Marked enhancement of interferon production in 5-bromodeoxyuridine treated human lymphoblastoid cells

Oromucosal interferon therapy: pharmacokinetics and pharmacodynamics

Oromucosal administration of [125I]-labeled recombinant human interferon-alpha1-8 (IFN-alpha1-8), which is biologically active in the mouse, resulted in readily detectable levels of radioactivity in the serum of animals within 5 min. Biologically active IFN could not be detected in the serum at any time after oromucosal administration, however, and SDS-PAGE analysis showed that the material present in the serum was of low molecular weight and most probably reflected absorption of degradation products following digestion of IFN in the stomach and small intestine. Furthermore, oromucosal administration of murine IFN-alpha/beta (MuIFN-alpha/beta) had no significant effect on the expression of IFN-responsive genes in either peripheral blood mononuclear cells or splenic lymphocytes even though in the same animals IFN treatment activated gene transcription locally in the lymphoid tissue of the oropharyngeal cavity and caused a marked systemic antiviral activity. Oromucosal administration of MuIFN-alpha/beta had no significant effect on either the number of circulating peripheral blood leukocytes or the number of granulocyte-macrophage colonies recovered from the bone marrow of IFN-treated animals. These results suggest that the mechanism of action of oromucosal IFN therapy is distinct from that of parenterally administered IFN and may involve, in the abundant lymphoid or epithelial tissue of the oropharyngeal cavity, either production of a soluble factor or activation of a specific cell population that enters the circulation to mediate the elimination of virus-infected or neoplastic cells.

Genomic footprinting: detection of putative regulatory proteins in the promoter region of the interferon alpha-1 gene in normal human tissues

Dimethyl sulfate (DMS) genomic footprinting revealed the presence of putative regulatory proteins attached to specific sequences of the promoter region of the interferon (IFN) alpha-1 gene in normal human tissue. The pattern of protein-DNA interactions observed for the human alpha-1 promoter in freshly isolated human spleen cells was identical to that seen in DNA from the B-cell line Namalwa. The protein interactions involving the human IFN alpha-1 promoter spanned a region from positions -38 to -174 relative to the cap site which encompasses that part of the IFN alpha-1 promoter previously shown by deletion analysis to confer virus inducibility on the IFN alpha-1 gene. DNase I footprinting performed on isolated nuclei revealed a pattern of protein-DNA interactions for the promoter region of the IFN alpha-1 gene similar to that obtained with DMS footprinting performed on whole cells, with the appearance or disappearance of only a few additional protected nucleotides outside the region identified by the use of DMS. These results provide the first direct evidence for the presence of proteins bound in vivo to those parts of the IFN alpha-1 promoter between positions -64 and -109 previously shown by deletion analysis to confer virus inducibility on the IFN alpha-1 gene. The pattern of protein-DNA interactions observed for the IFN alpha-1 promoter after virus induction was identical to that seen before induction, in keeping with the finding that many transcriptional activators are present in both induced and uninduced cells.

Genomic footprinting: detection of putative regulatory proteins in the promoter region of the interferon alpha-1 gene in normal human tissues

Dimethyl sulfate (DMS) genomic footprinting revealed the presence of putative regulatory proteins attached to specific sequences of the promoter region of the interferon (IFN) alpha-1 gene in normal human tissue. The pattern of protein-DNA interactions observed for the human alpha-1 promoter in freshly isolated human spleen cells was identical to that seen in DNA from the B-cell line Namalwa. The protein interactions involving the human IFN alpha-1 promoter spanned a region from positions -38 to -174 relative to the cap site which encompasses that part of the IFN alpha-1 promoter previously shown by deletion analysis to confer virus inducibility on the IFN alpha-1 gene. DNase I footprinting performed on isolated nuclei revealed a pattern of protein-DNA interactions for the promoter region of the IFN alpha-1 gene similar to that obtained with DMS footprinting performed on whole cells, with the appearance or disappearance of only a few additional protected nucleotides outside the region identified by the use of DMS. These results provide the first direct evidence for the presence of proteins bound in vivo to those parts of the IFN alpha-1 promoter between positions -64 and -109 previously shown by deletion analysis to confer virus inducibility on the IFN alpha-1 gene. The pattern of protein-DNA interactions observed for the IFN alpha-1 promoter after virus induction was identical to that seen before induction, in keeping with the finding that many transcriptional activators are present in both induced and uninduced cells.

Expression of the genes of interferons and other cytokines in normal and diseased tissues of man

Specific interferon genes are transcribed at low levels in the spleen, liver, and peripheral blood leukocytes of normal individuals in the apparent absence of virus infection while other interferon genes remain unexpressed in the same tissues. In contrast, the genes of cytokines such as IL-1, IL-6 and TNF are expressed at relatively high levels in the organs of normal individuals. The level of expression of the IL-1, IL-6 and TNF genes is markedly reduced in the livers of patients with autoimmune liver disease compared to the level of expression in the liver of normal individuals, whereas the expression of interferon genes is similar in both normal and diseased liver, suggesting that a defect in the expression of specific cytokines is associated with severe liver disease.

Selective deficiency in IL-2 production and refractoriness to extrinsic IL-2 in immunodeficiency with hyper-IgM

Various lymphokines are inducible by the stimulation of T-cell mitogens, phytohemagglutinin, and concanavalin A. A 32-year-old female with an atypical type of immunodeficiency with hyper-IgM was evaluated for possible defects in the production of several immunoregulatory lymphokines. Although the mitogens appeared to bind effectively to the specific surface receptors of patient peripheral blood lymphocyte (PBL), the proliferative responses were significantly decreased. The culture supernatant of patient PBL stimulated by the mitogens contained only a trace amount of interleukin 2 (IL-2) activity. Addition of recombinant IL-2 to the cultures concomitantly with the mitogens could not restore the decreased responses of patient PBL. Tac antigen expression of patient PBL induced by the mitogens was moderately impaired. These data suggest that there is a defect in both IL-2-producing and IL-2-responding cells. In contrast, the culture supernatant of mitogen-stimulated patient PBL contained B-cell growth and differentiation factors as well as interferon-gamma activities equal to those of the control. These results suggest that there are independent regulatory pathways for the production of IL-2 and other T-cell-derived lymphokines.

Ultrastructural findings in the acquired immunodeficiency syndrome (AIDS)

Ultrastructural studies have made significant contributions in evaluating the pathology and pathogenesis of AIDS. Three distinct types of abnormal cytomembranous inclusions in tissue specimens or peripheral blood mononuclear cells from AIDS patients are described--vesicular rosettes (VR), tubuloreticular inclusions (TRI), and cylindrical confronting lamellae (CCL).

Increased nuclease sensitivity of the human interferon-alpha 1-related genes and the interferon-beta 1 gene during induction by virus

The chromatin structure of the human interferon (IFN) genes was evaluated during induction of human lymphoblastoid (Namalwa) cells by Sendai virus. Namalwa cells were treated with bromodeoxyuridine (BrdUrd) for 36-48 h and induced with Sendai virus for 7 h; the nuclear fraction was isolated and treated with low levels of either micrococcal nuclease or DNAse I. DNA was extracted from the nuclease-treated chromatin, restricted with Eco RI and analyzed by Southern blotting using IFN-alpha 1 and -beta 1 cDNA probes. An increase in the digestibility of the IFN-alpha 1-related genes and the IFN-beta 1 gene was observed in chromatin prepared from BrdUrd-treated, Sendai virus-induced Namalwa cells as compared with chromatin from uninduced Namalwa cells. Our results indicate that, during IFN induction in Namalwa cells by Sendai virus, the IFN genes assume a more open conformation consistent with increased transcriptional activity across these genes.

Constitutive production and characterization of interferon-gamma in a human T-lymphoblastoid cell line transformed by a human retrovirus

A human T-lymphoblastoid cell line, TCL-Fuj, constitutively produced a large amount of human gamma interferon (IFN) in culture fluids and has sustained stable IFN production for more than two years. When cells were incubated in RPMI-1640 medium with 10% fetal calf serum for three days, IFN activity was detectable at a cell density of 6 X 10(4) cells/ml, whereas 2,000-16,000 units of IFN per ml were produced at 5-10 X 10(5) cells/ml. IFN production was also detected even in serumfree medium and as early as 2 hr after cultivation in fresh medium. IFN was inhibited by treatment of cells with either actinomycin D or cycloheximide, indicating the requirement of IFN-mRNA and protein for de novo synthesis. The molecular weight of the IFN was 45,000-60,000 as determined by Sephacryl S200 gel filtration. Two activity peaks corresponding to molecular weights of 22,000 and 39,000 were obtained by SDS-polyacrylamide gel electrophoresis. Analysis by isoelectric focusing revealed charge heterogeneity with four species at pIs of 6.0, 7.1, 8.6, and 9.3. Conventional IFN-gamma inducers, concanavalin A and 12-O-tetradecanoyl-phorbol-13-acetate, further enhanced the production of IFN in this cell line.

Lymphokines produced by herpesvirus-transformed marmoset monkey lymphoid cell lines. I. Characterization of a constitutively produced interferon

Conditioned media from cultures of marmoset monkey T-lymphoid cell lines transformed by Herpesvirus saimiri or Herpesvirus ateles were found to contain interferon (IFN) activity. Titers between individual cell lines varied by a factor of 100; large amounts (up to 10(5) units/ml, assayed on human cells) were produced in one of the cell lines. IFN production was enhanced by the diterpene tumor promoters, TPA and mezerein, but not by classical T-cell mitogens. The IFN resembles human IFN-gamma by the following criteria: lability at pH 2, stability against 2-mercaptoethanol, cross-species activity, shape of dose-response curves, and molecular weight determined by size-exclusion chromatography (50,000-55,000). Its activity was not inhibited, however, by antiserum against human IFN-gamma or antisera against human IFN-alpha or IFN-beta.

Induction of gamma-interferon activity by elevated temperatures in human B-lymphoblastoid cell lines

When the human B-lymphoblastoid cell lines GM3299 and GM4408 were heat shocked, elevated levels of antiviral activity were detected. This antiviral activity has been characterized as the result of de novo synthesis of interferon (IFN) gamma. Levels of antiviral activity as high as 20,000 units/ml per 10(6) cells were found after heat treatment. By using anti-IFN-alpha and anti-IFN-gamma sera, it was shown that the high antiviral activity in GM3299 after heat shock is due to a synergistic effect of constitutively produced IFN-alpha and induced IFN-gamma.

Differential expression of human interferon genes

We developed a method for quantitating closely related mRNAs by S1 mapping and used it to determine the levels of mRNAs for IFN-beta, IFN-gamma and various alpha IFNs (IFN-alpha 1, -alpha 2, -alpha 4, -alpha 5, -alpha 6, -alpha 7, -alpha 8 and -alpha 14) in human peripheral blood leukocytes, lymphoblastoid (Namalwa), HeLa and human fibroblastic cells, induced in different fashions. The ratio of alpha to beta IFN transcripts varied greatly, depending on the cell type. The levels of the individual IFN-alpha RNAs were very different: IFN-alpha 1, -alpha 2 and -alpha 4 RNAs constituted the major fraction of the IFN-alpha transcripts measured. Moreover, there was a striking difference in the proportion of individual IFN-alpha mRNA species in different cell types. Use of different induction protocols did not significantly affect the proportion of IFN mRNAs. IFN production was not proportional to mRNA level in all cases, as lymphoblastoid cells induced by incubation at high density and virus-induced HeLa cells contained high levels of IFN-beta but produced little antiviral activity.

Factors affecting the CEA secretion of human adenocarcinoma cell lines into the spent medium

CEA producing cell lines were established from human gastric cancer (HGC-Y1), pancreatic cancer (HPC-Y9) and lung cancer (HLC-Y1). The culture medium was used RPMI-1640 supplemented with 10% fetal bovine serum. The secretion of carcinoembryonic antigen (CEA) into the spent medium from these cultured cell lines was modified by several factors, such as theophylline, cyclic AMP (cAMP), dibutyryl cyclic AMP (dbcAMP), Bromodeoxyuridine (BrdUrd), dimethyl sulfoxide (DMSO), Prostaglandin E2 (PGE2) and human interferon (INF). CEA secretion was enhanced by theophylline, cAMP, PGE2 and INF. Theophylline had an optimal dose to maximally enhance CEA secretion. cAMP and INF apparently enhanced CEA secretion dose dependently. PGE2 appeared to enhance CEA secretion, although cell growth was markedly suppressed dose dependently, dbcAMP, DMSO and BrdUrd did not affect CEA secretion. Here, the kinetics of CEA secretion was discussed.

Expression of the native alpha and beta interferon genes in human cells

We have investigated the expression of human interferon (IFN)-related transcripts in Sendai virus-induced lymphoblastoid (Namalwa) cells and in poly(I) X poly(C)-induced fibroblast (FS-4) cells by electrophoresis of RNA through agarose-CH3HgOH gels followed by (a) blot hybridization of the RNA using IFN-alpha 1 and IFN-beta 1 cDNA probes, and (b) translation of the eluted RNA into biologically active IFN using the Xenopus laevis oocyte assay. In Namalwa cells induced with or without prior treatment with bromodeoxyuridine we can detect IFN-alpha 1 hybridizable, translationally active, cytoplasmic RNA of lengths 0.3-0.6, 2-3, 3.5-5, and 7-8 kb in addition to the expected 0.8-1.4-kb RNA and IFN-beta 1-hybridizable, translationally active, cytoplasmic RNA of lengths 0.9 kb and approximately 4 kb. However the translationally active 1.8-kb IFN-alpha L mRNA(s) in Namalwa cells (P. B. Sehgal, May, LaForge, and Inouye, Proc. Nat. Acad. Sci. USA 79, 6932-6936, 1982) appears to have less than 60-70% nucleotide sequence homology with IFN-alpha 1 in the coding region because it does not cross-hybridize IFN-alpha 1 cDNA even under very relaxed hybridization conditions. In induced FS-4 cells we can detect IFN-beta 1-hybridizable and translationally active cellular RNA of lengths 0.3-0.4, 0.65, 0.9, 1.8, 2-3, 3.5-5, and 7-8 kb. No hybridization is detected in RNA of length 1.3 kb ("IFN-beta 2 mRNA"). Direct comparisons between the translation and hybridization data using dot-blot hybridization procedures confirm that the apparently subcistronic 0.35-kb IFN-beta 1 hybridizable-RNA species detected in FS-4 cells is translationally active.

Interferon production potentials of various human lymphoblastoid cell lines

A number of human lymphoblastoid cells were examined concerning their ability to produce spontaneously liberated and virus-induced interferon (IFN). It was found that, in addition to B cells, various T and nonT-nonB lymphoblastoid cells responded well to Sendai virus infection to form IFN, the characterization of which has been recently reported (20). One B lymphoblastoid cell line from an infectious mononucleosis (IM) patient produced a large amount of IFN-alpha and might become an alternative source of IFN production. Among 68 cell lines examined, 35 cell lines liberated 10 U/ml or more of IFN spontaneously in culture fluid. The presence of Epstein-Barr virus (EBV) genome or its activation appears to have no correlation with the spontaneous liberation of IFN. Spontaneously produced IFN from three cell lines was characterized as IFN-alpha. Comparatively higher amounts of IFN were produced in cells from IM patients than those from Burkitt's lymphoma cases or healthy adults. Spontaneously produced IFN was detected more easily in cells transformed by EBV alone than in those transformed by EBV and a tumor promoter, TPA.

Spontaneous production of alpha- and beta-interferon in human lymphoblastoid and lymphoma cell lines

A large number of human haematopoietic cell lines was examined for spontaneous production of interferon. Unconcentrated culture supernatants from 70 out of 71 B-lymphoblastoid cell lines contained considerable amounts of interferon (median titer 22 units per ml); a few lines produced more than 100 units/ml with peak values up to 500 units/ml. In contrast, only one B-lymphoma line out of 18 genuine lymphoma, myeloma, and leukaemia cell lines tested spontaneously produced small amounts of interferon. Following treatment with 5-bromodeoxyuridine (BrdUrd), interferon was produced without further induction in most B-lymphoid cell lines, but not in any of the non-B, non-T, T-lymphoid or myeloid lines examined. Modulation of spontaneous interferon production by chemicals (sodium butyrate, dexamethasone, dimethylsulfoxide, a phorbol ester, and BrdUrd) was studied in more detail in three B-lymphoblastoid and four B-lymphoma cell lines. The patterns of responses observed were different for the action of different chemicals on a given cell line as well as between lymphoblastoid and lymphoma lines in general; furthermore, several lines of evidence suggest that chemicals can differentially influence spontaneous and virus-induced interferon production in an given cell line. The composition of spontaneously produced interferon was analysed using antisera specific for HuIFN-alpha and HuIFN-beta. Interferons produced by untreated as well as BrdUrd-treated lymphoblastoid cells contained more than 95 per cent IFN-alpha, whereas BrdUrd-treated lymphoma cells produced IFN-alpha as well as minor amounts (cell lines Namalwa and NC-37) or even over 90 per cent of IFN-beta (Daudi).

Protein synthesis in human lymphoblastoid cells (Namalwa) after treatment with butyrate and 5'-bromodeoxyuridine

The pattern of protein synthesis has been compared in Namalwa cells following treatment with butyrate and 5'-bromodeoxyuridine (BrdUrd). Although these treatments cause a substantial increase in Sendai virus-induced interferon synthesis (up to 300-fold) we observed no comparable effect on the synthesis of other cellular proteins. Using two-dimensional gel electrophoresis we have investigated the proteins synthesised before and 8 h after Sendai virus infection of treated cells. Only 2 of the 300 most abundant cellular proteins were reproducibly affected, these always showed increased rates of synthesis in butyrate-treated cells. The most significant was a 3-4-fold enhancement in synthesis of a 35,000 molecular weight protein which we have called BEP35. On individual occasions treatment caused changes in the rates of synthesis of other proteins, these were not reproducible and involved less than 4% of the proteins investigated. None of the Sendai virus structural proteins or virus-induced cellular proteins were affected by the treatment. We conclude that butyrate and BrdUrd treatments have a relatively specific effect on the synthesis of interferon in Namalwa cells, as the majority of protein synthesis remains unaffected.

Radioactive human lymphoblastoid interferon. One-step purification, regulation of heterogeneous species production and its use for radioimmunoassay

Human lymphoblastoid interferon (alpha type), labeled with [3H]leucine added to virus-induced Namalwa cells, was purified quantitatively and in one step from the culture fluid by immune precipitation. The material showed, upon polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate, only four radioactive bands with molecular weights ranging from 17000 to 21000, which coincided well with interferon activity. They coincided also with the four interferon protein bands in the electropherogram of unlabeled interferon purified by a different method. The purity of the labeled interferon was ascertained also by polyacrylamide gel electrophoresis in the absence of dodecyl sulfate. Pulse-labeling of interferon with [3H]leucine for 1 h at various times after induction indicated that the cells always synthesized and secreted the four interferon species in parallel during the interferon production period. Competitive radioimmunoassay for human interferon alpha was achieved by the use of purified radioactive interferon, anti-(interferon alpha) serum, and bacterial adsorbent. The immune precipitation of the labeled interferon was inhibited by unlabeled interferon alpha, and 100 international reference units of interferon alpha could be measured in this way.

Spontaneous production of gamma interferon and induced production of beta interferon by human T-lymphoblastoid cell lines

Two human T-lymphoblastoid cell lines, CCRF/CEM and Molt 4, produced beta interferon (IFN-beta) upon infection with Sendai virus. Molt 4, but not CCRF/CEM, spontaneously produced up to 300 U of IFN-gamma per ml, apparently not contaminated with IFN-alpha or -beta. Phytohemagglutinin, a T-cell mitogen, did not stimulate IFN production in these lines. A third T-lymphoblastoid line, CCRF/HSB2, produced no IFN either spontaneously or after infection with Sendai virus or treatment with phytohemagglutinin. The Molt 4 cells contained an mRNA which could be translated by oocytes to give IFN-gamma. Molt 4 cells therefore provide a convenient source of human IFN-gamma and its mRNA for experimental purposes.

Interferon production in human hematopoietic cell lines: response to chemicals and characterization of interferons

We have surveyed interferon production and its modulation by 5-bromodeoxyuridine, butyrate, dexamethasone, dimethylsulfoxide and tetradecanoylphorbolacetate in 20 human hematopoietic cell lines derived from leukemias, lymphomas, myelomas and normal leukocytes, representing various maturation stages of lymphoid and myeloid cells. Sendai virus-induced interferon production was enhanced by at least one of the chemicals in 13 out of 14 B-type lymphoid cell lines, whereas no enhancement was observed in any of the non-B, non-T-, T-lymphoid, or myeloid cell lines tested. Interferon produced by 11 cell lines was partially characterized using antisera specific for HuIFN-alpha and HuIFN-beta. Six cell lines produced both IFN-alpha and IFN-beta, two lines produced by IFN-alpha and three lines (including both T-cell lines tested) produced only IFN-beta. In all cases examined, enhancement by chemicals of total interferon yields was due to selective stimulation of production of IFN-alpha. Poly (I):(C) induction of interferon was studied in a number of B-cell lines. In general, a similar pattern of IFN-alpha and -beta synthesis was observed as in virus-induced cells, but the proportion of IFN-beta was relatively smaller. Treatment with butyrate enhanced interferon production to a similar extent accompanied by a similar shift in composition as in virus-induced cells. Our results demonstrate that even in closely related cell types, production of IFN-alpha and IFN-beta can be regulated differently in response to the same inducer. In a single cell type in response to a single inducer, expression of IFN-alpha and IFN-beta can be differentially affected by chemicals.

Use of cell differentiation effectors to select a human B lymphoblastoid cell line enriched in C3b receptors

A study was undertaken to establish conditions of growth to increase C3b receptor synthesis on a human B lymphoblastoid cell line (Raji) by use of cell differentiation effectors. It appears that whereas two polar compounds HMBA (2mM) and Me2SO(2%) have no or little effect, 5 BrdU (30microM) and db cAMP (5 x10(-4) M) are able to increase in 48 h and 36 h respectively the synthesis of C3b receptor on Raji cell surface. These two compounds help to select a variant in which 100% of cells have C3b receptors with a high density of receptors per cell. The mechanism of BrdU action on the regulation of C3b receptor synthesis is discussed.

Human lupus inclusions and interferon

Raji cells, a human B lymphoblastoid cell line of Burkitt lymphoma origin, formed lupus inclusions when grown in a medium conditioned by the growth of Raji cells whose DNA thymidine residues had been unifilarly (single-strandedly) substituted with bromodeoxyuridine. Ultracentrifugation of this medium in excess of that required to remove Epstein-Barr virus and all other known mammalian viruses did not prevent the formation of the inclusions, and treatment of the conditioned medium with pronase destroyed the activity. These results demonstrate the presence of a protein that is secreted from bromodeoxyuridine-substituted Raji cells and is capable of inducing nonbromodeoxyuridine-substituted cells to form lupus inclusions. Interferon (100 units per milliliter) was found in the conditioned medium. Inclusions also formed in Raji cells grown in fresh medium supplemented with human leukocyte or fibroblast interferon (100 units per milliliter).

Production of high levels of human leukocyte interferon from a continuous human myeloblast cell culture

A myeloblast cell line has proved to be an excellent source of human leukocyte interferon. These cells, primed with interferon and induced with Sendai virus, produced optimal levels of human leukocyte interferon. The cells grew readily in spinner flasks and in medium containing horse serum. Interferon production over several months yielded an average titer of 2 X 10(5) reference units of interferon per 10(7) cells. The interferon produced by these cells appeared to be predominantly species of human leukocyte interferon. Since these cells seemed to consist of myeloblasts, it is clear that cells other than B-lymphocytes can produce leukocyte interferon.

Spontaneous production of human interferon

Several established lines of human lymphoblastoid cells were evaluated for abilities to produce interferons. Some cell lines were able to produce interferon when induced with either Newcastle disease virus or Sendai virus, whereas others failed to produce detectable interferon when so induced. However, several cell lines were able to spontaneously produce interferon without induction. Spontaneously produced interferon was liberated by cells only during logarithmic growth phase, reaching levels ranging from about 10 reference units/ml of growth medium for some cell lines to 1000 reference units/ml for others. The interferons produced by induced lymphoblastoid cells and the spontaneously produced interferons were all characterized as type I human leukocyte interferon by high levels of cross-species antiviral activities on bovine cells and by neutralizations by antiserum to human leukocyte interferon but not by antiserum to human fibroblast interferon. However, analysis by electrophoresis in sodium dodecyl sulfate/polyacrylamide gels revealed that spontaneously produced interferon was less size heterogeneous than human leukocyte interferon, migrating as a single band of activity with a peak at 20,000 daltons, whereas human leukocyte interferon contained peaks of major activity at 23,000 and 18,000 daltons and virus-induced Namalva lymphoblastoid cell interferon migrated predominantly as the 18,000-dalton form. Also, although neither virus-induced primary leukocyte interferon nor any of the virus-induced lymphoblastoid cell interferons were neutralized by antiserum to mouse interferon, all of the spontaneously produced interferons were neutralized by antiserum to mouse interferons. These data suggest significant structural similarities between the active cores of certain interferons from phylogenetically diverse animal species.

Interferon production and virus replication in lymphoblastoid cells infected with different viruses

A semicontinuous infection system was used to test viral replication and interferon induction in lymphoblastoid cells: measles virus, Newcastle disease virus (NDV), Sendai virus, human parainfluenza virus (type II and III), Semliki forest virus (SFV) and Vesicular stomatitis virus (VSV). With the exception of Sendai virus, all viruses replicated in the Namalva cell line. Only measles virus was able to induce high levels of interferon. Three other cell lines, NC37, Raji (TK+-variant) and Raji (TK--variant) were tested using measles virus as inducer. The interferon yields from these cells were inferior to those obtained from Namalva cells.

Abnormal behavior of interferon-induced enzymatic activities in an interferon-resistant cell line

Interferon induces two double-stranded RNA-dependent enzymatic activities: an oligoisoadenylate synthetase that converts ATP to ppp(A2'p)n5'A, and a protein phosphokinase. We have explored the level and inducibility of these two enzymes in a human cell line (HEC-1) totally insensitive to both the antiviral and the anticellular actions of interferon. The activities of both enzymes are high in untreated cells and only minor changes occur after treatment with interferon, even at high concentrations. Interferon-treated HEC-1 cells do not contain an inhibitor of the oligoisoadenylate synthetase activity. The products of this HEC-1 oligoisoadenylate synthetase consist mainly of dimers, trimers, and tetramers as found in other cell lines after interferon treatment. The synthetase level is unaffected by treating the cells with anti-interferon antiserum, indicating that the results cannot be explained by a spontaneous low production of interferon by these cells. Furthermore, virus multiplication is not inhibited, even after treatment with interferon. These observations suggest that either the two enzymatic activities do not suffice for the establishment of an antiviral state in vivo or that a regulatory control mechanism, lost in these cells and common for both enzymes, is required for the expression of the antiviral action of interferon. This might explain both the constitutivity of the two enzymes and the interferon resistance observed.

Effects of sodium butyrate on a human lymphoblastoid cell line (Namalwa) and its interferon production

Treatment of lymphoblastoid cells with sodium butyrate before infection with Sendai virus increases the subsequent yield of interferon and of its messenger RNA. This treatment caused almost complete inhibition of cellular DNA synthesis and consequently cell division, and some inhibition of cellular RNA and protein synthesis. It also caused increased acetylation of histones and alterations in the plasma membrane. There was no decrease in cell viability or change in cell morphology but the cells were smaller than untreated cells and were all in the G1 phase. Sodium butyrate treatment had no effect on the course of Sendai virus infections. The observed increase in interferon yields after butyrate treatment did not correlate with its effects on DNA synthesis, size, cell division and histone acetylation, but did with its effects on RNA and protein synthesis.

Neutralizing antibodies against human leukocyte, lymphoblastoid and fibroblast interferons elicited by immunization with human leukocyte interferon

Guinea pigs, rabbits, and sheep were immunized with partially purified human leukocyte interferon. The antisera were tested for their neutralizing activities against human leukocyte, lymphoblastoid (Namalva) and fibroblast interferons. Rabbits and sheep developed high levels of neutralizing antibodies against all three interferons. The ratios of the neutralizing activities of leukocyte/lymphoblastoid interferons varied from 1 to 25 and those of leukocyte/fibroblast interferons from 2 to 500. The ratios increased with prolonged immunization. The guinea pigs developed relatively low levels of anti-leukocyte and anti-lymphoblastoid antibodies and as a rule failed to produce detectable neutralizing activity against fibroblast interferon. One sheep was given a booster injection of fibroblast interferon after preimmunization with leukocyte interferon. The booster injection stimulated a rise in antibody levels, not only for fibroblast interferon, but also for leukocyte and lymphoblastoid interferons. The antigenic relationships between leukocyte, lymphoblastoid and fibroblast interferons are discussed.