Identification of cyclin A as a molecular target of antinuclear antibodies (ANA) in hepatic and non-hepatic autoimmune diseases.
OBJECTIVE
Antinuclear antibodies (ANA) are a diagnostic hallmark of various autoimmune diseases and also of autoimmune hepatitis type 1. The designation ANA describes a heterogeneous group of autoantibodies. In liver diseases, only a few nuclear target antigens have been molecularly identified and characterized. Cyclins play a central role in cell cycle regulation, DNA transcription, and cell proliferation. Cyclin A was also identified as an integration site of the hepatitis B virus in a patient with hepatocellular carcinoma. In this study we identify cyclin A as a novel nuclear target protein of ANA.


METHODS
Sera of patients with autoimmune hepatitis (AIH) type 1 (n = 61), type 2 (n = 21), and type 3 (n = 39), primary biliary cirrhosis (PBC) (n = 107), rheumatic diseases (systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), mixed connective tissue disease (MCTD)) (n = 42) and normal controls (n = 100) were evaluated for ANA by indirect immunofluorescence. Baculovirus-generated recombinant human cyclin A protein was used for immunoblotting to study the prevalence of anti-cyclin A autoantibodies in these sera.


RESULTS
Sera of patients with AIH type 1 and rheumatic diseases had ANA detected by indirect immunofluorescence. In AIH type 1 12/61 (20%) and in rheumatic diseases 6/42 (14%) were immunoblot positive for autoantibodies against human cyclin A. In PBC, AIH type 3 and normal control sera negative for ANA by immunofluorescence, anti-cyclin A autoantibodies were present in 7-9%; in AIH type 2 and SLE they were undetectable by immunoblot. In some sera a typical cyclin A immunofluorescence was observed. Anti-cyclin A antibodies recognize a 45 and 50 kDa recombinant protein species, providing evidence for the recognition of at least two molecular epitopes.


CONCLUSIONS
This study has identified cyclin A as a human autoantigen in hepatic and non-hepatic autoimmune diseases. More studies are required to evaluate the clinical and pathophysiological significance of anti-cyclin A autoantibodies. The identification of human anti-cyclin A autoantibodies may additionally become a valuable tool for studying the function and regulation of cyclin A in mammalian and human cells.
Strassburg
C P
CP
Department of Gastroenterology and Hepatology, Medizinische Hochschule Hannover, Germany.
Alex
B
B
Zindy
F
F
Gerken
G
G
Lüttig
B
B
Meyer zum Büschenfelde
K H
KH
Bréchot
C
C
Manns
M P
MP
D000328:Adult; D000974:Antibodies, Antinuclear / Q000032:analysis*; D001323:Autoantibodies / Q000032:analysis*; D001324:Autoantigens / Q000276:immunology; D001327:Autoimmune Diseases / Q000276:immunology*; D016367:Baculoviridae / Q000235:genetics; D015153:Blotting, Western; D016213:Cyclins / Q000235:genetics / Q000276:immunology*; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D015151:Immunoblotting; D008107:Liver Diseases / Q000276:immunology*; D008180:Lupus Erythematosus, Systemic; D008875:Middle Aged; D011994:Recombinant Proteins
D000974:Antibodies, Antinuclear; D001323:Autoantibodies; D001324:Autoantigens; D016213:Cyclins; D011994:Recombinant Proteins; D004247:DNA