Rat monoclonal antibodies were produced against the C-terminus of Epstein-Barr virus nuclear antigens 2A (EBNA2A) and 2B (EBNA2B) expressed as bacterial trpE fusion proteins. The initial screening was performed using a soluble bacterial extract containing the fusion proteins. Positive hybridomas were confirmed by immunofluorescence on SF158 (Spodoptera frugiperda) insect cells infected with recombinant baculovirus (Autographa californica nuclear polyhedrosis virus) and expressing the complete EBNA2A or EBNA2B genes. We selected a panel of antibodies which reacted either with both antigens or specifically with EBNA2A or with EBNA2B. The antibodies were extensively characterized using immunoprecipitation, Western blotting, epitope mapping on synthesized peptide segments of EBNA2A, immunocytology, and immunohistology on both cryostat sections and paraffin sections of AIDS-associated primary central nervous system lymphomas.

This investigation was carried out on 100 bone marrow biopsies with metastases and 56 autopsies on patients with evidence of cancer. Leukoerythroblastosis was found in 44% of the patients with bone marrow mestastases and was more frequent in prostatic and gastric carcinoma. Moreover, the postmortem study of patients who died with cancer showed that leukoerythroblastosis was always the sign of bone marrow metastasis. A significant correlation was found between these blood changes and bone marrow fibrosis around the metastasis. Furthermore, leukoerythroblastosis seems caused by hepatosplenic extra medullary hematopoiesis.

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