Serum IgA cross-reactivity between glycine-alanine repeat sequence of EBNA-1 and keratin or collagen in nasopharyngeal carcinoma.
Inhibition studies were carried out to study possible cross-reactivity between a peptide fragment of the Epstein-Barr virus nuclear antigen, EBNA-1, and keratin/collagen. The 20-amino acid peptide (pAG), derived from a glycine-alanine repeat region of EBNA-1, uniquely makes up about one-third of the viral protein and is a dominant IgA antigenic epitope in patients with nasopharyngeal carcinoma (NPC). A small percentage of normal human sera (NHS) also binds pAG and this reactivity is examined in this study. Ten percent (2/20) and 13.4% (2/15) of IgA-pAG-positive NPC sera and NHS, respectively, were significantly inhibited by keratin in a competitive ELISA system. Conversely, 31.6% (6/19) and 30.8% (4/13) of IgA-keratin-positive NPC sera and NHS, respectively, were significantly inhibited by pAG. This indicated minimum cross-reactivity between IgA serum antibodies to EBNA-1 and keratin. Using collagen as inhibitor, none of 18 and only 2/13 IgA-pAG-positive NPC sera and NHS, respectively, were inhibited. In the collagen ELISA system, only 2/19 (10.5%) and 4/25 (16%) of IgA-collagen-positive NPC sera and NHS, respectively, were inhibited with pAG. Therefore, cross-reactivity with collagen was also low. IgA-pAG-positive NHS may therefore not be a false positive phenomenon, but whether it may represent an early serological profile related to NPC carcinogenesis remains to be determined.
Mathew
A
A
Nasopharyngeal Carcinoma Research Laboratory, University Malaya, Kuala Lumpur, Malaysia.
Cheng
H M
HM
Sam
C K
CK
Prasad
U
U
D000409:Alanine / Q000276:immunology*; D000595:Amino Acid Sequence; D000956:Antigens, Viral / Q000276:immunology*; D001667:Binding, Competitive; D003094:Collagen / Q000276:immunology*; D003429:Cross Reactions; D004268:DNA-Binding Proteins / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D019309:Epstein-Barr Virus Nuclear Antigens; D005998:Glycine / Q000276:immunology*; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood / Q000276:immunology*; D007633:Keratins / Q000276:immunology*; D008969:Molecular Sequence Data; D009303:Nasopharyngeal Neoplasms / Q000097:blood / Q000276:immunology*; D012091:Repetitive Sequences, Nucleic Acid
D000956:Antigens, Viral; D004268:DNA-Binding Proteins; D019309:Epstein-Barr Virus Nuclear Antigens; D007070:Immunoglobulin A; D007633:Keratins; D003094:Collagen; D000409:Alanine; D005998:Glycine