Anti-human immunodeficiency virus type 1 antibodies of noninfected subjects are not related to autoantibodies occurring in systemic diseases.

Indeterminate Western blot (WB) (immunoblot) patterns for anti-human immunodeficiency virus type 1 (HIV-1) antibodies are often observed when testing serum samples from noninfected individuals. We investigated here the possible involvement of some frequently occurring autoantibodies (anti-SmB/B', U1snRNP [68 kDa, A, and C], Ro/SS-A [60 and 52 kDa], and Jo-1) in the generation of such indeterminate HIV-1 WB. In particular, the role of a reported sequence homology between p24 gag and the SmB/B' autoantigen was investigated. Serum samples were obtained from 50 healthy controls, 51 patients with systemic lupus erythematosus (SLE), 46 with systemic sclerosis, 6 with Sjögren's disease, 3 with mixed connective tissue disease, and 41 healthy subjects with persistent indeterminate HIV-1 WB. Reactivity to HIV-1 p24 gag was slightly but not significantly more frequent in patients with SLE than in controls (25.5% versus 14.0%; P > 0.1), whereas reactivity to HIV-1 p17 gag was significantly more frequent in the former subjects (23.5% versus 8.0%; P = 0.03). Simultaneous reactivity to p17 and p24 was observed in patients with SLE (11.8%; P = 0.014) or systemic sclerosis (8.7%; P = 0.049) but not in controls. There was no association found between the presence of any autoantibody and the occurrence of indeterminate HIV-1 WB nor between the presence of p24-reactive antibodies and anti-SmB/B'; this indicates that most p24-reactive antibodies are directed to epitopes other than the proline-rich sequences shared by p24 gag and SmB/B'.