[125I] Clq-binding activity and its relationship with anti-Epstein—Barr virus antibodies in sera from nasopharyngeal carcinoma patients

The [ 125 I ] Clq-binding activity (Clq BA) and the antibody titre against Epstein-Barr (EB) viral capsid antigen (VCA), EB nuclear antigen (EBNA) and early antigen (EA) were determined in sera from 28 nasopharyngeal carcinoma patients and 66 matched controls from Tunisia. The geometric mean titres (GMT) of anti-VCA IgG and anti-EBNA, as well as the prevalence of anti-EA, antibodies were significantly higher among the patients than in the control group. The increased Clq BA of NPC sera, as compared to that of control sera, is likely to reflect the presence of soluble immune complexes, to which the contribution of the various autoantibodies found in this disease seems to be negligible. In individual sera from these patients, the Clq BA correlated positively with the titre of IgG ( P = 0.026), but not with that of IgA, anti-VCA antibodies, indicating that the age-dependency of these different parameters was not per se a sufficient condition for a positive correlation to appear. Since the correlation between Clq BA and anti-VCA titre was restricted to the class of Ig which binds Clq, an alternative explanation is proposed in which specific anti-EBV antibodies complexed to virion structural antigens account for part of the elevated Clq BA.