REACTIVITY OF SERA FROM SYSTEMIC LUPUS-ERYTHEMATOSUS AND SJOGRENS-SYNDROME PATIENTS WITH PEPTIDES DERIVED FROM HUMAN-IMMUNODEFICIENCY-VIRUSP24 CAPSID ANTIGEN

We have previously demonstrated that about one-third of patients with either Sjogren's syndrome (SS) or systemic lupus erythematosus (SLE) r eact to human immunodeficiency virus (HIV) p24 core protein antigen wi thout any evidence of exposure to, or infection,vith, HIV itself. Here in, we further characterize the specificity of this reaction using enz yme-linked immunosorbent assay to peptides representing fragments of p 24. Characteristic epitope-specific profiles were seen for SS and SLE patients. SS patients had significantly increased responses to peptide s F (p24 amino acids 69 to 86) and H (amino acids 101 to 111) and dimi nished reactivity to peptides A (amino acids 1 to 16) and P (amino aci ds 214 to 228). SLE patients had increased reactivity to peptides E (a mino acids 61 to 76), H, and P. Utilization of peptide P hyporeactivit y as the criterion to select for SS patients results in a screen that is moderately sensitive (64%) and specific (79.3%). Adding hyperreacti vity to one other peptide (F or H) as an additional criterion yields a n expected decrease in sensitivity (to 41%) while increasing specifici ty (to 93.1%). All sera-reactive peptides from regions of known struct ure of HIV p24 were located in the apex of the p24 molecule. Thus, the specificity of the peptide reactivities described here indicates a sp ecific pattern of a nonrandom cross-reactivity between HIV type 1 p24 and autoimmune sera which may be partially syndrome specific. The futu re focus of our work will be to optimize assays of the peptide as diag nostic tools.