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An epitope on Ki antigen recognized by autoantibodies from lupus patients shows homology with the SV40 large T antigen nuclear localization signal.

OBJECTIVE
Epitopes on Ki antigen were analyzed using synthetic peptides, including KILT, a 16-mer peptide with an amino acid sequence homologous to the SV40 large T antigen nuclear localization signal (SV40 T NLS).


METHODS
In addition to KILT, 4 synthetic peptides, all potential epitopes on Ki antigen according to computer analysis, were prepared and tested for reactivity with 49 anti-Ki-positive lupus sera by enzyme-linked immunosorbent assay.


RESULTS
Eighteen sera reacted with KILT, but not with other peptides. The reaction of anit-Ki sera with KILT was specifically inhibited by recombinant Ki antigen. Eight of 49 anti-Ki sera reacted with a 7-mer synthetic peptide of SV40 T NLS, and the reaction was specifically inhibited by KILT.


CONCLUSION
The 16-mer Ki peptide containing the sequence homologous to the SV40 T NLS is one of the antigenic epitopes recognized by anti-Ki antibodies in lupus sera.