The interferon-induced enzyme oligo-isoadenylate synthetase: rapid determination of its in vitro products

Mild hyperthermia modulates biological activities of interferons

A significant enhancement of antiviral activity of human IFN-alpha, -beta and -gamma and murine IFN-gamma is observed when cells are treated with mild hyperthermia (39 degrees C) during antiviral assays. Treatment of primary human fibroblast cells with mild hyperthermia for 4 and 24 hours prior to interferon antiviral assays (pre-assay hyperthermia) further enhances interferon antiviral activity. An enhancement of interferon induced enzyme, 2,5-oligoadenylate synthetase, is also observed in cells treated with interferon and mild hyperthermia. This increase in enzyme activity is, in part, responsible for the observed increase in interferon antiviral activity with hyperthermia. Besides antiviral activity, mild hyperthermia also increases interferon antiproliferative activity on different tumour cells beyond its effect at normal physiological temperatures. On the other hand, mild hyperthermia decreases human interferon production in both human and murine cells when challenged with a viral or non-viral inducer. Also, mild hyperthermia suppresses interferon-mediated enhancement of natural killer (NK) cell activity in human and murine cells. The findings demonstrate that, although mild hyperthermia has suppressive effects upon interferon production and NK cell activity, it significantly increases both antiviral and antiproliferative activities of all three human interferons. These observations have direct bearing upon clinical utilization of exogenously administered interferons to late stage cancer patients who for the most part have a weaker immune system. In these patients, the antiviral and antiproliferative efficacies of administered interferon can be enhanced by combining interferon and hyperthermia.

Bile acids modulate the interferon signalling pathway

We have previously shown that cholestasis and bile acids inhibit 2', 5' oligoadenylate synthetase (OAS) activity in the liver and in primary hepatocyte cultures. Here, we assessed the influence of bile acids on interferon (IFN) pathway activation in three hepatoma cell lines. In HepG2 cells, bile acids (100-200 micromol/L) inhibited IFN-induced 2',5' OAS activity to an extent depending on their surface activity index. In Western blot analysis, IFN-induced expression of two major antiviral proteins, MxA and OAS p100, was reduced by 54% +/- 8% and 44% +/- 12%, respectively, when cells were preincubated for 4 hours with 100 micromol/L chenodeoxycholic acid (CDCA). In the same conditions, CDCA did not modify the IFN-induced signal transducers and activators of transcription (STAT)s tyrosine phosphorylation. In contrast, it reduced IFN-induced MxA promoter activity by 60%. The inhibitory effect of CDCA was not mediated by a 4beta-phorbol 12beta-myristate 13alpha-acetate (PMA)-sensitive protein kinase C (PKC)-dependent pathway. Finally, using CHO cells stably expressing a functional human bile acid carrier (Na+-dependent taurocholate cotransporting polypeptide [NTCP]), we found that bile acid inhibition of the IFN pathway occurred in the range of more physiological concentrations (12-50 micromol/L). In summary, our results provide strong evidence that bile acids inhibit the induction of proteins involved in the antiviral activity of IFN. This might partly explain the lack of responsiveness to IFN therapy in some patients with advanced chronic viral liver diseases.

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.

Establishment of a nonradioactive assay for2’-5’ oligoadenylate synthetase and its application in chronic hepatitis C patients receiving interferon-α

AIM: To establish a nonradioactive assay for 2’-5’ oligoadenylate synthetase (2-5 AS) and to measure the 2-5AS in peripheral blood mononuclear cell (PBMC) extracts of patients with chronic hepatitis C before IFN-α injection, 24 h and one month after the first injection.

METHODS: 2-5AS in cell extracts of PBMCs from 10 normal persons and 15 chronic hepatitis C patients were determined with PEI cellulose thin-layer chromatography.

RESULTS: The assay of 2-5AS in human PBMC was found to be rapid, sensitive, specific and reliable. The 2-5AS activity of PBMC in normal persons was in a quite low level (2.0%), and it was increased about ten-folds after stimulation of IFN (19.7%), (P < 0.01). In 15 chronic hepatitic C patients, the basal levels of 2-5AS before IFN treatment were higher than those of normal persons, being much higher in the group showing poor response to IFN treatment, but 24h after the first injection of IFN-α the 2-5AS level showed a more rapid and much greater rise in those patients with a good response.

CONCLUSION: 2-5AS may be a useful parameter of biological response during the IFN therapy.

Evidence for a deficiency of interferon response in mononuclear cells from hepatitis C viremic patients

BACKGROUND/AIMS

The pathophysiology of chronic hepatitis C and the mechanisms of resistance to interferon alpha are poorly understood. The aim of this work was to assess the influence of HCV infection and the viral genotype on lymphocyte production of 2',5' oligo-adenylate synthetase activity and monocyte production of TNF alpha and IL1 beta.

METHODS

Mononuclear cells from 50 consecutive patients were studied after 6 months of interferon treatment. Patients with persistent viremia (PCR-positive, elevated ALT, n = 39) were compared with the PCR-negative patients with normal ALT activity (n = 11) of similar age and sex ratio.

RESULTS

Cells from the viremic patients showed lower basal and stimulated 2',5' oligo-adenylate synthetase activity, and a lower in vitro response capacity to human recombinant interferon. In contrast, no difference was observed in basal and stimulated TNF alpha or IL1 beta production between the two groups. In the PCR-positive patients the viral genotype had no significant influence on the response of mononuclear cells to interferon or endotoxin.

CONCLUSIONS

These results show that the presence of HCV in blood is associated with an elective defect in interferon system activation, independently of the viral genotype.

Effect of cholestasis and bile acids on interferon-induced 2',5'-adenylate synthetase and NK cell activities

BACKGROUND/AIMS

The mechanisms involved in resistance to interferon alfa in patients with chronic hepatitis C are unclear. Both cirrhosis and cholestasis have been shown to be predictive of resistance. The aim of this study was to evaluate the influence of cholestasis and bile acids on 2',5'-oligoadenylate synthetase and natural killer activities, which are both involved in the antiviral activity of interferon.

METHODS

2',5'-Oligoadenylate synthetase activity was evaluated in spleen, liver, and isolated hepatocytes from bile duct-ligated rats, and the effect of bile acids in vitro on interferon-induced 2',5'-oligoadenylate synthetase and natural killer activities was examined in fresh mononuclear cells from healthy subjects.

RESULTS

Cholestasis had a time-dependent inhibitory effect on 2',5'-oligoadenylate synthetase activity in liver, spleen, and isolated hepatocytes from cholestatic rats (-70%, 86%, and 70% relative to baseline, respectively). In vitro, endogenous bile acids had a concentration-dependent inhibitory effect on interferon-induced 2',5'-oligoadenylate synthetase and natural killer activities, which was related to their structure. This inhibitory effect correlated with the surface activity index.

CONCLUSIONS

Cholestasis and bile acids diminish the biological activity of interferon and natural killer activity. The results suggest a decrease in the antiviral defenses in cholestatic conditions.

De novo synthesis and secretion of a 36-kD protein by cells that form lupus inclusions in response to alpha-interferon

In response to the pure recombinant human alpha-IFN, IFLrA, Raji and Daudi were the only two cell lines among 19 human lymphoblastoid cell lines tested that formed the human lupus inclusions (LI) to a high frequency. Raji, Daudi, and five other cell lines were examined for protein changes that might accompany LI formation. Their selection was based upon T or B origin, association with Epstein-Barr virus, and ability to form LI. A trace protein of an estimated molecular mass of 36 kD (p36) and an isoelectric point of 5.6 was detected on two-dimensional gels only of alpha-IFN-treated Raji and Daudi cells. Gamma-IFN did not induce p36 or LI in any of these seven cell lines. In Daudi cells p36 and LI formed simultaneously in response to IFLrA, and persisted until the alpha-IFN-induced death of the culture. In Raji cells, p36 and LI appearance and disappearance coincided with the addition and removal of alpha-IFN. Fractionation of Raji cells with nonionic-detergent buffer placed p36 with the inclusions in the cytoplasmic supernatant. With detergent-free buffer p36 and LI were distributed evenly between the nuclear and cytoplasmic fractions. Pulse-chase experiments revealed that p36 was secreted. The de novo synthesis of p36 with alpha-IFN treatment was shown by labeling the cell proteins with [35S] methionine before and after the addition of alpha-IFN. These results along with previous results on the de novo synthesis of LI in the endoplasmic reticulum (which is involved in the processing and secretion of proteins) suggest a role for LI in the synthesis and secretion of p36.

Hormonal and immunological regulation of 2', 5'-oligoadenylate synthetase activity in human peripheral blood mononuclear cells

A newly developed method for assaying 2', 5'-oligoadenylate (2, 5A) synthetase activity by polyacrylamide gel electrophoresis was applied to peripheral blood mononuclear cells (PBMC) from normal subjects, HIV-positive subjects, and renal cell carcinoma (RCC) patients. Sex differences were observed in 2, 5A synthetase activity of PBMC from normal young adults, males having eightfold higher activities of this enzyme than females. Moreover, compared to values for postmenopausal (PM) females receiving estrogen replacement, untreated PM females had higher activities. Collectively, these results suggest that estrogen downregulates 2, 5A synthetase activity. Activities of 2, 5A synthetase were investigated in two disease states associated with altered immune function. In one patient with AIDS-related Kaposi's sarcoma, interferon-alpha (IFN-alpha) therapy increased 2, 5A synthetase activity twofold. In addition, combined therapy with interleukin-2 (IL-2) and IFN-alpha increased 2, 5A synthetase activities in eight of nine patients with RCC. Therefore, in patients receiving immunotherapy with IL-2 and IFN-alpha, our new assay could contribute to evaluation of immune stimulation. In general, studies in vitro confirmed these observations; however, exposure of PBMC from RCC patients revealed that in vitro IL-2 failed to induce this enzyme activity as it did in PBMC from normal volunteers.

Opposite sensitivity to the antiproliferative action of interferon-alpha and granulocyte-macrophage colony-stimulating factor in monoblastic U937 cells

Three variants of the human monoblastic cell line U937 with different degrees of sensitivity to the antiproliferative action of interferon-alpha (IFN-alpha were examined for phenotypic differences. The highly IFN-sensitive variant U937-V expressed twice as many IFN-alpha binding sites as both its IFN-alpha-resistant derivative U937-VR and the cell line U937 exhibiting a 20-fold reduction in IFN-alpha sensitivity as compared to U937-V cells. All three variants were IFN-reactive with regard to induction of 2',5'-oligoadenylate (2-5A) synthetase activity and were similarly sensitive to the growth-inhibiting action of IFN-gamma and tumor necrosis factor. Responsiveness to the antiproliferative effect of granulocyte-macrophage colony-stimulating factor (GM-CSF), however, was confined to cell lines U937 and U937-VR. Although expressing a comparable number of GM-CSF receptors, the highly IFN-sensitive variant U937-V was refractory to GM-CSF. Flow cytometry revealed a marked difference in the expression of the antigen CD11b which was detectable on 85% of cells of the U937-V line but only on approximately 25% of cells derived from the U937 and U937-VR lines. Results thus demonstrate opposite sensitivity of U937 cells to the growth-inhibiting action of IFN-alpha and GM-CSF, apparently dependent on the state of U937 differentiation as determined by expression of the CD11b antigen.

Pentoxifylline inhibits certain constitutive and tumor necrosis factor-alpha-induced activities of human normal dermal fibroblasts

Pentoxifylline (PFN), analog of theobromine, which phenotypically and functionally alters various cell types including dermal fibroblasts, has been reported to inhibit tumor necrosis factor-alpha (TNF alpha) activation of neutrophils. We investigated the ability of PFN to alter constitutive and TNF alpha-induced biosynthetic activities of human normal dermal fibroblasts. The sixteenfold increase over constitutive intracellular 2'-5' oligo-adenylate synthetase (2'-5' A synthetase) activity induced by TNF alpha (400 U/ml) failed to occur when PFN (1 mg/ml) was added prior to cytokine treatment. This loss of biologic activity paralleled a reduction in 2'-5' A synthetase proteins and 2'-5' A synthetase-specific m-RNA. PFN failed to inhibit constitutive or TNF alpha-induced IL-6 hybridoma proliferative activity, IL-6 protein, or IL-6-specific m-RNA levels. The presence of PFN (1 mg/ml) in fibroblast cultures reduced constitutive synthesis of collagen and glycosaminoglycan (GAG) by 87% and 45%, respectively, and blocked induction of their synthesis by TNF alpha (10(4) U/ml). Total non-collagenous protein synthesis was not inhibited following PFN treatment (1 mg/ml). PFN did not inhibit TNF alpha induction of only those biosynthetic activities also susceptible to PFN in the constitutive state, with PFN failing to reduce constitutive collagenolytic activity but reducing TNF alpha-induced enhanced collagenolytic activity by 26% and collagenase m-RNA by 51%. Furthermore, PFN did inhibit, by 98%, TNF alpha-dependent murine and human fibroblast cytotoxicity. The selective nature of PFN inhibition of certain TNF alpha activities, the failure of PFN (1 mg/ml) to alter constitutive and TNF alpha-induced levels of type 1 and 2 TNF alpha receptor m-RNA, and the finding that PFN-treated fibroblasts express a similar number of receptors, of similar molecular weight and high affinity for TNF alpha as control, untreated cells, suggest that inhibitory activities of PFN are mediated at a locus other than receptors for TNF alpha.

Tumor necrosis factor alpha modifies resistance to interferon alpha in vivo: first clinical data

Patients with Philadelphia-positive chronic-phase chronic myelogenous leukemia (CML) resistant to interferon (IFN) alpha were treated in a phase I/II study with recombinant human tumor necrosis factor alpha to overcome IFN alpha resistance. Doses of 40, 80, 120 or 160 micrograms/m2 TNF alpha were given as 2-h infusions on 5 consecutive days every 3 weeks. IFN alpha (4 x 10(6) IU/m2 s.c., daily) treatment was continued. Six patients were treated, completing 1-24 (median, 12) treatment cycles. Five of the six patients achieved partial hematological remission, while the remaining patient had to stop treatment because of WHO grade 4 thrombocytopenia following the first TNF alpha cycle. No complete hematologic remission or cytogenetic improvement was seen. Side-effects were similar to those described for both substances alone. Maximum tolerable TNF doses usually varied between 80 micrograms/m2 and 160 micrograms/m2. To examine possible pathways of TNF activity in these patients, interferon receptor status and (2'-5')-oligoadenylate synthetase levels were examined in peripheral blood mononuclear cells. Both parameters remained unchanged during TNF alpha treatment. These preliminary data point to significant clinical efficacy of additionally applied TNF alpha in IFN alpha-resistant CML patients.

Fractionation and characterization of 2',5'-oligoadenylates by polyacrylamide gel electrophoresis: an alternative method for assaying 2',5'-oligoadenylate synthetase

2',5'-Linked oligoadenylates of varying chain lengths (2,5As) are formed from ATP by an interferon (IFN)-induced enzyme, 2',5'-oligoadenylate synthetase (2-5A synthetase). To identify these multiple forms, a method was devised utilizing electrophoretic separation of 32P-labeled 2,5As in a thin 20% polyacrylamide gel containing 7 M urea. A mixture of 2,5As synthesized from rat liver nuclear suspension was fractionated by this method. Each species was eluted from the gel for characterization by specific nucleotidylic enzymes. All major species in the gel were identified, including dimeric, trimeric, and tetrameric forms with either 5' tri- or diphosphates, as well as dephosphorylated species. Thus, in a single step, this method produced a more complete assessment of newly synthesized 2,5As and their degradative products than conventional, multistep DEAE-cellulose chromatography. It also allowed more rapid screening of multiple samples than high-pressure liquid chromatography (HPLC). This method, used to assay 2-5A synthetase induction by IFN-alpha in human T-cell H9 and CEM-CM3 lines, should be applicable for routine analysis of clinical specimens.

Human lupus-type inclusions in umbilical cord blood mononuclear cells

Mononuclear cells purified from umbilical cord blood activated oligoadenylate synthetase and formed human lupus-type inclusions (LI) when cultured with the purified recombinant human leukocyte interferon, IFLrA. LI frequencies increased from 0% to a low of 0.75% and a high of 6.25% in 4-day cultures with IFLrA (100 units/ml). These interferon-induced responses in the mononuclear cells of neonates indicate that LI are solely an intrinsic product of normal cells, and not an exogenous virus or some other environmental agent.

2'-5' oligoadenylate synthetase and its relationship to HLA and genetic markers of insulin-dependent diabetes mellitus

Cytokines and their related enzyme pathways may play a part in the development of insulin-dependent diabetes mellitus (IDDM). We have therefore studied the activity of the enzyme 2'-5' oligoadenylate synthetase (which is induced by both interferon and the tumour necrosis factors) in circulating mononuclear cells from 40 subjects with IDDM and 32 healthy control subjects. There was no difference in mean basal enzyme activity between the two groups. A polymorphism of the 2'-5' oligoadenylate synthetase gene, not previously described, was found using the restriction enzyme Bam HI. There was no association of 2'-5' oligoadenylate synthetase genotypes with IDDM, but there was a significant correlation between basal 2'-5' oligoadenylate synthetase activity and 2'-5' oligoadenylate synthetase genotypes. Significantly higher mean basal levels of 2'-5' oligoadenylate synthetase activity were associated with HLA-DQA 4.6 phenotype (determined using the restriction enzyme Taq 1 and a DQA probe) and HLA-DR3 (determined serologically), whereas significantly lower mean levels of enzyme activity were associated with HLA-DQA 5.5 and HLA-DR7, in both IDDM and control subjects. An analysis of variance confirmed that these associations were independent 2'-5' oligoadenylate synthetase genotype. Likewise, a significantly higher mean level of enzyme activity was associated with the heterozygous 1/3 insulin-related genotype in the IDDM subjects only. This study therefore suggests that the possession of certain HLA haplotypes might be associated with differing levels of basal 2'-5' oligoadenylate synthetase activity.

Cloning of murine interferon gamma receptor cDNA: expression in human cells mediates high-affinity binding but is not sufficient to confer sensitivity to murine interferon gamma

A full-length cDNA encoding the murine interferon gamma (IFN-gamma) receptor was isolated from a lambda gt11 library using a human IFN-gamma receptor cDNA probe. The deduced amino acid sequence of the murine IFN-gamma receptor shows approximately 53% homology to its human counterpart but no homology to other known proteins. Murine IFN-gamma receptor cDNA was expressed in human HEp-2 cells, which do not bind murine IFN-gamma and are insensitive to its action. Transfectants displayed the same binding properties as mouse cells. The biological responsiveness of such transfectants to various biological effects of both human and murine IFN-gamma was investigated, including modulation of major histocompatibility complex class I and class II antigen expression, inhibition of cell growth, and antiviral activity. Like parental HEp-2 cells, these transfectants responded only to human, but not to murine, IFN-gamma. Inversely, mouse L929 cells transfected with human IFN-gamma receptor cDNA were insensitive to human IFN-gamma. These results confirm and extend previous findings, suggesting that species-specific cofactors are needed for IFN-gamma-mediated signal transduction.

Enhancement of interferon-induced 2-5 oligoadenylate synthetase activity by retinoic acid in human histiocytic lymphoma U937 cells and WISH cells

The effect of retinoic acid (RA) on the level of interferon (IFN)-induced 2-5 oligoadenylate (2-5A) synthetase activity was examined in human histiocytic lymphoma U937 cells and WISH cells** in order to ascertain the role of this polymerase in interaction between IFNs and RA. Cultures containing both IFNs (1-100 U/ml) and RA (0.1-10 microM) consistently had higher levels of enzyme activity than corresponding cells treated with IFN alone and this was true for all three types of IFNs in both cell lines. The potentiating effect of RA was dose- and time-dependent and under optimal conditions, the induction of the synthetase was synergistic between IFN-beta (10-100 U/ml) and RA (0.1-10 microM). Furthermore, pretreatment (but not posttreatment) with RA followed by subsequent treatment with IFNs preferentially induced higher levels of enzyme activity in U937 cells but not in WISH cells. In addition, our results indicated that the modulating effect of RA on IFNs did not involve interaction at the receptor level and the level of enhancement of 2-5A synthetase activity was not in parallel with either cell-growth arrest or promotion of differentiation. Lastly, the present study raises the possibility that interactions between IFNs and RA, in either a synergistic or antagonistic manner, may be mediated through amplification of the 2-5A system.

Differential modulating effects of retinoic acid on interferon antiviral activity

The effect of retinoic acid (RA) on the antiviral activity of interferons (IFNs) alpha and beta in the U937 and WISH cells was examined to ascertain whether or not RA could reduce the effectiveness of IFN-induced resistance to viral infection. Our results indicate that in the U937 cells, RA (0.1-1.0 microM) had neither enhancing nor suppressive effect on the antiviral activity of IFN-alpha or beta against the Semliki Forest virus (SFV). However, in the WISH cells, RA had different effects on IFNs alpha and beta. Thus, while RA (0.1-50 microM) invariably suppressed the activity of IFN-alpha, it enhanced the action of IFN-beta at low dose (0.1-1.0 microM) but became suppressive at higher concentrations (greater than or equal to 10 microM). Furthermore, higher antiviral activity was consistently obtained when RA (0.1-10 microM) was added prior to either IFN-alpha or IFN-beta comparing to cultures with IFN alone. In addition, direct correlation between antiviral activity and the amplitude of 2-5 oligoadenylate (A) synthetase activity was not observed. These results suggest that modulation of IFN antiviral activity by RA varies with different systems and is dependent on the sequence of treatment.

Effect of natural human interferon-beta on the replication of human cytomegalovirus

The antiviral effect of natural human interferon-beta (HuIFN-beta) against human cytomegalovirus (CMV) was evaluated in human embryonic lung fibroblasts (HEL). Natural HuIFN-beta, like other HuIFNs, inhibited the replication of CMV. Pretreatment of the cells with natural HuIFN-beta inhibited the appearance of immediate-early antigen (IEA) or pre-early nuclear antigen (PENA) as well as the production of infectious CMV. After a single treatment with natural HuIFN-beta, intracellular 2', 5'-oligoadenylate (2-5A) synthetase activity was induced and maintained at a high level for several days. The anti-CMV effect of natural HuIFN-beta correlated with the intracellular 2-5A synthetase activity.

Studies on the in vitro biological activities of recombinant bovine tumor necrosis factor (rBoTNF) alpha. I. Synergistic antiviral efficacy of rBoTNF alpha, recombinant bovine interferon gamma (rBoIFN gamma) and their combination

The recent demonstration of the antiviral activity of recombinant human TNF has launched an interest in the use of TNF alpha for antiviral therapy in veterinary medicine. In the precent report, we demonstrate that pretreatment of bovine cells with rBoTNF alpha reduces the yield of bovine herpesvirus type-1 (BHV-1) from infected cells. Reduction in yield was similar to that observed in the presence of rBoIFN gamma. Similarly, rBoTNF alpha was able to protect bovine cells from virus-induced cytopathology. Enhanced antiviral activity was demonstrated when rBoTNF alpha was administered in combination with rBoIFN gamma. Studies on the induction of 2',5'-oligoadenylate synthetase (2'-5' AS) production by cytokine-treated cells showed that although rBoTNF alpha by itself did not induce 2'-5' AS activity it was capable of enhancing the production of 2'-5' AS by rBoIFN gamma-treated cells. Combination of these two cytokines was also evident in the inhibition of proliferation of treated cells. In contrast, the cytotoxic effect of rBoTNF alpha towards actinomycin D-treated cells was not affected by the combination of rBoTNF alpha with rBoIFN gamma.

(2'-5')Oligoadenylate synthetase activity in intestinal mononuclear and epithelial cells of inflammatory bowel disease patients

The activity of (2'-5')oligoadenylate synthetase, an enzyme induced by and mediating the antiviral action of interferon, was measured in extracts of intestinal mononuclear and epithelial cells isolated from patients with Crohn's disease, ulcerative colitis, and a control group. No significant differences were detected among (2'-5')oligoadenylate synthetase activities of lamina propria mononuclear cells derived from inflammatory bowel disease-involved and histologically normal control mucosa. Similarly, epithelial cells from inflammatory bowel disease and control patients expressed comparable levels of the enzyme, but these were significantly higher (p less than 0.01) than those found in autologous mononuclear cells. These results indicate that interferon is locally produced along the human intestinal mucosa under normal and inflammatory conditions. While this study supports the contention that induction of an antiviral state does not play a significant role in the pathogenesis of inflammatory bowel disease, it does not exclude the activation of the interferon system for other immunologic functions.

Interferon gamma is active on human lymphoblastoid Namalva cells without inducing an antiviral state

We demonstrate the presence of high affinity receptors specific for interferon-gamma (IFN-gamma) in human lymphoblastoid Namalva cells. The presence of these receptors, whose binding affinity and cross-linking characteristics were not distinguishable from those of the corresponding receptors in sensitive cells, was not consistent with the lack of responsiveness of Namalva cells to IFN-gamma as regards growth inhibition, induction of 2'-5' oligoadenylate synthetase activity and inhibition of virus multiplication. Nevertheless, IFN-gamma enhanced the expression of two genes, HLA class II and c-myc. Although the mechanism of these IFN-gamma-mediated modifications is not understood, these results provide evidence that the IFN-gamma receptors present in Namalva cells are functional.

Effect of recombinant murine interferon-beta on the replication of murine cytomegalovirus

Pretreatment of mouse embryo fibroblasts (MEF) with recombinant murine interferon-beta (rMuIFN-beta) induced a high level of intracellular 2',5'-oligoadenylate (2-5A) synthetase activity. However, murine cytomegalovirus (MCMV) replicated under such condition, indicating that MCMV is relatively insensitive in vitro to rMuIFN-beta. Thus, there was a dissociation of 2-5A synthetase activity and antiviral activity against MCMV. In contrast to MCMV, the two parameters were closely associated in the case of vesicular stomatitis virus (VSV).

Interferons in rheumatoid arthritis: alterations in production and response related to disease activity

Various markers associated with the production of and response to interferons (IFNs) were studied in patients with either inactive rheumatoid arthritis (RA) or active RA, and in healthy subjects. The IFN markers assessed were serum and synovial fluid (SF) levels, the activity in peripheral blood leukocytes (PBL) of (2'-5') oligoadenylate synthetase (OAS), and the production in vitro by PBL of IFN-alpha/beta in response to Sendai virus or Poly(I):Poly(C) as inducers, and of IFN-gamma using PHA or Con A as inducers. IFN activity, tested by antiviral assays using two different cell lines, was not demonstrable in the serum of any patient with RA. The activity of (2'-5') OAS in PBL, which may indirectly indicate exposure of leukocytes to IFN, was increased in RA compared with healthy subjects, more so in patients with inactive RA. The production of IFN-alpha/beta by PBL in response to Sendai virus was low in active RA but high in inactive RA, relative to production in healthy subjects. The production of IFN-gamma by PBL in RA was lower than in healthy subjects, more so in active RA. Thus inactive RA (remission status) is marked by evidence of PBL having been influenced by interferon and being a state of augmented inducibility to an IFN-alpha/beta stimulus, whereas active RA is associated with low inducibility of PBL to an IFN stimulus, but no evidence of IFN production in vivo. Our findings underscore the relevance of interferon to remission/activity in rheumatoid arthritis.

Decreased Epstein-Barr virus-induced transformation, and elevated 2-5A synthetase and RNase L activity in peripheral blood mononuclear cells from patients treated with recombinant interferon alfa 2b

Patients with cutaneous T-cell lymphoma (CTCL) were treated with recombinant alfa 2b interferon (rIFN alfa 2b) by intramuscular injection. Therapy-induced changes in Epstein-Barr virus (EBV) induced transformation of patient peripheral blood lymphocytes, 2',5' oligoadenylate (2-5A) synthetase levels and RNase L activation in peripheral blood mononuclear cells were monitored. Inhibition of EBV-induced transformation and elevation of 2-5A synthetase levels correlated with increased activation of RNase L, which provides evidence that intramuscular administration of rIFN alfa 2b induces a sustained anti-EBV state in CTCL patient peripheral blood mononuclear cells which can be detected in vitro.

In vivo and in vitro induction of natural killer cells by cloned human tumor necrosis factor

The natural killer (NK) cell activity of mice in the peritoneal cavity is very low or undetectable and testing peritoneal NK cells is a useful model for studying the influence of activating substances upon local injection. Injection of tumor necrosis factor (TNF) at doses of 10-200 ng caused a marked activation of NK cell activity which was maximal after 24 h and declined rapidly on day 2. A similar effect was observed when interferons alpha and beta were injected, and there were additive results when interferon was injected together with TNF. The NK cell nature of the effector cells activated by TNF was substantiated by the finding that previous injection with anti-asialo GM 1 antibody prevented activation. Interferon could not be detected in the peritoneal wash fluid after injection of TNF suggesting interferon-independent activation. In further experiments after i.p. injection of TNF peritoneal exudate cells (PECs) only killed YAC-1 targets in a 4-h assay. There was no additional killing in an 18-h assay towards neither YAC-1 cells or P815 cells, suggesting that macrophages were not involved. Furthermore TNF was also active in vitro by activating NK cells in isolated human peripheral blood cells. However in the PECs stimulated in vitro no significant induction of cytotoxic capacities by TNF was measured. Our data suggest that the action of TNF is not restricted to the lysis of tumor cells but can also induce immunological properties in the host defense against virus infections and neoplasms.

Induction and measurement of 2',5'-oligoadenylate synthetase in Madin-Darby bovine kidney cells and in cattle

2',5'-Oligoadenylate [2',5'-oligo(A)] was separated from 14C-labeled nucleosides produced in the 2',5'-oligo(A) synthetase assay by using 100-microliters columns of Dowex 1. No detectable nucleoside remained on the column after elution with 20 column volumes of water, whereas less than 1% of oligonucleotides were eluted from the column. At least 99% of oligonucleotides were eluted from the column with 1 M NaCl, pH 2. The major product had properties consistent with 2',5'-oligo(A). Exposure to alpha-1 bovine interferon (IFN) caused an increase in cellular 2',5'-oligo(A) synthetase activity which was proportional to the concentration of IFN in the medium up to 10(4) U of IFN per ml and then leveled off at about 15 X control activity. Under the assay conditions used, 2',5'-oligo(A) synthetase activity was directly proportional to the amount of cell extract over a 10-fold range. Cattle inoculated with IBR/BVD/PI-3 modified live virus vaccine showed an increase in 2',5'-oligo(A) synthetase activity in peripheral blood mononuclear leukocytes which persisted for at least 3 days postvaccination. Intramuscular injection of cattle with IFN caused a similar increase in 2',5'-oligo(A) synthetase activity. Changes in 2',5'-oligo(A) synthetase activity should be of value in (i) assessing the response of cattle to experimental viral infections or inoculations with viral vaccines or IFN or (ii) indicating a possible viral etiology in disease.

Intracellular human gamma-interferon triggers an antiviral state in transformed murine L cells

Interaction of human gamma-interferon (IFN-gamma) with a cell-surface receptor is known to be essential for the cell to become resistant to viral infection. Here we demonstrate that IFN-gamma, when present inside the cell, is also capable of inducing a permanent antiviral state. Mouse cells transformed with a truncated human cDNA encoding a mature IFN-gamma protein lacking the signal peptide accumulate high levels of intracellular human IFN-gamma. Not only do these cells acquire a permanent resistance to viral infection, they also exhibit all the biochemical characteristics normally observed after exposure to exogenous IFN. The observed loss of species specificity normally associated with IFN-gamma suggests that this restriction is strictly dependent on the interaction of the molecule with the cell-surface receptor.

Immune resistance to Trypanosoma cruzi: synergy of specific antibodies and recombinant interferon gamma in vivo

The protective effects of interferon gamma (IFN-gamma) against infection by Trypanosoma cruzi were studied in vitro and in vivo in a murine model of infection. The possible synergy between IFN-gamma and trypomastigote-specific antibodies in the rejection of the parasite was also considered. Our results in vitro indicate that IFN-gamma activates macrophages to reject the parasite and this mechanism may lead to a decrease in parasitaemia in vivo. Finally, IFN production in vivo after infection by T. cruzi was compared among mice from different genetic backgrounds. Reduced parasitaemia and extended survival correlated with the early production of circulating IFN-gamma and anti-trypomastigote antibodies after infection. The appearance of an unusual type of circulating IFN in response to infection by T. cruzi was also detected; this IFN was resistant to neutralization by antibodies to IFN-alpha/beta and to IFN-gamma.

T lymphocyte population dynamics and function following a primary bovine herpesvirus type-1 infection

Following a primary bovine herpesvirus-1 (BHV-1) infection the concanavalin A (Con A) induced proliferative responses of peripheral blood T lymphocytes were suppressed. This suppression occurred in the absence of detectible serum suppressor factors, suppressor cell activity or decreased accessory cell function. However, regression analysis demonstrated a significant correlation between the percentage of T lymphocytes present within the peripheral blood mononuclear cell (PBMC) population and the amplitude of Con-A-induced lymphocyte proliferative responses (LPR). Direct evidence that a numerical deficit of responder T lymphocytes was limiting LPR was obtained by using an immunomagnetic microsphere (IMM) negative enrichment protocol to produce a PBMC population with a constant percentage (75 +/- 6%) of T lymphocytes. The Con-A-induced LPR of these enriched T lymphocytes remained constant following BHV-1 infection. Flow cytometric (FC) analysis of PBMC indicated that the decreased percentage of circulating T lymphocytes, associated with BHV-1 infection, was caused primarily by a selective depletion of the BoT8 subset. These FC data were consistent with the indirect evidence of increased TH activity, as indicated by elevated Con A-induced IL-2 production. Thus, 2 to 5 days following viral infection, the circulating T lymphocytes were activated as shown by elevated IL-2 production, increased recombinant bovine IL-2 (rBo

Antiviral effects of recombinant tumour necrosis factor in vitro

Tumour necrosis factor (TNF) was first described as a factor in the serum of mice injected with tubercle bacilli (BCG) and several days later with lipopolysaccharide (LPS). The gene encoding TNF has recently been cloned and pure recombinant human TNF is now available. TNF is known for its in vivo antitumour effect and in vitro cytotoxicity on certain transformed cell lines. Similarities in amino acid sequence and biological activity to lymphotoxin and cachectin have been reported, and very recently a growth-factor-like activity on diploid fibroblasts was observed. There is no similarity between these proteins and interferons (IFNs), which are also induced during in vivo induction of TNF. Here we describe the antiviral activity of pure recombinant human TNF in a typical in vitro antiviral assay which we discovered while investigating the possible role of TNF as an inducer of IFN.

Treatment with human recombinant leukocyte interferons inhibits in vitro invasive ability of human lung carcinoma cells

The effects of treatment of human lung carcinoma cell line A 549 with recombinant DNA-derived human leukocyte interferons A (rIFN-alpha A) or D (rIFN-alpha D), and human lymphoblastoid interferon (Wellferon) on in vitro cell invasion were investigated in a quantitative invasion assay using human amnion. The A 549 cells treated with IFN for one day were incubated on the denuded basement membrane of the amnion in the absence of IFN, and cells which penetrated the full thickness of the connective tissue barrier were measured after 4 days. A dose-dependent inhibition of cell invasion was produced by the recombinant IFNs. The one day treatment of cells with 2.4 X 10(3) to 1.8 X 10(4) units/ml of rIFN-alpha A resulted in a 60-80 per cent inhibition of invasiveness compared to untreated cells. After a one day exposure of cells to 2.2 X 10(4) units/ml of rIFN-alpha D, cell invasion was reduced by approximately 70 per cent; a concentration of 4.4 X 10(3) units/ml had no apparent effect. Similar treatment with lymphoblastoid IFN (6 X 10(4) units/ml) had no significant effect on cell invasion. Accompanying the one day exposure to rIFN-alpha A (1.8 X 10(4) units/ml) or rIFN-alpha D (2.2 X 10(4) units/ml), (2',5') oligo (A) synthetase activity was induced approximately 20-fold; a 4-fold induction of enzyme activity was found in cells exposed to lymphoblastoid IFN (6 X 10(4) units/ml). After exposure of A 549 cells to the three IFNs at these concentrations, no significant alteration of the ability of the cells to attach to the basement membrane was found. Moreover, none of the one day IFN treatment regimens were cytocidal, and cell proliferation ability was not affected. This model system may be useful for investigating anti-invasive activity of other IFN types and subtypes.

Expression of extracellular and intracellular human IFN-gamma in mouse L cells transformed with the human IFN-gamma cDNA gene

Cotransformation with a plasmid containing a thymidine kinase gene (pTK2) and a plasmid encoding human IFN-gamma (pTG11) has been used to establish murine L cell lines expressing human IFN-gamma. The HuIFN-gamma gene was present in 30% of the tk+ cell lines and some of these secreted low levels of IFN into the culture medium. Two of the clones obtained after transformation were selected for detailed analysis. Clone 1-12 constitutively secreted very low levels of HuIFN-gamma in the culture medium. This antiviral activity was characterized by its species specificity and antigenicity as authentic human IFN-gamma In contrast, clone 3-47 produced a HuIFN-gamma activity which could only be detected intracellularly. This clone was resistant to infection both by Vesicular stomatitis (VSV) and Mengo viruses and contained increased levels of enzymes known to be induced by interferon. Our results suggest that clone 3-47 produces a non-secreted HuIFN-gamma like molecule which is able to trigger an antiviral state in the murine cell independent of the interaction with a specific IFN-gamma surface receptor.

Interferon inhibits prostaglandin E2 synthesis and stimulates (2'-5')oligoadenylate synthetase activity in peripheral blood mononuclear cells of inflammatory bowel disease patients

The effect of interferon (IFN) on prostaglandin E2 (PGE2) synthesis by peripheral blood mononuclear cells of normal subjects and patients with inflammatory bowel disease was studied. Exposure of peripheral blood mononuclear cells, isolated from normal subjects and patients with active ulcerative colitis and Crohn's disease, to IFN reduced the release of PGE2 in a dose-dependent manner. The inhibitory effect was observed for at least 24 h after the removal of IFN. To correlate the effect of IFN on PGE2 synthesis with a known activity of IFN, the induction of (2'-5')oligoadenylate synthetase (OAS) was also studied in the same mononuclear cells. Low basal levels of this enzyme were detected in mononuclear cells isolated from normal subjects and patients with active ulcerative colitis and Crohn's disease. Moreover, IFN treatment in vitro resulted in a similar induction of this enzyme in patients and controls. There results indicate that peripheral blood mononuclear cells of patients with active ulcerative colitis and Crohn's disease have normal response to IFN. In addition, our data do not suggest that IFN has an important role in the pathogenesis of these diseases.

Identification of viral infections in pregnancy by assay of (2'-5')-oligo-isoadenylate synthetase

Interferons are produced in response to viral infections. Among the biochemical changes they cause in cells is the induction of the enzyme (2'-5')-oligo-isoadenylate synthetase. The activity of this enzyme can be measured and this can indicate exposure and response of cells to interferon. The efficacy of such an assay of peripheral blood of pregnant women may aid in establishing screening guidelines for potentially teratogenic viral infections. The blood of 44 primigravidas with complaints of fever, myalgia, cough, vaginal discharge and/or costovertebral angle tenderness was assayed for activity of the enzyme (2'-5')-oligo-isoadenylate synthetase and compared to assays of the enzyme activity in a group of 37 healthy primigravidas which served as a control group. It was found that the group with viral infections had an increase in enzyme activity from twice to 15 times the normal value, with characteristic rises of enzyme activity in several viruses known or suspected to cause human defects. Several general guidelines are proposed to assist the obstetrician in determining a viral etiology of acute illness in pregnancy, It is suggested that the assay of enzyme activity of (2'-5')-oligo-isoadenylate synthetase may provide a simple tool for rapid diagnosis of viral infections in pregnancy.

Increased 2',5'-oligoadenylate synthetase activity in blood mononuclear leukocytes from patients with advanced cutaneous T-cell lymphoma

The activity of the interferon-induced enzyme 2',5'-oligoadenylate synthetase (2',5' An synthetase) was found to be increased in the lysates of peripheral blood mononuclear leukocytes obtained from 10 of 25 (40%) patients with cutaneous T-cell lymphoma (mycosis fungoides and Sézary syndrome). A positive association was found between the level of mean total synthetase activity and extent of involvement (stage) of disease. However, the leukocytes from two patients with relatively high proportions of neoplastic T-cells in the blood (Sézary syndrome) had negligible enzyme activity. It is speculated that increased interferon production in vivo may account for the observed enzyme changes in normal blood leukocytes from these patients, and that the neoplastic T-cell population is the most likely source of the presumed interferon production. Possible mechanisms and biologic consequences of high levels of endogenous interferon in patients with cutaneous T-cell lymphoma are discussed.

Clinical effect of interferon in malignant brain tumours

Phase I and phase II clinical studies of interferon (IFN) were conducted in malignant brain tumours (47 cases of glioblastoma, medulloblastoma and others) using three preparations of the drug. The drug was administered daily in doses 3.0 - 9.0 X 10(6) I.U. locally or intravenously (beta-type) or intramuscularly (alpha-type). The administration was continued as many days as possible, eight weeks being the shortest period. The efficacy of the therapy was assessed mainly by the CT findings (computed volume of the tumour). As for efficacy against glioblastomas, the highest effectiveness rate (40%) was obtained with Human Fibroblast IFN (HFIF) (beta-type) (Toray) (one case of complete remission and seven cases of partial remission out of 20 cases) as compared to Human Lymphoblastoid IFN (HLBI) (alpha a-type) (Wellcome) (one case of partial remission out of three cases) and recombinant IFN (rIFN-alpha A) (alpha-type) (Roche) (two cases of partial remission out of nine cases). The high rate of responsiveness of HFIF seems to be largely attributable to the local, rather than systemic, administration of the drug. Our pharmacokinetic study revealed that, by means of intrathecal administration a much higher IFN titre was detected in the cerebrospinal fluid, while by intravenous or intramuscular route, the IFN titre in the CSF was undetectably low. The generally lower incidence of side-effects with HFIF compared to other preparations was also largely ascribable to the route of administration. IFN therapy in combination with radiotherapy and/or chemotherapy should also be investigated.

Interferon-induced cytotoxicity and (2'-5') oligo(A) synthetase activity in T cells. Differences in responsiveness among T cells from various individuals and among lymphoblastoid T-cell lines

Peripheral blood T lymphocytes became cytotoxic toward Daudi lymphoblastoid cells when incubated in vitro with interferon (IFN). The degree and rate of response to IFN varied markedly from one blood donor to another. "Low responders," who reproducibly showed a slower response to IFN, as well as "high responders" could be identified. The rate of increase in (2'-5') oligo(A) synthetase activity in IFN-treated cells also varied and appeared to correlate to the rate of increase in cytotoxicity. Three lymphoblastoid T-cell lines (Molt 4, Peer, HPB-ALL) also became cytotoxic towards Daudi cells when incubated with IFN and in these cells too the rate of induction of cytotoxicity appeared to correlate to the rate of increase in (2'-5') oligo(A) synthetase activity. Differences in responsiveness of T cells to IFN-mediated cytotoxicity might, therefore, reflect differences in responsiveness to IFN in general. Thus, quantitation of these differences might yield useful information for assessing the dosage and frequency of IFN administration to patients undergoing therapy.

(2'-5')oligo(A) synthetase as a monitor of interferon action in juvenile laryngeal papillomatosis

Four children with juvenile laryngeal papillomatosis were treated with human leukocyte interferon (IFN-alpha) by intravenous infusions. In three cases the clinical course of the disease was effected favorably. Serum IFN titers and (2'-5')oligo(A) synthetase (OAS) levels in lymphocytes of the patients were measured once a week during therapy. Levels of serum IFN determined 15 min after the end of 1 h infusions corresponded to only 15%-40% of the amount infused. Comparable OAS activities in the four children were measured before infusion, i.e., one, two, or three days, respectively, after the preceding infusion, though mean IFN titers of the patients differed from each other (200-400 and 400-600 u/ml). This suggests a saturation of the lymphocytes' antiviral system by these IFN levels. A discontinuation for two weeks in the early phase of IFN treatment, accompanied by a decrease of the OAS activity in the lymphocytes to the basal level, resulted in a deterioration of the patient's condition. A change in treatment schedule causing a decrease of OAS activity to a lower, though still elevated level, for six weeks until the present did not influence the course of therapy. Therefore, we suppose that the maintenance of elevated levels of OAS activity in lymphocytes for some months may be a necessary, even though not always a sufficient, criterion for a successful therapy schedule in IFN treatment of juvenile laryngeal papillomatosis. In addition, our results suggest OAS activity to be suitable in monitoring effects of an IFN therapy.

A sensitive immunoenzymometric assay for 2',5'-oligoadenylate. Detection of elevated 2',5'-oligoadenylate synthetase in human peripheral mononuclear cells

A competition immunoenzymometric assay for 2',5'-oligoadenylate was developed and employed to measure the interferon-inducible enzyme 2',5'-oligoadenylate synthetase in cell extracts. Microtiter plates coated with a novel conjugate of p5'A2'p5'A2'p5'A and N-(2-aminoethyl)-carbamylmethylated-Ficoll (AECM-Ficoll) bound rabbit polyclonal or mouse monoclonal antibody directed against 2',5'-oligoadenylate. Binding was inhibited by soluble 2',5'-oligoadenylate. Estimates of 2',5'-oligoadenylate concentrations based on inhibition of antibody binding compared favorably with those obtained using a protein synthesis inhibition assay. Low concentrations of 2',5'-oligoadenylate synthesized in vitro by extracts of human peripheral mononuclear cells were conveniently estimated using less than or equal to 10(6) cells. Virtually identical results were obtained when either total extract or synthetase bound to poly(I) . poly(C)-agarose was used for the in vitro incubation. When peripheral mononuclear cells were incubated in vitro with interferon, the normally low levels of 2',5'-oligo(A) synthetase rose dramatically. The assay was employed to measure synthetase levels in peripheral mononuclear cells isolated from patients with systemic lupus erythematosus. Some of these patients were found to have elevated levels of 2',5'-oligoadenylate synthetase.

Assay and the levels of 2-5A-synthetase in lymphocytes of patients with viral, bacterial and autoimmune diseases

The level of 2-5A-synthetase in extracts of peripheral blood lymphocytes was estimated by the capacity of the enzyme to synthesize 2-5A in the presence of ATP. The 2-5A was then purified on a small column of DEAE-cellulose. Here we show that under or experimental conditions, the amount of 2-5A formed is proportional to the level of the enzyme. The concentration of 2-5A (nmol of AMP/10(6) lymphocytes) in an assay therefore reflects the level of the enzyme. Enhanced levels of 2-5A synthetase were observed in the lymphocytes of patients with viral and bacterial infections. In most of the cases studied, these enhanced levels of the enzyme decreased during the course of infection parallel to recovery. Thus, the level of 2-5A synthetase may indicate the state of the disease and its evolution during the period of treatment; furthermore, it may be a useful marker in monitoring the return to a normal physiological condition. In addition to patients with viral and bacterial infections, enhanced levels of 2-5A synthetase were observed in patients suffering from autoimmune diseases. In five patients studied here, the enhanced levels of 2-5A synthetase remained high at different periods during the course of the disease. These results suggest the presence of circulating interferon throughout the disease.

Assay of 2',5'-oligoadenylate phosphodiesterase activity in mouse L-cell extracts

A rapid and convenient assay for adenylyl(2' leads to 5')adenosine(A2'p5'A) or adenylyl(3' leads to 5')adenosine(A3'p5'A) phosphodiesterase activities is described. The dinucleotides A3'p5'A and A2'p5'A were labeled to a high specific activity by means of a catalytic-exchange procedure. Degradation studies of each of these labeled dinucleotides showed an asymmetrical distribution of label between the two adenine bases. Enzymatic degradation of [3H]A3'p5'A or [3H]A2'p5'A could be quantitated by first digesting the reaction products with bacterial alkaline phosphatase and then adding a slurry of DEAE-Sephadex. Under conditions described, adenosine did not adsorb to the resin, whereas dinucleotides as well as AMP did adsorb. As a consequence, when liquid scintillation fluid was added to the DEAE-Sephadex reaction mixture slurry, the radioactivity of the dinucleotides and AMP was severely quenched. This permitted a direct estimation of the amount of adenosine liberated during the phosphodiesterase degradation and subsequent alkaline phosphatase digestion. This method was applied to the measurement of A2'p5'A degrading activities in extracts of mouse L cells. Extracts from control mouse L cells were as active in degrading A2'p5'A as extracts from interferon pretreated cells.

Preferential effect of gamma interferon on the synthesis of HLA antigens and their mRNAs in human cells

Interferons produce a variety of biological effects on cells. They induce resistance to virus proliferation, inhibit cell growth, modify cell structure and differentiation, stimulate some immune functions and inhibit others. However, the different interferon (IFN) species may vary in their mechanism of action and, hence, in their relative efficiency for inducing each of the effect. IFN-gamma (type II) appears to show stronger immunoregulatory and growth inhibitory effects than antiviral effects, but this conclusion has been challenged in other reports. The aim of the present work is to compare the action of IFN-gamma and other (type I) interferons on the induction of (2'-5') oligo(A) synthetase which is probably part of the antiviral response and the induction of the histocompatibility HLA-A,-B,-C antigens. We have shown previously that the induction of both proteins is regulated by interferons at the mRNA level, but show here that IFN-gamma from stimulated human lymphocytes and from monkey cells transfected by cloned human IFN-gamma cDNA induced the HLA-A,-B,-C and beta 2-microglobulin mRNAs or proteins at concentrations over 100 times lower than those needed to induce the (2'-5')oligo(A) synthetase and the antiviral state. This difference was not found with IFN-alpha and -beta (type I).

Secretory proteins induced in human fibroblasts under conditions used for the production of interferon beta

Human fibroblast cells treated with a combination of inhibitors of protein and RNA synthesis [cycloheximide and actinomycin D as used to superinduce interferon beta (IFN-beta)] secrete two proteins with molecular masses of 22000 and 27000 kilodaltons (called 22-kDal and 27-kDal) that are precipitable with an antiserum raised against impure IFN-beta but are antigenically distinct from IFN-beta 1. Translation in vitro of mRNA extracted from human fibroblast cells induced for the production of IFN-beta leads to the synthesis of a 26-kDal protein that is structurally closely related to the 22- and 27-kDal proteins. This 26-kDal protein mRNA is relatively abundant and also appears in human fibroblasts induced only with cycloheximide. It has been partially purified by sucrose gradient centrifugation and more extensively by diazobenzyloxymethyl-cellulose hybridization to plasmid DNA from a bacterial cDNA clone. When translated in an in vitro reticulocyte system supplemented with dog pancreas microsomes, the 26-kDal protein and two other intermediates corresponding presumably to its signal-cleaved (19-kDal) and partially glycosylated (24-kDal) forms were observed. Crude, partially purified, and highly purified 26-kDal mRNA failed to program the synthesis of antiviral or ppp(A2'p5')nA synthetase-inducing activity when translated in Xenopus laevis oocytes. Moreover, partially purified 22-kDal and 27-kDal (i.e., the in vivo equivalents of the 26-kDal protein) are also devoid of antiviral or ppp(A2'p5')nA synthetase-inducing activity. Hence, this 26-kDal mRNA, although presumably identical to the human IFN-beta 2 mRNA described by Weissenbach et al. [Weissenbach, J., Chernajovsky, Y., Zeevi, M., Shulman, K., Soreq, H., Nir. U., Wallach, D., Perricaudet, M., Tiollais, P. & Revel, M. (1980) Proc. Natl. Acad. Sci. USA 77, 7152-7156], cannot be considered to be a fibroblast interferon mRNA.

Interferon-dependent induction of mRNA for the major histocompatibility antigens in human fibroblasts and lymphoblastoid cells

In human cells treated with interferons, there is an increase in the amount of HLA-A,B,C and beta 2-microglobulin exposed on the cell surface. We have used a cloned HLA-A,B,C cDNA probe to demonstrate by molecular hybridization that this effect of interferon is preceded by a large increase in the amount of HLA mRNA in the cell. This effect was found in five different human cell lines, with purified leukocyte and fibroblast interferons. The increase in HLA mRNA is comparable in its kinetics and dose-response to the induction of (2'-5') oligo(A) synthetase mRNA by interferons. Therefore, interferons seem to activate at least two cellular genes which have different biochemical functions.

Regulation of susceptibility to natural killer cells' cytotoxicity and regulation of HLA synthesis: differing efficacies of alpha, beta, and gamma interferons

Interferon (IFN) is an effective activator of the natural killer (NK) cells but can also induce, in a variety of target cells, resistance to the NK induced cytolysis. We have compared the ability of the various types of human IFN to carry out this function, by quantitating the cytolysis induced by NK cells in cultured fibroblasts pretreated with each IFN and comparing this effect of the IFNs to their effectivity in suppressing viral replication. Relative to their antiviral potency, preparations of IFN-gamma were significantly more effective than the alpha or beta interferons in inducing what we call the "anti-NK" effect. Significant inhibition of the natural killing was observed with IFN-gamma even at concentrations at which no antiviral effect was induced. Preparations of IFN-gamma were also more effective than the other interferons in suppressing cell growth. While the induction of the enzyme oligo-isoadenylate synthetase correlated to the antiviral effectivity of the interferons, the quantitation of the HLA proteins in the cells had shown that their induction by the interferons correlates to the induction of the anti-NK effect, being stimulated much more effectively by IFN-gamma than by IFN-alpha or IFN-beta. The anti-NK, HLA and antiviral-inducing activities co-purified in fractionation of IFN-gamma preparations. These findings suggest the existence of several independent mechanisms for the regulation of cell functions by interferons. The gamma IFN is particularly effective in regulating functions involved in the interaction of cells with the immune system while the gamma virus-induced IFN-alpha and -beta are more effective as inducers of resistance to viral growth.

Variation of (2'-5') oligo A synthetase level in lymphocytes and granulocytes of patients with viral infections and leukemia

Using a simplified technique for the determination of oligoisoadenylate synthetase activity, we have compared the cellular level of this interferon (IFN)-induced enzyme in multiple samples of peripheral blood leukocytes. In mononuclear cells (PBMC) of healthy donors the enzyme level was remarkably constant, but in the cells of about 85% of patients with viral infections enzyme activity was significantly elevated. In contrast, the incidence of elevated activity in bacterial infections was low. Synthetase activity could be also detected in granulocytes, although normally its level in these cells was considerably lower than in PBMC. A sharp increase in the enzyme level in granulocytes was found in cells exposed in vitro to IFN, as well as in cells from patients undergoing IFN therapy. Increased synthetase activity was also detected in the granulocytes of patients with viral infections. We have also determined the level of the enzyme in patients with various types of leukemias. In a large proportion of the patients with acute lymphoblastic leukemia (ALL) we found severely decreased enzyme levels (10-20% of control value). The decreased activity could usually be correlated to predominance of blast cells in the peripheral blood.

Comparison of (2'-5') oligo-adenylate synthetase and interferon blood-levels in mice early after viral infection

The level of the IFN-induced enzyme (2'-5') oligo A synthetase in the peripheral blood mononuclear cells (PBMC) was determined in mice at different times following virus infection. There was a significant increase (4-7-fold) of the enzyme level within less than 12 h after i.p. injection of either VSV (10(7) pfu) or Sindbis virus (2.10(4) pfu). The elevated level was maintained for about a week and then the activity returned to normal. There was, however, a marked difference in the pattern of serum level of IFN during infection by the two viruses; while in the mice infected by VSV, serum IFN was very high on the first day and declined to an undetectable level by the fourth day, in the mice infected with Sindbis virus, serum IFN was barely detectable at the first day and then increased towards the fourth day of infection. Antiviral antibodies could be detected in the serum only about a week after infection. We conclude that viral infection can result in a rapid elevation of (2'-5') oligo A synthetase in the PBMC, even when serum IFN remains low. Thus, quantitation of the enzyme level can be a useful diagnostic aid in viral infection particularly in the early stages and in cases in which antiviral antibodies and IFN can not be detected.

Assay of an interferon-induced enzyme in white blood cells as a diagnostic aid in viral diseases

Interferon is part of the system of defence against viral infections and has important cell-regulatory and immunoregulatory functions. It is, however, not always possible to quantify circulating interferon in patients. An assay has been developed to measure an interferon-induced enzyme in white blood cells. The activity of this enzyme is constant in healthy subjects but increases by 2-10 times in 85% of patients with acute viral infections. It is also enhanced in autoimmune diseases and in virus-related malignancies and neurological disorders. The enzyme level was not raised in bacterial infections or non-infectious diseases studied. This simple and rapid biochemical assay of the interferon system could be used for diagnosis and evaluation of many diseases.