus induces, either directly or indirectly, autoimmune reactivities that are commonly observed in human autoimmune diseases such as rheumatoid arthritis or systemic lupus erythematosis.