INTERFERONS

Ahmed A. FouadMBBCh – Ain Shams University

Discovery of InterferonsThe British virologist Alick Isaacs and

the Swiss researcher Jean Lindenmann, at the National Institute for Medical Research in London.

in 1957.Did an experiment using chicken cell

culturesFound a substance that interfered with

viral replication and was therefore named interferon

What are Interferons?• Naturally occurring proteins and

glycoproteins.• Secreted by eukaryotic cells in

response to viral infections, tumors, and other biological inducers.

• Produce clinical benefits for disease states such as hepatitis, various cancers, multiple sclerosis, and many other diseases.

What are Interferons?Interferons are made by cells in

response to an appropriate stimulus, and are released into the surrounding medium; they then bind to receptors on target cells and induce transcription of approximately 20-30 genes in the target cells, and this results in an anti-viral state in the target cells.

What are Interferons?Structurally, they are part of the

helical cytokine family which are characterized by an amino acid chain that is 145-166 amino acids long.

Mechanism of Action Interferons are small proteins released by

macrophages, lymphocytes, and tissue cells infected with a virus.

When a tissue cell is infected by a virus, it releases interferon.

Interferon will diffuse to the surrounding cells. When it binds to receptors on the surface of

those adjacent cells, they begin the production of a protein that prevents the synthesis of viral proteins.

This prevents the spread of the virus throughout the body.

Mechanism of Action

TYPES OF INTERFERON

Type I Interferons• Type I: alpha and beta• Alpha Interferons are produced by

leukocytes• Beta Interferons are produced by

fibroblasts• Both bind to interferon cell

receptors type 1 and both encoded on chromosome 9

• They have different binding affinities but similar biological effects

• Viral infection is the stimulus for alpha and beta expression

• Used to mobilize our 1st line of defense against invading organisms

• Largest group and are secreted by almost all cell types

Mechanism of Action Of Type I The exact mechanism of type

I Interferons are not fully understood.

Alpha and beta bind to heterodimeric receptor on cell surface.

Alpha receptor is made up of at least 2 polypeptide chains: IFNa-R1 and IFNa-R2

IFNa-R1 is involved in signal transduction

IFNa-R2 is the ligand-binding chain that also plays a role in signal transduction

Mechanism of Action Of Type I Ligation induces

oligomerisation and initiation of the signal transduction pathway.

This results in phosphorylation of signal transductors and activators of transcription proteins, which translocate to the nucleous as a trimeric complex, ISGF-3.

ISGF-3 activates transcription of interferon stimulated genes, with many biological effects.

Mechanism of Action Of Type I

Type II Interferon gInterferon-gamma

(immune interferon) is produced by certain activated T-cells and NK cells.

Interferon-gamma is made in response to antigen (including viral antigens) or mitogen stimulation of lymphocytes.

Mechanism of ActionBind to type 2 receptors and its genes are

encoded on chromosome 12 Initially believed that T helper cell type 1

lymphocytes, cytotoxic lymphocytes and natural killer cells only produced IFN g, now evidence that B cells, natural killer T cells and professional antigen-presenting cells secrete IFN g also.

Gamma production follows activation with immune and inflammatory stimuli rather than viral infection.

This production is controlled by cytokines secreted by interleukin 12 and 18.

Interferon g Receptor and Signaling Pathway Receptors are encoded by separate

genes (IFN g R1 and IFNgR2, respectively) that are located on different chromosomes.

As the ligand-binding (or a) chains interact with IFN-g they dimerise and become associated with two signal-transducing chains.

Receptor assembly leads to activation of the Janus kinases JAK1 and JAK2 and phosphorylation of a tyrosine residue on the intracellular domain of IFN-gR1.

This leads to the recruitment and phosphorylation of STAT1, which forms homodimers and translocates to the nucleus to activate a range of IFN-g-responsive genes.

After this, the ligand-binding chains are internalised and dissociate.

The chains are then recycled to the cell surface.

THERAPEUTIC USES OF INTERFERONS Interferons-alpha and -beta have been used to

treat various viral infections. One currently approved use for various types of

interferon-a 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, leishmaniasis, toxoplasmosis.

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

SIDE EFFECTS OF INTERFERONS

Common side effects of Interferons:

fever, malaise, fatigue, muscle pains

High levels of interferons can cause kidney, liver, bone marrow and heart toxicity.

Different Interferon Drugs• 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-2b drug name Intron A• Alpha-n1 drug name Wellferon• Alpha-n3 drug name AlferonN• Alpha-con1 drug name Infergen

• 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.

These problems were resolved by pegylating alpha-2a resulting in peginterferon alpha-2a that is named Pegasys.

Pegylated Interferon-2a (Pegasys)

Pegasys is recombinant interferon alpha-2a that is covalently conjugated with bis-monomethoxy polyethylene glycol (PEG)

Structure:• PEG moieties are inert, longchain amphiphilic

molecules that are produced by linking repeating units of ethylene oxide.

• Can be linear or branched in their structure• Increasing the size with PEG, the absorption and ½

life are prolonged and the clearance of the IFN is decreased.

• Goal of pegylation is to decrease clearance, retention of biological activity, get a stable linkage and enhance water solubility

• Pegylation is achieved by the covalent attachment of PEG derivatives that utilize amino groups of lysines and the N-terminus of polypeptide molecules as the modification site

Interferon Beta-2a (Avonex)

• FDA approval on May 17 1996 for Relapsing Remitting MS• Clinical trials showed that it slowed MS progression and had an

extra benefit of slowing or preventing the development of MS-related brain atrophy.

• The exact mechanism of IFN beta activity in treating MS is unknown, but studies have shown that interleukin 10 levels in the cerebrospinal fluid were increased in patients

• 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

Interferon Beta-2a (Avonex)• Some side effects include:

Flu-like symptoms

Muscle aches

Chills

Combination Therapy with Ribavirin

Many times interferons and peginterferons are used in combination with Ribavirin.

It is a purine nucleoside analogue with a modified base and a D-ribose sugar moiety

1st made in 1970 by Drs. Joseph Witkowski and Roland Robins

It inhibits the replication of a variety of RNA and DNA viruses and is serves as an immunomodulator to enhance type 1 cytokine production.

This increases the end of treatment response and reduces post-treatment relapse.

Mechanism is not well known.

ConclusionInterferons have overlapping but

different biological activitiesTheir mechanisms of action are

not fully understood, therefore there is a lot of room for future growth within this field

Interferon based strategies can possibly be further tailored to each individual patient according to early response dynamics

Thank You