Interferon-induced 2'-5' adenylate synthetase in vivo and interferon production in vitro by lymphocytes from systemic lupus erythematosus patients with and without circulating interferon.

The interferon (IFN)-induced enzyme 2-5A synthetase was elevated in mononuclear cells from both serum IFN-positive and -negative systemic lupus erythematosus (SLE) patients. This suggests that a much higher percentage of patients than previously thought produce endogenous IFN. These results may partly explain findings that mononuclear cells from SLE patients are deficient in IFN production in vitro in response to certain IFN inducers. Although normal lymphocytes can produce an acid-labile alpha IFN after stimulation with C. parvum in vitro, the reason for endogenous production of this unusual alpha IFN by SLE patients remains unknown.

A selective defect of interferon alpha production in human immunodeficiency virus-infected monocytes.

Interferon alpha (IFN-alpha) induces significant antiretroviral activities that affect the ability of human immunodeficiency virus (HIV) to infect and replicate in its principal target cells, CD4+ T cells and macrophages. A major endogenous source of IFN-alpha during any infection is the macrophage. Thus, macrophages have the potential to produce both IFN-alpha and HIV. In this study, we examined the production of IFN-alpha and other cytokines by macrophage colony-stimulating factor (M-CSF)-treated cultured monocytes during HIV infection. Tumor necrosis factor alpha (TNF-alpha), interleukin 1 beta (IL-1 beta), IL-6, IFN-omega, or IFN-beta were not detected nor was the mRNA expressed in either uninfected or HIV-infected monocytes. However, both uninfected and HIV-infected monocytes produced high levels of each of these cytokines after treatment with synthetic double-stranded RNA [poly(I).poly(C)]. Uninfected monocytes also produced high levels of IFN-alpha after treatment with poly(I).poly(C), Newcastle disease virus, or herpes simplex virus. In marked contrast to the preceding observations, HIV-infected monocytes produced little or no IFN-alpha before or after treatment with any of these agents. The absence of detectable IFN-alpha activity and mRNA in poly(I).poly(C)-treated HIV-infected monocytes was coincident with high levels of 2',5' oligoadenylate synthetase and complete ablation of HIV gene expression. The antiviral activity induced by poly(I).poly(C) may be a direct effect of this synthetic double-stranded RNA or secondary to the low levels of IFN-beta and IFN-omega produced by infected cells. The markedly diminished capacity of HIV-infected monocytes to produce IFN-alpha may reflect a specific adaptive mechanism of virus to alter basic microbicidal functions of this cell. The inevitable result of this HIV-induced cytokine dysregulation is virus replication and persistence in mononuclear phagocytes.

Interferon binding: the first step in establishment of antiviral activity.

Chick cells incubated at 1 degrees C with interferon fail to develop antiviral activity, but this activity appears subsequent to a 7-hour incubation at 37 degrees C after removal of interferon by repeated washings. Treatment with actinomycin D blocks the development of the latter activity. Cells incubated with interferon at 1 degrees C for up to 1 hour and then washed and incubated for 2 hours at 37 degrees C develop a degree of antiviral activity proportional to the concentration of interferon at initial incubation; at any concentration, the antiviral activity increased with the duration of initial incubation at 1 degrees C, but a maximal response was reached at 10 or 20 minutes. Treatment with trypsin after incubation with interferon at 1 degrees C inhibited development of antiviral activity. Interferon is rapidly bound to a superficial cell site, and this binding is necessary for development of antiviral activity in chick cells.

Actinomycin D: inhibition of phospholipid synthesis in chick embryo cells.

When chick embryo fibroblasts are exposed to actinomycin D for 30 minutes to 3 hours, there is progressive inhibition of phospholipid synthesis, so that by 3 hours the inhibition is 40 percent. All phospholipids are affected. Since this inhibition is twice as great as the inhibition of protein synthesis, some effects of actinomycin D previously ascribed to decreased protein synthesis must be reevaluated.

Selective inhibition of glycoprotein and membrane protein of vesicular stomatitis virus from interferon-treated cells.

A 200-fold inhibition in the titer of infectious vesicular stomatitis virus (VSV) was produced in cultures of Ly cells treated with 30 reference units of interferon per milliliter. Virus particle production, as measured by VSV particle-associated transcriptase, or nucleocapsid protein was inhibited by a maximum of tenfold. The glycoprotein and membrane protein content was reduced in VSV derived from interferon-treated cells. Thus interferon-treated cells may have produced VSV particles with low infectivity, which may be related to the reduced amount of glycoprotein incorporated into such particles. These findings resemble those reported in interferon-treated cells infected with murine leukemia viruses.

Interferon: production by chick erythrocytes activated by cell fusion.

In the presence of Sendai virus inactivated with ultraviolet light, nucleated chick erythrocytes can be fused with several types of human cells to form heterokaryons. Although chick erythrocytes alone cannot be stimulated by Sendai virus to produce interferon, fusion with a human cell (AH-1) which itself may produce human interferon results in heterokaryons in which the erythrocyte genome is activated and chick interferon is produced. When nucleated chick erythrocytes are fused with another type of human cell (HeLa clone S-3) which does not produce human interferon when stimulated, no chick interferon is detectable, despite morphologic changes suggestive of activation of the erythrocyte nuclei.

Expression of gene rrg is associated with reversion of NIH 3T3 transformed by LTR-c-H-ras.

A partial complementary DNA was isolated for a gene (rrg) that is normally expressed in mouse NIH 3T3 cells, but is down-regulated after cellular transformation by long terminal repeat (LTR)-activated c-H-ras (LTR-c-H-ras). This gene was reexpressed in a nontumorigenic persistent revertant cell line created by prolonged treatment of the transformed cells with mouse interferon alpha/beta. Persistent revertants stably transfected with rrg complementary DNA antisense expression vectors appeared transformed, had decreased amounts of rrg messenger RNA, and were tumorigenic in nude mice. Stable transfection with sense constructs did not alter the normal morphology, message level, or nontumorigenicity of the persistent revertant cell line.

Systemic lupus erythematosus: presence in human serum of an unusual acid-labile leukocyte interferon.

A previously undescribed species of human leukocyte, or alpha, interferon is present in the serum of many patients with systemic lupus erythematosus. It was shown to be alpha-interferon by neutralization with specific antiserums, affinity column chromatography, and antiviral activity on bovine cells. However, 23 of 30 interferon samples tested were inactivated by incubation at pH 2, a characteristic of human "immune," or gamma, interferon. Multiple samples of interferon from the same patient had similar biological properties, but samples from different patients were not all identical, suggesting that several variants of this species of human alpha-interferon may exist.

Tunicamycin enhances the antiviral and anticellular activity of interferon.

The inhibitory effects of interferon on virus multiplication and cell growth are significantly enhanced by treatment with tunicamycin. Potentiation of antiviral activity was found only with enveloped viruses and not with nonbudding viruses. Changes in the plasma membrane of treated cells may account for this effect, since enveloped viruses bud from the cell surface as a terminal step.

Connectivity of neuronal populations within and between areas of primate somatosensory cortex.

Functions of the cerebral cortex emerge via interactions of horizontally distributed neuronal populations within and across areas. However, the connectional underpinning of these interactions is not well understood. The present study explores the circuitry of column-size cortical domains within the hierarchically organized somatosensory cortical areas 3b and 1 using tract tracing and optical intrinsic signal imaging (OIS). The anatomical findings reveal that feedforward connections exhibit high topographic specificity, while intrinsic and feedback connections have a more widespread distribution. Both intrinsic and inter-areal connections are topographically oriented across the finger representations. Compared to area 3b, the low clustering of connections and small cortical magnification factor supports that the circuitry of area 1 scaffolds a sparse functional representation that integrates peripheral information from a large area that is fed back to area 3b. Fast information exchange between areas is ensured by thick axons forming a topographically organized, reciprocal pathway. Moreover, the highest density of projecting neurons and groups of axon arborization patches corresponds well with the size and locations of the functional population response reported by OIS. The findings establish connectional motifs at the mesoscopic level that underpin the functional organization of the cerebral cortex.

Interferon-induced revertants of ras-transformed cells: resistance to transformation by specific oncogenes and retransformation by 5-azacytidine.

Prolonged alpha/beta interferon (IFN-alpha/beta) treatment of NIH 3T3 cells transformed by a long terminal repeat-activated Ha-ras proto-oncogene resulted in revertants that maintained a nontransformed phenotype long after IFN treatment had been discontinued. Cloned persistent revertants (PRs) produced large amounts of the ras-encoded p21 and were refractile to transformation by EJras DNA and by transforming retroviruses which carried the v-Ha-ras, v-Ki-ras, v-abl, or v-fes oncogene. Transient treatment either in vitro or in vivo with cytidine analogs that alter gene expression by inhibiting DNA methylation resulted in transformation of PR, but not of NIH 3T3, cells. The PR retransformants reverted again with IFN, suggesting that DNA methylation is involved in IFN-induced persistent reversion.

Transcriptional inhibition of Ha-ras in interferon-induced revertants of ras-transformed mouse cells.

Elevation in Ha-ras expression, due to transcriptional activation or gene amplification, is associated with oncogenic transformation of NIH 3T3 cells. We have previously shown that murine interferon (IFN)-alpha/beta induced phenotypic reversion of NIH 3T3 cells transformed by long terminal repeat (LTR)-activated c-Ha-ras. The revertants produced decreased amounts of ras-encoded Mr 21,000 protein. We have now determined the molecular level at which LTR-ras regulation occurred. Nuclear run-on experiments revealed a selective inhibition of ras transcription in IFN-treated revertants. There was no apparent additional posttranscriptional control by IFN as judged by the unchanged half-life of ras transcripts. Inhibition of ras RNA synthesis was seen only in conjunction with long-term IFN treatment and was limited to the revertants, a population of cells that maintained sensitivity to IFN during the prolonged exposure. The reduction in ras activity appeared responsible in part for the loss of tumorigenicity in treated cells and was stable for several weeks after treatment had been discontinued.

Relationships of the structure and function of the interferon receptor to hormone receptors and establishment of the antiviral state.

This report describes similarities between the structure and function of the interferon receptor and receptors for glycoprotein hormones and several bacterial toxins. Specifically, it describes several common molecular and mechanistic elements, including: (a) the presence of a glycoprotein as well as a ganglioside component in the receptor; (b) changes in membrane structure as a consequence of interferon action; (c) interferon-induced intracellular cyclic adenosine 3':5'-monophosphate changes; and (d) alterations in the flux of certain ions across the membrane. Since interferon has an antiviral effect, these results define a relationship between hormonal perturbation of cellular events and the ability of an agent to prevent or suppress viral infections of cells. Further definition of these relationships should be important to our understanding of the oncogenic state, of hormonal effects on the oncogenic state, and of other human diseases in which hormonal perturbations of non-target tissues or cross-reactivity of receptors could be pathogenic.

Enhanced in vivo therapeutic response to interferon in mice with an in vitro interferon-resistant B-cell lymphoma.

A stable subline of 38C13 B-cell lymphoma (SIR-1) resistant to the antiproliferative effects of alpha-interferon (IFN) was isolated. In addition to defects in antiproliferative effects of IFN, SIR-1 is defective in IFN-mediated antiviral activity against both encephalomyocarditis virus and vesicularstomatitis virus. It is also defective in the induction of 2'-5'-oligoadenylate synthetase mRNA and enzyme activity, enhancement of H-2 antigen expression, and transient induction and subsequent repression of c-myc by IFN. SIR-1, although completely resistant to IFN in vitro, is more sensitive to IFN than the parental cell line in vivo. IFN treatment at 10(4) units, three times weekly, resulted in a 28% increase in mean survival time and a 1.4% long term survival rate in the IFN-sensitive 38C13 cell line but resulted in a 275% increase in mean survival rate and a 27% long term survival rate in the interferon-resistant SIR-1 mutant. Statistical analysis of 38C13 and SIR-1 with and without IFN treatment demonstrate that: a) the SIR-1 mutant remains sensitive to the cytotoxic effects of IFN in vivo (P less than 0.0001); and b) the mean survival and long term survival of animals with the SIR-1 mutant is significantly greater than for animals with the IFN-sensitive 38C13 cell line (P less than 0.0001). Two additional independently isolated IFN-resistant cell lines (SIR-111 and SIR-E102) also demonstrate significantly enhanced in vivo response to IFN compared to the interferon-sensitive parental (38C13) cells. These results indicate that, for this cell line, the antitumor effects of IFN are mediated by activation of host defenses and that resistance to the in vitro cytotoxic effects of IFN results in a tumor phenotype that is more readily recognized by host defenses and eliminated.

The effect of lanthanide ions on enteropeptidase-catalyzed activation of trypsinogen.

Rare earths were found to be powerful inhibitors of enteropeptidase-catalyzed (enterokinase, EC 3.4.21.9) activation of trypsinogen. Inhibition was complete at a La3+ concentration of 12.5-10(-6) M in the assay system used and still detectable at a concentration of 1.25-10(-6) M. Inhibition was observed with all lanthanides tested. No significant differences between individual metals could be established under the conditions of the inhibition assay. Increasing ionic strength decreased enzyme activity and progressively diminished the inhibitory effect of rare earth ions suggesting an electrostatic basis for the mechanism of this inhibition. La3+ did not significantly affect enteropeptidase-mediated hydrolysis of N-benzoyl-L-arginine ethyl ester. Its inhibitory effect on activation of trypsinogen by enteropeptidase, therefore, must be attributed to interaction with the zymogen rather than the enzyme. Kinetic measurements show that inhibition by rare earths is noncompetitive in nature. Binding of lanthanides to the tetraaspartyl sequence near the aminoterminus of trypsinogen may prevent this group from interacting with a critical specificity subsite on the enzyme.

Studies on the mechanism of interferon action.

Interferon does not inactivate viruses or viral RNA. Virus growth is inhibited in interferon-treated cells, but apart from conferring resistance to virus growth, no other effect of interferon on cells has been definitely shown to take place. Interferon binds to cells even in the cold, but a period of incubation at 37 degrees C is required for development of antiviral activity. Cytoplasmic uptake of interferon has not been unequivocally demonstrated. Studies with antimetabolites indicate that the antiviral action of interferon requires host RNA and protein synthesis. Experiments with 2-mercapto-1(beta-4-pyridethyl) benzimidazole (MPB) suggest that an additional step is required between the binding and the synthesis of macromolecules. Interferon does not affect the adsorption, penetration, or uncoating of RNA or DNA viruses, but viral RNA synthesis is inhibited in cells infected with RNA viruses. The main action of interferon appears to be the inhibition of the translation of virus genetic information probably by inhibiting the initiation of virus protein synthesis.

Vascular distribution patterns in monochorionic twin placentas.

Several recent publications have focused on the association between the occurrence of twin-to-twin transfusion syndrome (TTTS) in diamniotic-monochorionic twins and the presence of a number of selected anatomic placental characteristics (distribution of vascular territory, cord insertion, type and number of inter-twin anastomoses). In contrast, the potential importance of the vascular distribution patterns of the individual twins remains to be elucidated. Based on its gross architectural distribution pattern, chorionic vasculature is traditionally described as disperse, magistral or mixed. The aim of this study was (1) to determine the relative prevalence of these vascular distribution patterns in monochorionic twin placentas, and (2) to correlate these patterns with the presence of TTTS and known anatomic placental features linked to TTTS. The placentas of 89 consecutive diamniotic-monochorionic twins (15 with TTTS, 74 without TTTS), examined at Women and Infants Hospital, were studied. Disperse vascular patterns were seen in 53% of twins, and magistral or mixed patterns in 47%. The prevalence of magistral/mixed vascular patterns was significantly higher in TTTS gestations than in non-TTTS gestations (60% versus 44%, P<0.05) and, in TTTS gestations, much higher in donor twins than in recipient twins (87% versus 33%, P<0.005). A strong association was found between the presence of magistral/mixed patterns and marginal/velamentous cord insertion, low number of inter-twin anastomoses, and uneven distribution of the vascular territories. These findings suggest that the magistral/mixed vascular distribution pattern may represent an important placental architectural feature contributing to the complex pathophysiology of TTTS.

Antagonism of 2-5 A-mediated inhibition of protein synthesis in intact cells by 2',5'-(pA)3.

In vitro studies have shown that the translational inhibitory activity of 2-5 A can be blocked by the oligoribonucleotide 2',5'-(pA)3. We have examined the effect of simultaneous introduction of inhibitor and antagonist into intact mouse cells using calcium phosphate coprecipitation. Upon introduction of 10(-4) M 2',5'-(pA)3 and 10(-6) M 2-5 A, inhibition of protein synthesis was prevented. Efficiency of calcium phosphate precipitation of 2-5 A in the presence or absence of 2',5'-(pA)3 was comparable. Introduction of 2',5'-(pA)3 analogs showed that nucleotides which do not bind well to the 2-5 A dependent endonuclease do not prevent 2-5 A inhibitory activity. Thus, 2',5'-(pA)3 functions as an antagonist of 2-5 A in vivo.

Reversion by deletion of transforming oncogene following interferon-beta and retinoic acid treatment.

We have previously shown that prolonged interferon-beta (IFN-beta) treatment of RS485 cells (NIH3T3 cells transformed with multiple copies of an LTR-cHa-ras oncogene) resulted in the phenotypic reversion of 1%-5% of the culture, depending on the conditions used. This reversion persisted after IFN-beta was discontinued, although the revertants retained the LTR-cHa-ras and continued to express ras mRNA and p21. Clones were prepared of such persistent revertant cell lines (PRs). Expression of lysyl oxidase (LOX), which appears to act as a suppressor of ras transformation, was downregulated in RS485 and upregulated in the PRs. When retinoic acid (RA) was combined with IFN-beta treatment of the RS485 cultures, a different mechanism of reversion predominated. Following 60 days of treatment with 20 IU/ml of IFN-beta and 10 microM RA, all of the multiple (3-5) copies of the transforming LTR-c-Ha-ras originally present in RS485 cells were deleted from the genome in 72% of 54 revertant cell lines isolated. As in the case of revertants observed after treatment with IFN-beta alone, LOX mRNA expression was upregulated in all of the revertants that resulted from the treatment with IFN plus RA. The level of LOX mRNA expression acts, therefore, as an indicator of transformation in this system.