Anti-tRNP(ser)sec/SLA/LP autoantibodies. Comparative study using in-house ELISA with a recombinant 48.8 kDa protein, immunoblot, and analysis of immunoprecipitated RNAs.
BACKGROUND
Antibodies against tRNP((ser)sec) (ribonucleoproteins, RNP) have been described in our laboratory as markers of poor outcome in type 1 autoimmune hepatitis (AIH). The antigenic protein has been sequenced and cloned as a 48.8 kDa protein and identified with soluble liver antigen (SLA) and liver-pancreas (LP) antigen. The aim of this paper was to determine the best assay by which to detect these antibodies in type 1 AIH.


METHODS
A simple and reliable enzyme linked immunoassay based on prokaryotically expressed protein was compared with an immunoblot assay using prokaryotically- and eukaryotically-expressed proteins and an assay based on immunoprecipitated RNAs from HeLa cell extracts. Eighty-one sera from 58 patients with type 1 AIH, 168 sera from patients with autoimmune diseases or chronic hepatitis C, and 60 sera from healthy subjects were similarly tested.


RESULTS
The specificity of the assays was 100%, but the frequency of seropositivity was higher in the assay based on immunoprecipitated RNAs (44.4%) than in the enzyme-linked immunosorbent assay (ELISA) (16%) and the immunoblot assay with prokaryotically (12.34%) and eukaryotically (14.8%)-expressed protein. There were no clinical differences between the patients positive by ELISA, immunoblot assay, or immunoprecipitated RNAs.


CONCLUSIONS
These results suggest that the analysis of the immunoprecipitated RNAs is the most useful, sensitive and specific method to detect anti-tRNP((ser)sec)/SLA/LP autoantibodies.
Torres-Collado
Antoni Xavier
AX
Department of Immunology, Hospital de la Santa Creu i Sant Pau, Avnda. S. Antoni Ma Claret 167, 08025-Barcelona, Spain.
Czaja
Albert J
AJ
Gelpí
Carmen
C
D001323:Autoantibodies / Q000032:analysis*; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D019693:Hepatitis, Autoimmune / Q000276:immunology* / Q000503:physiopathology; D006521:Hepatitis, Chronic / Q000276:immunology* / Q000503:physiopathology; D006801:Humans; D015151:Immunoblotting; D008297:Male; D011336:Probability; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology*; D012261:Ribonucleoproteins / Q000032:analysis / Q000276:immunology; D012494:Sampling Studies; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D011994:Recombinant Proteins; D012261:Ribonucleoproteins