INTERFERONS

Abdul MannanM. Phil Scholar

Deptt. Of Pathobiology FVS, BZU Multan

WHAT ARE INTERFERONS? Naturally occurring proteins and

glycoproteins Secreted by eukaryotoc cells in

response to viral inections, tumors and other biological inducers

Structurally, they are part of the helical cytokine family which are characterized by an amino acid chain that is 145-166 amino acids long

DISCOVERY OF INTERFERONS 1957 Isaacs and Lindenmann Did an experiment using chicken cell cultures Found a substance that interfered with viral

replication and was therefore named interferon (“Interference factors”)

Nagano and Kojima also independently discovered this soluble antiviral protein

INTERFERON BASICS Interferons play an important role in the

first line of defense against viral infections

Interferons are part of the non-specific immune system

First recognized by their ability to interfere with viral infections in cultured cells.

Does not protect the virus infected cell that produces it.

Itself is not the antiviral agent.It moves to other cells where it induces an antiviral state.(By inhibiting viral replication)

IMPORTANT FEATURES

7

TYPES OF INTERFERON

TYPE I:Interferon-alpha (leukocyte interferon, about 20 related proteins)

leukocytes, etc

Interferon-beta (fibroblast interferon)fibroblasts, epithelial cells, etc

TYPE II:Interferon-gamma (immune interferon)

certain activated T-cells, NK cells

A. IFN-α & β (Type-I- IFNs)

When prototypic cell of origin is exposed to

-Viruses

-Double stranded RNA

- Cytokines

B. IFN- (Type-II- IFNs)

Following a number of immunological stimuli including :-

-T-cell specific antigen-Staphylococcal enterotoxin -A And -Mitogens ( Phyto haemagglutinin ,Phorbol Ester etc)

INDUCTION OF INTERFERON

Morley,Michael.The pharmacology of lymphocytes.Barlin Heidelberg.Springer.1988.print

Properties Alpha Beta Gamma

Current Nomenclature IFN-α IFN-β IFN-

Former Designation Leukocyte Fibroblast Immune Interferon

Type Designation Type I Type I Type II

No. Of Genes that code for Family ≥20 1 1

Principal Cell Source Most Cell Types

Most cell Types Lymphocytes

Inducing Agent Viruses; dsRNA

Viruses; dsRNA

Mitogens

Stability at pH 2.0 Stable Stable Labile

Chromosomal location of genes 9 9 12

Size of secreted protein (Number of amino acids)

165 166 143

IFN receptors IFNAR IFNAR IFNGR

INTERFERON SIGNALING Interferon signaling mediated by JAKs and STATS

JAKs (Janus Kinases) or just another kinase! STATS (Signal transducers and activators of transcription)

Binding of Interferon to receptor causes receptor dimerization JAKs associate to receptor before interferon binding

Binding causes them to get activated and phosphorylate receptor and collaborating JAKs

Phosphorylated receptors behave as docking sites for STATs JAKs phosphorylate STATs once they dock to receptors Phosphorylated STATs dimerize and translocate to nucleus JAK-STAT pathway is extremely rapid

STAT binding to DNA can be detected within minutes of interferon receptor binding

Over 100 genes can be induced via interferon signaling Rapidity is needed to respond to danger

IFN binds with the respective IFN-Receptors(IFNRs)

Oligomerization of the receptor followed by phosphorylation of the tail of receptor

molecule

Phosphorylated STAT ( Signal Transducers and activators of transcription ) released from the receptor molecules and translocate to the

nucleus

Activation of trancription of IFN-Stimulated gene. This results in

synthesis of several enzymes

MODE OF ACTIVATION OF IFN’S STIMULATED GENES

Interferons ά and β bind to the same receptor, which is composed of two subunits

The binding of either interferon- ά or interferon- β to this receptor results in the activation of Janus tyrosine kinases Jak1 and Tyk2, which results in the phosphorylation of signal transducers and activators of transcription 1 and 2 (STAT1 and STAT2).

INTERFERON SIGNALING

STAT1 and STAT2 phosphorylation results in their heterodimerization, dissociation from the interferon receptor, and translocation to the nucleus.

In nucleus, the STAT complex associates with DNA-binding protein p48 (interferon-stimulated gene factor 3) (ISGF3),which binds to the interferon-stimulated response element of ά- and β-responsive genes.

induction of interferon target genes, responsible for the biologic effects of interferons ά and β .

INTERFERON- γ Interferon-γ binds as a

homodimer to the specific interferon-γ receptor

Dimerization of the receptor activates the Janus tyrosine kinases Jak1 and Jak2, which ultimately results in the phosphorylation of STAT proteins.

Instead of activating STAT1 and STAT2( as with type I interferon receptor) interferon-γ activates two separate STAT1 molecules.

form a homodimer known as

the - γ activated factor (GAF)

translocates to the nucleus and binds to γ -activating sequences (GAS), elements of interferon- γ inducible genes (Zitzmann, Kathrin, et al. in 2008 als0 reported so)

INTERFERON- γ

ANTIVIRAL MECHANISIM OF INTERFERON

However its best understood anti-viral mechanism is: 1. Block viral mRNA synthesis 2. Block translation of viral mRNA

Mx proteins 2',5' oligo(A) synthetase and ribonuclease L PKR, double stranded RNA dependent protein kinase

Mx proteins (myxovirus proteins) are induced by interferon Block viral RNA polymerase Block transport of viral nucleoproteins (influenza virus) into nucleus

2',5' oligo(A) synthetase and ribonuclease L This enzyme gets activated by dsRNA Unique ability to synthesize oligos of A in the 2'- 5' linkage, norm is 3'-5'

linkage Poly(A) oligos bind ribonuclease L and activate it mRNA is destroyed Both cellular and viral cells may die

ANTIVIRAL MECHANISM OF INTERFERON

THERAPEUTIC USES OF INTERFERONS

Interferons-alpha and -beta have been used to treat various viral infections.

One currently approved use of interferon- IFN-α

is in the treatment of certain cases of acute and chronic hepatitis C and chronic hepatitis B.

Interferon-gamma has been used to treat a variety of disease in which macrophage activation might play an important role in recovery, eg. lepromatous leprosy, .

Since interferons have anti-proliferative effects, they have also been used to treat certain tumors such as melanoma and Kaposi’s sarcoma.

Interferon alfa-n3 (Alferon-N)

genital and perianal warts 

Interferon beta-1b (Betaseron) and beta-1a(Avonex)

multiple sclerosis

Interferon gamma-1B (Actimmune)

chronic granulomatous disease and severe, malignant osteopetrosis.

Interferon alfa-2b chronic hepatitis C and chronic hepatitis B 

CLINICAL TOXICITY OF INTERFERON ADMINISTRATION Most common toxicities Schedule and dose dependent. Acute administration can result in

-fever, , headache, nausea, vomiting, and fatigue. - Fatigue usually increases with repetitive dosing .

Appropriate timing of administration (e.g., at or just before bedtime) can limit the impact of symptoms.

Anorexia and weight loss -commonly seen with higher-dose regimens

HEMATOLOGIC TOXICITIES Hematologic toxicities

-anemia, neutropenia, and thrombocytopenia. Appear to be dose related, rarely reported in lower-dose

regimens.

Neutropenia requiring dosage reduction reported in 26% to 60% of patients receiving high-dose interferon-α.

Neutropenic fevers or infections requiring antibiotic administration or hospitalization are quite rare.

Thrombocytopenia -rarely severe enough to warrant dosage reductions.

ORGAN TOXICITIES

o Kidneys -Reversible proteinuria - 15% to 20% of patients -Interstitial nephritis. .

Skin -macular rashes , skin reactions –resolve

Acute hepatic toxicity High-dose interferon regimens

- manifested as increase in serum levels Alanine transaminase (ALT) Aspartate aminotransferase (AST).

- fatal complications can be avoided with careful monitoring and appropriate dosage modification.

with discontinuation of therapy.

DIFFERENT INTERFERON DRUGSAVAILABLE IN MARKET• Interferons are broken down into recombinant versions of a

specific interferon subtype and purified blends of natural human interferon.

• Many of these are in clinical use and are given intramuscularly or subcutaneously

• Recombinant forms of alpha interferon include:

• Alpha-2a drug name Roferon

• Alpha-n3 drug name AlferonN

• Recombinant forms of beta interferon include:

• Beta-1a drug name Avonex

• Beta-1b drug name Betaseron

• Recombinant forms of gamma interferon include:

• Gamma-1b drug name Acimmune

ALPHA INTERFERON-2A (ROFERON A)

Protein chain that is 165 amino acids long

Produced using recombinant DNA technology

Non-glycosylated protein Short half life, short terminal

elimination of half life, a large volume of distribution, and a larger reduction in renal clearance.

INTERFERON BETA-2A (AVONEX)

• Structurally IFNb-2a is a 166 amino acid glycoprotein.

• Produced by recombinant DNA technology using genetically engineered mammalian cells which the human beta gene has been introduced into

• Amino acid sequence is the same as human beta interferon. They are both glycosylated at the asparagines residue at position 80

REFERENCES: Morley,Michael.The pharmacology of lymphocytes.Barlin

Heidelberg.Springer.1988.print Zitzmann, Kathrin, et al. SOCS1 silencing enhances antitumor activity of

type I IFNs by regulating apoptosis in neuroendocrine tumor cells. Cancer research 67.10 (2007): 5025-5032

Jonasch E and Haluska FG. Interferon 2001;6(1):34-55. Rijckborst V and Janssen Harry L.A. The Role of Interferon in Oncological

Practice: Review of Interferon Biology, Clinical Applications, and Toxicities. Oncologist in Hepatitis B therapy. Curr Hepatitis Rep 2010;9:231-238.

Kanda T, Imazeki F and Yokosuka O. New Antiviral Therapies for Chronic Hepatitis C. Hepatol Int 2010;4:548-561

Hayden FG and Gwalthey JM jr. Intranasal interferon-alpha 2 treatment of experimental rhinoviral colds. J Infect Dis. 2003 ;150(2):174-80.