This document discusses interferons (IFNs), which are signaling proteins produced by immune cells in response to challenges like viruses and tumors. It describes the three main types of IFNs (Type I, II, and III), their functions in activating the immune system and inhibiting viral replication, and the JAK-STAT signaling pathway involved in their mechanism of action. The document also outlines some applications of IFNs in treating conditions like hepatitis, cancer, and multiple sclerosis as well as potential adverse effects.

1. Interferons
Dr. Kanwal Deep Singh Lyall

2. • Immune system
• Cytokines
• Definition
• History
• Classification
• Functions
• Components
• Mechanism of action
• Negative regulators & antagonists
• Applications
• Adverse effects
• References

3. Immune System

4. Immunity
Innate Acquired
natural Artificial
Active passive Active
passive
Antigens or pathogens
entering naturally
Immune response
Antibodies
(placental or colostrum)
Antigen introduction
(vaccines)
Performed
antibodies (Ig)

5. INNATE IMMUNITY
Rapid responses to a
broad range of microbes
ACQUIRED IMMUNITY
Slower responses to
specific microbes
External defenses Internal defenses
Skin
Mucous membranes
Secretions
Phagocytic cells
Antimicrobial proteins
Inflammatory response
Natural killer cells
Humoral response
(antibodies)
Cell-mediated response
(cytotoxic
lymphocytes)
Invading
microbes
(pathogens)
Innate & Acquired Immunity

6. Innate Immune Response
• Activated rapidly and functions within hours
infection
• Considerable interplay occurs between the adaptive
and innate immune defenses.
• Important components are
• cytokines
• complement
• collectins
• natural killer (NK) cells

7. Nonspecific Host Defenses & Host Systems
• Nonspecific Host Defenses – act on any type of
invading agent
• Types of Nonspecific Defenses
• Physical Barriers
• Chemical Barriers
• Cellular Defenses
• Inflammation
• Fever
• Molecular Defenses

8. Cytokines
• Regulatory proteins that mediate intercellular
communication during an antiviral defense
• 1st indicators of host infection
• Paracrine, autocrine, endocrine
• control inflammation, induce antiviral state in cells
& regulate adaptive immune response.
• Exert activities by binding to specific receptors &
activating gene expression
• Interferons are the members of cytokine family

9. Definition
• Interferons (IFNs) are natural cell-signaling
proteins produced by the cells of immune
system of most vertebrates in response to
challenges such as viruses, parasites & tumor
cells
• Belong to large class of glycoproteins k/a
cytokines
• Produced by a wide variety of cells in response
to ds-RNA, a key indicator of viral infection.

10. History

11. • Japanese virologists , Yasu-ichi Nagano &
Yasuhiko Kojima - Institute for Infectious
Diseases at university of Tokyo
• Improved small pox vaccine - rabbit-skin or
testis previously inoculated with UV-
inactivated virus - inhibition of viral growth
when re-infected at same site with live virus
• some inhibitory factor & began to
characterize it
• published these findings in 1954

12. • British virologist Alick Isaacs & Swiss
researcher Jean Lindenmann, - National
Institute Of Medical Research, London
• Noticed an interference effect caused by heat-
inactivated influenza virus on growth of live
influenza virus in chicken egg membranes
in a nutritive solution chorioallantoic
membrane

13. • Published results in 1957,
• In this paper coined term ‘interferon’
• Today that specific interfering agent is k/a
a ‘Type I interferon’

14. Classification

15. IFNs
Type I (viral IFNs)
IFN α (leucocytes)
IFN β (fibroblasts)
IFN ω (leucocytes)
IFN τ (trophoblasts)
•Induced by viral
infections
•Have different binding
affinities but similar
biological effects
Type II (immune IFNs)
IFN γ
•Mitogenic or antigenic stimuli,
inflammatory stimuli
•NK, CD4 TH1, CD8 B cells
• Production controlled by
cytokines secreted by IL 12 & 18

16. General properties
• Species specific , not virus specific
• Inactivated by proteolytic enzymes not nuclease &
lipases
• Resist heating @ 56- - 60° c x 30 – 60 mnts
• Stable at Ph 2-10 (not γ, labile at ph 2)
• Mol. Weight 17000
• Non-dialysable & non-sedmentable
• Poorly antigenic
• Potency expressed in IU/ml
• Non-toxic , diffuses freely in body
• Wide spectrum antiviral activity

17. Inducers
Viral
• Live viruses
• Attenuated viruses
• ds DNA
Non-virals
• Mycobacterial
• Fungi
• Protozoa
• Endotoxins
• Phytoagglutinins
• Polyribonucleotides
• Polyphosphates
• Polysulphates
• Prayons

18. Biological effects
• Anti-viral - resistance to virus infec.
• Antimicrobial – resistance to i/c pathogens – toxoplasma,
chalmydia
• Cellular effects -Negative cell growth regulator & inhibits
proliferations ,inhibits DNA & protein synthesis
• Increased expression of MHC antigens
• Immunomodulator – enhanced cytotoxity of NK, K & T
cells
• Activation of macrophage cytocidal activity
• Modulation of antibody formation
• Activation of supp. T cells & suppression of DTH

19. • Inhibition of tumor cell growth
• Activation of T and natural killer
• Cell cytotoxicity,
• Stimulation of macrophages
• Up-regulation of cell surface MHC class I
molecules
• Promotion of T helper type 1 responses
• Inhibition of angiogenesis

20. Immunomodulation Effects
• Activate NK cells
• Increase MHC class I expression
• Activate macrophages
• Kill cells
• Increase MHC II expression, antigen
• Presentation to helper T cells

21. IFN α , IFN β
• IFN α produced by leukocytes
• IFN β produced by fibroblasts
• Both bind to interferon cell receptors type 1
• Both encoded on chromosome 9
• Different binding affinities but similar biological effects
• Viral infection is stimulus for expression
• Used to mobilize 1st line of defense
• Largest group and are secreted by almost all cell types

22. IFN ω
• Antigenically distinct from ifnα
• Antiviral & antiproliferative activity
• Intratumoral therapy reduces growth of
human tumors

23. IFN-τ
• Responsible for maternal recognition of the
fetus in ruminants
• IFN-τ inhibits HIV replication more strongly
than human IFN-α
• Efficiently inhibits early steps of the biological
cycle of HIV, decreasing i/c HIV RNA &
inhibiting initiation of the reverse transcription
of viral RNA into proviral DNA
• Ovine recombinant IFN-τ cross species barrier

24. IFN alpha IFN beta IFN gamma
Monocytes, B –
lymphocytes
Fibroblasts & epithelial
cells
ActivaNK, CD4 TH1, CD8
B cellsted T-cells,
Max. antiviral activity Intermediate antiviral
activity
More lyphokine activity
than antiviral
13 genes 1 gene 1 gene
Chr. 9 Chr. 9
Type 1 receptors Type 1 receptors Type 2 receptors
Homology with IFN α-80-
95%
30-50% Less than 10%

25. Components of IFN system
• IFNs
• IFN genes
• IFN receptors
• Enzymes (JAK, STAT pathway)
• cis-acting DNA elements (ISRE & GAS)
• IRP (IFN regulated proteins)

26. IFN genes
• Large no. of viral genes in humans
• 13 IFN α genes, 1IFN β, 1 IFN ω – short arm
of chr. 9
• single IFN γ gene - long arm of chr.12

27. IFN receptors
• Act through cell surface receptors-species
specific
• Present on all cells except erythrocytes
• α, β, ω - common receptor-consisting of 2
subunits, IFNAR-1 & IFNAR-2
• γ – receptor used by α,γ – consists of 2
subunits, IFNGR-1 & IFNGR-2
• IFN α, β receptor null mice – unable to
survive in viral state

28. JAKs, STATs
• STATs = signal transducer and activator of
transcription
• 7 STAT proteins – stat 14, 5a, 5b & 6
• JAKs =Janus family of tyrosine kinase
(JAK) enzymes
• 4 JAKs – jak 1-3 & Tyk-2

29. Mechanism Of Action

30. Virus infected cell
IFN
IFN attaches with receptor on neighbor cell
Inactive RNAase L
2-5A synthesase + dsDNA
Activate RNAase L
Preotein
kinases +
ds DNA
Phosphorilates
elF-2
Degrades DNA
Inhibits protein synthesis

31. General action of cytokines

32. General action of IFNs

33. Interferon Mediated Signaling

34. Jak-Stat pathway

35. Activation of
receptor assoc. jaks

36. leads to the
phosphorylation and
dimerization of the Stat-
1 (p91) and Stat-2
(p113) proteins

37. •Subsequent translocation,
along with IRF-9 (p48) to
nucleus.
•The complex of these three
proteins, k/a IFN-stimulated
gene factor 3 (ISGF-3)

38. Activates the transcription of
IFN-α/β inducible genes
through the ISRE (IFN
stimulated response element)

39. The Jak-1 and
Jak-2 kinases are
activated by IFN -γ

40. phosphorylation
and
homodimerization of
the Stat-1 protein
and subsequent
translocation
to the nucleus

41. activates the
transcription
of IFN- γ-
inducible
genes

42. General Action Of IFNs

43. Interferon-induced Proteins
• Protein Kinase (PKR)
• 2,5-oligoadenylate synthetase (OAS) &
RNase L
• RNA-specific adenosine deaminase (ADAR),
• Mx protein GTPases

45. •Phosphorylation of
protein synthesis
initiation factor (eIF-2)

46. •Minimal basal expression
• Increase 10-1000 fold in
response to IFN
• In the presence of ds RNA -
synthesize 2’-5’-linked
oligoadenylates

47. Deamination of
adenosine to inosine-
edits ds-RNA

48. Family of Mx protein
GTPases- targets viral
nucleocapsids

49. Induaction of nitric
oxide synthesae –
increased
intracellular conc. Of
nitric oxide –
inhibition of viral
replication

50. •Upregulation of
MHC class I & class II
antigens expression
•Enhance activation &
effector function of
cytotoxic T cells capable of
destroying virus infected
cells

51. Negative Regulators &
Antagonists

52. Cellular Negative Regulators Of IFN Signaling
• The family of suppressors of cytokine
signaling (SOCS) - binds to JAKs - inhibits
signaling - inhibits the tyrosine
phosphorylation & nuclear translocation of
Stat-1
• STAT-induced STAT inhibitors (SSI)

53. • Cytokine inducible SH2 protein (CIS)
• Protein inhibitors of activated Stat (PIAS)
PIAS 1 & PIAS 3 - directly associate with
Stat-1 & Stat-3, - block the DNA-binding
activity - Stat-1-mediated gene activation

54. Viral Antagonists of IFN Signaling
• viruses encode proteins – impair activity of
JAK-STAT signaling pathway
• Molecular mimicry - viruses encode
products- mimic cellular components of the
IFN signal pathway- antagonist- impairs
development of antiviral state

55. • Poxviruses- encode soluble IFN receptor
homologues (vIFN-Rc)- secreted from
poxvirus-infected cells- bind IFNs- prevent
them from acting through their natural
receptors
• Adenovirus- E1A protein-inhibits DNA
binding activity of ISGF-3

57. Applications
• For human use they are produced by buffy
coat leucocyes from blood banks NDV and
Sendai virus as inducers
• Many of these are in clinical use and are
given intramuscularly or subcutaneously

58. Uses
• IFN alpha
• Condyloma acuminata
• Ch HBV & HCV infections
• Prophylax. & treatment in
immunosupressed patients
exposed to VZV , HSV 1&2
• Prophylaxis in CMV infect
(renal transplant pts)
AIDS associated kaposi’
sracoma
• Hairy cell leukaemia
• IFN gamma
• Immunostimulant in onco.
And immunoedeficients

59. Antiviral
• Chronic HCV
• HBV
• In combination with ribavirin in HIV
• HPV
• HHV8
• CMV
• Human Rhinovirus
• Herpes virus

60. Antitumor
• Cell differentiation & growth regulatory
properties
• Metastatic melanoma
• Hematological cancers
• Solid cancers
• Hairy cell leukemia
• Renal cell ca
• Life threatening hemangiomas
• Chronic myelogenous leukemia
• Follicular non-hodgkin’s lymphoma

61. Multiple Sclerosis (MS)
• Relentlessly progressive neurodegenerative
disease - remissions and relapses - associated
with demyelinationof nerves
• Based on the immunomodulatory properties of
the interferons
• i/m IFN-β- reduction in the annual rate of
relapses of MS
• Addition of natalizumab, a recombinant
monoclonal antibody augments the ability of
IFN- β

62. Recombinant forms of α IFN
• 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

63. Recombinant forms of β IFN
• Beta-1a drug name Avonex
• Beta-1b drug name Betaseron
Recombinant forms of γ IFN
• Gamma-1b drug name Acimmune

64. Pegylation
• Attaching a molecule of polyethylene glycol
• PEG-inert, long chain amphiphilic molecules
• Linear or branched structure
• Increase size of IFN - prolonged absorption
and ½ life & decreased clearance
• retention of biological activity, stable
compound & enhance water solubility

66. α IFN-2a (Roferon A)
• 165 amino acids long protein chain
• Recombinant DNA technology
• Non-glycosylated protein
• Short ½ life, large volume of distribution, larger
renal clearance.
• These problems were resolved by pegylating alpha-
2a resulting in peginterferon alpha-2a that is
named Pegasys.

67. Adverse Effects
• Flu-like symptoms: increased body temperature,
feeling ill, fatigue, headache, muscle pain,
convulsion, dizziness, hair thinning, and depression
• Erythema, pain and hardness on the spot of injection
• Immunosuppression , in particular though
neutropenia
• High level toxicity (Kidney, liver, bone marrow and
heart)
• All known adverse effects usually reversible
• Disappear a few days after the therapy

68. References
• Antiviral Actions of Interferons,Charles E. Samuel. Clin
Microb Rev, Oct. 2001, p. 778–809
• Clinical uses of interferons, Robert M. Friedman, British
Journal of Clinical Pharmacology
• Antitumor Effects of Interferon-v: In Vivo Therapy of
Human Tumor Xenografts
• in Nude Mice, Holly M. Horton,1 Pepe Hernandez,
Suezanne E. Parker, and Kerry M. Barnhart, [CANCER
RESEARCH 59, 4064–4068, August 15, 1999]
• Anti-Human Immunodeficiency Virus Activity of Tau
Interferon in Human Macrophages: Involvement of
Cellular Factors and β-Chemokines Christine Rogez, et
al. J Virol. 2003 December; 77(23): 12914–12920