Samuel Baron

Circulating Interferon in Mice after Intravenous Injection of Virus

Circulating interferon was detectable in mouse serum within 1 hour after the intravenous injection of various types of virus and it reached maximum levels in about 4 hours. Rapidly produced interferon may play a role in the pathogenesis of viral infection and in viral interference.

Herpetic Keratoconjunctivitis: Therapy with Synthetic Double-Stranded RNA

A study was undertaken in rabbits to determine how late in the course of keratoconjunctivitis caused by herpes simplex recovery could be effected by an inducer of interferon. Interferon was induced by means of synthetic double-stranded RNA copolymer formed with polynosinic acid: polycytidilic acid RNA. Therapy promotes recovery from severe and fully established keratoconjunctivitis for which treatment was begun as late as 3 days after virus inoculation. No drug toxicity was observed in the therapeutic dose range. These findings further support the proposed role of the interferon mechanism in the natural recovery of already established viral infection. They also suggest the usefulness of interferon inducers in viral infections of man.

Mechanism of Recovery from Viral Infection

Publisher Summary This chapter discusses the mechanism of recovery from viral infection. The two stages of viral infection are— namely, (1) resistance (either low or high) to the establishment of infection, and (2) recovery from an established infection. The chapter considers evidence that relates various immune and non-immune host reactions to resistance and recovery. The appearance of neutralizing antibody, induced by infection or noninfectious antigens, is correlated in time with resistance. In order for antibody to prevent establishment of infection at a particular site of implantation of virus, antibody must be present at that site in sufficient concentration. In contrast to the role of antibody in resistance to establishment of infection, analysis of factors responsible for recovery from an already established infection does not always implicate antibody as a necessary factor. The discovery of interferon provided a rational basis for considering the resistance of interference as a manifestation of the recovery process because it provided a mechanism whereby a viral inhibitory effect could be generated by the relatively few cells, which are infected early in the course of viral disease. The chapter explains the role of interferon in naturally occurring infections.

Antiproliferative Properties of Type I and Type II Interferon

The clinical possibilities of interferon (IFN) became apparent with early studies demonstrating that it was capable of inhibiting tumor cells in culture and in vivo using animal models. IFN gained the distinction of being the first recombinant cytokine to be licensed in the USA for the treatment of a malignancy in 1986, with the approval of IFN-α2a (Hoffman-La Roche) and IFN-α2b (Schering-Plough) for the treatment of Hairy Cell Leukemia. In addition to this application, other approved antitumor applications for IFN-α2a are AIDS-related Kaposi’s Sarcoma and Chronic Myelogenous Leukemia (CML) and other approved antitumor applications for IFN-α2b are Malignant Melanoma, Follicular Lymphoma, and AIDS-related Kapoisi’s Sarcoma. In the ensuing years, a considerable number of studies have been conducted to establish the mechanisms of the induction and action of IFN’s anti-tumor activity. These include identifying the role of Interferon Regulatory Factor 9 (IRF9) as a key factor in eliciting the antiproliferative effects of IFN-α as well as identifying genes induced by IFN that are involved in recognition of tumor cells. Recent studies also show that IFN-activated human monocytes can be used to achieve >95% eradication of select tumor cells. The signaling pathways by which IFN induces apoptosis can vary. IFN treatment induces the tumor suppressor gene p53, which plays a role in apoptosis for some tumors, but it is not essential for the apoptotic response. IFN-α also activates phosphatidylinositol 3-kinase (PI3K), which is associated with cell survival. Downstream of PI3K is the mammalian target of rapamycin (mTOR) which, in conjunction with PI3K, may act in signaling induced by growth factors after IFN treatment. This paper will explore the mechanisms by which IFN acts to elicit its antiproliferative effects and more closely examine the clinical applications for the anti-tumor potential of IFN.

Studies on the mechanism of action of interferon

Abstract An investigation into the biochemical action of interferon has been carried out. When uninfected chick embryo fibroblast tissue culture cells were exposed for 18–24 hours to interferon at levels 10 times that which would cause a 50% inhibition in virus growth, no regular effects were found on the rate of synthesis of protein, DNA, rapidly labeled RNA, or of a number of smaller molecules. In CEF cells infected with Sindbis virus, on the other hand, interferon inhibited the synthesis of rapidly labeled, phenol-released RNA, both early in the course of infection, when little or no virus RNA was being made, and later. In other experiments, a 15-minute pulse exposure of cells to radioactive uridine was followed by a cold uridine “chase,” and slowly labeled RNA was studied. Pretreatment of the cells with interferon led to a decreased amount of radioactivity in the slowly labeled RNA in infected and uninfected cells. It is tentatively suggested that this latter effect is due to an inhibition of transfer from rapidly labeled to slowly labeled RNA.Abstract An investigation into the biochemical action of interferon has been carried out. When uninfected chick embryo fibroblast tissue culture cells were exposed for 18–24 hours to interferon at levels 10 times that which would cause a 50% inhibition in virus growth, no regular effects were found on the rate of synthesis of protein, DNA, rapidly labeled RNA, or of a number of smaller molecules. In CEF cells infected with Sindbis virus, on the other hand, interferon inhibited the synthesis of rapidly labeled, phenol-released RNA, both early in the course of infection, when little or no virus RNA was being made, and later. In other experiments, a 15-minute pulse exposure of cells to radioactive uridine was followed by a cold uridine “chase,” and slowly labeled RNA was studied. Pretreatment of the cells with interferon led to a decreased amount of radioactivity in the slowly labeled RNA in infected and uninfected cells. It is tentatively suggested that this latter effect is due to an inhibition of transfer from rapidly labeled to slowly labeled RNA.

Improved Assays for a Variety of Interferons

Summary Improved assays for a variety of interferons, based on the inhibition of yield of viral hemagglutinin, have been developed. These assays are advantageous because they combine the characteristics of rapidity, simplicity, reliability, sensitivity and inhibition of viral multiplication during a single cycle of growth. Since Sindbis virus produces hemagglutinin in a wide variety of animal cells, it is applicable for comparative interferon studies.

[1] Definition and classification of the interferons

Publisher Summary Interferon (IF), the bodys most rapidly produced defense against viruses, is a protein secreted by body cells when they are stimulated by viruses, bacteria, foreign cells, foreign macromolecules, or numerous other compounds. The secreted interferon then stimulates surrounding cells to produce other proteins, which, in turn, may regulate virus multiplication, the immune response, cell growth, and other cell functions. There are three distinct types of interferon––leukocyte interferon, fibroblast interferon, and immune interferon––depending on the type of stimulus and the type of cell stimulated. These are coded by different structural genes as determined by distinct amino acid sequences and distinct antigenicities. The binding of interferon to a cellular surface receptor initiates the induction of some intracellular proteins. The variety of functional cellular effects of interferon suggests a corresponding variety of biochemical effects. For production of a particular type of interferon, it is necessary to select an appropriate producer cell and an appropriate stimulus. Moreover, medical studies indicate that interferon is promising as a treatment for virus infections and, perhaps, cancer and autoimmune diseases, so that great interest in the interferons is generated.

The effect of interferon on SV40 T antigen production in SV40-transformed cells

Abstract Continuous passage in the presence of interferon failed to reduce the content of SV40 T antigen in a line of SV40-transformed mouse cells (3T3). However, marked inhibition of SV40 T antigen formation resulted when normal 3T3 cells were pretreated with interferon and subsequently infected with SV40 virus. The implications of the undiminished translation of viral genetic information in transformed cells in which an interferon-induced antiviral state exists are discussed. It is suggested that SV40-transformed cells produce molecules of messenger RNA (mRNA) containing both host and viral information, and that the presence of some host genetic information on the mRNA molecule renders it insensitive to the interferon system.

Protection against herpes virus and encephalomyocarditis virus encephalitis with a double-stranded RNA inducer of interferon.

Summary The interferon sensitivities of intracerebrally administered HSV (VR3 strain) and EMCV (r+ strain) were determined in mice with a potent inducer of circulating interferon, polyinosinic·polycytidylic ribonucleic acid (In·Cn). With the treatment as described, delay in mortality occurred at most challenge doses of HSV and EMCV. Significant delay in mortality and increased survival was obtained with 1000 and 100 TCID50 of EMCV, whereas, significant protection was achieved for only 1 TCID50 of HSV with mortality decreasing to about 12–20% as compared to 52–58% in the controls. The data show that sufficient interferon can be induced in the mouse with In·Cn to significantly alter intracerebral infection with HSV and EMCV. The protective effect of In·Cn against intracerebral infection of mice with HSV and EMCV was equal only when the challenge dose of each was sufficiently low. The protective effect against HSV was lost with increasing virus doses of virus whereas the protective effect against EMCV decreased only slightly with increasing virus dose.

Induction of the interferon mechanism by single-stranded RNA: potentiation by polybasic substances

Summary A study was undertaken to determine whether the interferon-stimulating capacity of single-stranded RNA could be enhanced by substances which are known to combine with RNA, to enhance uptake of RNA into cells and to inhibit degradation of RNA by ribonuclease. The results demonstrated that the polybasic substances diethylaminoethyl-dextran (DEAE-dextran), methylated albumin, neomycin, streptomycin, and protamine sulfate markedly enhanced the induction of the interferon mechanism by single-stranded and by double-stranded synthetic RNAs. The demonstration that all the synthetic single-stranded preparations of polyinosinic acid and polycytidylic acid induced the interferon mechanism in the presence of the polybasic substances is strong evidence against the hypothesis that only double-stranded RNA is capable of inducing the interferon mechanism. In addition to the theoretical implications the present findings point to the possibility that the polybasic substances may be useful to enhance the antiviral action of RNAs for the control of viral infections. The authors acknowledge the technical assistance of Miss Carol Millikan and Miss Sharon Brandon.