4-imino-1-3-diazabicyclo(3.1.0)hexan-2-one and Severe-Combined-Immunodeficiency

The effects of two immunomodulators were investigated in severe combined immunodeficient mice reconstituted with human peripheral blood lymphocytes (hu-PBL-SCID mice). Both immunomodulators, maleic anhydride divinyl ether (MVE-2) and 4-imino-1,3-diazobicyclo-(3.1.0)-hexan-2- one (imexon), have been previously studied by us in retrovirus-infected mice. To determine the effects of these compounds as they may function in humans, 24 SCID mice were each reconstituted with 20 x 10(6) ficoll-purified lymphocytes from a single donor. Five weeks after reconstitution, the mice received 16 mg/kg/day of MVE-2 intraperitoneally (i.p.) on days 0, 7, and 14 or 110 mg/kg/day of imexon i.p. daily for 14 days. Spleens were removed and splenocytes labeled with monoclonal antibodies for T- and B-cell enumeration as determined by flow cytometry 24 h after final treatment. Imexon-treated mice demonstrated a slight increase in total T cells and T cell subsets compared to control mice. T helper/T suppressor cell ratios in imexon-treated mice were brought to a normal 3:2 ratio compared to placebo-treated mice. Human immunoglobulin levels were markedly increased in imexon-treated mice. MVE-2-treated hu-PBL-SCID mice had significantly reduced numbers of total T cells compared to controls. The T-cell population results using human cells in SCID mice were similar to the effects of these immunomodulators on murine cells in immunologically competent mice.

Topics: Adjuvants, Immunologic; Animals; Antibodies, Monoclonal; B-Lymphocytes; Cell Count; Disease Models, Animal; Female; Flow Cytometry; Hexanones; Immunoglobulins; Injections, Intraperitoneal; Mice; Mice, SCID; Pyran Copolymer; Severe Combined Immunodeficiency; Spleen; T-Lymphocyte Subsets

Severe combined immune-deficient (SCID) mice accept human cell xenografts. SCID mice inoculated intraperitoneally with human peripheral blood mononuclear cells (PBMCs) from EBV-seropositive donors develop a form of disseminated human large cell lymphoma similar to that seen in transplant recipients and AIDS patients. Imexon (4-imino-1,4-diazobicyclo-3.1.0-hexan-2-one), a cyanoziridine immunomodulator with a selective inhibitory effect on B cells, was tested for its effect on this lymphoma development. Imexon started 2 weeks after PBMC inoculation significantly reduced the number of animals with lymphoma and the number of lymphomas sites per animal. The lymphoma was widely metastatic in the control animals but limited to the peritoneal cavity in the treated animals. Morphological and molecular parameters were used to confirm the reduced takes in the treated animals. Imexon was not myelosuppressive as determined by measurement of white blood cell counts. Imexon did not significantly suppress human IgG levels in the animals' serum. The tumor growth and lethality of human B lymphoblastoid cell lines in SCID mice was also suppressed by imexon treatment. A relatively nontoxic class of drugs that can suppress the development and/or growth of EBV-related lymphoma should be explored with priority for potential use in patients at high risk of this type of lymphoma.

Topics: Animals; Antineoplastic Agents; Disease Models, Animal; Herpesvirus 4, Human; Hexanones; Humans; Immunoglobulin G; Immunologic Factors; Injections, Intraperitoneal; Leukocyte Count; Lymphoma, Large B-Cell, Diffuse; Mice; Mice, SCID; Severe Combined Immunodeficiency; Tumor Cells, Cultured