Suppressor cell activity after isoprinosine treatment of lymphocytes from normal mice

Inosine pranobex in the treatment of HIV infection: a review

Inosine pranobex (InPx) could prove a valuable and innovative approach to the treatment of HIV-infected patients, since InPx administration has been shown in two multicenter trials to effectively delay the progression of HIV infection to overt AIDS. However, further studies are strongly required to optimize both the dosage of inosine pranobex and the administration schedules. Furthermore, clinical trials evaluating combination therapy of HIV infection with both InPx and zidovudine should ultimately provide an important advance in the management of HIV-infected patients. Our finding that concomitantly administered InPx to zidovudine-receiving patients increased the plasma levels of zidovudine as well as prolonged zidovudine mean half-life during InPx treatment suggests several potential advantages of the combination treatment with both InPx and zidovudine, such as a need for lower zidovudine dosage and a longer interval period between administering zidovudine to obtain sustained plasma levels as well as a potential to enhance residue immune function resulting from inosine pranobex treatment.

Influence of isoprinosine on bovine herpesvirus type-1 infection in cattle

A study was conducted to determine the in vivo efficacy of isoprinosine (ISO) in calves infected with bovine herpesvirus type-1 (BHV-1). Calves were infected with BHV-1 on day 0 and received ISO daily for 14 days. Clinical signs of disease, shedding of BHV-1, lymphocyte proliferative responses to mitogens, interleukin-2 production, and alveolar macrophage bactericidal activity were monitored during the study. Rectal temperatures were increased (P less than 0.05) in BHV-1 and ISO-BHV-1 calves at days 3 to 7 postinfection (PI). Isoprinosine did not influence BHV-1 shedding in calves. Lymphocyte proliferative responses to phytohemagglutinin (PHA) were lower (P less than 0.01) in BHV-1 calves when compared to control or ISO calves at day 4 PI, but ISO did not ameliorate this effect. Interleukin-2 activity was greater (P less than 0.05) in ISO-BHV-1 calves on days 4 and 8 PI in PHA-stimulated lymphocytes and on day 8 PI in concanavalin A-stimulated lymphocytes when compared to control, ISO or BHV-1 calves. Isoprinosine treatment of BHV-1-infected calves tended to decrease alveolar macrophage bactericidal activity. These data suggest that ISO does not reverse BHV-1 suppression of lymphocyte proliferation, but may enhance IL-2 production in BHV-1 infected calves.

Inosine pranobex. A preliminary review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Inosine pranobex is a synthetic compound formed from the p-acetamido benzoate salt of N-N dimethylamino-2-propanol and inosine in a 3:1 molar ratio. It has been reported to exert antiviral and antitumour activities in vivo which are secondary to an immunomodulating effect, and early results suggest beneficial clinical effects in several diseases and infections including mucocutaneous Herpes simplex infections, subacute sclerosing panencephalitis, genital warts, influenza, zoster, and type B viral hepatitis, as well as in homosexual men with persistent generalised lymphadenopathy. However, many of the studies have been preliminary in nature and deficient in design or in the reporting of their results. One must therefore conclude that while inosine pranobex may prove to be a valuable and innovative therapy for a number of diseases and infections for which no satisfactory therapy exist, further long term well controlled studies in larger numbers of patients are required before definitive conclusions about the efficacy of inosine pranobex in these disorders will be possible.

The selectivity of isoprinosine, NPT 15392, avridine and cyclophosphamide on multiple immune responses in rats

Multiple concomitant immune responses were assessed in individual rats following treatment with the immunoenhancing drugs, isoprinosine (5 or 50 mg/kg), NPT 15392 (0.1 or 1.0 mg/kg) and avridine (1 or 25 mg/kg), or the immunosuppressant, cyclophosphamide (75 mg/kg). Immune responses assessed in each rat were specific antibody synthesis, delayed-type hypersensitivity (DTH), natural killer cell (NKC) cytotoxicity and production of three immunoregulatory cytokines, interleukin 1 (IL1), interleukin 2 (IL2) and prostaglandin E2 (PGE2). Spleen and thymus weights and numbers of splenocytes and resident peritoneal cells were also recorded. Rats treated with isoprinosine had dose-related, significant increases in spleen weights and DTH reactions. Rats treated with NPT 15392 had significantly enhanced DTH reactions at the 0.1 mg/kg dose. Rats treated with the 25 mg/kg dose of avridine had significantly increased spleen weights, DTH reactions and NKC cytotoxicity. The effect of avridine treatment on DTH reactions and IL1 and IL2 production was inverse to the dose administered, while the NKC response was directly related to the dose. Thymus weights, antibody production and PGE2 synthesis were not significantly altered in rats treated with isoprinosine, NPT 15392 or avridine. Cyclophosphamide-treated rats had significantly reduced spleen and thymus weights, antibody synthesis, DTH reactions, NKC cytotoxicity and IL2 production, but IL1 and PGE2 synthesis were significantly elevated. It can be concluded that isoprinosine, NPT 15392 and avridine act as general immunostimulants in the rat, with avridine having the greatest effect under these experimental conditions. It also appears that these drugs are differentially immunoselective in the rat and this effect is at least partially related to the dose administered. These results could be of significance in the selective therapeutic manipulation of different arms of the immune system. Also, enhanced production of PGE2 following cyclophosphamide treatment may contribute to the immunosuppressive effects of this drug.

Modulation of T- and B-lymphocyte functions by isoprinosine in homosexual subjects with prodromata and in patients with acquired immune deficiency syndrome (AIDS)

Male prodromal homosexuals and patients with acquired immune deficiency syndrome (AIDS) exhibited similar immunological abnormalities but by different degrees. A reduction in the number of circulating T lymphocytes bearing the T-4 surface marker led to an altered ratio of Th to Ts subpopulations in both groups of subjects. Total numbers of suppressor cells (Ts) remained virtually similar in both study groups to that of the control subjects. Proliferative responses to T-cell mitogen (PHA) and T cell-dependent B-cell mitogen (PWM) were severely impaired in prodromal subjects and more so in the AIDS group. The response to PWM was unrelated to the total number of suppressor T cells but was associated with a significant decrease in helper T-cell number. The impaired lymphocyte functions of immunosuppressed subjects were potentiated by coincubation with isoprinosine in a selective fashion. While the percentage of upward modulation among homosexuals with normal lymphocyte functions was comparable to that obtained in control subjects, a higher degree of augmentation was achieved in AIDS patients and in prodromal subjects with impaired blastogenic responses. In none of the AIDS patients with severe immunodeficiencies, however, was the lymphocyte functions restored to the normal range established in the heterosexual controls. These results suggest the feasibility of eventual prophylactic utilization of isoprinosine in male homosexuals at high risk of developing AIDS.

Effect of isoprinosine on natural killer cell activity of blood mononuclear cells in vitro and in vivo

Addition of isoprinosine to cultures of blood mononuclear cells was shown to inhibit natural killer (NK) cell activity against the K562 myeloid cells and melanoma cells. This appeared to be due to inhibitory influences of monocytes in that after removal of adherent cells isoprinosine appeared to stimulate NK activity. Similar effects were noted on T cells separated by E rosette procedures. Administration of isoprinosine in vivo had variable effects on NK activity during drug administration but there was a significant increase in NK activity 3 days after cessation of the drug. These changes in NK activity may reflect different threshold levels of the drug on suppressor and NK cell populations and the relative proportions of different lymphocyte populations in individual subjects. Further studies with a wider range of drug doses and more frequent monitoring of responses are required to further evaluate the effect of isoprinosine on NK activity.

Effect of isoprinosine on interleukin 1 and 2 production and on suppressor cell activity in pokeweed mitogen stimulated cultures of B and T cells

Isoprinosine appeared to potentiate the production of interleukin 1 and interleukin 2 in cultures of lipopolysaccharide stimulated human monocytes and phytohemagglutinin stimulated cultures of blood mononuclear cells respectively at pharmacological drug levels. Administration of the drug in vivo was associated with increased activity of radiation sensitive suppressor T cell activity against immunoglobulin production in pokeweed mitogen stimulated cultures of B and T cells. Addition of isoprinosine to the latter cultures in vitro appeared to enhance immunoglobulin production consistent with inhibition of suppressor cell activity or stimulation of helper activity. It is not clear from these studies whether the contrasting effects of the drug in vitro and in vivo represent different actions of metabolites or alteration of the proportion of lymphocyte subsets in the circulation. Further studies are required to answer these questions and to determine whether the changes persist with long term administration of the drug.

Immunoenhancing effect of flavonoid compounds on lymphocyte proliferation and immunoglobulin synthesis

Flavonoid compounds are lipophilic agents which can interact with membrane lipids and may affect responsiveness of immune cells. We therefore studied whether cianidanol ((+)-catechin), the O-methyl-derivative (+)-3-methoxy-5,7,3',4'-tetrahydroxyflavan and palmitoyl-derivative (+)-3-palmitoyl-5,7,3',4'-tetrahydroxyflavan influence T and B cell functions. In addition, immunomodulatory property of ubiquinone 50 was also investigated. As controls were used cyclosporin A and inosine which are known to inhibit or enhance immune responses, respectively. The in vitro spontaneous, antigen and mitogen induced proliferation as well as immunoglobulin synthesis of peripheral blood mononuclear cells from healthy individuals was determined in the presence of different concentrations of the agents. All flavonoid compounds and ubiquinone 50 significantly increased (p less than 0.05 - less than 0.01) the spontaneous lymphocyte transformation but hardly affected antigen, alloantigen and mitogen induced proliferative response. Only cianidanol and O-methyl-derivative enhanced significantly (p less than 0.05 - less than 0.01) spontaneous, pokeweedmitogen and Staphylococcus aureus Cowan I induced immunoglobulin synthesis while the palmitoyl-derivative and ubiquinone 50 had only minor influence on B cell function. In contrast, Staphylococcus aureus induced immunoglobulin production was neither increased by inosine nor suppressed by cyclosporin A. These studies show that especially cianidanol and the O-methyl-derivative can exert an immunoenhancing effect on T and B cell functions.

Immunomodulatory activity of isoprinosine on experimental viral infections in avian models

The immunomodulatory activity of Isoprinosine treatments have been experimentally verified on chicken infected by three different viruses: Newcastle disease, fowl plague and avian infectious bronchitis. In protection tests, positive variations in the mean day of death rather than in the mortality rate were found depending on the modality of treatment. A stimulatory influence on primary anti-Newcastle disease virus antibody response was observed. In the avian model the Isoprinosine antiviral effect appears as due mainly to the enhancement of interferon production and to a synergistic interferon-isoprinosine interaction.

Enhancement and restoration of contact sensitivity reactions by isoprinosine

Isoprinosine (50 mg/kg i.p.) increased the ear swelling reaction in mice sensitized with trinitro-chlorobenzene (picryl chloride) and challenged with the same agent. Enhancements were observed when the drug was administered either simultaneously to the sensitization or to the challenge with picryl chloride. Similar results were obtained when lymphoid cells from sensitized animals were transferred i.v. to normal animals which were then challenged with picryl chloride. Using the same cell transfer system, we found that treatment of cell donors with Isoprinosine (50 mg/kg/day, i.p.) counteracts the inhibition induced by cyclophosphamide. Isoprinosine (50 mg/kg/day, i.p.) inhibited also the generation of antigen-specific suppressor cells induced by picryl-sulfonic acid as shown by transfer to normal recipients of suppressor cells together with lymphoid cells from sensitized animals. These results indicate that Isoprinosine enhances normal contact sensitivity reactions and can counteract, under certain circumstances, antigen-specific as well as nonspecific immunosuppression.

Modulation of human T lymphocyte functions by isoprinosine

Isoprinosine was shown to alter certain T cell functions. In vitro, it has previously been shown to induce suppressor cell activity in both mouse and human lymphocytes. Our in vitro results suggest that Isoprinosine acts on immune balance by increasing the number of non-suppressor T cells and, at least partially blocks Con A induced suppressor activity. In vitro NK activity remained unaltered.

Inosiplex therapy in subacute sclerosing panencephalitis. A multicentre, non-randomised study in 98 patients

Inosiplex was administered to 98 patients with subacute sclerosing panencephalitis (SSPE) in the United States and Canada for variable periods of time up to 9.5 years. Survival data from these 98 patients were compared by life-table analysis with survival in three SSPE control groups drawn from SSPE patients contracting the disease in Israel, Lebanon, or the United States at about the same time as the inosiplex-treated patients but treated differently or not at all. In the inosiplex-treated patients the actuarial probability of survival at 2, 4, 6, and 8 years from onset of SSPE was 78%, 69%, 65%, and 61%, compared with 38%, 20%, 14%, and 8% in a composite control group (p less than 0.01 for all four comparisons). Statistical adjustments for time-to-treatment bias did not affect this result: a modified logrank procedure demonstrated that the risk of dying in the treatment group was 43% of that in the controls. Inosiplex seems to be able to prolong life in patients with SSPE.

Long-term follow-up of patients with subacute sclerosing panencephalitis treated with inosiplex

During the past five years, 15 patients with subacute sclerosing panencephalitis (SSPE) were treated with inosiplex. Using a disability index specifically designed for the disease, this study monitored the course of SSPE in each patient before and during inosiplex therapy. Posttreatment follow-up ranged from 2 to 144 months. Inosiplex had an apparently beneficial effect on morbidity and mortality in 10 of the 15 patients tested. Eight improved immediately after treatment, 2 had a delayed improvement, and 1 patient stabilized. Four patients followed a typical course for SSPE and died a mean 9 months after onset. Treatment was not associated with adverse reactions. Due to its low risk-benefit ratio, inosiplex is recommended for continuous use in SSPE even after extended remissions.

Effect of isoprinosine on in vitro proliferative responses of human lymphocytes stimulated by antigen

Isoprinosine, a synthetic purine derivative, did not significantly interfere with the thymidine uptake of triggered normal lymphocytes, nor exhibit a detectable mitogenic activity. Isoprinosine was able to significantly enhance specific proliferative responses of human lymphocytes from sensitized donors to soluble antigens. Isoprinosine did not alter the early interaction of human mononuclear cells with 125I-labelled antigen, nor the expression of their membrane receptors for immunoglobulin Fc fragments. The agent could not replace the accessory rôle of adherent cells in proliferative responses to antigens. The enhancing effect of isoprinosine on antigen specific responses of T-cells was observed upon adding the compound on any one of the seven days of culture. Isoprinosine partially restored the inhibited proliferation of lymphocytes cultured in the presence of deoxyadenosine and deoxycoformycin. Data suggest that metabolic changes involving purines may account for the effect of isoprinosine on the expression of T-cell responses.