Effect of interferon on early interferon production

Biology and pathogenesis of chikungunya virus

Chikungunya virus (CHIKV) is a re-emerging mosquito-borne alphavirus responsible for a recent, unexpectedly severe epidemic in countries of the Indian Ocean region. Although many alphaviruses have been well studied, little was known about the biology and pathogenesis of CHIKV at the time of the 2005 outbreak. Over the past 5 years there has been a multidisciplinary effort aimed at deciphering the clinical, physiopathological, immunological and virological features of CHIKV infection. This Review highlights some of the most recent advances in our understanding of the biology of CHIKV and its interactions with the host.

Neutralizing interferon alpha as a therapeutic approach to autoimmune diseases

Therapeutic antibodies directed against tumor necrosis factor alpha (TNF-alpha) for the treatment of rheumatoid arthritis, and against the human EGF receptor-2 (HER2) receptor for the treatment of breast cancer have provided significant clinical benefit for the patients. The success of these antibodies has also provided strong support for the possibility that increased activity of cytokines or growth factors is causally implicated in a variety of human diseases. Interferon alpha (IFN-alpha) is induced by viruses (linked by epidemiological studies to autoimmune diseases), has significant direct effects on both epithelial cells and the immune system, and then can be further induced by the autoantibodies and apoptotic cells generated by the actions of IFN-alpha. The direct and deleterious impact on target tissues, the ability to induce an autoimmune response, and the potential for a self-sustaining cycle of induction and damage suggests that IFN-alpha could be a pivotal factor in the development of autoimmune diseases. This review will evaluate the rationale for, possible approaches to, and safety concerns associated with, targeting interferon alpha (IFN-alpha) as a therapeutic strategy for the treatment of autoimmune diseases. While the approach may be applicable to several autoimmune diseases, there will be an emphasis on systemic lupus erythematosus and insulin dependent diabetes mellitus.

Poly I:CLC induction of the interferon system in mice: an initial study of four detection methods

Induction of a large number of the components of the interferon (IFN) system (IFN genes, their mRNAs, IFN proteins, IFN receptors, IFN signaling molecules, the IFN response genes, and their effector proteins) has been studied. Less well studied is the comparative induction of these components in vivo. Induction of IFN by double-stranded RNA (dsRNA) treatment mimics certain aspects of viral infection and induces the components of the IFN system. To determine the comparative sensitivity of detection of induction in mice, we initially studied the limiting concentrations of polyribinosinic-polyribocytidylic acid, polylysine complex (poly I:CLC, a synthetic dsRNA preparation), for induction of four representative components of the IFN system: (1) IFN in serum, (2) the IFN response gene mRNA ISG54 in spleen and liver, (3) the IFN-beta mRNA in spleen, and (4) resistance of mice to Banzi viral infection. The results of this initial study showed that resistance to infection was 7-fold more sensitive for detection of the IFN response than was ISG54 mRNA and 70-fold more sensitive than either IFN-beta mRNA or IFN production in serum. In comparison, mouse cells in vitro treated with poly I:CLC were 3-10-fold less sensitive to its antiviral action than is the mouse. The results demonstrate that in the four tests in mice, the most sensitive indicator of poly I:CLC induction of the IFN system was protection against Banzi viral infection, followed by ISG54 mRNA levels, IFN-beta mRNA, and IFN protein levels. It is hypothesized that the highest sensitivity of mouse protection may be due to priming by the initial poly I:CLC-induced IFN of the subsequent Banzi virus-induced IFN, resulting in rapid and high concentrations of IFN at the local site of viral replication. Future studies are needed to study other molecular components of the IFN system to identify those that cause the unanticipated high sensitivity of mice to protection against Banzi virus.

Beta interferon production in primed and unprimed cells infected with human cytomegalovirus

Human cytomegalovirus induced beta interferon in cultures of human foreskin cells. The inhibitor was first released between 8 and 16 hours after infection, about 48 hours before progeny virus. In cultures infected with low concentrations of virus, interferon was produced as the infection spread, and then in amounts larger than expected. After infection with cytomegalovirus, cells which had been primed for 48 hours with purified beta interferon produced significantly more interferon than unprimed cells, and the interferon was produced earlier, between 2 and 8 hours after infection. CMV-induced interferon also was able to prime cells. The data suggest that the relatively large quantities of interferon detected in cultures infected with low concentrations of cytomegalovirus result from endogenous priming: those cells infected early first produce interferon which primes uninfected cells, then virus which induces the primed cells to produce interferon in relatively high concentrations.

Priming of leukocytes selectively increases the level of some interferon-alpha subtypes and not others

The effect of pretreatment with interferon (IFN) ('priming') on the production of individual IFN subtypes was studied in subpopulations of human peripheral blood mononuclear cells and in the myeloid cell line KG-1. It was found that priming had a selective enhancing effect on the production of certain IFN-alpha subtypes (IFN-alpha 20K and IFN-alpha 21K) and not on others. KG-1 cells produce both IFN-alpha and -beta; however, only the production of IFN-alpha was enhanced by priming with either IFN-alpha, beta or gamma.

Platelet-derived growth factor (PDGF) inhibits priming in synchronous mouse or human fibroblasts producing interferon

Monolayer cultures of Lpa and FS-4, mouse and human fibroblasts that are good producers of interferon were synchronized by contact inhibition and by incubation in 5% platelet poor plasma serum (PPPS) medium. When the quiescent cultures were stimulated for growth by PDGF, pre-treatment with homologous interferon before induction with virus or poly (rI) . poly (rC) did not increase interferon yields. Under similar experimental conditions priming (increased interferon synthesis) was demonstrated in the asynchronous or quiescent Lpa or FS-4 cells pre-treated with homologous interferon. The unprimed cells, whether stimulated for growth with PDGF or not, produced normal amounts of interferon after appropriate induction. We suggest that growth factor (PDGF), a hormone with opposing action to interferon, can inhibit priming but it has little, if any, effect on the basic process of induction of interferon synthesis.

Mutagenic factors in cooked foods

The charred surface of fish and beef showed strong mutagenic activity in Salmonella typhimurium test strains when activated by S-9 mix of rat liver. The pyrolysis products of proteins and amino acids were also highly mutagenic. Among the pyrolysis products of amino acids, those of tryptophan, serine, and glutamic acid were most active. The new gamma-carboline derivatives, 3-amino-1,4-dimethyl-5H-pyrido[4,3-b]indole and 3-amino-1-methyl-5H-pyrido[4,3-b]indole, were purified from the pyrolysis products of tryptophan. These new compounds were stronger mutagens than aflatoxin B1 towards S. typhimurium TA98, a frameshift type mutant, and they also transformed cryopreserved Syrian hamster embryo cells in vitro. Tryptophan pyrolysate also contained the beta-carboline derivatives, norharman and harman, which are not mutagenic alone, but act as comutagens. A mixture of norharman or harman and nonmutagenic aniline or o-toluidine was strongly mutagenic. The mutagenicities of charred products of other foods, such as seaweed and garlic, are reviewed in this article. Flavonoids, such as kaempferol and quercetin, and glycosides of these flavonoles were mutagenic. The mutagenicity of cooked vegetables depends partly on these flavonoid derivatives. The already-known existence of benzol[a]pyrene and nitroso compounds in cooked food is also reviewed.

The mode of production of endotoxin-induced interferon in rabbit tissue cells. I. Development of priming by pretreatment with interferon

In vitro production of endotoxin-induced interferon in rabbit tissue cell cultures could be enhanced by pretreatment with interferon. The enhancible state developed from the first hr of incubation at 37 C and a maximal priming effect was attained at 6 hr of incubation. Yields of interferon from unprimed cultures were usually 20-200 units/ml. In contrast, the primed cultures constantly yielded 1,000-2,500 units/ml of interferon. The pretreatment with interferon seemed to cause an earlier appearance of detectable interferon and the primed cells became more sensitive to endotoxin. It turned out that 10--30 units/ml of rabbit interferon were enough to develop the maximal priming. Even when cells were pretreated with higher doses of rabbit interferon such as 1.0 x 10(4) - 1.0 x 10(5) units/ml, the same level of priming effect was always observed without diminution. Various types of homologous (rabbit) and heterologous (human and mouse) interferon preparations showed similar dose-dependent enhancement of interferon production in proportion to the antiviral titers of these preparations as tested with RK-13 cells of rabbit origin.

Increased Interferon Production in Human Cells Irradiated with Ultraviolet Light

Polyinosinate-polycytidylate [poly(I)·poly(C)]-induced interferon production in cultures of human foreskin fibroblast strains was increased by ultraviolet irradiation of cells at the time of exposure to inducer or at 2 h after induction. Incubation of cells with interferon prior to induction (priming) and ultraviolet irradiation exerted a cooperative enhancing effect on interferon production. The resulting interferon yields were generally somewhat higher than the yields from cultures subjected to sequential treatment with cycloheximide and actinomycin D.

Post-exposure prophylaxis of murine rabies with polyinosinic-polycytidylic acid and chlorite-oxidized amylose

Chlorite-oxidized amylose (COAM), polyinosinic-polycytidylic acid [poly(I:C)], and combinations of the two drugs were evaluated for their interferon-inducing properties and their ability to protect mice against rabies infection. Post-exposure administration of one or two doses (100 mug each) of poly(I:C) significantly protected mice against rabies infection. Pretreatment of mice with COAM 3 h before poly(I:C) stimulation resulted in an enhancement of the interferon response. However, the increased interferon titers were not reflected by increased protection against rabies infection over that achieved with poly(I:C) therapy alone. Therapy with COAM alone did not protect mice against rabies but, rather, was associated with enhanced mortality.

Studies on the mechanism of the priming effect of interferon on interferon production by cell cultures exposed to poly(rI)-poly(rC)

Interferon induction by poly(rI).poly(rC) in primary rabbit kidney and mouse L-929 cell cultures was markedly increased if the cells were previously treated with homologous interferon. This priming effect has been established with different times of exposure of the cells to poly(rI).poly(rC), and was most pronounced for short pulses of contact of the polynucleotide with the cells (10 s, 1 min). Treatment of the cells with pancreatic ribonuclease immediately after their exposure to poly(rI).poly(rC) brought about a relatively greater reduction of the interferon response in interferon-primed cells than it did in unprimed cell cultures. Priming of the cells with interferon did not increase cell-binding of poly(rI).poly(rC), whether this cell-binding was measured quantitatively (by radioactivity, upon exposure of the cells to radiolabeled polymer) or qualitatively (by antiviral activity, by assaying the cell extract for virus plaque reduction). Similarly, interferon priming did not alter the sensitivity of cell-associated poly(rI).poly(rC) to extraneous ribonuclease treatment. Finally, priming with interferon did not decrease the rate of degradation of cell-bound poly(rI).poly(rC) by cellular nucleases nor did it increase the anti-nuclease potency of the cells. The exact mechanism by which previous exposure of the cells to interferon enhances subsequent interferon production, induced by either synthetic polynucleotides or viruses, has not yet been resolved.

Chlorite-oxidized amylose as an adjuvant for interferon production

Chlorite-oxidized amylose (COAM), when given intraperitoneally to mice and to cats, increased the titer of serum interferon subsequently induced by polyinosinic.polycytidylic acid (In.Cn). Increases ranged from 6- to 100-fold. Maximal effect was observed when COAM was given 3 h prior to In.Cn. COAM given intravenously prior to Newcastle disease virus also significantly increased serum interferon titers.

Priming: a nonantiviral function of interferon

No interferon is made by L cells when they are infected with MM virus. However, several thousand units of interferon are produced when interferon-treated L cells are infected with MM virus. We call the conversion of cells, from nonproducers to producers, priming. The time required for cells to become fully primed is dependent on the interferon concentration with which they are incubated. Primed cells produced interferon earlier than normal cells stimulated by other inducers. Cells which were exposed to interferon in the presence of inhibitors of protein synthesis became fully primed yet developed no virus resistance. Also, primed cells produced interferon in response to low concentrations of polyriboinosinic acid . polyribocytidylic acid that did not induce interferon in normal cells. Therefore, priming appears to be a function of interferon separable from its antiviral activity. Several other picornaviruses that failed to induce interferon in L cells, human embryonic lung cells, or monkey kidney cells did induce interferon when these cells had been primed by homologous interferons.

Interferon-inducing characteristics of MM virus

Interferon induction by MM virus in mice and in L cells was studied. In mice the virus readily induced interferon. The time of appearance was dose-dependent. A large virus dose induced interferon by 4 hr, whereas a small dose resulted in interferon production which paralleled virus replication 24 hr after infection. In L cells the interferon-inducing capacity of the virus was rapidly destroyed by ultraviolet light irradiation. Heating (56 C) of the virus, on the other hand, greatly increased its ability to induce interferon. Interferon production could also be increased by prior treatment of the cells with homologous interferon (priming). The increase in interferon production after priming was dependent on the concentration of interferon used for priming, the length of interferon treatment, and the multiplicity of infection. It is suggested that MM virus might be useful for the further study of the mechanisms involved in the production and action of interferon.