PURIFIED RECOMBINANT EBV DEOXYRIBONUCLEASE IN SEROLOGICAL DIAGNOSIS OF NASOPHARYNGEAL CARCINOMA

To evaluate applications of highly purified recombinant EBV DNAase in the diagnosis and prognosis of NPC, we tested sera from patients with NPC, other EBV-associated diseases and EBV-seropositive and -seronegat ive healthy subjects by immunoblotting and DNAase inhibitory assay. Th e results were compared with those obtained by the conventional immuno fluorescence assays against the EBV-specified early antigens and capsi d antigens. The antigenic specificity of the immunoblotting assay for Ige antibody against the viral enzyme, but not that for the IgA antibo dy, was correlated with DNAase-inhibitory activity of the sera and the ir titers of IgG antibodies against the viral early antigens. Purified IgA as well as IgG from NPC sera inhibited enzyme activity with simil ar efficiency. The use of highly purified viral DNase has increased th e sensitivity of detection of the corresponding antibodies by immunobl otting, with the IgG antibody being detected in all but one, and IgA a ntibody in all but 2, of the 174 NPC sera tested. The IgG antibody was also commonly detected in the other groups of control sera, while the IgA antibody was detected in about 10% of African Burkitt's lymphoma and Algerian Hodgkin's lymphoma patients and less than 3% of the other control subjects. These results suggest that IgA antibody against rec ombinant EBV DNAase may be useful in the diagnosis of NPC, but the lev el of this antibody did not appear to be related to clinical stages of this cancer. (C) 1996 Wiley-Liss, Inc.