Acid-stable IFN-α & IFN-β 30% amino aicd identity bind to same receptor induce similar activities

IFN-γ evolutionarily distinct from other interferons binds to separate receptor induces different range of activity

Interferons Flashcards by Aoife Minihan

3 distinct classes of interferon

IFN-α
IFN-β
IFN-γ

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Interferon

A substance secreted by virally infected cells that mediate resistance

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Functions of interferons

Induction of cellular resistance to viral attack
Regulation of immune function
Regulation of growth and differentiation of many cell types
Sustenancce of early phases of pregnancy in some animal species

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Type I interferons

Acid-stable

IFN-α & IFN-β

30% amino aicd identity
bind to same receptor
induce similar activities

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Type II interferon

IFN-γ

evolutionarily distinct from other interferons
binds to separate receptor
induces different range of activity

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Biological effects of type I interferons

Antiviral activity
Anti-proliferative effect

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Anti-tumour effects of type I interferons

Have ability to increase NK and T-cytotoxic cell acitivity

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Biological effects of type II interferons

Weak antiviral and anti-proliferative activity.
Represents main macrophage-activating factor

IFN-γ

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Macrophage-mediated effects

Destruction of invading microbes
Destruction of intracellular pathogens
Tumour toxicity
Increased MHC antigen expression leading to enhanced activation of lymphocytes via antigen presentation

IFN-γ

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What happens when IFN-γ is co-administered with type I interferons

Potentiates the antiviral and anti-proliferation activities of IFN-α & IFN-β

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Initial therapeutic application of interferons

Identified in late 1950s but therapeutic application rendered impractical due to low levels produced by the body.
Large scale purification from sources like blood was non viable.
Interferons exhibit species preference - only human derived interferons can be used in human medicine

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First production of interferon in small quantities

Until 1970s
Sourced from human leukocytes obtained from transfused blood supplies
only 1% pure
contained mixture of various IFN-αs

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First production of interferon in large quantities

late 1970s
mammalian cell culture
cancer cell lines were found to secrete greater quantities of interferons and were amenable to large scale culture due to their transformed nature

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Namalaw cell line

A specific strain of human lymphoblastoid cells
- the major industrial source of interferon

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Interferon production from namalwa cell line

Cells propagated in animal cell fermenters
The additon of an inducing virus (sendai virus)
Results in production of leukocyte interferon.
Final product contained 9 IFN-α subtypes

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Tradename given to one of first approved interferon products

Wellferon

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Most interferons currently in medical use

Recombinant human products produced by E. coli

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Clinical Studies of IFN-α

Conducted in the late 1970s
Found that IFN-α could induce regression of tumors in breast cancer, certain lymphomas, and multiple myeloma.
Could also delay the recurrence of tumor growth after surgery in patients with osteogenic sarcoma.

First recombinant interferon to become available for clinical studies

IFN-α2a (Intron A)
In 1980

Schering Plough’s rhIFN-α2b (Intron A)

First approved in 1986 in US for hairy celll leukaemia - now 50+ countries

Now approved in the US for hepatitis B and C

What is the producer microbe for Intron A and where is it expressed?

E. coli.
Expressed intracellularly and harbors a cytoplasmic expression vector (KMAC-43) containing the interferon gene.

Where are the manufacturing facilities for Intron A located and how is the processing undertaken?

New Jersey and in Brinny, Co. Cork.
1. The upstream processing (fermentation) and downstream processing (purification and formulation) are physically separated, being undertaken in separate buildings.
2. Fermentation is undertaken in 42,000L stainless steel vessels.
3. After recovery, a number of chromatographic purification steps are undertaken within a large cold-room adapted to function under cleanroom conditions.
4. Crystallization of the IFN-α2b is then undertaken as a final purification step.

Modified recombinant IFN-αs

PEGlyated interferons

PEG Intron A
ViraferonPeg

Sythetic interferons

Infergen

ViraferonPeg

PEGylated
Approved EU since 2000
Differs by presence of covalently attached PEG
Schering Plough
Treats chronic hepatitis C
Displays prolonged half-life compared to non-PEG
(13-25 hours compared to 4 hours)

How does the biological activity of PEGylated interferons compare to non-PEGylated interferons?

Essentially the same. Half life different: * PEGylated 13-25hrs * non-PEGylated 4hrs

What is the advantage of using PEGylated interferons?

The PEGylated product displays a significantly prolonged plasma half-life (13-25 hrs, compared to 4 hrs for the unpegylated species).

Infergen

* Interferonalfacon-1 or consensus interferon * Engineered interferon * treats hepatitis C * Development entailed inital sequence comparisions between a range of IFN-αs * Amino acid sequence reflects most frequently occurring amino acid residue in each corresponding position of these native interferons

Medicinal uses of IFN-β

treatment of relapsing-remitting multiple sclerosis (MS)

IFN-β prepartions approved for use

* Betaferon * Betaseron * Avonex * Rebif

How does IFN-β mediate its affect

Inhibiting the production of IFN-α & IFN-γ; thus mediating down-regulation of the pro-inflammatory response

What is the typical reduction in relapse frequency observed with IFN-β-based drugs in multiple sclerosis (MS) patients?

IFN-β-based drugs reduce the frequency of relapses by approximately 30%.

Medicinal use of IFN-γ

Treatment of chronic granulonatous disease (CGD) a rare genetic disorder

CGD Chronic granulonatous disease

* CGD is a genetic defect in the mulitcomponent NADH oxidase system. * This system produces oxidative species that are lethal to pathogens

Traditional treatment of CGD

Prophylactic administraion of antimicrobial agents in attempt to prevent occurrence of infection

Why is prophylactic admin. not favourable?

* Destroys the microbiota creating a resevoir for antimicrobial resistance for immunocompromised patients * Creates major public health risk * Creates environment for superbugs to evolve

Recombinant human IFN-γ used therapeutically

* Produced in E.coli * Termed IFN-γ1b * Displays same bio activity but lacks carbohydrate compound

IFN-γ1b product

Tradename: Actimmune Manufactured: Genetech

Actimmune clinical trial results

* Reduction in the incidence of life threatening infections by > 50% * Reduction in the incidence of total infections by > 50% * Reduction in the number of days of hospitilisaiton by 3-fold

How does IFN-γ work?

Functions as a potent activator of phagocytes, improving their ability to generate toxic oxidative products (via the NADPH oxidase system)

Additional function of IFN-γ

Also promotes increased expression of IgGFc receptors on the surface of phagocytes – thus increasing the phagocyte’s ability to destroy opsonized infectious agents.

What are some conditions that IFN-γ shows promise for treating?

Treatment of: * Leishmaniasis caused by the parasitic protozan of the genus Leishmania, * Lepromatous leprosy caused by Mycobacterium leprae.

Additional interferons

* IFN-τ (trophoblastin) * IFN-ω (omega)

IFN-ω (omega)

* 170 aa glycoprotein * Exhibits 50-60% aa identity to INF-αs * Even more closely related to IFN-τ. * Found in humans, pigs and other mammals. * A recombinant form of feline IFN-ω has been approved for the reduction of parvoviral infections in young dogs.

IFN-τ (trophoblastin)

* Type I - but exhibits lower toxicity * Amino acid sequence and functional similarities with IFN-α * can promote inhibition of reverse transcriptase activity in cells infected with HIV * 3 - 4 functional genes in sheep & cattle