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

Inosine Pranobex: A Key Player in the Game Against a Wide Range of Viral Infections and Non-Infectious Diseases

Inosine pranobex (IP), commonly known as inosine acedoben dimepranol, isoprinosine and methisoprinol, has been proven to positively impact the host’s immune system, by enhancing T-cell lymphocyte proliferation and activity of natural killer cells, increasing levels of pro-inflammatory cytokines, and thereby restoring deficient responses in immunosuppressed patients. At the same time, it has been shown that it can affect viral RNA levels and hence inhibit growth of several viruses. Due to its immunomodulatory and antiviral properties, and its safety profile, it has been widely used since 1971 against viral infections and diseases, among which subacute sclerosis panencephalitis, herpes simplex virus, human papilloma virus, human immunodeficiency virus, influenza and acute respiratory infections, cytomegalovirus and Epstein–Barr virus infections. Following an analysis of almost five decades of scientific literature since its original approval, we here summarize in vivo and in vitro studies manifesting the means in which IP impacts the host’s immune system. We also provide a synopsis of therapeutic trials in the majority of which IP was found to have a beneficial effect. Lastly, positive results from limited studies, suggesting the putative future use of IP in new therapeutic indications are briefly described. In order to support use of IP against viral infections apart from those already approved, and to establish its use in clinical practice, further well-designed and executed trials are warranted.

Funding: Ewopharma International.

Immunotherapy with isoprinosine as an adjuvant or independent method of treatment for patientswith papilloma viral infection

Isoprinosine (an immunotropic drug) has been well-known since the 1970s and is registered in most European countries. One of indications for its use is treatment of patients with papilloma viral infection. This article describes methods and efficacy of using Isoprinosine for such patients. The drug is administered as an adjuvant therapy in addition to destructive treatment methods or as a monotherapy. The literature review given in the article shows that the use of Isoprinosine increases the efficacy of destructive treatment methods, reduces the frequency of recurrences, normalizes the morphological picture of exocervix and endocervix, and results in the termination of the release of human papilloma virus from lesions.

Isoprinosine affects serum cytokine levels in healthy adults

Isoprinosine is a synthetic purine derivative with immunomodulatory and antiviral properties, which result from an apparent in vivo enhancement of host immune responses. To evaluate the serum levels of certain cytokines during and after isoprinosine treatment, we assigned 10 healthy volunteers to receive isoprinosine 1 g, 3 times daily, 5 consecutive days weekly. Both treatment and follow-up phase last 3 weeks. Interferon-gamma (IFN-gamma), interleukin-2 (IL-2), IL-10, and tumor necrosis factor-alpha (TNF-alpha) were measured in serum using commercial ELISA kits at baseline, 7th, 10th, 14th, 21st, 28th, 35th, and 42nd day. We observed an increase in serum levels of all measured cytokines at 7th to 10th day. The levels of IL-2 had another raise at 42nd day after drop to initial values (P < 0.05; P < 0.001, respectively). Those of IL-10 held up enhanced from 7th to 28th day of measurement (P < 0.01). There was a nearly flat line of values of TNF-alpha after initial slight increase at 10th day. We found a moderate negative correlation between IFN-gamma and IL-2, IL-10, and TNF-alpha (Spearman's r: -0.63, -0.62, -0.63; P < 0.05, respectively). We have demonstrated the immunomodulating properties of isoprinosine in healthy adults. It suggests resumption of the research with up-to-date methods to elucidate the mechanisms of action of inosine pranobex and maybe the other inosine compounds in different clinical settings.

One-year follow-up on the safety and efficacy of isoprinosine for human immunodeficiency virus infection. Scandinavian Isoprinosine Study Group

The safety and clinical impact of isoprinosine in HIV-infected individuals were assessed in a multicentre, randomized, double-blind, 24-week study phase, followed by an optional 24-week open treatment phase. The results of the double-blind phase have been reported. Of 866 HIV-seropositive patients randomized, 832 subjects were eligible for efficacy analysis. On completion of the double-blind phase, 596 patients started open treatment. All patients were evaluated with regard to progression to AIDS and/or death. Within 48 weeks, 10/412 (2.4%) patients assigned isoprinosine and 27/420 (6.4%) patients assigned placebo progressed to AIDS (P = 0.005). Intention-to-treat analysis showed identical results. Viewing the open treatment phase in isolation revealed no difference in progression rates between those treated and those not receiving the drug, perhaps reflecting the higher proportion of patients receiving zidovudine or PCP prophylaxis in the latter group. No severe adverse reactions or toxicities were observed. We conclude that HIV-seropositive patients without AIDS may be safely and effectively treated with isoprinosine.

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.

Pharmacologic immunoenhancement in the elderly: in vitro effects of isoprinosine

The loss of immune competence that occurs with aging may be responsible for increased morbidity and mortality in elderly individuals. Pharmacologic modulation of the immune response might reverse the immunologic aberrations associated with aging. We, therefore, investigated the effects of isoprinosine, an immunoenhancing drug, on selected in vitro immune responses in elderly subjects. Subjects studied were 65 years of age or older, and all had chronic diseases. We chose this population since they were at greatest risk for morbid events. Isoprinosine significantly enhanced mitogen-stimulated mononuclear cell proliferation, did not affect unstimulated cell growth, and needed to be present for the entire culture period for maximum effect. Isoprinosine is a potent in vitro immunoenhancing agent in aged humans.

Effect of histamine and antihistamines on interleukin-1 production by human monocytes

This study was carried out on the effect of histamine hydrochloride and its antagonists on the production of interleukin-1 (IL-1) by lipopolysaccharide (LPS)-stimulated adherent human monocytes (AHM) from normal healthy blood donors. IL-1 activity was evaluated by incorporation of [3H]-thymidine in mouse thymocytes in samples of 1:3 dilution. The result indicated that histamine hydrochloride significantly suppressed IL-1 production by AHM at 10(-3) M and 10(-10) M in 14 donors with maximal suppression observed at 10(-3) M. A 1-hr incubation with histamine hydrochloride (10(-3) M) before addition of LPS was found to be appropriate. Cimetidine, an H2-antagonist at 10(-3) M, 10(-5) M, and 10(-7) M significantly inhibited the effect of histamine hydrochloride (10(-3) M) and gave maximum inhibition at 10(-5) M, whereas chlorpheniramine maleate, and H1-antagonist had no significant inhibitory effect at the concentrations studied (10(-4) M, 10(-5) M, and 10(-7) M). Histamine hydrochloride (10(-3) M) added alone had no significant suppressive effect, while cimetidine (10(-5) M) alone had a significant stimulatory effect on IL-1 production by AHM.

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.

Immunological effects of recombinant interferon alfa-2a in patients with disseminated melanoma

Twenty patients with disseminated melanoma were treated with interferon alfa-2a, given by intramuscular (IM) injection three times a week in escalating doses from 15 to 50 X 10(6) U/m2. Of 18 patients considered evaluable, two had complete remission and in two others the disease was stabilized. Laboratory tests 6 hours after injection of interferon alfa-2a indicated a marked lymphopenia and a reduction in natural killer (NK) cell activity. Sequential changes (measured before injection of interferon alfa-2a on days 3, 10, and 31) consisted of neutropenia, thrombocytopenia, and a slight increase in OKT4 positive T cells compared with OKT8 positive T cells. NK activity against the K562 target cells was increased in most patients during the first week of treatment, returning to near or below pretreatment levels thereafter. This response contrasted with a delayed increase against melanoma target cells in 10 patients. The latter correlated with an increase in mitogen-stimulated interleukin-2 (IL2) production, and may indicate that the cytotoxic activity resulted from lymphokine-activated killer (LAK) cells. Changes in cortisol levels may explain some effects on the immune system, such as depression of IL2 and immunoglobulin production in vitro, and the differences noted in clinical responses during the present study compared with those observed with interferon alfa-2b given by intravenous (IV) injection in 5-day cycles. These results suggest that interferon alfa-2a has antitumor activity in certain melanoma patients, in particular those with metastases to pulmonary or subcutaneous sites. Assays of IL2 production and LAK activity may assist in the selection of patients who respond to interferon alfa-2a and help to optimize treatment regimens.

Effect of isoprinosine on sialylation of interleukin-2

The effects of Isoprinosine (ISO) on interleukin-2 (IL-2) production by human peripheral blood mononuclear cells (PBMC) were investigated. Treatment (of human PBMC) with ISO enhanced IL-2 production by PBMC from 7 of 10 normal individuals. However, no augmentation of IL-2 production was observed when cultures of HUT-78 cells, a human leukemic T cell line, were treated with ISO. IL-2 purified from supernatants of human PBMC treated with ISO exhibited pI values of 5.5 and 6.4. IL-2 prepared from untreated PBMC exhibited a single pI value of 8.2. The pI value of IL-2 prepared from ISO-treated PBMC shifted to 8.2 after treatment with neuraminidase, demonstrating that the IL-2 molecules isolated from ISO-treated PBMC possessed sialic acid. The pI values of the IL-2 isolated from ISO-treated and untreated HUT-78 culture supernatants were identical (pI = 7.8) and were not modified by neuraminidase treatment. These results suggest that the increase in IL-2 production following treatment of PBMC with ISO may be mediated through the activation of a distinct subset of IL-2 producing cells. Furthermore, the sialylation of IL-2 may be of physiologic and immunopharmacologic importance.

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.

Effects of isoprinosine and NPT 15392 on interleukin-2 (IL-2) production

Two purine immunoenhancing drugs, isoprinosine and NPT 15392, were evaluated as inducers of IL-2 or enhancers of IL-2 induction by phytohemagglutinin (PHA). Both drugs were found to have significant enhancing activity on PHA induction of IL-2 by human lymphocytes over a wide range of concentrations. Alone they were unable to consistently induce IL-2 activity. NPT 15392 was able to enhance PHA-induced IL-2 production at 10-100 times lower concentrations than isoprinosine. The actions of these compounds to enhance IL-2 production may explain their effects on PHA-induced lymphocyte proliferation.

Increased interleukin-1 and modulation of interleukin-2 production by murine macrophages and lymphocytes treated with LF 1695

Previous results have demonstrated that lectin-induced T cell proliferation was potentiated or suppressed by LF 1695, a synthetic immunomodulator, depending on the dose used. Therefore the activity of this compound was investigated on murine IL-1 and IL-2 production. Adherent peritoneal cells, incubated with LF 1695, could secrete high levels of IL-1 with only a slight elevation in intracellular IL-1. This effect apparent at 5 and 10 micrograms/ml was linked to a transient state of activation. At low doses, LF 1695 increased IL-2 production by Con A-stimulated spleen cells. A decrease was found at higher doses only when cells were preincubated 20 h with the compound. In murine macrophages stimulated either by A 23187 or LPS PGE2 synthesis was inhibited by LF 1695 even at low doses. However, supernatant LTB4 level was increased in LF 1695-treated culture with a time-dependent effect. Therefore modulation of lectin-induced T cell proliferation by LF 1695 may be IL-2 production-mediated. Inhibition of the cyclooxygenase and stimulation of the lipoxygenase pathway of arachidonic acid metabolism may be responsible for this pattern of activity.

Isoprinosine effects on interleukin-1 production in acquired immune deficiency syndrome (AIDS)

The in vitro effects of isoprinosine (ISO) on the production of IL-1 in AIDS patients and normal controls were investigated in this study. IL-1 production from adherent cells was measured by an indirect method using EL-4 cells. Five of eleven AIDS patients had depressed IL-1 production. Various concentrations of ISO were used to treat the adherent cells in vitro and the optimal concentration for stimulating IL-1 production was determined to be 100 micrograms/ml/10(6) cells. IL-1 production was augmented to normal or to near normal levels in four of five AIDS patients. Our results indicate that depressed immunity seen in some AIDS patients may be partly due to the depressed in IL-1 production and also that ISO can act as an immune potentiation in enhancing the production of this lymphokine in vitro.

Immunosenescence. Clinical and pharmacologic considerations

The effect of aging on the immune response is highly variable. Many individuals appear to maintain adequate immunologic function throughout life, whereas others have severely depressed immunologic responses accounting for disease activity. Both cellular- and humoral-mediated responses may be abnormal in the elderly. Aberrant function of immunoregulatory cells, effector T cells, and antibody-producing B cells contribute to poor immunity in the aged. Immunoenhancement in the elderly by pharmacologic agents appears promising. Several agents have been demonstrated to improve immune responses when administered to aging animals and humans. Although these studies are encouraging, it is not known if enhancement of immune responses in the elderly will be associated with clinical benefits. This issue must still be examined.