Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0036421 (PSS)
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Five recombinant fusion proteins with overlapping amino acid sequences encompassing the entire DNA topoisomerase I (topo I) molecule were generated, purified, and used as antigens for an enzyme-linked immunosorbent assay (ELISA). IgG, IgA, IgM, and "total" (total of IgG, IgA, and IgM isotypes) anti-topo I antibodies were measured using a mixture of these five fusion proteins in 73 systemic sclerosis (SSc) sera positive for anti-topo I antibody by double immunodiffusion (DID) and 184 control sera negative for anti-topo I antibody by DID. Fragment-specific anti-topo I antibodies were also measured by ELISA using each topo I recombinant protein as antigen. IgG, IgA, IgM, and total anti-topo I antibodies were detected in 67 (92%), 56 (77%), 16 (22%), and 70 (96%) of 73 SSc sera positive for anti-topo I antibody by DID, respectively. The specificity of the total anti-topo I ELISA was 99% when compared with DID. The total anti-topo I ELISA levels were strongly correlated with DID titers (r = 0.907, P < 0.0001). Three sera which recognized a conformational epitope on native topo I or had predominantly IgM anti-topo I antibody showed a false-negative result with the total anti-topo I ELISA. Three SSc sera negative for anti-topo I antibody by DID were positive by the total anti-topo I ELISA, and two were confirmed to recognize the N-terminus of topo I. IgG and IgA antibody levels to the N-terminal and central portion of topo I were correlated with each other, but those to the C-terminus were not. These findings indicate that the ELISA using recombinant fusion proteins is a highly sensitive and specific alternative to conventional DID for the detection of anti-topo I antibody.
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PMID:Detection of anti-DNA topoisomerase I antibody by an enzyme-linked immunosorbent assay using overlapping recombinant polypeptides. 755 48

Auto-antibodies against topoisomerase I (topo I) are frequently detected in sera of systemic sclerosis (SSc) patients. Anti-topo I auto-antibodies are considered to be associated with the diffuse cutaneous form of systemic sclerosis (dcSSc). However, anti-topo I auto-antibodies are also detected in limited cutaneous systemic sclerosis (lcSSc) and systemic lupus erythematosus (SLE). In this study, we compared the epitope specificity of anti-topo I auto-antibodies present in sera of dcSSc, lcSSc and SLE patients. We have constructed an antigen fragment library displayed on bacteriophage lambda and screened this library with IgG purified from patients' sera. Regions of topo I selected from the library were expressed as recombinant fusion proteins and were tested with ELISA and western blot. We unexpectedly found that antibodies against a fragment of topo I [fragment F4 [amino acid (AA)] 451-593] could be detected in sera of healthy individuals and patients with inflammatory rheumatic diseases other than SSc and SLE. Using sera of dcSSc, lcSSc and SLE patients, we showed that the pattern of recognized epitopes is different between these patient groups. Fragment F4 was recognized by all patients. Fragment F1 (AA 5-30) was recognized by 9 of 34 dcSSc patients. Fragment F8 (AA 350-400) was recognized by four of eight SLE patients. Analysis of clinical data revealed a significant difference between the F1-negative and F1-positive groups of SSc patients in age and in the duration of the disease. According to our results, the newly identified fragments F1 and F8 could represent characteristic epitopes for dcSSc and SLE, respectively.
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PMID:Naturally occurring and disease-associated auto-antibodies against topoisomerase I: a fine epitope mapping study in systemic sclerosis and systemic lupus erythematosus. 1921 83