Sensitive method to detect non-complement-fixing antibodies to Epstein-Barr virus nuclear antigne.

The anti-complement immunofluorescence (ACIF) test was modified to detect non-complement-fixing antibodies to Epstein-Barr (EB) virus nuclear antigen (IBNA). These EBNA antibodies belong to the immunoglobulin classes IgA and IgG. In our method anti-human gamma-globulin (AHG) was bound to the EBNA antibodies before the complement was added. If only non-complement-fixing antibodies are present the complement can be fixed to the AHG. Within only a few weeks of the onset of infectious mononucleosis (IM) the non-complement-fixing EBNA antibodies reach high titers while the complement-fixing antibodies (detected by the ACIF test) are not yet present. Anti-EBNA-IgM antibodies were not found in the IgM fractions of sera taken at different stages of IM.