Interferons Flashcards
3 distinct classes of interferon
- IFN-α
- IFN-β
- IFN-γ
Interferon
A substance secreted by virally infected cells that mediate resistance
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
Type I interferons
- Acid-stable
IFN-α & IFN-β
- 30% amino aicd identity
- bind to same receptor
- induce similar activities
Type II interferon
IFN-γ
- evolutionarily distinct from other interferons
- binds to separate receptor
- induces different range of activity
Biological effects of type I interferons
Antiviral activity
Anti-proliferative effect
Anti-tumour effects of type I interferons
Have ability to increase NK and T-cytotoxic cell acitivity
Biological effects of type II interferons
Weak antiviral and anti-proliferative activity.
Represents main macrophage-activating factor
IFN-γ
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
What happens when IFN-γ is co-administered with type I interferons
Potentiates the antiviral and anti-proliferation activities of IFN-α & IFN-β
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
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
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
Namalaw cell line
A specific strain of human lymphoblastoid cells
- the major industrial source of interferon
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
Tradename given to one of first approved interferon products
Wellferon
Most interferons currently in medical use
Recombinant human products produced by E. coli
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
