Effects of granulocyte-macrophage colony-stimulating factor on 3'-azido-3'-deoxythymidine uptake, phosphorylation and nucleotide retention in human U-937 cells

Granulocyte macrophage colony-stimulating factor has come of age: From a vaccine adjuvant to antiviral immunotherapy

GM-CSF acts as a pro-inflammatory cytokine and a key growth factor produced by several immune cells such as macrophages and activated T cells. In this review, we discuss recent studies that point to the crucial role of GM-CSF in the immune response against infections. Upon induction, GM-CSF activates four main signalling networks including the JAK/STAT, PI3K, MAPK, and NFκB pathways. Many of these transduction pathways such as JAK/STAT signal via proteins commonly activated with other antiviral signalling cascades, such as those induced by IFNs. GM-CSF also helps defend against respiratory infections by regulating alveolar macrophage differentiation and enhancing innate immunity in the lungs. Here, we also summarize the numerous clinical trials that have taken advantage of GM-CSF's mechanistic attributes in immunotherapy. Moreover, we discuss how GM-CSF is used as an adjuvant in vaccines and how its activity is interfered with to reduce inflammation such as in the case of COVID-19. This review brings forth the current knowledge on the antiviral actions of GM-CSF, the associated signalling cascades, and its application in immunotherapy.

S-1153 inhibits replication of known drug-resistant strains of human immunodeficiency virus type 1

S-1153 is a new imidazole compound that inhibits human immunodeficiency virus (HIV) type 1 (HIV-1) replication by acting as a nonnucleoside reverse transcriptase inhibitor (NNRTI). This compound inhibits replication of HIV-1 strains that are resistant to nucleoside and nonnucleoside reverse transcriptase inhibitors. S-1153 has a 50% effective concentration in the range of 0.3 to 7 ng/ml for strains with single amino acid substitutions that cause NNRTI resistance, including the Y181C mutant, and also has potent activity against clinical isolates. The emergence of S-1153-resistant variants is slower than that for nevirapine, and S-1153-resistant variants contained at least two amino acid substitutions, including F227L or L234I. S-1153-resistant variants are still sensitive to the nucleoside reverse transcriptase inhibitors zidovudine (AZT) and lamivudine. In a mouse and MT-4 (human T-cell line) in vivo HIV replication model, S-1153 and AZT administered orally showed a marked synergy for the inhibition of HIV-1 replication. S-1153 shows a significant accumulation in lymph nodes, where most HIV-1 infection is thought to occur. S-1153 may be an appropriate candidate for two-to three-drug combination therapy for HIV infection.

A physiologically based pharmacokinetic model of zidovudine (AZT) in the mouse: model development and scale-up to humans

After having been used in treating HIV infection for a decade, zidovudine (AZT) continues to be an essential component of antiretroviral regimens. Because antiviral responses and toxicity of AZT seem to be related to cells in specific target tissues, being able to understand and predict the distribution of AZT into different pharmacologically and toxicologically relevant tissues is therefore critically important to improving the efficacy and minimizing the toxicity of AZT therapy. This study was designed to develop a physiologically based pharmacokinetic model to help describe and predict the time course of AZT levels in different tissues. The model was developed in the mouse and then scaled up to predict human situations.

Hematologic disorders and growth factor support in HIV infection

During the course of HIV disease a broad spectrum of hematologic disorders develop including abnormalities in blood cell generation, survival, and function Alterations in coagulation parameters may evolve associated with disruption of immunoglobulin or factor production. This article reviews the manifestations and pathophysiology of these abnormalities and discusses the role for growth factor support.

Lack of in vivo effect of granulocyte-macrophage colony-stimulating factor on human immunodeficiency virus type 1

Neutropenia complicates HIV disease or its treatment in a large proportion of patients. Hematopoietic growth factor support has been tested in a number of clinical settings in HIV disease and has been demonstrated to be of benefit for specific parameters. One consideration regarding the use of hematopoietic growth factors in HIV disease is their potential effect on HIV viral burden, since alterations in HIV expression have been documented with certain cytokines in vitro. It has also been reported that some cytokines, notably GM-CSF, potentiate the antiviral properties of thymidine analogs such as zidovudine (AZT) in vitro. We tested these observations in vivo. Twelve HIV-positive patients with a CD4 cell count < or = 200/mm3 or HIV plasma viremia who were receiving a stable dose of zidovudine were enrolled into three dose cohorts of yeast-derived GM-CSF at 50, 125, or 250 micrograms/m2 daily by subcutaneous self-injection for 28 days. Measurements of HIV activity included serum acid-dissociated HIV p24 antigen levels, plasma and peripheral blood mononuclear cell (PBMC) limiting dilution HIV culture, and plasma HIV quantitative competitive polymerase chain reaction (PCR). Serum and intracellular zidovudine levels were measured as well as hematologic, immunologic, and toxicity parameters. Virologic measures showed neither significant upregulation nor downregulation of serum acid-dissociated HIV p24 antigen, plasma and PBMC HIV culture, or PCR in association with GM-CSF administration. A trend toward increased intracellular AZT levels was noted, but this did not achieve statistical significance (p = 0.073). CD4 and CD8 lymphocytes were essentially unaffected while absolute neutrophil counts increased with GM-CSF administration as expected. These data suggest that administration of GM-CSF does not perturb HIV activity or immunologic parameters in patients receiving AZT for advanced HIV disease. No potentiation of AZT antiviral effect was demonstrated.

Metabolism of Zidovudine

1. The anti-HIV drug zidovudine (3'-azido-2',3'-dideoxythymidine; ZDV) has three important pathways of metabolism. ZDV is a prodrug and must be phosphorylated in lymphocytes in order to exert its antiviral action. However, in quantitative terms this is a minor pathway probably accounting for less than 1% of the overall metabolic profile. The predominant pathway of metabolism is glucuronidation to GZDV and the metabolite is renally excreted. A further metabolite, derived by reduction of the azido moiety is 3'-amino-3'-deoxythymidine (AMT). 2. Zidovudine glucuronidation has been characterised in human liver microsomes. A number of drugs (e.g., naproxen, indomethacin and probenecid) have been shown to inhibit the in vitro conjugation of ZDV. Some of these drugs have also been co-administered with ZDV in HIV-positive patients. Significant pharmacokinetic interactions have been demonstrated with probenecid, naproxen and fluconazole. 3. 3'-amino-3'-deoxythymidine formation is probably mediated by both cytochrome P450 isozymes and NADPH-cytochrome P450 reductase. Peak plasma concentrations of AMT are approximately 10-15% of ZDV in patients. This is a potentially important metabolite because of its alleged cytotoxicity. 4. Measurement of intracellular ZDV phosphates in patients provides the key to our understanding of both the efficacy and toxicity of ZDV. Important recent work has demonstrated that as patients deteriorate (i.e., CD4 counts decrease below 100 x 10(6)/L), there is a corresponding increase in intracellular ZDV-monophosphate. This could have toxicological implications.

Management of antiretroviral drug therapy in human immunodeficiency virus infection

Nucleoside analog reverse transcriptase inhibitors, including zidovudine, didanosine, and zalcitabine, remain the cornerstone of therapy against human immunodeficiency virus (HIV) infection, the cause of AIDS. Although therapeutic regimens have been designed that are effective in slowing the progression of disease, therapy with these agents has not been optimized. Ultimately, therapy is destined to fail in most patients. Decisions regarding when to begin therapy and the course of action to take when failure of therapy occurs are largely in the hands of the patient's physician, and currently must be made without the support of conclusive clinical data. In addition to an understanding of the recommended dosing guidelines, proper management of AIDS therapy requires a fundamental knowledge of the disease process, the pharmacology and limitations of the agents employed against the virus, and close cooperation with the clinical laboratory. Therefore, this article reviews the pharmacology of the three drugs currently approved for treatment of HIV infection, and the current guidelines for their use. The article also reviews the clinical and laboratory management of these agents, including the use of surrogate markers and the potential for pharmacokinetic optimization of therapy.

Zidovudine. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine remains the mainstay in the treatment of patients infected with human immunodeficiency virus (HIV). The drug delays disease progression to acquired immunodeficiency syndrome (AIDS) and to AIDS-related complex (ARC), reduces opportunistic infections, and increases survival in patients with advanced HIV infection. There is evidence to suggest that zidovudine also delays disease progression in patients with mild symptomatic disease. Although one study has shown zidovudine to have no significant beneficial effects on survival or disease progression in patients with asymptomatic HIV infection, several other studies have shown zidovudine to delay disease progression in this patient group. Results from related ongoing studies are awaited with interest. Zidovudine reduces the incidence of AIDS dementia complex (ADC) and appears to prolong survival in these patients, and improves other neurological complications of HIV infection. The drug also appears to enhance the efficacy of interferon-alpha in patients with Kaposi's sarcoma. Although zidovudine is widely used as postexposure prophylaxis following accidental exposure to HIV, its efficacy in preventing seroconversion is unclear. Whether zidovudine prevents vertical transmission also remains to be determined. The overall efficacy of zidovudine in the treatment of children with HIV infection appears similar to that in adults despite more rapid disease progression in younger patients. Zidovudine-resistant isolates can emerge as early as after 2 months' therapy, and primary infection with zidovudine-resistant strains has been documented. Both zidovudine resistance and the syncytium-inducing HIV phenotype appear to be associated with poor clinical outcome. However, zidovudine resistance may revert on drug withdrawal or switching to an alternative therapy. Zidovudine-associated haematotoxicity may be dose-limiting. Nonhaematological adverse events associated with zidovudine therapy are generally mild and usually resolve spontaneously. Dosages of approximately 500 to 600 mg/day appear to be at least as effective as dosages of 1200 to 1500 mg/day and are better tolerated in patients with less advanced disease. However, optimal dosage are unclear. Despite beneficial effects, zidovudine monotherapy is not curative. There is evidence to suggest that the concomitant administration of zidovudine with didanosine or zalcitabine is effective in patients with HIV disease progression despite receiving zidovudine monotherapy, and there is some evidence that concomitant zidovudine plus didanosine therapy is more effective than alternating monotherapy. However, results from studies of combination therapy in asymptomatic patients, and from comparative combination therapy studies are awaited. Cotherapy with agents that augment haematopoiesis allows the continuation of therapeutic zidovudine dosages.(ABSTRACT TRUNCATED AT 400 WORDS)

Simultaneous analysis of azidothymidine and its mono-, di- and triphosphate derivatives in biological fluids, tissue and cultured cells by a rapid high-performance liquid chromatographic method

A rapid high-performance liquid chromatographic (HPLC) method for the simultaneous analysis of the antiviral drug azidothymidine (AZT), AZT monophosphate, AZT diphosphate and AZT triphosphate, with ultraviolet detection in the nanomolar range, is described. Determination of these compounds in vitro in the human MT-4 lymphocyte cell line did not require a prior extraction, and AZT and its phosphorylated derivatives could be accurately analysed in one HPLC run. However, plasma, bile, liver homogenate and urine samples could not be injected directly into the chromatograph. Therefore, a solid-phase extraction procedure was developed, using azidodideoxyinosine as internal standard. The extractions of the compounds of interest from all but urine samples were reproducible, with recoveries between 65% (AZT triphosphate from plasma) and 100% (AZT from plasma).

The immunology of HIV infection: implications for therapy

It is known that antiretroviral drugs can induce immunologic improvement in patients with acquired immunodeficiency syndrome (AIDS) and other manifestations of HIV infection. However, the improvements so attained are often partial and transient. This may result from a number of factors, including incomplete inhibition of human immunodeficiency virus (HIV) replication by available agents, the development of viral drug resistance, the effect of cytokines, or thymic damage. An understanding of this problem may be important in further development of AIDS therapies. It will also be important to learn how to best assess the response to various therapies. In this regard, the CD4 count is evolving as a mortality risk indicator in AIDS and as such may find utility in assessing new therapeutic approaches. We have observed that in a cohort of gay men receiving antiretroviral therapy in a research environment, nearly all deaths occurred in individuals with fewer than 50 CD4 cells/mm3. However, the relationship between the CD4 count and the hazard of dying may be influenced by a number of factors (e.g., active intravenous drug use, extreme poverty, etc.), and further studies are needed to define the relationship between CD4 and clinical endpoints under a variety of conditions.

Different pattern of activity of inhibitors of the human immunodeficiency virus in lymphocytes and monocyte/macrophages

Monocyte/macrophages (M/M) are important targets for HIV in the body, and represent the majority of cells infected by the virus in some body compartments such as the central nervous system (CNS). M/M can be different from T-lymphocytes in terms of surface antigens, cell replication and drug metabolism. Thus, we evaluated, in M/M and in T-lymphocytes, the pattern of viral inhibition induced by various anti-HIV drugs, and assessed some of the mechanisms of action related to such antiviral activity. Inhibitors of HIV binding on CD4 receptors have similar activity in M/M and T-lymphocytes, while AZT and other dideoxynucleosides (ddN) are in general more active against HIV in M/M than in T-lymphocytes. This phenomenon can be related to the increased ratio in M/M of ddN-triphosphate/deoxynucleoside-triphosphate, and can at least in part explain the ability of zidovudine and didanosine in improving neurological dysfunctions in AIDS patients. Moreover, the antiviral activity of AZT (but not of other ddN- or HIV-binding inhibitors) is potently enhanced by cytokines like granulocyte-macrophage colony stimulating factor (GM-CSF) in M/M, while anti-HIV activity of TIBO compounds in M/M is not down-modulated by GM-CSF and other cytokines. Finally, non-toxic concentrations of adriamycin, an anticancer drug reported to be active against DNA viruses, can inhibit HIV replication in M/M (but not in T-lymphocytes). Taken together, these results suggest that M/M are selective targets for HIV with peculiarities different from those of T-lymphocytes. Thus, promising anti-HIV compounds should be evaluated both in T-cells and in M/M before reaching clinical trials. This may help in selecting drugs with good chances of being effective in patients with HIV-related disease.