Characterization of a 75-kDa Epstein-Barr virus capsid protein using a new monoclonal antibody H250

A monoclonal antibody (mAb) designated H250, directed against an Epstein-Barr virus (EBV) capsid antigen, was obtained following immunization of BALB/c mice with naked particles from the producer cell line B95.8. This antigen was present in the producer lines B95.8, P3HR1, M81, RI and CA, and absent from the non-producer lines BJAB, Raji and 1022. H250 did not inhibit the transformation of cord blood lymphocytes by the B95.8 virus, nor did it inhibit EA induction on Raji cells by the P3HR1 virus. In addition, H250 showed no fluorescence on living B95.8 cells. This indicates that H250 does not recognize a membrane antigen. By indirect immunofluorescence, no fluorescence was observed on induced Raji cells or on PAA-treated B95.8 cells. Thus, H250 recognized a late antigen of the EBV virus replication cycle. Agglutination of naked virus by H250 showed it was directed against a capsid antigen. Positive fluorescence was observed on cells treated with tunicamycin, indicating that H250 recognized a protein. The molecular weight of this protein was obtained by Western blot and was approximately 75 kDa. The blocking tests carried out with H250 seemed to indicate that this Ab appeared late in patient sera during primary infection.