2',5'-oligoadenylate synthetase in interferon-alpha- and acyclovir-treated herpes simplex virus-infected cells

Precipitating factors and targeted therapies in combating the perils of sickle cell disease--- A special nutritional consideration

Nutritional research in sickle cell disease has been the focus in recent times owing to not only specific nutritional deficiencies, but also the improvements associated with less painful episodes. Though hydroxyurea remains the drug of choice, certain adverse health effects on long term supplementation makes room for researches of different compounds. Macro and micro nutrient deficiencies, along with vitamins, play an important role in not only meeting the calorific needs, but also reducing clinical complications and growth abnormalities. Symptoms of hyper protein metabolism, increased cell turnover, increased cardiac output, and appetite suppression due to enhanced cytokine production, might give us leads for better understanding of the mechanisms involved. Different nutritional approaches comprising of traditional herbal therapies, antioxidants, flavonoids, vitamins, minerals etc., reducing oxidative stress and blood aggregation, have been tried out to increase the health potential. Nutritional therapies may also serve complementary to the newer therapies using ozone, hematopoietic stem cell transplantation, antifungal medications, erythropoietin etc. Herein we try to present a holistic picture of the different patho-physiological mechanisms, and nutritional strategies adopted.

Gene expression profiles of erythroid precursors characterise several mechanisms of the action of hydroxycarbamide in sickle cell anaemia

Hydroxycarbamide (HC) (or hydroxyurea) has been reported to increase fetal haemoglobin levels and improve clinical symptoms in sickle cell anaemia (SCA) patients. However, the complete pathway by which HC acts remains unclear. To study the mechanisms involved in the action of HC, global gene expression profiles were obtained from the bone marrow cells of a SCA patient before and after HC treatment using serial analysis of gene expression. In the comparison of both profiles, 147 differentially expressed transcripts were identified. The functional classification of these transcripts revealed a group of gene categories associated with transcriptional and translational regulation, e.g. EGR-1, CENTB1, ARHGAP4 and RIN3, suggesting a possible role for these pathways in the improvement of clinical symptoms of SCA patients. The genes involved in these mechanisms may represent potential tools for the identification of new targets for SCA therapy.

The murine double-stranded RNA-dependent protein kinase PKR and the murine 2',5'-oligoadenylate synthetase-dependent RNase L are required for IFN-beta-mediated resistance against herpes simplex virus type 1 in primary trigeminal ganglion culture

A study was undertaken to evaluate the efficacy of an adenoviral construct expressing the murine interferon-beta (IFN-beta) transgene (Ad:IFN-beta) against herpes simplex virus type 1 (HSV-1) infection in a primary trigeminal ganglion (TG) cell culture. The transduction efficiency ranged from 0.2 to 11.0% depending on the multiplicity of infection (m.o.i.) of the adenoviral vector (0.5-50.0). Moreover, neurons were the main target of the adenoviral transduction. TG cultures transduced with Ad:IFN-beta displayed up to a 19-fold reduction in viral titers compared with cells transduced with an Ad:Null or nontransduced TG culture controls. Transduction with Ad:IFN-beta up-regulated two critical antiviral genes, double-stranded RNA-dependent protein kinase R (PKR) and 2',5'-oligoadenylate synthetase (OAS). The absence of PKR or RNase L (downstream effector molecule of OAS) attenuated Ad:IFN-beta efficacy against HSV-1 replication, implicating a critical role for PKR and OAS/RNase systems in the establishment of IFN-induced resistance against HSV-1 in TG cells.

Exercise in sickle cell anemia: effect on inflammatory and vasoactive mediators

The aim of this study was to determine the response of inflammatory and vasoactive mediators to 3 consecutive days of exercise in African-American women with and without sickle cell anemia (SCA). Circulating inflammatory mediators [C-reactive protein (CRP), interleukin-6 (IL-6), tumor necrosis factor alpha (TNFalpha)] were measured before, and vasoactive mediators [endothelin-1 (ET-1), nitric oxide metabolites (NOx)] before and after each exercise bout in ten subjects with SCA and ten controls. Exercise did not affect ET-1, IL-6 or CRP concentrations (p >.05). TNFalpha was higher in SCA than controls (p < or = .0005) at all times; however, the response pattern was similar for the groups: no change from day 1 to day 2, but a decrease from day 2 to day 3 (p < or = .05). NOx increased significantly after exercise (p < or = .0001) but returned to baseline by 24 h afterward. On the 3rd day, NOx increased after exercise in SCA but not in the controls (p < or = .05). In conclusion, exercise did not cause a harmful inflammatory response in these individuals with SCA. However, NOx increased after exercise on all 3 days in SCA but appeared attenuated after 2 days in controls.

Interferon coordinately inhibits the disruption of PML-positive ND10 and immediate-early gene expression by herpes simplex virus

Interferons (IFNs) are important components of the innate immune response, limiting herpes simplex virus (HSV) infection. In recombinant HSV-infected cells, IFN inhibited expression of beta-galactosidase from the immediate-early gene, ICP4, promoter. The extent of inhibition was dependent on IFN dose, IFN type, cell type, and multiplicity of infection (moi). IFN inhibited gene transcription, leading to a complete block in ICP4 promoter-driven gene expression in 90% of cells. The same IFN treatments resulted in an increase in the size and number of nuclear domain 10 (ND10) structures that stained positive by immunofluorescence for the promyelocytic leukemia (PML) protein. In cultures infected at low moi with a recombinant HSV producing ICP4 as a fusion protein with green fluorescence protein, the appearance of green fluorescence in the nucleus coincided with loss of PML-positive ND10 in the same nucleus, even in the rare ICP4-expressing IFN-treated cells. IFN-dependent inhibition was nearly complete when the immediate-early promoter was in the viral genome but was minimal when the promoter was stably integrated into the cellular genome. These data reveal that IFN can completely block viral gene expression in infected cells and that enhancement of the ND10 structure, which is the site of initiation of HSV replication, correlates with the block in viral gene expression.

IFN-alpha1 plasmid construct affords protection against HSV-1 infection in transfected L929 fibroblasts

The purpose of the present study was to evaluate the resistance against herpes simplex virus type 1 (HSV-1) using an interferon-alpha1 (IFN-alpha1) transgene in specifically targeted cells in vitro. Transfection of mouse fibroblast L929 cells with an IFN-alpha1 plasmid construct reduced viral load and viral gene expression in a time-dependent fashion. Supernatants from IFN-alpha1-transfected cells augmented natural killer (NK) cell activity, and such an effect was antagonized with neutralizing antibody to IFN-alpha/beta. In addition, transfected cells displayed an increase in the IFN inducible genes (2',5'-oligoadenylate synthetase [2',5'-OAS], T cell-specific guanine nucleotide triphosphate-binding protein, IFN regulatory factor 1 [IRF-1], and major histocompatibility complex [MHC] class I) compared with plasmid vector-treated controls. Collectively, these results show that IFN-alpha1 transfection of cells in vitro induces or upregulates a spectrum of IFN-regulated genes involved in the direct or indirect antiviral action of this cytokine. In addition, the transgene significantly increases the resistance of transfected cells in vitro to HSV-1 infection.

The 2-5A system: modulation of viral and cellular processes through acceleration of RNA degradation

The 2-5A system is an RNA degradation pathway that can be induced by the interferons (IFNs). Treatment of cells with IFN activates genes encoding several double-stranded RNA (dsRNA)-dependent synthetases. These enzymes generate 5'-triphosphorylated, 2',5'-phosphodiester-linked oligoadenylates (2-5A) from ATP. The effects of 2-5A in cells are transient since 2-5A is unstable in cells due to the activities of phosphodiesterase and phosphatase. 2-5A activates the endoribonuclease 2-5A-dependent RNase L, causing degradation of single-stranded RNA with moderate specificity. The human 2-5A-dependent RNase is an 83.5 kDa polypeptide that has little, if any, RNase activity, unless 2-5A is present. 2-5A binding to RNase L switches the enzyme from its off-state to its on-state. At least three 2',5'-linked oligoadenylates and a single 5'-phosphoryl group are required for maximal activation of the RNase. Even though the constitutive presence of 2-5A-dependent RNase is observed in nearly all mammalian cell types, cellular amounts of 2-5A-dependent mRNA and activity can increase after IFN treatment. One well-established role of the 2-5A system is as a host defense against some types of viruses. Since virus infection of cells results in the production and secretion of IFNs, and since dsRNA is both a frequent product of virus infection and an activator of 2-5A synthesis, the replication of encephalomyocarditis virus, which produces dsRNA during its life cycle, is greatly suppressed in IFN-treated cells as a direct result of RNA decay by the activated 2-5A-dependent RNase. This review covers the organic chemistry, enzymology, and molecular biology of 2-5A and its associated enzymes. Additional possible biological roles of the 2-5A system, such as in cell growth and differentiation, human immunodeficiency virus replication, heat shock, atherosclerotic plaque, pathogenesis of Type I diabetes, and apoptosis, are presented.

The comparative anti-herpes simplex virus effects of human interferons

The mechanism(s) of anti-herpes simplex virus (HSV) activity of interferons (IFNs) have not been clearly identified. We have tested natural and recombinant human IFN-alpha, IFN-beta, and IFN-gamma preparations for their relative anti-HSV activity in human corneal and Vero monkey kidney cells. The relative anti-HSV activities in corneal cells were IFN-beta > rIFN-gamma > IFN-alpha (lymphoblastoid) > rIFN-beta2a = rIFN-alphaA/D. IFN-beta at 100 IU/ml reduced virus yield by 59+/-24%. The relative anti-HSV activity in Vero cells was rIFN-gamma > IFN-beta = IFN-alpha (lymphoblastoid) > rIFN-alphaA/D > rIFN-alpha2a. IFN-gamma at 100 IU/ml reduced virus yields by 90+/-4%. Reducing the multiplicity of infection significantly increased the apparent antiviral activity of all IFNs. The antiviral activity of IFNs could be detected by 4 h after treatment of Vero cells but not until 8 h in corneal cells. Western blot analysis showed that none of the IFNs detectably reduced the levels of immediate-early HSV protein, ICP4, but some reduced ICP0 levels early during infection, the extent and duration of the reduction varying with both IFN and cell type. The greatest effects on viral protein levels were detected in IFN-y-treated Vero cells. These data indicated that the targets of the anti-HSV activities of IFNs can vary with both IFN and cell type.

In vitro suppression of the normal mitogenic T lymphocyte response by steady state sickle cell disease sera

This study is part of a long term evaluation of sickle cell disease (SCD) as a paradigm for immunosuppression. Serum was obtained from 43 SCD patients during the steady (healthy) state. Peripheral blood mononuclear cells (PBMC), separated by density gradient were obtained from 8 normal healthy donors. PBMC were utilized in assays directly or as a source for obtaining, total T (CD3) and helper T (CD4) cell populations separated by specific T cell columns. Standard in vitro phytohemagglutinin (PHA) stimulation of lymphocyte cultures was done with culture media containing 10% SCD serum, as compared to normal pooled O, Rh+ (O+) serum. Mitogenic responses were expressed as mean counts per minute (cpm) and stimulation index of triplicate cultures. Results revealed PHA responses were positive in all experiments when a standard stimulation index of 10 or greater was used as a test parameter for comparison. Positive results were demonstrated in 43/43 (100%) of triplicate cultures regardless of serum type in all experiments. Conversely, by using mean cpm as the test criterion, suppression of PHA response was shown in SCD serum supplemented cells as follow; 36/43 (84%) of PBMC, 35/43 (81%) of CD3 and 37/43 (86%) of CD4 cultures. The degree of suppression ranged from > 10% to 98% in individual experiments, as compared to O+ serum. Inhibitors of normal T lymphocyte in vitro PHA response appear to be present in a significant percentage of SCD sera even during the healthy state of disease. Type 2 cytokines which suppress cell mediated immunity would seem to be the most likely inhibitory agents.

Production of ISG-15, an interferon-inducible protein, in human corneal cells

ISG-15, a 15-kDa protein encoded by an interferon (IFN)-stimulated gene (ISG), was produced in human corneal cell cultures prepared from donor corneas in response to each of three major types of IFN, IFN-alpha, IFN-beta, and IFN-gamma. IFN-alpha and IFN-beta induced more ISG-15 in the first 24 h of treatment than did IFN-gamma. ISG-15 was detectable within the first 3 h of treatment with either type I IFN, and production peaked at 24 h, whereas IFN-gamma did not induce detectable ISG-15 until 16 h and did not induce peak production until 48 h. Conjugates of ISG-15 to cellular proteins were detectable by Western blot beginning at 9 h after IFN-alpha or IFN-beta treatment. ISG-15 persisted in IFN-treated cells for as long as 96 h. Free, unconjugated, ISG-15 was secreted by keratocytes into cell culture medium. The extent and kinetics of production, the conjugation of ISG-15 to cell proteins, and the secretion of ISG-15 in human fibroblast derived from corneas were IFN type dependent and dose dependent.

In vitro lymphocyte blastogenic responses and cytokine production in sickle cell disease patients with acute pneumonia

BACKGROUND

Pulmonary infections continue to be a major cause of morbidity and mortality in patients with sickle cell disease (SCD).

METHODS

In this study cell-mediated immunity in vitro was evaluated in 62 SCD patients (62 steady state and 16 with acute pneumonia) and compared with 44 normal controls (30 healthy and 14 with acute pneumonia). Lymphocyte blastogenic responses to phytohemagglutinin, tetanus toxoid and Candida albicans antigen were assessed in all subjects. In addition production of tumor necrosis factor, alpha- and gamma-interferon (IFN) were assayed.

RESULTS

The results revealed comparable blastogenic responses to all three stimuli in all subjects except SCD patients with pneumonia. This group showed poor responses to all stimuli. The mean counts per minute were decreased 65 to 90% when compared with the other patients. Cytokine production of IFN-alpha and TNF was equivalent in all subjects. Conversely IFN-gamma production in both SCD groups, steady state (35 +/- 6 U/ml) and SCD with pneumonia (14 +/- 6 U/ml), was significantly decreased when compared with those in normal healthy controls (65 +/- 14 U/ml) and with pneumonia (48 +/- 17 U/ml). On analysis of individual titers 15 of 62 (24%) steady state and 10 of 16 (63%) SCD patients with pneumonia were deficient in IFN-gamma production in vitro.

CONCLUSIONS

Acute pulmonary infections seem to have a profound effect on cell-mediated immunity in SCD. IFN-gamma deficiency, along with quantitative and qualitative T cell abnormalities, may represent significant factors to explain the frequent and severe infections seen in SCD.