Inhibition and enhancement of Friend leukemia virus by pyran copolymer. (1/26)

Inhibition or enhancement of Friend leukemia virus disease could be produced by treatment of mice with the immunopotentiator, pyran copolymer. The result depended on the route of inoculation of the drug. Prophylactic administration of the drug i.p. retarded splenomegaly, reduced splenic foci, and increased survival time of mice infected with Friend leukemia virus. Conversely, when the same dose and regimen of pyran was administered i.v., splenomegaly was enhanced, splenic foci were increased, and survival time was decreased. Histopathological examination of the spleens of mice revealed that i.p. pyran administration caused a marked increase in the splenic marginal zone with some increase in erythropoiesis in the red pulp, while i.v. pyran administration did not markedly change the splenic marginal zone but caused an early and sustained increase in erythropoiesis in the red pulp.  (+info)

Enhancement of a tumor allograft in BALB/c x DBA/2 F1 mice by pyran copolymer. (2/26)

Pyran copolymer (NSC 46015) was evaluated with respect to its effect on the rejection of a murine leukemic allograft by BALB/c x DBA/2 F1 (CD2F1) mice. Significant prolongation of allograft survival with production of progressively growing lethal tumors was found following pyran administration. This phenomenon occurred at nontoxic doses of the drug and appeared to be closely related to the timing of pyran injection. Nonspecifically stimulated lymphocyte blast transformation by concanavalin A was not impaired by pyran when lymphocytes were exposed in vitro to the drug. The mechanism of tumor allograft enhancement remains obscure but may be related to allograft size at the time of pyran administration.  (+info)

Immune response of BALB/c X DBA/2F1 mice to a tumor allograft during pyran copolymer-induced tumor enhancement. (3/26)

The immune response of BALB/c x DBA/2 F1 mice to a transplantable Moloney leukemia virus-induced tumor allograft (MBL-2) was studied to determine the mechanism of pyran copolymer-induced tumor enhancement. The relative levels of humoral, lymphocyte, and macrophage response were followed chronologically by in vitro cytotoxic microassays using 51Cr-labeled target cells. Although pyran increased the titer of humoral cytotoxic antibody, levels of humoral factors capable of abrogating lymphocytoxicity were not enhanced. Furthermore, splenic lymphocyte-mediated cytotoxicity, although slightly diminished in pyran-treated mice, was not significantly affected. Macrophages harvested from allograft-bearing animals exhibited marked tumoricidal activity, which was augmented by pyran treatment. This macrophage-associated activity was specific for MBL-2 cells and not attributable to cytotoxins elaborated into the culture medium. Pyran slightly activated macrophages from nonsensitized mice to become cytotoxic for MBL-2 cells; activation was not T-cell dependent. However, strikingly fewer macrophages infiltrated the allograft in pyran-treated animals as judged by both histopathology and direct measurement. The defect in the migration or deposit of macrophages at the allograft site may have contributed to tumor enhancement.  (+info)

Specific potentiation of L1210 vaccine by pyran copolymer. (4/26)

Pyran copolymer (NSC 46015) was found to potentiate strongly the immune response of C57BL/6J X DBA/2 F1 mice to 10(4) live L1210 tumor cells following suboptimal vaccination with 10(7) radiation-inactivated L1210 cells. Optimal immunity to challenge was produced by concomitant i.p administration of pyran and L1210 vaccine, and activity was dependent upon both pyran and vaccine dosages. In addition, this immunopotentiation seemed to be related to the intrinsic viscosity of different pyran preparations tested, although all the pyran compounds had significant activity. Furthermore, the increased immunity of subsequent live tumor challenge appeared to be specific for the vaccinating cell type.  (+info)

Selective depletion of liver and splenic macrophages using liposomes encapsulating the drug dichloromethylene diphosphonate: effects on antimicrobial resistance. (5/26)

The current results provide direct evidence for a role of tissue macrophages (M phi) in natural immunity and support the use of immunomodulators to enhance antiviral resistance in immunocompromised individuals. In this study, macrophages (M phi) in the spleen and liver were eliminated by intravenous (i.v.) injection of the drug dichloromethylene diphosphonate (DMDP) encapsulated in liposomes. The effect of this depletion system on peritoneal M phi, peripheral blood leukocytes, splenic natural killer (NK) activity, and natural and immunomodulator-induced host resistance was then assessed. Barrier-maintained CD-1 female mice were inoculated i.v. either with DMDP liposomes, free liposomes (containing no DMDP), or saline on day -2 or on days -3 and -1 before cell population analysis or infection. Single or double treatment with DMDP liposomes had no effect on peritoneal M phi as indicated by no changes in total number, differential counts, or ectoenzyme patterns. Double treatment with DMDP liposomes caused a marked leukocytosis in blood, primarily of lymphocytes and polymorphonuclear leukocytes (PMN), and a transient depression of spontaneous and interferon-inducible splenic NK activity. The effects on host resistance to i.v. infection with Listeria monocytogenes or herpes simplex virus type 2 (HSV-2) indicated that i.v. treatment with DMDP liposomes significantly reduced natural resistance to these microorganisms as evidenced by increased mortality and decreased median survival time. When DMDP liposomes-treated mice were given the immunomodulator maleic anhydride divinyl ether copolymer (MVE-2) intraperitoneally the day before infection with HSV-2, the immunosuppressive effect of DMDP liposomes treatment was significantly reversed.  (+info)

Inhibition of deoxyribonucleic acid polymerases from human cells and from simian sarcoma virus by pyran. (6/26)

Pyrans are co-polymers of divinyl ether and maleic anhydride. Four pyrans of various molecular weights more potently inhibited terminal deoxyribonucleotidyltransferase (EC from a human cell line of acute lymphoblastic leukemia origin (Molt-4) than they did DNA polymerases alpha, beta and gamma from these cells and DNA polymerase from simian sarcoma virus. For example, the concentrations of one pyran required for 50% inhibition of terminal deoxynucleotidyltransferase, DNA polymerases alpha, beta and gamma and viral DNA polymerase were 0.9, 110, 125, 35 and 47 microgram/ml respectively. Quantitatively similar results were obtained with the other pyrans. Inhibition of these enzymes by pyran was dependent on the concentrations of both the bivalent cation and template/primer or initiator in assay mixtures, but not on the concentrations of the substrate (deoxyribonucleoside 5'-triphosphate), enzyme, or bovine serum albumin. These results suggested that pyran inhibited these enzymes by complexing bivalent cations, which caused a decreased affinity of template/primer or initiator for each enzyme and a decrease in enzyme activity.  (+info)

Antimicrobial activity of various immunomodulators: independence from normal levels of circulating monocytes and natural killer cells. (7/26)

The effects of 89Sr treatment on the natural host resistance of CD-1 mice and the enhancement of resistance by immunomodulators to infection with Listeria monocytogenes or herpes simplex virus type 2 (HSV-2) were determined. In the CD-1 mouse, single-dose treatment with 89Sr caused a profound decrease in the number of circulating monocytes (Mo), lymphocytes, and polymorphonuclear leukocytes (PMN) within 1 week. There was also marked functional impairment of the Mo inflammatory response, as well as markedly decreased spontaneous and activatable cytotoxicity by splenic natural killer (NK) cells. Despite this profound cellular suppression, there was no significant change in natural resistance of CD-1 mice to L. monocytogenes or HSV-2 infection. Furthermore, prophylactic treatment of mice with the biologic immunomodulator Corynebacterium parvum or the synthetic immunomodulators maleic anhydride-divinyl ether or avridine in liposomes resulted in comparable enhancement of resistance in 89Sr-treated and normal mice. These data indicate that natural and immunomodulator-enhanced resistance of CD-1 mice to microbial infections do not depend on normal levels of Mo, PMN, or NK cells. The resistance enhancement may rely on activated tissue macrophages (M phi). In contrast to the early changes in circulating leukocytes, the resident peritoneal cell populations were not markedly altered until after day 30. There then was a distinct decline in lymphocytes and a gradual decline in M phi; the change in M phi was apparently due to the lack of an age-related increase in the peritoneal M phi population in 89Sr-treated mice in comparison with a slight increase in resident M phi in normal mice. After CD-1 mice were treated with 89Sr, the number of PMN and the function of NK cells generally recovered by about day 50 and was followed by partial recovery of circulating Mo, unless a second dose of 89Sr was administered.  (+info)

In vivo induction of terminal differentiation of malignant myelopoietic progenitor cells by CSF-inducing biological response modifiers. (8/26)

We have investigated the mechanisms by which colony-stimulating factor (CSF)-inducing biological response modifiers (BRM) may have beneficial effects on tumor-bearing hosts undergoing anti-tumor therapy. First, we have documented that treatment of mice with the chemically defined BRM maleic anhydride divinyl ether copolymer (MVE-2), which induces CSF secretion by macrophages (M phi) and bone marrow cells (BMC), significantly increased growth and differentiation of normal myelopoietic cells and counteracted the myelosuppressive effects of cyclophosphamide (CY). Second, we established that MVE-2 may exert CSF-mediated antitumor effects on certain leukemic tumor cells. Serum from mice pretreated in vivo with MVE-2, which contained CSF, induced terminal differentiation of cloned tumor cells from the CSF responsive WEHI-3B D+ subline in vitro, but not from the WEHI-3B D- subline, which is unresponsive to CSF. In vivo experiments showed that treatment of mice bearing the WEHI-3B D+ tumor first with CY and three days later with the CSF inducer MVE-2, significantly increased their survival time and rendered 20% to 50% of the tumor-bearing mice disease free. No such effects were obtained in mice bearing the WEHI-3B D- tumor. Thus, the induction of CSF or other differentiation factors by some BRMs may result in therapeutic effects against certain leukemias based on at least two distinct mechanisms: In addition to their restorative effects on normal bone marrow functions, CSF-inducing BRMs may also prevent further leukemogenesis by induction of terminal differentiation of leukemic cells.  (+info)