Nonrheumatoid IgM in human hepatitis C virus-associated type II cryoglobulinemia recognize mimotopes of the CD4-like LAG-3 protein.
Type II mixed cryoglobulinemia (CryoII) is an autoimmune disorder frequently associated to human hepatitis C virus (HCV) infection and characterized by the presence of cold-insoluble immunocomplexes containing IgM with rheumatoid activity. To identify disease-related epitopes, we screened a phage-displayed random peptide library using purified IgM from patients with HCV-associated CryoII(CryoII/HCV). A dominant population of phage isolates bearing the HPLAP pentapeptide consensus motif was identified and shown to be recognized by a nonrheumatoid IgM species strongly associated to CryoII/HCV. The phage-borne mimotopes (phagotopes) displayed a strong homology with an exposed extra-loop region of human lymphocyte activation 3 gene (LAG-3) product. Consistently, rabbit sera raised against a synthetic LAG-3 peptide efficiently recognized the selected phagotopes. Furthermore, one such phagotope was revealed to be a good immunogenic mimic of LAG-3 when injected into rabbits. IgM purified from CryoII/HCV patients' sera specifically reacted with the LAG-3 peptide in ELISA, and this binding was inhibited by the selected phagotopes. These results provide experimental support for a general strategy to identify novel autoantigens.
Mecchia
M
M
P. Angeletti Institute of Research in Molecular Biology, Pomezia (Rome), Italy.
Casato
M
M
Tafi
R
R
Filocamo
G
G
Bonomo
L
L
Fiorilli
M
M
Cortese
R
R
Migliaccio
G
G
Nicosia
A
A
D000595:Amino Acid Sequence; D000818:Animals; D000918:Antibody Specificity; D015703:Antigens, CD; D001324:Autoantigens / Q000235:genetics; D001327:Autoimmune Diseases / Q000150:complications* / Q000276:immunology*; D001483:Base Sequence; D015704:CD4 Antigens / Q000235:genetics; D003449:Cryoglobulinemia / Q000145:classification / Q000150:complications* / Q000276:immunology*; D018076:DNA, Complementary / Q000235:genetics; D000939:Epitopes / Q000235:genetics; D006526:Hepatitis C / Q000150:complications* / Q000276:immunology*; D006801:Humans; D007075:Immunoglobulin M / Q000097:blood*; D008565:Membrane Proteins / Q000235:genetics / Q000276:immunology*; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000235:genetics / Q000276:immunology; D011817:Rabbits; D012217:Rheumatoid Factor / Q000097:blood; D000093322:Lymphocyte Activation Gene 3 Protein
D015703:Antigens, CD; D001324:Autoantigens; D015704:CD4 Antigens; D018076:DNA, Complementary; D000939:Epitopes; D007075:Immunoglobulin M; D008565:Membrane Proteins; D009842:Oligopeptides; D012217:Rheumatoid Factor; D000093322:Lymphocyte Activation Gene 3 Protein