Partial restoration of impaired interleukin-2 production and Tac antigen (putative interleukin-2 receptor) expression in patients with acquired immune deficiency syndrome by isoprinosine treatment in vitro

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.

Inosine Acedoben Dimepranol promotes an early and sustained increase in the natural killer cell component of circulating lymphocytes: A clinical trial supporting anti-viral indications

Inosine Acedoben Dimepranol (IAD), licensed for the treatment of cell-mediated immune deficiencies associated with viral infections, has been reported to impact a variety of immune parameters both in vitro and in vivo. Here we report the results from a clinical trial where multiple lymphocyte subsets - CD19+ B cells, CD3+ T cells, CD4+ T-helper cells, FoxP3^hi/CD25^hi/CD127^lo regulatory T cells (Tregs), CD3-/CD56+ NK cells, and CD3+/CD56+ NKT cells - were, together with serum immunoglobulins and IgG subclasses, followed during 14days of IAD administration to ten healthy volunteers; these selected from 27 individuals pre-screened in vitro for their capacity to respond to IAD as gauged by increases in the percentage of Treg and/or NKT cells arising in PHA-stimulated cultures. While a transient spike and dip in Treg and T-helper fractions, respectively, was noted, the outstanding consequence of IAD administration (1g po, qds) was an early and durable rise in NK cells. For half the cohort, NK cells increased as a percentage of total peripheral blood lymphocytes within 1.5h of receiving drug. By Day 5, all but one of the volunteers displayed higher NK cell percentages, such elevation - effectively a doubling or greater - being maintained at termination of study. The IAD-induced populations were as replete in Granzyme A and Perforin as basal NK cells. The novel finding of IAD boosting phenotypically competent NK numbers in healthy individuals supports the drug's indicated benefit in conditions associated with viral infection and reinforces the potential for uplift where immune performance may be compromised.

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.

Membrane-bound/soluble IL-2 receptor (IL-2R) and levels of IL-1 alpha, IL-2, and IL-6 in the serum and in the PBMC culture supernatants from 17 patients with hematological malignancies

The present study investigated the peripheral blood mononuclear cells (PBMC) blastic responses to PHA, PHA plus recombinant IL-2 (rIL-2) and rIL-2 alone; the expression of membrane-bound IL-2R on PHA-stimulated PBMC; and the levels of IL-1 alpha, IL-2, IL-6, and sIL-2R in serum and in culture supernatants from PHA-stimulated PBMC in 17 patients with with non-Hodgkin's lymphoma (NHL), 4 with Hodgkin's lymphoma (HL), 5 with Hairy cell leukemia, 1 with chronic myelogenous leukemia, and 1 with chronic lymphocytic leukemia. The patients with HL and NHL with active disease (AD) were separated from those in clinical remission. The patients with AD were studied at diagnosis (obviously before therapy) and the patients in clinical remission were out of therapy since at least 6 mo. The lymphocyte blastogenic response to PHA was significantly lower in patients with HL and NHL with AD than in the control group. The response to rIL-2 alone was in the same range in the control group and in HL and NHL AD patients. By adding rIL-2 to PHA there was an increase of the blastogenic response of the same patients. The percentage of CD25 expressed on PHA-stimulated lymphocytes from patients with HL and NHL AD and from normal subjects is in the same range. Serum levels of IL-2, IL-6, and sIL-2R were significantly higher in HL and NHL AD patients than in controls as well as in all other hematological malignancies. Supernatants derived from PHA-stimulated PBMC were assessed for the presence of cytokines and sIL-2R by ELISA. The levels of IL-2, IL-6, and sIL-2R were significantly lower in HL and NHL AD patients than in controls as well as in all other hematological malignancies.

A placebo-controlled trial of isoprinosine in patients with multiple sclerosis

Isoprinosine was used under double-blind, randomised, and placebo-controlled conditions in 52 patients with relapsing/remitting or progressive multiple sclerosis. All patients received pulsed treatment with methylprednisolone. There was no significant effect of treatment on clinical disability or the accumulation of MRI abnormalities, after correction of results for multiple comparisons. It is concluded that isoprinosine is not effective therapy for multiple sclerosis.

Application of chemical immunomodulators to the treatment of cancer and AIDS

A number of potential advantages, development of promising new agents, and the discovery of synergy with cytokines or cell products continue to spur research into the application of chemical immunomodulators for the treatment of cancer and AIDS. In preclinical in vitro and in vivo systems, chemical immunomodulators definitely modulate the immune system and have therapeutic efficacy. Although clinical trials have shown the ability of these agents to modulate the human immune system, thus far chemical immunomodulators have generally not fulfilled the therapeutic promise generated in animal models for the treatment of human diseases. While the discrepancy in results between animal models and human trials is obvious, the basis is not apparent. Species differences in elimination kinetics, presentation of active drug at the site of action, and the development of tachyphylaxis have been postulated as reasons for the minimal activity of these agents in humans. In addition, the use of investigational techniques established for cytotoxic agents may not be appropriate for immunomodulators. As with any immunomodulator, determining an optimal immunostimulatory dose and schedule and applying the therapy to patients with minimal tumor burden would perhaps be more appropriate than use of a maximally tolerated dose in patients with advanced disease. A dose-immunological effect relationship has recently been demonstrated for levamisole at doses higher than those used for many years in levamisole trials (99). While research and clinical investigation have identified several potentially useful chemical immunomodulators, the elementary understanding of the biochemical mechanisms involved in immunoregulation remains basic. Future research must elucidate these mechanisms, particularly in humans, to maximize the benefits of chemical immunomodulators as single agents or combined with cytotoxic chemotherapeutic agents, surgery, radiation therapy, other immunomodulators, and antiviral agents.

Relationship between IL-2 receptor expression and proliferative responses in lymphocytes from HIV-1 seropositive homosexual men

Previous studies have shown that exogenous IL-2 does not correct the reduction in phytohaemagglutinin (PHA)-induced proliferation of lymphocytes from HIV-1 infected (HIV+) individuals. We investigated the mechanism of this reduction to determine if reduced expression of the complete IL-2 receptor (IL-2R) was responsible. In a series of experiments, PHA-stimulated lymphocytes from a total of 89 HIV- and 93 HIV+ homosexual men from the Baltimore Multicentre AIDS Cohort Study (MACS) were studied to determine the expression of messages for the alpha and beta subunits of the IL-2R, the binding of 125I-IL-2 to high affinity IL-2R, and the effect of IL-2 on cell proliferation. Compared to HIV- donors, PHA-stimulated lymphocytes from most HIV+ donors demonstrated (i) a reduction in high affinity IL-2R expression that correlated with the reduction in the IL-2-induced proliferative response; and (ii) a reduction in expression of both IL-2R alpha- and beta-chain mRNA which may be responsible for decreased high affinity IL-2R expression. However, lymphocytes from some HIV+ individuals had borderline low IL-2-induced proliferation despite normal or elevated expression of high affinity IL-2R. These results suggest that decreased expression of IL-2R may account, at least in part, for the lower proliferative response of cells from HIV+ donors.

Membrane-bound and soluble IL-2 receptors (p55 and p75 chains) on peripheral blood mononuclear cells from patients with solid malignancies

The aim of the investigation was to study directly the IL-2 receptor (IL-2R) and its subunits, p55 and p75 chains, either membrane-bound or soluble, on PBMC of patients with solid malignancies and, indirectly, the same patients' PBMC ability to produce IL-2. Fifty-eight cancer patients, 29 men and 29 women, were studied: their mean age was 57.3 yr, range 35-79. Twenty-two healthy age-sex-matched subjects served as controls. The tumors were the most common and the most representative among human cancers, i.e., breast, lung, head and neck, digestive tract and liver, prostate and gynecologic cancers: they were generally in advanced stages and in 23 cases metastatic. The PBMC proliferative response to PHA, PHA plus IL-2, and IL-2 was evaluated along with the response to PHA in the presence of anti-p55, anti-p75 monoclonal antibodies, or both. Moreover, membrane-bound IL-2R (p55 and p75 chains) on PHA-stimulated PBMC was detected, along with soluble IL-2R in the serum and in the culture supernatants. The conclusions suggest that in solid malignancies: the membrane-bound IL-2Rs, both p55 and p75 chains, are expressed normally, there is an high serum level of soluble IL-2R, there is a normal release of soluble IL-2R in culture, and there is an indirect evidence of a lack of IL-2 production. Therefore, no primary impairment of IL-2R was found in solid tumors. Moreover, in our study we have found no difference in any parameter studied between patients with and patients without metastases.

Heterogeneous effects of exogenous IL-2 on HIV-specific cell-mediated immunity (CMI)

A characteristic feature associated with HIV-1 infection of the human host is a chronic decline in circulating CD4+ T helper/inducer cell numbers. Impaired cell-mediated immune functions usually occur in parallel with the decline in CD4+ T cells. Activated CD4+ T helper cells are a major source of endogenous IL-2 which is required for the immunoregulation of both antigen-specific B cells and CD8+ T cells. HIV-specific T cell proliferative responses are said to be weak and inconsistent, even during the asymptomatic phase of disease. We thus wished to determine how exogenous IL-2 affected HIV-specific T cell proliferation at different stages of the disease. Our cohort of 81 included both asymptomatic and symptomatic HIV-infected patients as well as uninfected normal donors. Proliferative responses of peripheral blood mononuclear cells (PBMC) that were elicited during culture with an immunodominant gp41-derived synthetic peptide, gp41[8], and which were known to be CD8+ cell-associated in asymptomatics only, were used to analyse the effects of exogenous IL-2. IL-2 had three main effects on HIV-specific proliferation, namely (i) an additive effect, (ii) a synergistic effect, and (iii) an induced effect. More specifically, low dose exogenous IL-2 frequently augmented lymphoproliferation in both asymptomatic and symptomatic gp41[8] responders. In most symptomatics, however, who were predominantly gp41[8] non-responders, exogenous IL-2 induced lymphoproliferation. Flow cytometric analyses using dual immunofluorescence were used to analyse the T cell subset distribution of proliferating PBMC cultures. During culture with gp41[8], both CD4+ and CD8+ T cell numbers increased. However, after the addition of exogenous IL-2 to gp41[8]-containing cultures, CD8+ cell-associated lymphoproliferative responses were preferentially augmented. These results suggest that in symptomatics there is an inadequate supply of endogenous IL-2 to help maintain the strong and effective CD8+ cell-associated anti-viral immunity, and an exogenous supply of IL-2 may be required.

Expression of interleukin 2 receptors by monocytes from patients with acquired immunodeficiency syndrome and induction of monocyte interleukin 2 receptors by human immunodeficiency virus in vitro

A population of circulating mononuclear cells from patients with AIDS was identified which expressed interleukin 2 receptors (IL-2R). By dual-fluorescence flow microfluorometry, the patients' IL-2R+ cells were further identified as Leu M3+ monocytes (29.4 +/- 5.2% of the Leu M3+ cells were IL-2R+, n = 15), whereas Leu M3+ monocytes from normal subjects were IL-2R negative (2.0 +/- 0.42%; P less than 0.001). By Northern analysis, monocytes from AIDS patients, but not control subjects, constitutively expressed steady-state levels of IL-2R mRNA. Functionally, the IL-2R+ monocytes were capable of depleting IL-2 from culture supernatants, suggesting a mechanism for the reduced IL-2 levels commonly seen in AIDS patients. IL-2R+ monocytes also expressed increased levels of surface HLA-DR which may favor monocyte T-cell interactions and the transmission of human immunodeficiency virus (HIV). In additional studies, normal monocytes were infected with a macrophage-tropic HIV isolate in vitro and monitored for IL-2R and HLA-DR expression. Within 24-48 h after exposure to HIV in vitro, but before evidence of productive infection, greater than 25% of the monocytes became IL-2R+ with increasing numbers of IL-2R+ cells and HLA-DR levels through day 6. These early signaling effects of HIV could be mimicked by adding purified HIV envelope glycoprotein gp120 to the monocytes. This stimulation of monocytes before or independent of productive infection of the cells by HIV is consistent with in vivo observations of activated and/or abnormal functions by monocytes that do not appear to be infected with HIV in AIDS patients.

The potential role of serum ferritin in the pathogenesis of acquired immune deficiency syndrome (AIDS)

Elevated serum ferritin levels have been observed in several disease states including various malignancies, inflammatory states, and the acquired immunodeficiency syndrome (AIDS). This discussion will examine the normal sequence of events in T cell activation and proliferation, as well as the various defects in these events, and monocyte/macrophage and NK cell activity seen in AIDS patients. Further, the potential role of a serum suppressor factor as a contributor to the profound immunosuppression seen in AIDS will be discussed, as will evidence suggesting that ferritin may be this factor. A model is presented to explain mechanisms by which ferritin might suppress immune function and further studies to elaborate these mechanisms are proposed.

Nutrition, immune function, and inflammation: an overview

The collective evidence suggests that nutritional insult to both cell-mediated and humoral immunity in the presence of protein-energy malnutrition contributes to abnormalities of inflammation. The primary goal of nutritional support in inflammatory disease is to provide adequate energy and protein to meet endogenous requirements for tissue repair, IL-1 production, and restored cellular function, thus preventing secondary infection. Substrate provision should aim at improving the acute phase of injury while avoiding immune dysfunction. This goal may be achieved by altering the eicosanoid pathway toward a more regulated inflammatory state. In the context of allograft response, macrophages are central to the initiation of allosensitization by virtue of their ability to present antigen to T-cells. Activated T-cells may further modulate macrophage function by the secretion of lymphokines. Manipulation of macrophage eicosanoid production by dietary omega-3 PUFA may reduce cellular immune response. (table; see text) Nutritional support should also focus on providing essential micronutrients, with their potentially immunomodulating role, as adjunctive therapy in order to protect the host from toxic effects of free-radicals and chemicals released during inflammatory events. (Feeding regimens currently under investigation and development are presented in Table 4.) By integrating dietary immunotherapy with the use of recombinant hormones, monoclonal antibodies, and various available monokines, an optimal outcome for each patient may be achieved. However, effective application of immunotherapy to nutritional supplementation will require accurate monitoring of immune function in individual patients in order to avoid inappropriate treatment.

Soluble Il-2 receptor serum levels--a marker for disease progression in patients with HIV-1 infection

Serum levels of soluble Il-2 receptors (sIl-2R) were measured in 88 patients with HIV infection, 28 patients from high-risk groups, and 28 normal donors. Elevated sIl-2R levels were found in 46% of asymptomatic seropositive patients, in 68% of patients with persistent generalized lymphadenopathy, and in 81% of patients with AIDS. Mean sIl-2R values increased with the progression of the disease and were most pronounced in patients with AIDS. A close correlation was found between sIl-2R levels and beta2-microglobulin (p less than 0.0001) and other prognostic parameters known to parallel clinical activity. In addition to being a valuable parameter in monitoring the course of the HIV infection, elevated sIl-2R levels may also be involved in the down-regulation of Il-2-dependent immune functions in AIDS.

Impairment in T-lymphocyte responses during early infection with the human immunodeficiency virus

Uncertainty has existed as to whether a T-cell deficiency exists in human immunodeficiency virus (HIV) infection different from that inherent in the reduced T-cell numbers characteristic of the disease. Heretofore, methods for measuring T-cell responses in patients have been carried out with systems requiring monocytes as accessory cells. In the presence of high concentrations of interleukin-2, however, highly purified T cells respond in a monocyte-independent fashion to antibody reactive with the CD3 component of the antigen receptor complex Ti/CD3. Highly purified T cells of HIV-infected patients responded subnormally in this anti-CD3/IL-2 system, even in the case of patients who were asymptomatic or had only lymphadenopathy. The defective T-cell responses occurred over a wide range of concentrations of the anti-CD3. Neither poor IL-2 receptor function as reflected by responses to limiting dilutions of IL-2 nor IL-1 receptor function as defined by incremental proliferation when IL-1 is added accounted for this defect, which also correlated poorly with T4 and T8 numbers. These results suggested that the T-cell abnormality was closely related to Ti/CD3 function, was not specifically or restrictively associated with T4 cells, and was not due to defective IL-2- or IL-1-receptor functions. The amount of HIV RNA in 10(5) T lymphocytes from the patients amounted to less than that found in one cell of a standard HIV infected laboratory cell line (CEM), using slot-blot hybridization. Thus the T-cell deficiency we have observed was not likely to be due directly to cell killing by HIV resident in the T4 cells. Other factors may be important in inducing the immunodeficiency, some of which are discussed.

Effect of isoprinosine on lymphocyte proliferation and natural killer cell activity following thermal injury

The effect of in vivo administration of Isoprinosine (ISO) on, i) the proliferation of splenic lymphocytes in response to the T-cell mitogen, concanavalin-A (Con-A) and, ii) the natural killer (NK) cell cytotoxicity was studied following a full skin thickness burn injury in a rat model. Administration of ISO (100 mg/kg body wt/day) twice daily, resulted in significant augmentation of the proliferative responses of lymphocytes compared to non-treated burned animals, at 7 days post injury. However, it did not effect the lymphoproliferation at 14 days post injury, the time period at which a complete suppression of lymphocyte proliferation was observed in burned non-treated animals. Also, the proliferation of lymphocytes from normal nonburned animals was not affected by treatment with ISO. ISO treatment of the burned animals resulted in a significant increase in the NK cytotoxicity compared to non-treated burned animals. As with Con-A responses, ISO administered to control nonburned animals did not have any effect on NK cell cytotoxicity. Our studies thus indicate that ISO can be a potential immunomodulator of suppressed immune function following thermal injury, particularly in patients whose lymphocyte responses to T cell mitogen Con-A are not completely suppressed.

Effects of interleukin 2 and large envelope glycoprotein (gp 120) of human immunodeficiency virus (HIV) on lymphocyte proliferative responses to cytomegalovirus

Lymphocytes from many HIV-infected asymptomatic individuals or patients with AIDS-related conditions (ARC) and from all AIDS patients were unable to proliferate in vitro in response to UV-inactivated cytomegalovirus (CMV). The addition of recombinant IL2 (rIL2) restored proliferative responses of lymphocytes from most HIV-infected asymptomatic individuals and ARC patients to levels similar to those of HIV-seronegative (HIV-) CMV-seropositive (CMV+) individuals. In contrast, rIL2 augmented CMV-specific lymphocyte proliferation of only 33% (6/18) of AIDS patients. Proliferative responses to CMV with or without rIL2 did not correlate well with the levels of CD4+ lymphocytes, HIV antigen levels or ratios of CD4+ and CD8+ lymphocytes. Proliferative responses to CMV were inhibited by relatively high concentrations (greater than or equal to 10 micrograms/ml) of recombinant HIV envelope glycoprotein (rgp120) and this immunosuppression was completely overcome by rIL2. These results indicate that defects in antigen-driven lymphocyte responses of HIV-infected individuals are not simply the result of reduced numbers of CD4+ lymphocytes but are influenced by defects in IL2 pathways and by immunosuppressive effects of HIV gp120.

Defective T-cell colony formation and IL-2 receptor expression at all stages of HIV infection

The T-cell colony assay is a highly sensitive measure of immunological dysfunction. The present study evaluated this in vitro response in asymptomatic HIV-infected homosexuals, those with chronic adenopathy as their only clinical manifestation and patients with either ARC or AIDS. The mean colony count in antibody-positive asymptomatic individuals was significantly reduced when compared to either heterosexual controls or antibody-negative homosexuals. Furthermore, there were no differences in the responses of these antibody-positive individuals and those with chronic lymphadenopathy as their only clinical manifestation. By contrast, patients with AIDS or ARC showed a profound defect; this suggests that the colony assay can detect a functional gradient across the spectrum of HIV infections. Colony growth was correlated with the absolute number of T-helper cells and the ability of PHA-stimulated lymphocytes to express IL-2 receptors; no correlation was found with the number of suppressor/cytotoxic cells or in vitro production of IL-2. Recent HIV seroconverters had normal colony counts but impaired ability to express IL-2 receptors. These data suggest a sequential loss of T-cell function as a result of HIV infection; the earliest manifestations are impaired expression of IL-2 receptors and reduced proliferative responses, as measured in the colony assay.

Inosiplex enhances the growth of Epstein-Barr nuclear antigen-positive B-cells from patients with rheumatoid arthritis and infectious mononucleosis

The in vitro effects of inosiplex (INO) on proliferation of Epstein-Barr virus (EBV)-carrying B-cells were evaluated. As measured by 3H-thymidine uptake, INO significantly augmented the proliferation of long-term cultured Epstein-Barr nuclear antigen (EBNA)-positive B-cells which were obtained from patients with rheumatoid arthritis (RA) and infectious mononucleosis (IM). In co-culture experiments, INO and anti-immunoglobulin M antibodies coupled to sepharose (anti-mu) had additive effects on proliferation of EBNA-positive B-cells. We conclude that its direct effects on B-cell function should be considered when INO is used for the treatment of diseases characterized by B-cell hyperreactivity.

Soluble interleukin 2 receptors are elevated in patients with AIDS or at risk of developing AIDS

Utilizing an enzyme-linked immunosorbent assay, we detected elevated serum levels of soluble interleukin 2 receptors (SIL-2R) in 73% of patients with acquired immunodeficiency syndrome (AIDS), 80% of AIDS-related complex patients, 78% of anti-HIV-positive lymphadenopathy syndrome patients, 85% of HIV-antibody-positive hemophiliacs, and 80% of anti-HIV-positive asymptomatic homosexual males, iv drug abusers, and heterosexual contacts. Of the subjects with no demonstrable antibody to HIV, 29% of hemophiliacs, 12% of adult homosexual males and iv drug abusers, and none of the patients with lymphadenopathy had elevated SIL-2R. Overall, only 5 of 40 antibody-negative "high-risk" individuals had SIL-2R values greater than the reference interval whereas 108 of 138 antibody-positive individuals had elevated values (chi 2 = 57.85, P less than 0.001).

Interleukin 2 and its receptor: structure, function and therapeutic potential

In this review, salient molecular, biochemical and functional features of human interleukin 2 (IL-2), its membrane receptor, and its clinical relevance are outlined. We also describe experimental systems, where observed biological or pharmacological effects of IL-2 could be applied to corresponding clinical situations. In particular, IL-2 has been intensively studied in the context of cancer therapy. We discuss the rationale for the use of IL-2 in cancer treatment and our experience in this area. A better understanding of the IL-2 system and, specifically, the nature of signals transduced through it will allow us to manipulate the immune response in a variety of different ways, resulting in new approaches to investigation of immune responsiveness in general. This may have a profound impact on clinical medicine.

Isoprinosine-induced modulation of T-helper-cell subsets and antigen-presenting monocytes (Leu M3 + Ia +) resulted in improvement of T- and B-lymphocyte functions, in vitro in ARC and AIDS patients

Peripheral blood leukocytes from ARC and AIDS patients were analyzed following phytohemagglutinin- and pokeweed mitogen-induced lymphocyte transformation by dual-color flow cytometry using monoclonal antibodies that identify developmental (HLA-DR) and functional (Leu8) subsets of T cells and monocytes. Significant decreases in both the suppressor regulating helper T subset (Leu3+ Leu8+) and the reciprocal inducer helper T subset (Leu3+ Leu8-) responsible for inducing differentiation of B cells were observed. Simultaneously, the percentages of the effector suppressor T cells and the precursor suppressor T cells were increased, both of which were required for generation of suppression of cell-mediated immunity. There was also a progressive selection of Ia+ cells bearing the Leu2 (Ts) markers and a concurrent reduction of the percentage of antigen-presenting monocytes and activated helper T cells. These results suggest that the functional deficiencies in AIDS may be caused by defects in T-cell activation as well as antigen presentation by monocytes. Isoprinosine induced an increase in both regulator Th (Leu3+ Leu8+) and inducer Th (Leu3+ Leu8+) subsets of helper T cells while potentiating the expression of Ia antigen on helper T cells and monocytes during mitogen-driven DNA synthesis. These events initiated a cascade of cellular interactions leading to partial restoration of cell-mediated immune responses. These interferences with the defective helper/suppressor regulatory pathways may have important therapeutic implications.

Humoral-mediated suppression of interleukin 2-dependent target cell proliferation in acquired immune deficiency syndrome (AIDS): interference with normal IL-2 receptor expression

Sera from patients with acquired immune deficiency syndrome (AIDS) were analysed for effects on normal lymphocyte interleukin 2 (IL-2) production, IL-2 receptor (IL-2R) expression and levels of IL-2 dependent T cell proliferation. The presence of AIDS serum appeared to reduce significantly IL-2 production by cultures of mitogen-activated normal human peripheral blood mononuclear cells (PBMC). However, dilution analyses of the culture supernatants indicated that the primary inhibitory effect occurred at the level of the IL-2 responsive target cell. Furthermore, eight of nine AIDS sera, but none of the normal human sera (NHS) tested, suppressed the capacity of IL-2-dependent CTL-20 cells to proliferate in response to human IL-2. Fractionation of AIDS sera by gel filtration on Sephacryl S-200 revealed that inhibitory activity coeluted with the immunoglobulin fraction. Pretreatment of human IL-2R+ lymphoblasts with AIDS serum did not interfere with the binding of monoclonal antibody (anti-Tac) specific for the human IL-2R; however, significant reductions in the levels of phytohaemagglutinin-induced IL-2R expression were observed when normal human PBMC were cultured in the presence of AIDS serum. These findings indicate that the inhibitor present in many AIDS sera does not suppress lymphocyte proliferation by interfering directly with the IL-2 receptor, and suggest that inhibition occurs at a later stage of the cell cycle. One of the primary consequences of the activity of this serum inhibitory factor is a decline in the levels of lymphocytic IL-2R expression.

A randomized double-blind study of inosiplex (isoprinosine) therapy in patients with alopecia totalis

Twenty-five of 34 patients with alopecia totalis of at least 1 year's duration and associated defects in cell-mediated immunity completed a randomized, double-blind, placebo-controlled crossover trial of the therapeutic effect of inosiplex, a synthetic immunomodulator. Each patient received 20 weeks of treatment with inosiplex and 20 weeks with placebo in randomized order. Eleven patients were identified clinically as responders to inosiplex in terms of hair regrowth. Scalp biopsy results correlated well with drug therapy. Enhanced immune function was found in the majority of responding patients; however, statistical analysis of the results of the entire patient population revealed limited significant differences. No patient experienced adverse side effects attributable to therapy. These results show that inosiplex is a safe and effective therapy for certain patients with alopecia totalis.

More exact quantification of interleukin-2 production by addition of anti-Tac monoclonal antibody to cultures of stimulated lymphocytes

Human T-cells produce interleukin-2 (IL-2) in response to in vitro stimulation with mitogens and antigens. Precise measurement of IL-2 production in vitro is hampered by binding of IL-2 to IL-2 receptors on activated T-cells which results in IL-2 consumption. In an attempt to prevent IL-2 consumption, we supplemented the cultures with anti-Tac, a monoclonal antibody that functionally blocks the human lymphocyte receptor for IL-2. Addition of anti-Tac to cultures of mitogen-stimulated peripheral blood mononuclear cells resulted in a 2-4-fold increase of maximal levels of IL-2 in the supernatants. No decline of IL-2 concentrations beyond 18-24 h of culture was observed, indicating that anti-Tac effectively blocked IL-2 consumption. Comparison of the kinetics of IL-2 accumulation in the presence and absence of anti-Tac revealed that IL-2 consumption by mitogen-stimulated cells occurred as early as 6 h after culture initiation. Addition of anti-Tac to cultures of antigen-stimulated cells similarly resulted in higher IL-2 levels in the culture supernatants, and prevented the rapid decline of IL-2 concentrations at prolonged culture time. We conclude that addition of anti-Tac to lymphocyte cultures enables more exact quantification of in vitro IL-2 production, presumably by blocking IL-2 consumption. This finding offers new possibilities for the study of abnormalities of IL-2 production in different disease conditions.

Peripheral blood adherent cells from AIDS patients inhibit normal T-colony growth through decreased expression of interleukin 2-receptors and production of interleukin 2

Adherent cells display an important accessory role on normal T-cell colony formation. Since the in-vitro proliferation of T colony-forming cells (T-CFC) from AIDS patients is extremely impaired we studied the effect of patients' adherent cells on T-CFC growth. Patients' peripheral blood mononuclear cells (PBMC) were fractionated on the basis of rosette formation with sheep red blood cells and complement-mediated cytotoxicity with OKT3 monoclonal antibody (E-T3-). Both mature (E+) T cells and E-OKT3- cell fractions failed to generate T-cell colonies although colony growth could be obtained from unfractionated PBMC. In five out of 12 AIDS patients, adherent cell-depletion of PBMC enhanced the plating efficiency. Moreover, patients' but not normal adherent cells could inhibit normal T-cell colony growth in a dose-dependent manner. Media conditioned by patients' unstimulated adherent cells (LCM-A+p) also inhibit normal T-cell colony formation. In addition, LCM-A+p were capable of inhibiting interleukin 2-receptor (IL2-R) expression and interleukin 2 (IL2) production by normal mitogen-stimulated T cells. These LCM-A+p did not contain detectable reverse transcriptase activity nor could they infect the CEM T-cell line which is permissive to human immunodeficiency virus (HIV). Conversely, this adherent cell-derived inhibitory activity could be abrogated by heating or treatment with proteolytic enzymes. These findings indicate that the low T-cell colony formation in some AIDS patients could be due to adherent cell-derived inhibitory activity(ies).

Interleukin 2 production and responsiveness in individuals with acquired immunodeficiency syndrome and the generalized lymphadenopathy syndrome

Proliferative responsiveness to, and production of, interleukin 2 (IL-2) was determined in 9 homosexually active men with the acquired immunodeficiency syndrome (AIDS) and in 28 homosexually active men with the persistent generalized lymphadenopathy syndrome (PGL). All were seropositive for antibody to human T-lymphotrophic virus type III/lymphadenopathy-associated virus (HTLV-III/LAV). Purified T lymphocytes from individuals with AIDS and PGL had a significantly decreased (P less than 0.01) proliferative response to a saturating amount of exogenous, purified IL-2 as compared to seronegative male controls. Similarly, T4+-enriched T lymphocytes also had a significantly decreased proliferative responsiveness to IL-2 (AIDS, P less than 0.05; PGL, P less than 0.005). T8+-enriched T lymphocytes from individuals with AIDS or PGL did not suppress the IL-2-induced proliferation of autologous T4+ T lymphocytes. In addition, production of IL-2 was significantly decreased in the AIDS group (P less than 0.01) and the PGL group (P less than 0.005) with median values of IL-2 produced being 0.1 and 1.0 U/ml, respectively, compared to 9.9 U/ml for control. These findings demonstrate that substantial quantitative and qualitative abnormalities of the IL-2-T-lymphocyte system exist in patients with AIDS as well as in relatively healthy individuals with PGL. These defects are likely important contributing factors to the depressed T-lymphocyte functions commonly observed in HTLV-III/LAV-associated diseases.

Cytotoxic studies in human newborns: lessened allogeneic cell-induced (augmented) cytotoxicity but strong lymphokine-activated cytotoxicity of cord mononuclear cells

Nonspecific cytotoxic responses such as natural killer activity can be increased in vitro by incubating effector cells with soluble factors or allogeneic cells. We sought to determine if newborn cells, known to be deficient in most cytotoxic responses, including resting NK activity, could develop enhanced cytotoxic responses following incubation with allogeneic cells (augmented cytotoxicity) or with lymphokines (lymphokine-activated cytotoxicity). Cord whole mononuclear cells (WMC) incubated with irradiated Raji cells for 5 days develop lower levels of cytotoxicity toward K562 targets at both a 20:1 effector:target (E:T) ratio (39 +/- 2.7% vs 49 +/- 3.6%) and a 10:1 E:T ratio (29 +/- 2.6% vs 40 +/- 3.6%) than do adult cells. Lessened specific cytotoxicity of cord cells developed toward the sensitizing Raji cells was also observed at both E:T ratios. Attempts to enhance the induced cytotoxicity by incubation with interferon or isoprinosine were unsuccessful. In contrast, lymphokine (i.e., interleukin 2)-activated killer (LAK) cytotoxicity is not deficient in cord WMC. Indeed, the level of LAK cytotoxicity is equivalent to that observed with similarly treated adult cells despite a lower baseline level of cytotoxicity toward the target cells. In the presence of purified IL-2 for 5 days, cord WMC cytotoxicity against K562 cells increased from 12 +/- 2.6 to 71 +/- 4.2% and against Raji cells increased from 9.6 +/- 2.5 to 48 +/- 6.7%. Similarly treated adult cells increased their killing against K562 from 23 +/- 4.2 to 61 +/- 4.5% and against Raji from 12 +/- 3.0 to 36 +/- 5.3%. This substantial lymphokine-activated cytotoxicity of newborn cells suggests the possibility of therapeutic intervention with purified lymphokines in neonatal infections or neoplasms.

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.

Inhibition of interleukin-2-induced T-cell proliferation by sera from patients with the acquired immune deficiency syndrome

Sera from 22 patients with either lymphadenopathy syndrome (LAS), acquired immune deficiency syndrome (AIDS)-related complex (ARC), or acquired immune deficiency syndrome were examined for their effect on the interleukin-2 (IL-2)-induced proliferative response of an IL-2-dependent cytotoxic T-cell line, CTL-20. All of the patient sera included in this study were positive for the presence of antibodies against human T-cell lymphotropic virus type III (HTLV-III) as determined by an HTLV-III-specific enzyme-linked immunosorbent assay (ELISA). Eighteen of the 22 patient sera examined (81.8%) exhibited at least a modest suppressive effect on the proliferative response of CTL-20 cells. The inhibitory effect was dose-dependent and varied in intensity for each individual serum. In many cases, the magnitude of suppression was absolute in that it totally abrogated IL-2-induced DNA synthesis. Normal human serum (NHS) exerted no suppressive influence on the IL-2-induced proliferative response of identical control cultures. This same panel of 22 patient sera exhibited no significant inhibitory effects on the levels of protein synthesis in cultures of a non-IL-2-dependent human T-cell line, CCRF-HSB-2, indicating that the suppressive effect was not mediated by nonspecific serum cytotoxicity. The inhibitory effect of patient sera in the IL-2-dependent target cell assay correlated with the ability of these same sera to suppress the mitogen-induced proliferative response of normal human peripheral blood lymphocytes (PBL). These observations are particularly striking in view of the recognized defects of IL-2-dependent effector T-cell functions in AIDS.

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.