Determination of an epitope of the diffuse systemic sclerosis marker antigen DNA topoisomerase I: sequence similarity with retroviral p30gag protein suggests a possible cause for autoimmunity in systemic sclerosis.

We report the initial molecular characterization of the autoimmune response against DNA topoisomerase I ( t o p I; Scl-70). Sera from 36 patients with scleroderma and 4 healthy control subjects were studied using 6 subcloned portions of topo I. Twenty-three sera recognized at least 2 independent epitopes on the molecule. Therefore, anti-topo I, like other non-organ-specific autoantibodies characterized to date, is polyclonal and multifocal. The cloned protein should prove suitable for sensitive early detection of anti-top0 I in the clinical setting.Circulating antibodies to nuclear proteins are found in 40-98% of patients with scleroderma and related connective tissue diseases, and are virtually

Section: Discussionmentioning

confidence: 70%

“…A nonadecapeptide that contains 11 residues from this region of topoisomerase I flanked by 8 residues that are unrelated to topoisomerase 1 was recognized by a panel of 9 patient sera (26). Interestingly, this peptide contains a stretch of 6 residues (741-746) that are also found in the p30gag molecule from feline sarcoma virus.…”

Section: Discussionmentioning

confidence: 99%

Use of molecular cloning methods to map the distribution of epitopes on topoisomerase I (Scl‐70) recognized by sera of scleroderma patients

D’Arpa

White-Cooper

Cleveland

et al. 1990

“…Maul and coworkers (30) suggested that a retroviral agent may be involved in the pathogenesis of SSc, since 6 sequential amino acid residues on top0 I, 741-746, are identical to a sequence present in the group-specific antigen p30gag of some mammalian retroviruses. However, the majority of patient sera recognized multiple epitopes, none of which contain this sequence.…”

Section: Discussionmentioning

confidence: 99%

Autoantigenic epitopes on dna topoisomerase i

Kuwana

Kaburaki

Mimori

et al. 1993

Objective. To elucidate the clinical and immunogenetic associations with reactivity to autoantigenic epitopes on DNA topoisomerase I (topo I) recognized by sera from patients with systemic sclerosis (SSc). Methods. Autoantigenic epitopes on topo I were identified by screening an epitope library constructed from topo I complementary DNA restriction fragments using autoimmune anti–topo I–positive sera as a probe. Epitope reactivities of sera from 43 anti–topo I–positive SSc patients were surveyed by immunoblotting, and associations with clinical symptoms and HLA–DR types were examined. Results. Four different epitope regions were identified on the topo I molecule. Immunoreactivity to the region encompassing amino acid residues 658–700, termed ER4, was found to be associated with diffuse cutaneous SSc, progressive pulmonary interstitial fibrosis, and poor prognosis for 15‐year survival. SSc patients with ER4 reactivity frequently displayed the DR2/DRw52 phenotype. Conclusion. Molecular analysis of precise antigenic epitopes on topo I is helpful in classifying clinical subsets of SSc.

“…However, in another recent study using oligopeptides, anti-top0 I antibody was found to crossreact with a retroviral protein, p30gag, through 6 amino acid residues commonly possessed by the 2 molecules (18). This may support the role of molecular mimicry in anti-top0 I antibody production.…”

mentioning

confidence: 82%

Identification of a Universal B Cell Epitope on Dna Topoisomerase I, an Autoantigen Associated With Scleroderma

Kato

Yamamoto

Takeuchi

et al. 1993

Objective. To investigate the distribution of B cell autoepitopes of human DNA topoisomerase I (topo I), an autoantigen associated with scleroderma. Methods. A complementary DNA clone, T1B, was used to produce recombinant proteins of topo I as β‐galactosidase fusion proteins. Immunoreactivity to these fusion proteins was then tested in 35 anti–topo I–positive sera from patients with scleroderma, by immunoblotting, enzyme‐linked immunosorbent assay, and double immunodiffusion. Results. One epitope was found to be universally recognized by all sera tested. Thirty‐two of the samples recognized multiple antigenic regions, but sera from the remaining 3 patients recognized only this universal epitope, and in longitudinal studies of 1 of these 3 patients, the serum recognized only this epitope for more than 2 years, even though multiple, potent, antigenic regions were found on topo I. Conclusion. Recognition of multiple epitopes in most patients suggests that the topo I molecule itself would drive the autoimmunity on topo I. However, antigen‐driven autoimmunity could not explain the production of the monoreactive anti–topo I antibody seen in the 3 patients. We thus hypothesize that there is a process whereby recognition of the universal epitope by cross‐reaction develops into antigen‐driven autoimmunity.